From 5ad746166341e3c07250ee09518d7e4ab5cfb966 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:45:56 +0200
Subject: [PATCH 01/14] bpf: Add verifier diagnostics report helpers

Add the initial diagnostics renderer for verifier reports and wire it into
the BPF build. The helper emits the common failure header through the
verifier log.

Later patches add prose wrapping, reusable report sections, and source and
instruction context for category-specific diagnostics.

Gate the helpers on normal verifier log output from the start, so
BPF_LOG_STATS-only loads do not collect or render diagnostics.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-2-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/Makefile      |  2 +-
 kernel/bpf/diagnostics.c | 47 ++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h | 14 ++++++++++++
 3 files changed, 62 insertions(+), 1 deletion(-)
 create mode 100644 kernel/bpf/diagnostics.c
 create mode 100644 kernel/bpf/diagnostics.h

diff --git a/kernel/bpf/Makefile b/kernel/bpf/Makefile
index 4dc41bf5780c..90255d80e5be 100644
--- a/kernel/bpf/Makefile
+++ b/kernel/bpf/Makefile
@@ -6,7 +6,7 @@ cflags-nogcse-$(CONFIG_X86)$(CONFIG_CC_IS_GCC) := -fno-gcse
 endif
 CFLAGS_core.o += -Wno-override-init $(cflags-nogcse-yy)
 
-obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o cnum.o log.o token.o liveness.o const_fold.o
+obj-$(CONFIG_BPF_SYSCALL) += syscall.o verifier.o inode.o helpers.o tnum.o cnum.o log.o token.o liveness.o const_fold.o diagnostics.o
 obj-$(CONFIG_BPF_SYSCALL) += bpf_iter.o map_iter.o task_iter.o prog_iter.o link_iter.o
 obj-$(CONFIG_BPF_SYSCALL) += hashtab.o arraymap.o percpu_freelist.o bpf_lru_list.o lpm_trie.o map_in_map.o bloom_filter.o
 obj-$(CONFIG_BPF_SYSCALL) += local_storage.o queue_stack_maps.o ringbuf.o bpf_insn_array.o
diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
new file mode 100644
index 000000000000..e75753552a4d
--- /dev/null
+++ b/kernel/bpf/diagnostics.c
@@ -0,0 +1,47 @@
+// SPDX-License-Identifier: GPL-2.0-only
+// Copyright (c) 2026 Meta Platforms, Inc. and affiliates.
+
+#include <linux/bpf_verifier.h>
+#include <linux/ctype.h>
+#include <linux/stdarg.h>
+
+#include "diagnostics.h"
+
+bool bpf_diag_enabled(const struct bpf_verifier_env *env)
+{
+	return env->log.level & BPF_LOG_LEVEL;
+}
+
+static void diag_write(struct bpf_verifier_env *env, const char *fmt, ...) __printf(2, 3);
+
+static void diag_write(struct bpf_verifier_env *env, const char *fmt, ...)
+{
+	va_list args;
+
+	if (!bpf_diag_enabled(env))
+		return;
+
+	va_start(args, fmt);
+	bpf_verifier_vlog(&env->log, fmt, args);
+	va_end(args);
+}
+
+static void bpf_diag_header(struct bpf_verifier_env *env, const char *category,
+			    const char *problem)
+{
+	char first;
+
+	if (!bpf_diag_enabled(env))
+		return;
+
+	category = category ?: "Verifier Error";
+	problem = problem ?: "";
+
+	if (!problem[0]) {
+		diag_write(env, "\nVerification failed: %s\n", category);
+		return;
+	}
+
+	first = toupper(problem[0]);
+	diag_write(env, "\nVerification failed: %s: %c%s\n", category, first, problem + 1);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
new file mode 100644
index 000000000000..f51aa39f0909
--- /dev/null
+++ b/kernel/bpf/diagnostics.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/* Copyright (c) 2026 Meta Platforms, Inc. and affiliates. */
+
+#ifndef __BPF_DIAGNOSTICS_H
+#define __BPF_DIAGNOSTICS_H
+
+#include <linux/compiler_attributes.h>
+#include <linux/types.h>
+
+struct bpf_verifier_env;
+
+bool bpf_diag_enabled(const struct bpf_verifier_env *env);
+
+#endif /* __BPF_DIAGNOSTICS_H */

From b9c5d822f677e065971481c4bafe5d84b5451082 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:45:57 +0200
Subject: [PATCH 02/14] bpf: Add source and instruction diagnostic context

Teach verifier diagnostics to annotate an instruction with BTF source
line information and nearby BPF instructions. The renderer keeps source
text in a fixed-width lane and prints instructions in a stable right-hand
gutter.

Wrap annotation text under the source line so long error labels remain
readable while the source and instruction lanes keep their fixed layout.

Keeping source and instruction context in one commit preserves the visual
layout contract that later diagnostic reports rely on.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-3-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 include/linux/bpf.h          |  12 +-
 include/linux/bpf_verifier.h |   4 +
 include/linux/btf.h          |   1 +
 kernel/bpf/btf.c             |  10 +
 kernel/bpf/core.c            |  35 ++-
 kernel/bpf/diagnostics.c     | 490 +++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h     |   7 +
 kernel/bpf/verifier.c        |  47 +++-
 8 files changed, 576 insertions(+), 30 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 04cadd987169..ffa5626411ac 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -4147,8 +4147,16 @@ static inline bool bpf_is_subprog(const struct bpf_prog *prog)
 }
 
 const struct bpf_line_info *bpf_find_linfo(const struct bpf_prog *prog, u32 insn_off);
-void bpf_get_linfo_file_line(struct btf *btf, const struct bpf_line_info *linfo,
-			     const char **filep, const char **linep, int *nump);
+struct bpf_linfo_source {
+	const char *file;
+	const char *line;
+	u32 file_name_off;
+	int line_num;
+	int line_col;
+};
+
+void bpf_get_linfo_source(struct btf *btf, const struct bpf_line_info *linfo,
+			  struct bpf_linfo_source *src);
 int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char **filep,
 			   const char **linep, int *nump);
 struct bpf_prog *bpf_prog_find_from_stack(void);
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 27b43fda9b17..579a288bc8de 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -833,6 +833,7 @@ static inline u16 bpf_in_stack_arg_cnt(const struct bpf_subprog_info *sub)
 	return 0;
 }
 
+struct bpf_diag;
 struct bpf_verifier_env;
 
 struct backtrack_state {
@@ -950,6 +951,7 @@ struct bpf_verifier_env {
 	struct bpf_insn_aux_data *insn_aux_data; /* array of per-insn state */
 	const struct bpf_line_info *prev_linfo;
 	struct bpf_verifier_log log;
+	struct bpf_diag *diag;
 	struct bpf_subprog_info subprog_info[BPF_MAX_SUBPROGS + 2]; /* max + 2 for the fake and exception subprogs */
 	/* subprog indices sorted in topological order: leaves first, callers last */
 	int subprog_topo_order[BPF_MAX_SUBPROGS + 2];
@@ -1433,8 +1435,10 @@ void print_verifier_state(struct bpf_verifier_env *env, const struct bpf_verifie
 void print_insn_state(struct bpf_verifier_env *env, const struct bpf_verifier_state *vstate,
 		      u32 frameno);
 u32 bpf_vlog_alignment(u32 pos);
+const char *bpf_disasm_kfunc_name(void *data, const struct bpf_insn *insn);
 
 struct bpf_subprog_info *bpf_find_containing_subprog(struct bpf_verifier_env *env, int off);
+const char *bpf_subprog_name(const struct bpf_verifier_env *env, int subprog);
 int bpf_jmp_offset(struct bpf_insn *insn);
 struct bpf_iarray *bpf_insn_successors(struct bpf_verifier_env *env, u32 idx);
 void bpf_fmt_stack_mask(char *buf, ssize_t buf_sz, u64 stack_mask);
diff --git a/include/linux/btf.h b/include/linux/btf.h
index 3f5255d095a2..7ea13768c979 100644
--- a/include/linux/btf.h
+++ b/include/linux/btf.h
@@ -214,6 +214,7 @@ int btf_type_seq_show_flags(const struct btf *btf, u32 type_id, void *obj,
  */
 int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj,
 			   char *buf, int len, u64 flags);
+int btf_type_name_to_buf(const struct btf *btf, u32 type_id, char *buf, int len);
 
 int btf_get_fd_by_id(u32 id);
 u32 btf_obj_id(const struct btf *btf);
diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
index 87ffde865a50..5b9d767895c9 100644
--- a/kernel/bpf/btf.c
+++ b/kernel/bpf/btf.c
@@ -8316,6 +8316,16 @@ int btf_type_snprintf_show(const struct btf *btf, u32 type_id, void *obj,
 	return ssnprintf.len;
 }
 
+int btf_type_name_to_buf(const struct btf *btf, u32 type_id, char *buf, int len)
+{
+	struct btf_show show = {
+		.btf = btf,
+		.state.type_id = type_id,
+	};
+
+	return snprintf(buf, len, "%s", btf_show_name(&show));
+}
+
 #ifdef CONFIG_PROC_FS
 static void bpf_btf_show_fdinfo(struct seq_file *m, struct file *filp)
 {
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 6a94370a2448..d55e737ed75a 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -3461,24 +3461,14 @@ EXPORT_TRACEPOINT_SYMBOL_GPL(xdp_bulk_tx);
 
 #ifdef CONFIG_BPF_SYSCALL
 
-void bpf_get_linfo_file_line(struct btf *btf, const struct bpf_line_info *linfo,
-			     const char **filep, const char **linep, int *nump)
+void bpf_get_linfo_source(struct btf *btf, const struct bpf_line_info *linfo,
+			  struct bpf_linfo_source *src)
 {
-	/* Get base component of the file path. */
-	if (filep) {
-		*filep = btf_name_by_offset(btf, linfo->file_name_off);
-		*filep = kbasename(*filep);
-	}
-
-	/* Obtain the source line, and strip whitespace in prefix. */
-	if (linep) {
-		*linep = btf_name_by_offset(btf, linfo->line_off);
-		while (isspace(**linep))
-			*linep += 1;
-	}
-
-	if (nump)
-		*nump = BPF_LINE_INFO_LINE_NUM(linfo->line_col);
+	src->file = kbasename(btf_name_by_offset(btf, linfo->file_name_off));
+	src->line = btf_name_by_offset(btf, linfo->line_off);
+	src->file_name_off = linfo->file_name_off;
+	src->line_num = BPF_LINE_INFO_LINE_NUM(linfo->line_col);
+	src->line_col = BPF_LINE_INFO_LINE_COL(linfo->line_col);
 }
 
 const struct bpf_line_info *bpf_find_linfo(const struct bpf_prog *prog, u32 insn_off)
@@ -3521,6 +3511,7 @@ const struct bpf_line_info *bpf_find_linfo(const struct bpf_prog *prog, u32 insn
 int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char **filep,
 			   const char **linep, int *nump)
 {
+	struct bpf_linfo_source src;
 	int idx = -1, insn_start, insn_end, len;
 	struct bpf_line_info *linfo;
 	void **jited_linfo;
@@ -3552,7 +3543,15 @@ int bpf_prog_get_file_line(struct bpf_prog *prog, unsigned long ip, const char *
 	if (idx == -1)
 		return -ENOENT;
 
-	bpf_get_linfo_file_line(btf, &linfo[idx], filep, linep, nump);
+	bpf_get_linfo_source(btf, &linfo[idx], &src);
+	while (isspace(*src.line))
+		src.line++;
+	if (filep)
+		*filep = src.file;
+	if (linep)
+		*linep = src.line;
+	if (nump)
+		*nump = src.line_num;
 	return 0;
 }
 
diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index e75753552a4d..815aa7938b50 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -1,12 +1,61 @@
 // SPDX-License-Identifier: GPL-2.0-only
 // Copyright (c) 2026 Meta Platforms, Inc. and affiliates.
 
+#include <linux/bpf.h>
 #include <linux/bpf_verifier.h>
+#include <linux/btf.h>
 #include <linux/ctype.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/seq_buf.h>
+#include <linux/slab.h>
 #include <linux/stdarg.h>
+#include <linux/string.h>
 
+#include "disasm.h"
 #include "diagnostics.h"
 
+#define BPF_DIAG_TEXT_WIDTH 100
+#define BPF_DIAG_CONTEXT 2
+#define BPF_DIAG_CONTEXT_CNT (1 + BPF_DIAG_CONTEXT * 2)
+#define BPF_DIAG_SOURCE_LANE_WIDTH 88
+#define BPF_DIAG_TAB_WIDTH 8
+#define BPF_DIAG_FMT_CHUNK_SIZE (PAGE_SIZE - sizeof(struct diag_fmt_chunk))
+#define BPF_DIAG_FMT_BUF_SIZE 256
+#define DISASM_LINE_LEN 160
+
+struct disasm_line {
+	char text[DISASM_LINE_LEN];
+	int idx;
+	bool valid;
+};
+
+struct disasm_ctx {
+	struct bpf_verifier_env *env;
+	struct seq_buf seq;
+};
+
+struct diag_fmt_chunk {
+	struct list_head node;
+	struct seq_buf seq;
+	char data[];
+};
+
+struct diag_fmt_mark {
+	struct diag_fmt_chunk *chunk;
+	size_t len;
+};
+
+struct bpf_diag_scratch {
+	struct bpf_linfo_source source_lines[BPF_DIAG_CONTEXT_CNT];
+	struct disasm_line disasm_lines[BPF_DIAG_CONTEXT_CNT];
+};
+
+struct bpf_diag {
+	struct bpf_diag_scratch scratch;
+	struct list_head fmt_chunks;
+};
+
 bool bpf_diag_enabled(const struct bpf_verifier_env *env)
 {
 	return env->log.level & BPF_LOG_LEVEL;
@@ -14,6 +63,138 @@ bool bpf_diag_enabled(const struct bpf_verifier_env *env)
 
 static void diag_write(struct bpf_verifier_env *env, const char *fmt, ...) __printf(2, 3);
 
+int bpf_diag_init(struct bpf_verifier_env *env)
+{
+	if (!bpf_diag_enabled(env))
+		return 0;
+
+	env->diag = kzalloc_obj(struct bpf_diag, GFP_KERNEL_ACCOUNT);
+	if (!env->diag)
+		return -ENOMEM;
+
+	INIT_LIST_HEAD(&env->diag->fmt_chunks);
+	return 0;
+}
+
+static char *diag_fmt_alloc(struct bpf_verifier_env *env, size_t size)
+{
+	struct bpf_diag *diag = env->diag;
+	struct diag_fmt_chunk *chunk;
+	size_t capacity, available;
+	char *buf;
+
+	if (!diag || !size || size > INT_MAX)
+		return NULL;
+
+	if (!list_empty(&diag->fmt_chunks)) {
+		chunk = list_last_entry(&diag->fmt_chunks, struct diag_fmt_chunk, node);
+		available = seq_buf_get_buf(&chunk->seq, &buf);
+		if (available >= size)
+			goto commit;
+	}
+
+	capacity = max_t(size_t, BPF_DIAG_FMT_CHUNK_SIZE, size);
+	chunk = kmalloc(struct_size(chunk, data, capacity), GFP_KERNEL_ACCOUNT);
+	if (!chunk)
+		return NULL;
+
+	seq_buf_init(&chunk->seq, chunk->data, capacity);
+	list_add_tail(&chunk->node, &diag->fmt_chunks);
+	available = seq_buf_get_buf(&chunk->seq, &buf);
+	if (WARN_ON_ONCE(available < size))
+		return NULL;
+
+commit:
+	seq_buf_commit(&chunk->seq, size);
+	return buf;
+}
+
+char *bpf_diag_fmt_buf(struct bpf_verifier_env *env, size_t size)
+{
+	char *buf;
+
+	buf = diag_fmt_alloc(env, size);
+	if (buf)
+		buf[0] = '\0';
+	return buf;
+}
+
+const char *bpf_diag_vfmt(struct bpf_verifier_env *env, const char *fmt, va_list args)
+{
+	va_list copy;
+	char *buf;
+	int len;
+
+	va_copy(copy, args);
+	len = vsnprintf(NULL, 0, fmt, copy);
+	va_end(copy);
+	if (len < 0 || len == INT_MAX)
+		return "";
+
+	buf = diag_fmt_alloc(env, len + 1);
+	if (buf)
+		vsnprintf(buf, len + 1, fmt, args);
+	return buf ?: "";
+}
+
+const char *bpf_diag_fmt(struct bpf_verifier_env *env, const char *fmt, ...)
+{
+	const char *buf;
+	va_list args;
+
+	va_start(args, fmt);
+	buf = bpf_diag_vfmt(env, fmt, args);
+	va_end(args);
+	return buf;
+}
+
+static struct diag_fmt_mark diag_fmt_save(struct bpf_verifier_env *env)
+{
+	struct bpf_diag *diag = env->diag;
+	struct diag_fmt_mark mark = {};
+
+	if (!diag || list_empty(&diag->fmt_chunks))
+		return mark;
+
+	mark.chunk = list_last_entry(&diag->fmt_chunks, struct diag_fmt_chunk, node);
+	mark.len = mark.chunk->seq.len;
+	return mark;
+}
+
+static void diag_fmt_restore(struct bpf_verifier_env *env, struct diag_fmt_mark mark)
+{
+	struct bpf_diag *diag = env->diag;
+	struct diag_fmt_chunk *chunk;
+
+	if (!diag)
+		return;
+
+	while (!list_empty(&diag->fmt_chunks)) {
+		chunk = list_last_entry(&diag->fmt_chunks, struct diag_fmt_chunk, node);
+		if (chunk == mark.chunk)
+			break;
+		list_del(&chunk->node);
+		kfree(chunk);
+	}
+
+	if (mark.chunk) {
+		mark.chunk->seq.len = mark.len;
+		seq_buf_str(&mark.chunk->seq);
+	}
+}
+
+void bpf_diag_free(struct bpf_verifier_env *env)
+{
+	struct bpf_diag *diag = env->diag;
+
+	if (!diag)
+		return;
+
+	diag_fmt_restore(env, (struct diag_fmt_mark){});
+	kfree(diag);
+	env->diag = NULL;
+}
+
 static void diag_write(struct bpf_verifier_env *env, const char *fmt, ...)
 {
 	va_list args;
@@ -26,6 +207,179 @@ static void diag_write(struct bpf_verifier_env *env, const char *fmt, ...)
 	va_end(args);
 }
 
+static void diag_print_wrapped_prefixed(struct bpf_verifier_env *env, const char *first_prefix,
+					const char *next_prefix, const char *text)
+{
+	const char *prefix = first_prefix;
+
+	while (*text) {
+		const char *line = text;
+		int prefix_len = strlen(prefix);
+		int text_width = BPF_DIAG_TEXT_WIDTH - prefix_len;
+		int len = 0, last_space = -1;
+
+		if (text_width < 1)
+			text_width = 1;
+
+		while (line[len] && line[len] != '\n' && len < text_width) {
+			if (line[len] == ' ')
+				last_space = len;
+			len++;
+		}
+
+		if (line[len] && line[len] != '\n' && line[len] != ' ' && last_space > 0)
+			len = last_space;
+
+		diag_write(env, "%s%.*s\n", prefix, len, line);
+
+		text = line + len;
+		while (*text == ' ')
+			text++;
+		if (*text == '\n')
+			text++;
+
+		prefix = next_prefix;
+	}
+}
+
+static int diag_line_width(unsigned int line)
+{
+	int width = 1;
+
+	while (line >= 10) {
+		line /= 10;
+		width++;
+	}
+
+	return width;
+}
+
+static int diag_line_indent(const char *line)
+{
+	int indent = 0;
+
+	while (*line == ' ' || *line == '\t') {
+		if (*line == '\t')
+			indent = round_up(indent + 1, BPF_DIAG_TAB_WIDTH);
+		else
+			indent++;
+		line++;
+	}
+
+	return indent;
+}
+
+static void disasm_print(void *private_data, const char *fmt, ...) __printf(2, 3);
+
+static void disasm_print(void *private_data, const char *fmt, ...)
+{
+	struct disasm_ctx *ctx = private_data;
+	va_list args;
+
+	va_start(args, fmt);
+	seq_buf_vprintf(&ctx->seq, fmt, args);
+	va_end(args);
+}
+
+static const char *disasm_kfunc_name(void *private_data, const struct bpf_insn *insn)
+{
+	struct disasm_ctx *ctx = private_data;
+
+	return bpf_disasm_kfunc_name(ctx->env, insn);
+}
+
+static void format_disasm_line(struct bpf_verifier_env *env, int insn_idx,
+			       struct disasm_line *line)
+{
+	struct disasm_ctx ctx = { .env = env };
+	struct bpf_insn *insn;
+	const struct bpf_insn_cbs cbs = {
+		.cb_call = disasm_kfunc_name,
+		.cb_print = disasm_print,
+		.private_data = &ctx,
+	};
+
+	line->idx = insn_idx;
+	line->valid = false;
+	seq_buf_init(&ctx.seq, line->text, sizeof(line->text));
+
+	if (insn_idx < 0 || insn_idx >= env->prog->len)
+		return;
+
+	if (insn_idx > 0 && bpf_is_ldimm64(&env->prog->insnsi[insn_idx - 1]))
+		return;
+
+	insn = &env->prog->insnsi[insn_idx];
+	if (bpf_is_ldimm64(insn) && insn_idx + 1 >= env->prog->len)
+		return;
+
+	print_bpf_insn(&cbs, insn, env->allow_ptr_leaks);
+	seq_buf_str(&ctx.seq);
+	ctx.seq.len = strnlen(line->text, sizeof(line->text));
+	while (ctx.seq.len && line->text[ctx.seq.len - 1] == '\n')
+		seq_buf_pop(&ctx.seq);
+	seq_buf_str(&ctx.seq);
+
+	line->valid = true;
+}
+
+static void diag_format_source_text(char *buf, size_t size, const char *line, int width)
+{
+	int col = 0, len = 0;
+
+	if (!size)
+		return;
+	if (width <= 0) {
+		buf[0] = '\0';
+		return;
+	}
+
+	line = line ?: "...";
+	while (*line && col < width && len + 1 < size) {
+		if (*line == '\t') {
+			int next = round_up(col + 1, BPF_DIAG_TAB_WIDTH);
+
+			while (col < next && col < width && len + 1 < size) {
+				buf[len++] = ' ';
+				col++;
+			}
+			line++;
+			continue;
+		}
+
+		buf[len++] = *line++;
+		col++;
+	}
+
+	if (*line) {
+		int ellipsis_len = min(3, width);
+
+		while (len > 0 && col > width - ellipsis_len) {
+			len--;
+			col--;
+		}
+		while (ellipsis_len-- && len + 1 < size)
+			buf[len++] = '.';
+	}
+
+	buf[len] = '\0';
+}
+
+static void diag_format_source_lane(char *buf, size_t size, const char *source_prefix,
+				    int source_line_width, int line_num, const char *line)
+{
+	int len, text_width;
+
+	if (line_num <= 0) {
+		buf[0] = '\0';
+		return;
+	}
+
+	len = scnprintf(buf, size, "%s%*d | ", source_prefix, source_line_width, line_num);
+	text_width = BPF_DIAG_SOURCE_LANE_WIDTH - len;
+	diag_format_source_text(buf + len, size - len, line, text_width);
+}
+
 static void bpf_diag_header(struct bpf_verifier_env *env, const char *category,
 			    const char *problem)
 {
@@ -45,3 +399,139 @@ static void bpf_diag_header(struct bpf_verifier_env *env, const char *category,
 	first = toupper(problem[0]);
 	diag_write(env, "\nVerification failed: %s: %c%s\n", category, first, problem + 1);
 }
+
+static void diag_print_source_annotation(struct bpf_verifier_env *env, int line_width, int indent,
+					 const char *label, const char *msg)
+{
+	const char *first_prefix, *next_prefix, *text;
+
+	indent = min_t(int, indent, max_t(int, 0, BPF_DIAG_SOURCE_LANE_WIDTH - line_width - 8));
+	text = bpf_diag_fmt(env, "%s: %s", label, msg);
+	first_prefix = bpf_diag_fmt(env, "  %*s | %*s^-- ", line_width + 4, "", indent, "");
+	next_prefix = bpf_diag_fmt(env, "  %*s | %*s    ", line_width + 4, "", indent, "");
+
+	diag_print_wrapped_prefixed(env, first_prefix, next_prefix, text);
+}
+
+static void diag_print_insn_context(struct bpf_verifier_env *env, u32 insn_idx,
+				    struct disasm_line *disasm_lines)
+{
+	int insn_width = diag_line_width(env->prog->len ? env->prog->len - 1 : 0);
+	int i;
+
+	for (i = 0; i < BPF_DIAG_CONTEXT_CNT; i++) {
+		int row = i - BPF_DIAG_CONTEXT;
+
+		format_disasm_line(env, insn_idx + row, &disasm_lines[i]);
+	}
+
+	diag_write(env, "  Instruction context:\n");
+	for (i = 0; i < BPF_DIAG_CONTEXT_CNT; i++) {
+		struct disasm_line *line = &disasm_lines[i];
+
+		if (line->valid)
+			diag_write(env, "  %s%*d | %s\n",
+				   line->idx == insn_idx ? ">>> " : "    ",
+				   insn_width, line->idx, line->text);
+	}
+}
+
+static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const char *label,
+			    const char *fmt, ...)
+{
+	struct bpf_diag_scratch *scratch;
+	struct bpf_linfo_source *source_lines;
+	struct disasm_line *disasm_lines;
+	struct bpf_linfo_source src = {};
+	struct diag_fmt_mark mark;
+	const struct bpf_line_info *linfo;
+	const struct bpf_subprog_info *subprog;
+	struct btf *btf = env->prog->aux->btf;
+	char *source_lane;
+	const char *msg;
+	const char *func;
+	int start_line, end_line, width, indent, subprogno, linfo_start, linfo_end, i;
+	va_list args;
+
+	if (!bpf_diag_enabled(env))
+		return;
+	if (!env->diag)
+		return;
+
+	mark = diag_fmt_save(env);
+	label = label ?: "note";
+	scratch = &env->diag->scratch;
+	source_lines = scratch->source_lines;
+	disasm_lines = scratch->disasm_lines;
+	memset(source_lines, 0, sizeof(scratch->source_lines));
+	memset(disasm_lines, 0, sizeof(scratch->disasm_lines));
+
+	va_start(args, fmt);
+	msg = bpf_diag_vfmt(env, fmt, args);
+	va_end(args);
+	if (!*msg)
+		msg = "<failed to allocate diagnostic text>";
+
+	linfo = bpf_find_linfo(env->prog, insn_idx);
+	if (btf && linfo)
+		bpf_get_linfo_source(btf, linfo, &src);
+	if (!src.file || !*src.file || !src.line || !*src.line) {
+		diag_write(env, "  insn %u\n", insn_idx);
+		diag_print_source_annotation(env, 0, 0, label, msg);
+		diag_print_insn_context(env, insn_idx, disasm_lines);
+		goto out_restore;
+	}
+
+	subprog = bpf_find_containing_subprog(env, insn_idx);
+	subprogno = subprog ? subprog - env->subprog_info : -ENOENT;
+	func = subprogno >= 0 ? bpf_subprog_name(env, subprogno) : NULL;
+	if (func && *func)
+		diag_write(env, "  %s @ %s:%d:%d\n", func, src.file, src.line_num, src.line_col);
+	else
+		diag_write(env, "  %s:%d:%d\n", src.file, src.line_num, src.line_col);
+
+	start_line = src.line_num - BPF_DIAG_CONTEXT;
+	end_line = src.line_num + BPF_DIAG_CONTEXT;
+	width = diag_line_width(end_line);
+	indent = diag_line_indent(src.line);
+	for (i = 0; i < BPF_DIAG_CONTEXT_CNT; i++)
+		source_lines[i].line_num = start_line + i;
+
+	linfo = env->prog->aux->linfo;
+	linfo_start = subprog ? subprog->linfo_idx : 0;
+	linfo_end = subprogno >= 0 && subprogno + 1 < env->subprog_cnt ?
+		    env->subprog_info[subprogno + 1].linfo_idx : env->prog->aux->nr_linfo;
+	for (i = linfo_start; i < linfo_end; i++) {
+		struct bpf_linfo_source line_src;
+		int idx;
+
+		bpf_get_linfo_source(btf, &linfo[i], &line_src);
+		if (line_src.file_name_off != src.file_name_off ||
+		    line_src.line_num < start_line || line_src.line_num > end_line ||
+		    !line_src.line || !*line_src.line)
+			continue;
+
+		idx = line_src.line_num - start_line;
+		if (!source_lines[idx].line)
+			source_lines[idx] = line_src;
+	}
+
+	diag_write(env, "  Source context:\n");
+	source_lane = bpf_diag_fmt_buf(env, BPF_DIAG_FMT_BUF_SIZE);
+	if (!source_lane)
+		goto out_restore;
+	for (i = 0; i < BPF_DIAG_CONTEXT_CNT; i++) {
+		const char *source_prefix;
+
+		source_prefix = source_lines[i].line_num == src.line_num ? ">>> " : "    ";
+		diag_format_source_lane(source_lane, BPF_DIAG_FMT_BUF_SIZE, source_prefix, width,
+					source_lines[i].line_num, source_lines[i].line);
+		diag_write(env, "  %s\n", source_lane);
+		if (source_lines[i].line_num == src.line_num)
+			diag_print_source_annotation(env, width, indent, label, msg);
+	}
+	diag_print_insn_context(env, insn_idx, disasm_lines);
+
+out_restore:
+	diag_fmt_restore(env, mark);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index f51aa39f0909..ba268b589ac9 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -5,10 +5,17 @@
 #define __BPF_DIAGNOSTICS_H
 
 #include <linux/compiler_attributes.h>
+#include <linux/stdarg.h>
 #include <linux/types.h>
 
 struct bpf_verifier_env;
 
 bool bpf_diag_enabled(const struct bpf_verifier_env *env);
+int bpf_diag_init(struct bpf_verifier_env *env);
+char *bpf_diag_fmt_buf(struct bpf_verifier_env *env, size_t size);
+const char *bpf_diag_vfmt(struct bpf_verifier_env *env, const char *fmt, va_list args)
+	__printf(2, 0);
+const char *bpf_diag_fmt(struct bpf_verifier_env *env, const char *fmt, ...) __printf(2, 3);
+void bpf_diag_free(struct bpf_verifier_env *env);
 
 #endif /* __BPF_DIAGNOSTICS_H */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6ac1afced20b..2f330230f8d5 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -34,6 +34,7 @@
 #include <linux/trace_events.h>
 #include <linux/kallsyms.h>
 
+#include "diagnostics.h"
 #include "disasm.h"
 
 static const struct bpf_verifier_ops * const bpf_verifier_ops[] = {
@@ -405,7 +406,7 @@ static bool subprog_returns_void(struct bpf_verifier_env *env, int subprog)
 	return btf_type_is_void(type);
 }
 
-static const char *subprog_name(const struct bpf_verifier_env *env, int subprog)
+const char *bpf_subprog_name(const struct bpf_verifier_env *env, int subprog)
 {
 	struct bpf_func_info *info;
 
@@ -2624,6 +2625,26 @@ static struct btf *find_kfunc_desc_btf(struct bpf_verifier_env *env, s16 offset)
 	return btf_vmlinux ?: ERR_PTR(-ENOENT);
 }
 
+static struct btf *find_kfunc_desc_btf_cached(struct bpf_verifier_env *env, s16 offset)
+{
+	struct bpf_kfunc_btf kf_btf = { .offset = offset };
+	struct bpf_kfunc_btf_tab *tab;
+	struct bpf_kfunc_btf *b;
+
+	if (!offset)
+		return btf_vmlinux ?: ERR_PTR(-ENOENT);
+	if (offset < 0)
+		return ERR_PTR(-EINVAL);
+
+	tab = env->prog->aux->kfunc_btf_tab;
+	if (!tab)
+		return ERR_PTR(-ENOENT);
+
+	b = bsearch(&kf_btf, tab->descs, tab->nr_descs,
+		    sizeof(tab->descs[0]), kfunc_btf_cmp_by_off);
+	return b ? b->btf : ERR_PTR(-ENOENT);
+}
+
 #define KF_IMPL_SUFFIX "_impl"
 
 static const struct btf_type *find_kfunc_impl_proto(struct bpf_verifier_log *log,
@@ -3031,8 +3052,8 @@ static int sort_subprogs_topo(struct bpf_verifier_env *env)
 					if (bpf_pseudo_func(&insn[idx]))
 						continue;
 					verbose(env, "recursive call from %s() to %s()\n",
-						subprog_name(env, cur),
-						subprog_name(env, callee));
+						bpf_subprog_name(env, cur),
+						bpf_subprog_name(env, callee));
 					ret = -EINVAL;
 					goto out;
 				}
@@ -3053,7 +3074,7 @@ static int sort_subprogs_topo(struct bpf_verifier_env *env)
 	if (env->log.level & BPF_LOG_LEVEL2)
 		for (i = 0; i < cnt; i++)
 			verbose(env, "topo_order[%d] = %s\n",
-				i, subprog_name(env, env->subprog_topo_order[i]));
+				i, bpf_subprog_name(env, env->subprog_topo_order[i]));
 out:
 	kvfree(dfs_stack);
 	kvfree(color);
@@ -3197,7 +3218,7 @@ static void linked_regs_unpack(u64 val, struct linked_regs *s)
 	}
 }
 
-static const char *disasm_kfunc_name(void *data, const struct bpf_insn *insn)
+const char *bpf_disasm_kfunc_name(void *data, const struct bpf_insn *insn)
 {
 	const struct btf_type *func;
 	struct btf *desc_btf;
@@ -3205,18 +3226,20 @@ static const char *disasm_kfunc_name(void *data, const struct bpf_insn *insn)
 	if (insn->src_reg != BPF_PSEUDO_KFUNC_CALL)
 		return NULL;
 
-	desc_btf = find_kfunc_desc_btf(data, insn->off);
+	desc_btf = find_kfunc_desc_btf_cached(data, insn->off);
 	if (IS_ERR(desc_btf))
 		return "<error>";
 
 	func = btf_type_by_id(desc_btf, insn->imm);
+	if (!func || !btf_type_is_func(func))
+		return "<error>";
 	return btf_name_by_offset(desc_btf, func->name_off);
 }
 
 void bpf_verbose_insn(struct bpf_verifier_env *env, struct bpf_insn *insn)
 {
 	const struct bpf_insn_cbs cbs = {
-		.cb_call	= disasm_kfunc_name,
+		.cb_call	= bpf_disasm_kfunc_name,
 		.cb_print	= verbose,
 		.private_data	= env,
 	};
@@ -9408,7 +9431,7 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	if (err == -EFAULT)
 		return err;
 	if (bpf_subprog_is_global(env, subprog)) {
-		const char *sub_name = subprog_name(env, subprog);
+		const char *sub_name = bpf_subprog_name(env, subprog);
 
 		if (env->cur_state->active_locks) {
 			verbose(env, "global function calls are not allowed while holding a lock,\n"
@@ -18479,7 +18502,7 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
 
 	regs = state->frame[state->curframe]->regs;
 	if (subprog || env->prog->type == BPF_PROG_TYPE_EXT) {
-		const char *sub_name = subprog_name(env, subprog);
+		const char *sub_name = bpf_subprog_name(env, subprog);
 		struct bpf_subprog_arg_info *arg;
 		struct bpf_reg_state *reg;
 
@@ -18656,7 +18679,7 @@ static int do_check_subprogs(struct bpf_verifier_env *env)
 			return ret;
 		} else if (env->log.level & BPF_LOG_LEVEL) {
 			verbose(env, "Func#%d ('%s') is safe for any args that match its prototype\n",
-				i, subprog_name(env, i));
+				i, bpf_subprog_name(env, i));
 		}
 
 		/* We verified new global subprog, it might have called some
@@ -20188,6 +20211,9 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
 	ret = bpf_vlog_init(&env->log, attr_log->level, attr_log->ubuf, attr_log->size);
 	if (ret)
 		goto err_free_env;
+	ret = bpf_diag_init(env);
+	if (ret)
+		goto err_prep;
 	if (env->signature) {
 		ret = bpf_prog_calc_tag(env->prog);
 		if (ret < 0)
@@ -20478,6 +20504,7 @@ int bpf_check(struct bpf_prog **prog, union bpf_attr *attr, bpfptr_t uattr,
 	kvfree(env->scc_info);
 	kvfree(env->succ);
 	kvfree(env->gotox_tmp_buf);
+	bpf_diag_free(env);
 	kvfree(env);
 	return ret;
 }

From daf8248701b621d8df7ea134793dbb750d4887c0 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:45:58 +0200
Subject: [PATCH 03/14] bpf: Add verifier diagnostic event log

Add an environment-owned diagnostic history for verifier reports. Event
payloads keep the user-facing branch history shape, while storage lives
in bpf_verifier_env and follows the active verifier path.

Grow the event array geometrically up to a 64 MiB limit. Once storage
reaches the limit, or an allocation fails, overwrite the oldest event so
diagnostics retain the newest useful suffix without adding per-event
metadata.

Represent saved positions as absolute logical sequence numbers. A restore
truncates to a retained position. If its prefix has already been evicted,
clear the abandoned suffix and preserve the missing-history position. This
keeps marks stable across rotation without increasing their size.

Add the branch event renderer and branch recording.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-4-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c | 130 +++++++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h |   3 +
 kernel/bpf/verifier.c    |  21 +++++++
 3 files changed, 154 insertions(+)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 815aa7938b50..8f21b46adeca 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -22,8 +22,24 @@
 #define BPF_DIAG_TAB_WIDTH 8
 #define BPF_DIAG_FMT_CHUNK_SIZE (PAGE_SIZE - sizeof(struct diag_fmt_chunk))
 #define BPF_DIAG_FMT_BUF_SIZE 256
+#define BPF_DIAG_EVENT_LOG_MAX_SIZE (64U << 20)
 #define DISASM_LINE_LEN 160
 
+enum bpf_diag_history_kind {
+	BPF_DIAG_HISTORY_BRANCH,
+};
+
+struct bpf_diag_history_event {
+	u32 insn_idx : 24;
+	u32 kind : 8;
+	u8 in_lineage : 1;
+	union {
+		struct {
+			bool cond_true;
+		} branch;
+	};
+};
+
 struct disasm_line {
 	char text[DISASM_LINE_LEN];
 	int idx;
@@ -46,12 +62,23 @@ struct diag_fmt_mark {
 	size_t len;
 };
 
+struct bpf_diag_log {
+	struct bpf_diag_history_event *events;
+	/* Sequence number of the oldest retained event on the active path. */
+	u64 first_seq;
+	u32 cnt;
+	u32 cap;
+	u32 head;
+	bool growth_failed;
+};
+
 struct bpf_diag_scratch {
 	struct bpf_linfo_source source_lines[BPF_DIAG_CONTEXT_CNT];
 	struct disasm_line disasm_lines[BPF_DIAG_CONTEXT_CNT];
 };
 
 struct bpf_diag {
+	struct bpf_diag_log log;
 	struct bpf_diag_scratch scratch;
 	struct list_head fmt_chunks;
 };
@@ -191,6 +218,7 @@ void bpf_diag_free(struct bpf_verifier_env *env)
 		return;
 
 	diag_fmt_restore(env, (struct diag_fmt_mark){});
+	kvfree(diag->log.events);
 	kfree(diag);
 	env->diag = NULL;
 }
@@ -207,6 +235,95 @@ static void diag_write(struct bpf_verifier_env *env, const char *fmt, ...)
 	va_end(args);
 }
 
+static u64 log_end(const struct bpf_diag_log *log)
+{
+	return log->first_seq + log->cnt;
+}
+
+static u32 log_pos(const struct bpf_diag_log *log, u32 idx)
+{
+	u32 pos = log->head + idx;
+
+	return pos < log->cap ? pos : pos - log->cap;
+}
+
+u64 bpf_diag_event_log_save(struct bpf_verifier_env *env)
+{
+	struct bpf_diag *diag = env->diag;
+
+	return diag ? log_end(&diag->log) : 0;
+}
+
+void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos)
+{
+	struct bpf_diag *diag = env->diag;
+	struct bpf_diag_log *log;
+	u64 end_seq;
+
+	if (!diag)
+		return;
+
+	log = &diag->log;
+	end_seq = log_end(log);
+	if (WARN_ON_ONCE(log_pos > end_seq))
+		log_pos = end_seq;
+
+	/*
+	 * A deep abandoned path may have rotated away the shared prefix. In
+	 * that case, restart with an empty retained suffix and remember that
+	 * every event before the restored mark is unavailable.
+	 */
+	if (log_pos <= log->first_seq) {
+		log->first_seq = log_pos;
+		log->head = 0;
+		log->cnt = 0;
+		return;
+	}
+
+	log->cnt = log_pos - log->first_seq;
+}
+
+static void diag_append_history(struct bpf_verifier_env *env,
+				const struct bpf_diag_history_event *event)
+{
+	struct bpf_diag_history_event *events;
+	struct bpf_diag *diag = env->diag;
+	struct bpf_diag_log *log;
+	u32 cap, max_events;
+
+	if (!diag)
+		return;
+	log = &diag->log;
+
+	if (log->cnt < log->cap) {
+		log->events[log_pos(log, log->cnt++)] = *event;
+		return;
+	}
+
+	max_events = BPF_DIAG_EVENT_LOG_MAX_SIZE / sizeof(*events);
+	if (log->growth_failed || log->cap == max_events)
+		goto rotate;
+
+	cap = min(log->cap ? log->cap * 2 : 64, max_events);
+	events = kvrealloc(log->events, array_size(cap, sizeof(*events)), GFP_KERNEL_ACCOUNT);
+	if (!events) {
+		log->growth_failed = true;
+		goto rotate;
+	}
+	log->events = events;
+	log->cap = cap;
+	log->events[log->cnt++] = *event;
+	return;
+
+rotate:
+	if (log->cap) {
+		log->events[log->head++] = *event;
+		if (log->head == log->cap)
+			log->head = 0;
+	}
+	log->first_seq++;
+}
+
 static void diag_print_wrapped_prefixed(struct bpf_verifier_env *env, const char *first_prefix,
 					const char *next_prefix, const char *text)
 {
@@ -535,3 +652,16 @@ static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const ch
 out_restore:
 	diag_fmt_restore(env, mark);
 }
+
+void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true)
+{
+	struct bpf_diag_history_event event = {
+		.insn_idx = insn_idx,
+		.kind = BPF_DIAG_HISTORY_BRANCH,
+		.branch = {
+			.cond_true = cond_true,
+		},
+	};
+
+	diag_append_history(env, &event);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index ba268b589ac9..6eda2fd65ee1 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -16,6 +16,9 @@ char *bpf_diag_fmt_buf(struct bpf_verifier_env *env, size_t size);
 const char *bpf_diag_vfmt(struct bpf_verifier_env *env, const char *fmt, va_list args)
 	__printf(2, 0);
 const char *bpf_diag_fmt(struct bpf_verifier_env *env, const char *fmt, ...) __printf(2, 3);
+u64 bpf_diag_event_log_save(struct bpf_verifier_env *env);
+void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos);
 void bpf_diag_free(struct bpf_verifier_env *env);
+void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 
 #endif /* __BPF_DIAGNOSTICS_H */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2f330230f8d5..60dcb87a2417 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -17439,6 +17439,27 @@ static int do_check(struct bpf_verifier_env *env)
 
 		state->last_insn_idx = env->prev_insn_idx;
 		state->insn_idx = env->insn_idx;
+		/*
+		 * Record the incoming edge so active and queued paths use the same
+		 * branch-recording path. A zero-offset conditional has identical
+		 * successors, so its outcome cannot be reconstructed from the edge.
+		 */
+		if (!state->speculative && prev_insn_idx >= 0 && prev_insn_idx < insn_cnt) {
+			struct bpf_insn *prev_insn = &insns[prev_insn_idx];
+			int fallthrough_idx = prev_insn_idx + 1;
+			int branch_idx = prev_insn_idx + bpf_jmp_offset(prev_insn) + 1;
+			u8 class = BPF_CLASS(prev_insn->code);
+			u8 opcode = BPF_OP(prev_insn->code);
+
+			if ((class == BPF_JMP || class == BPF_JMP32) &&
+			    opcode != BPF_JA && opcode != BPF_CALL && opcode != BPF_EXIT &&
+			    opcode <= BPF_JCOND && branch_idx != fallthrough_idx) {
+				if (env->insn_idx == branch_idx)
+					bpf_diag_record_branch(env, prev_insn_idx, true);
+				else if (env->insn_idx == fallthrough_idx)
+					bpf_diag_record_branch(env, prev_insn_idx, false);
+			}
+		}
 
 		if (bpf_is_prune_point(env, env->insn_idx)) {
 			err = bpf_is_state_visited(env, env->insn_idx);

From a6debd5f25c9c79f534074e9cb460cf6495d6daf Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:45:59 +0200
Subject: [PATCH 04/14] bpf: Prune verifier diagnostics when switching paths

Save the diagnostic event-log position with each verifier stack entry and
reset the environment-owned stream together with the normal verifier log
when a queued state is popped. Also reset the diagnostic stream after
successful subprogram verification even when level-2 logging preserves the
normal verifier log.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-5-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/verifier.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 60dcb87a2417..db644690ac4b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -194,6 +194,7 @@ struct bpf_verifier_stack_elem {
 	struct bpf_verifier_stack_elem *next;
 	/* length of verifier log at the time this state was pushed on stack */
 	u32 log_pos;
+	u64 diag_log_pos;
 };
 
 #define BPF_COMPLEXITY_LIMIT_JMP_SEQ	8192
@@ -1700,6 +1701,7 @@ static int pop_stack(struct bpf_verifier_env *env, int *prev_insn_idx,
 		err = bpf_copy_verifier_state(cur, &head->st);
 		if (err)
 			return err;
+		bpf_diag_event_log_restore(env, head->diag_log_pos);
 	}
 	if (pop_log)
 		bpf_vlog_reset(&env->log, head->log_pos);
@@ -1743,6 +1745,7 @@ static struct bpf_verifier_state *push_stack(struct bpf_verifier_env *env,
 	elem->prev_insn_idx = prev_insn_idx;
 	elem->next = env->head;
 	elem->log_pos = env->log.end_pos;
+	elem->diag_log_pos = bpf_diag_event_log_save(env);
 	env->head = elem;
 	env->stack_size++;
 	err = bpf_copy_verifier_state(&elem->st, cur);
@@ -2264,6 +2267,7 @@ static struct bpf_verifier_state *push_async_cb(struct bpf_verifier_env *env,
 	elem->prev_insn_idx = prev_insn_idx;
 	elem->next = env->head;
 	elem->log_pos = env->log.end_pos;
+	elem->diag_log_pos = bpf_diag_event_log_save(env);
 	env->head = elem;
 	env->stack_size++;
 	if (env->stack_size > BPF_COMPLEXITY_LIMIT_JMP_SEQ) {
@@ -18635,8 +18639,11 @@ static int do_check_common(struct bpf_verifier_env *env, int subprog)
 	ret = do_check(env);
 out:
 	account_current_path(env);
-	if (!ret && pop_log)
-		bpf_vlog_reset(&env->log, 0);
+	if (!ret) {
+		if (pop_log)
+			bpf_vlog_reset(&env->log, 0);
+		bpf_diag_event_log_restore(env, 0);
+	}
 	free_states(env);
 
 	/*

From af4ea6e20fff383cdc2f01b9a372b4c7a0abf5ff Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:00 +0200
Subject: [PATCH 05/14] bpf: Track verifier register diagnostic events

Record material register and outgoing stack argument changes so diagnostics can
explain how a value reached its current type, bounds, or unreadable state.

Store old and new register types, scalar ranges, tnum value and mask, map and
BTF type identity, and basic operand metadata in the environment-owned
diagnostic event stream.

Record invalidations when packet data moves, references are released, or
borrowed references leave their protected region. Register-scoped history
starts at the latest matching modification and then shows later branch
outcomes.

Also record fixed stack spills and overwrites, and tag register fills from
stack so register-scoped history can follow value flow through spilled stack
slots.

The type_is_map_ptr() helper previously lived as a static function in
kernel/bpf/log.c since commit 0c95c9fdb696 ("bpf: emit map name in register
state if applicable and available"). Move it verbatim to
include/linux/bpf_verifier.h as a static inline, next to the other type
classifiers, so diagnostics.c can reuse it without duplicating the case list.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-6-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 include/linux/bpf_verifier.h |  17 ++
 kernel/bpf/diagnostics.c     | 356 +++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h     |  23 +++
 kernel/bpf/log.c             |  11 --
 kernel/bpf/verifier.c        | 131 +++++++++++--
 5 files changed, 515 insertions(+), 23 deletions(-)

diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h
index 579a288bc8de..bc2af02547fe 100644
--- a/include/linux/bpf_verifier.h
+++ b/include/linux/bpf_verifier.h
@@ -354,6 +354,11 @@ struct bpf_func_state {
 	 * 0 = main function, 1 = first callee.
 	 */
 	u32 frameno;
+	/*
+	 * Unique diagnostic identity for this function invocation. Frame depth is
+	 * reused after returns, while this ID is preserved across state clones.
+	 */
+	u32 diag_frame_id;
 	/* subprog number == index within subprog_info
 	 * zero == main subprog
 	 */
@@ -1351,6 +1356,18 @@ static inline bool type_is_non_owning_ref(u32 type)
 	return type_is_ptr_alloc_obj(type) && type_flag(type) & NON_OWN_REF;
 }
 
+static inline bool type_is_map_ptr(enum bpf_reg_type type)
+{
+	switch (base_type(type)) {
+	case CONST_PTR_TO_MAP:
+	case PTR_TO_MAP_KEY:
+	case PTR_TO_MAP_VALUE:
+		return true;
+	default:
+		return false;
+	}
+}
+
 static inline bool type_is_pkt_pointer(enum bpf_reg_type type)
 {
 	type = base_type(type);
diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 8f21b46adeca..2e8e75815581 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -25,8 +25,83 @@
 #define BPF_DIAG_EVENT_LOG_MAX_SIZE (64U << 20)
 #define DISASM_LINE_LEN 160
 
+enum bpf_diag_mod_target_kind {
+	BPF_DIAG_MOD_TARGET_NONE,
+	BPF_DIAG_MOD_TARGET_REG,
+	BPF_DIAG_MOD_TARGET_STACK_ARG,
+	BPF_DIAG_MOD_TARGET_STACK_SLOT,
+	BPF_DIAG_MOD_TARGET_STACK_RANGE,
+};
+
+struct bpf_diag_mod_target {
+	u32 frame_id;
+	union {
+		struct {
+			s16 min_off;
+			s16 max_off;
+		} range;
+		u16 spi;
+		u8 regno;
+		u8 stack_arg;
+	};
+	u8 frameno;
+	u8 kind;
+};
+
+static struct bpf_diag_mod_target diag_reg_target(u32 frame_id, u8 frameno, u8 regno)
+{
+	return (struct bpf_diag_mod_target){
+		.frame_id = frame_id,
+		.frameno = frameno,
+		.kind = BPF_DIAG_MOD_TARGET_REG,
+		.regno = regno,
+	};
+}
+
+static struct bpf_diag_mod_target diag_stack_arg_target(u32 frame_id, u8 frameno, u8 slot)
+{
+	return (struct bpf_diag_mod_target){
+		.frame_id = frame_id,
+		.frameno = frameno,
+		.kind = BPF_DIAG_MOD_TARGET_STACK_ARG,
+		.stack_arg = slot,
+	};
+}
+
+static struct bpf_diag_mod_target diag_stack_slot_target(u32 frame_id, u8 frameno, u16 spi)
+{
+	return (struct bpf_diag_mod_target){
+		.frame_id = frame_id,
+		.frameno = frameno,
+		.kind = BPF_DIAG_MOD_TARGET_STACK_SLOT,
+		.spi = spi,
+	};
+}
+
+static struct bpf_diag_mod_target diag_stack_range_target(u32 frame_id, u8 frameno,
+							  s16 min_off, s16 max_off)
+{
+	return (struct bpf_diag_mod_target){
+		.frame_id = frame_id,
+		.frameno = frameno,
+		.kind = BPF_DIAG_MOD_TARGET_STACK_RANGE,
+		.range.min_off = min_off,
+		.range.max_off = max_off,
+	};
+}
+
+struct bpf_diag_reg_snapshot {
+	u32 type;
+	u32 btf_id;
+	const struct bpf_map *map_ptr;
+	const struct btf *btf;
+	struct tnum var_off;
+	struct cnum64 r64;
+};
+
 enum bpf_diag_history_kind {
 	BPF_DIAG_HISTORY_BRANCH,
+	BPF_DIAG_HISTORY_MOD,
 };
 
 struct bpf_diag_history_event {
@@ -37,6 +112,13 @@ struct bpf_diag_history_event {
 		struct {
 			bool cond_true;
 		} branch;
+		struct {
+			struct bpf_diag_mod_target target;
+			struct bpf_diag_mod_target origin;
+			struct bpf_diag_reg_snapshot old, new;
+			u8 reason;
+			bool origin_valid;
+		} mod;
 	};
 };
 
@@ -77,10 +159,22 @@ struct bpf_diag_scratch {
 	struct disasm_line disasm_lines[BPF_DIAG_CONTEXT_CNT];
 };
 
+struct bpf_diag_mod_scope {
+	struct bpf_reg_state target_reg_snapshot;
+	struct bpf_diag_mod_target target;
+	struct bpf_diag_mod_target origin;
+	enum bpf_diag_mod_reason reason;
+	u32 insn_idx;
+	bool active;
+	bool origin_valid;
+};
+
 struct bpf_diag {
 	struct bpf_diag_log log;
 	struct bpf_diag_scratch scratch;
 	struct list_head fmt_chunks;
+	struct bpf_diag_mod_scope mod;
+	u32 frame_id_gen;
 };
 
 bool bpf_diag_enabled(const struct bpf_verifier_env *env)
@@ -103,6 +197,12 @@ int bpf_diag_init(struct bpf_verifier_env *env)
 	return 0;
 }
 
+void bpf_diag_init_frame(struct bpf_verifier_env *env, struct bpf_func_state *state)
+{
+	if (env->diag)
+		state->diag_frame_id = ++env->diag->frame_id_gen;
+}
+
 static char *diag_fmt_alloc(struct bpf_verifier_env *env, size_t size)
 {
 	struct bpf_diag *diag = env->diag;
@@ -359,6 +459,28 @@ static void diag_print_wrapped_prefixed(struct bpf_verifier_env *env, const char
 	}
 }
 
+const char *bpf_diag_fmt_btf_type(struct bpf_verifier_env *env, const struct btf *btf, u32 type_id)
+{
+	char *buf = bpf_diag_fmt_buf(env, BPF_DIAG_FMT_BUF_SIZE);
+	size_t len;
+	int ret;
+
+	if (!buf)
+		return "";
+
+	buf[0] = '\0';
+	ret = btf_type_name_to_buf(btf, type_id, buf, BPF_DIAG_FMT_BUF_SIZE);
+	if (ret < 0 || !buf[0]) {
+		scnprintf(buf, BPF_DIAG_FMT_BUF_SIZE, "BTF type ID %u", type_id);
+		return buf;
+	}
+
+	len = strlen(buf);
+	if (len && buf[len - 1] == '{')
+		buf[len - 1] = '\0';
+	return buf;
+}
+
 static int diag_line_width(unsigned int line)
 {
 	int width = 1;
@@ -665,3 +787,237 @@ void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool con
 
 	diag_append_history(env, &event);
 }
+
+static void diag_snapshot_reg(struct bpf_diag_reg_snapshot *snapshot,
+			      const struct bpf_reg_state *reg)
+{
+	snapshot->type = reg->type;
+	if (type_is_map_ptr(reg->type))
+		snapshot->map_ptr = reg->map_ptr;
+	if (base_type(reg->type) == PTR_TO_BTF_ID && reg->btf && reg->btf_id) {
+		snapshot->btf_id = reg->btf_id;
+		snapshot->btf = reg->btf;
+	}
+	snapshot->var_off = reg->var_off;
+	snapshot->r64 = reg->r64;
+}
+
+static bool diag_mod_insn_origin(struct bpf_verifier_env *env, u32 insn_idx,
+				 const struct bpf_diag_mod_target *target,
+				 struct bpf_diag_mod_target *origin)
+{
+	const struct bpf_insn *insn = &env->prog->insnsi[insn_idx];
+	u8 class = BPF_CLASS(insn->code);
+	const struct bpf_func_state *state;
+
+	if (target->kind == BPF_DIAG_MOD_TARGET_REG && (class == BPF_ALU || class == BPF_ALU64) &&
+	    BPF_OP(insn->code) == BPF_MOV && BPF_SRC(insn->code) == BPF_X) {
+		*origin = diag_reg_target(target->frame_id, target->frameno, insn->src_reg);
+		return true;
+	}
+
+	if ((target->kind != BPF_DIAG_MOD_TARGET_STACK_ARG &&
+	     target->kind != BPF_DIAG_MOD_TARGET_STACK_SLOT) ||
+	    class != BPF_STX)
+		return false;
+
+	state = env->cur_state->frame[env->cur_state->curframe];
+	*origin = diag_reg_target(state->diag_frame_id, state->frameno, insn->src_reg);
+	return true;
+}
+
+static bool diag_mod_keeps_lineage(struct bpf_verifier_env *env,
+				   const struct bpf_diag_history_event *event)
+{
+	const struct bpf_insn *insn;
+	u8 class;
+
+	if (event->mod.reason != BPF_DIAG_MOD_WRITE ||
+	    event->mod.target.kind != BPF_DIAG_MOD_TARGET_REG)
+		return false;
+
+	insn = &env->prog->insnsi[event->insn_idx];
+	class = BPF_CLASS(insn->code);
+	if (class != BPF_ALU && class != BPF_ALU64)
+		return false;
+
+	switch (BPF_OP(insn->code)) {
+	case BPF_ADD:
+	case BPF_SUB:
+	case BPF_MUL:
+	case BPF_OR:
+	case BPF_AND:
+	case BPF_LSH:
+	case BPF_RSH:
+	case BPF_ARSH:
+	case BPF_XOR:
+	case BPF_NEG:
+	case BPF_END:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static void diag_record_mod(struct bpf_verifier_env *env, u32 insn_idx,
+			    struct bpf_diag_mod_target target,
+			    enum bpf_diag_mod_reason reason,
+			    const struct bpf_reg_state *old_reg,
+			    const struct bpf_reg_state *new_reg,
+			    const struct bpf_diag_mod_target *origin)
+{
+	struct bpf_diag_history_event event = {
+		.insn_idx = insn_idx,
+		.kind = BPF_DIAG_HISTORY_MOD,
+		.mod = {
+			.target = target,
+			.reason = reason,
+		},
+	};
+
+	if (old_reg)
+		diag_snapshot_reg(&event.mod.old, old_reg);
+	if (new_reg)
+		diag_snapshot_reg(&event.mod.new, new_reg);
+	if (origin) {
+		event.mod.origin = *origin;
+		event.mod.origin_valid = true;
+	} else if (diag_mod_insn_origin(env, insn_idx, &target, &event.mod.origin)) {
+		event.mod.origin_valid = true;
+	}
+	if (old_reg && new_reg &&
+	    (reason == BPF_DIAG_MOD_WRITE || reason == BPF_DIAG_MOD_SPILL) &&
+	    !memcmp(&event.mod.old, &event.mod.new, sizeof(event.mod.old)) &&
+	    !event.mod.origin_valid &&
+	    diag_mod_keeps_lineage(env, &event))
+		return;
+
+	diag_append_history(env, &event);
+}
+
+static struct bpf_reg_state *target_to_reg(struct bpf_verifier_env *env,
+					   const struct bpf_diag_mod_target *target)
+{
+	struct bpf_verifier_state *vstate = env->cur_state;
+	struct bpf_func_state *state;
+
+	state = target->frameno <= vstate->curframe ? vstate->frame[target->frameno] : NULL;
+
+	if (!state)
+		return NULL;
+	if (state->diag_frame_id != target->frame_id)
+		return NULL;
+
+	switch (target->kind) {
+	case BPF_DIAG_MOD_TARGET_REG:
+		if (target->regno >= MAX_BPF_REG)
+			return NULL;
+		return &state->regs[target->regno];
+	case BPF_DIAG_MOD_TARGET_STACK_ARG:
+		if (target->stack_arg >= state->out_stack_arg_cnt)
+			return NULL;
+		return &state->stack_arg_regs[target->stack_arg];
+	case BPF_DIAG_MOD_TARGET_STACK_SLOT:
+		if (target->spi >= state->allocated_stack / BPF_REG_SIZE)
+			return NULL;
+		return &state->stack[target->spi].spilled_ptr;
+	default:
+		return NULL;
+	}
+}
+
+static bool reg_to_target(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
+			  struct bpf_diag_mod_target *target)
+{
+	struct bpf_verifier_state *vstate = env->cur_state;
+	unsigned long addr = (unsigned long)reg;
+	int frame;
+
+	for (frame = 0; frame <= vstate->curframe; frame++) {
+		struct bpf_func_state *state = vstate->frame[frame];
+		unsigned long start, end;
+		u32 nslots = state->allocated_stack / BPF_REG_SIZE;
+		int spi;
+
+		start = (unsigned long)state->regs;
+		end = (unsigned long)(state->regs + MAX_BPF_REG);
+		if (addr >= start && addr < end) {
+			*target = diag_reg_target(state->diag_frame_id, state->frameno,
+						  reg - state->regs);
+			return true;
+		}
+
+		start = (unsigned long)state->stack_arg_regs;
+		end = (unsigned long)(state->stack_arg_regs + state->out_stack_arg_cnt);
+		if (state->out_stack_arg_cnt && addr >= start && addr < end) {
+			*target = diag_stack_arg_target(state->diag_frame_id, state->frameno,
+							reg - state->stack_arg_regs);
+			return true;
+		}
+
+		start = (unsigned long)state->stack;
+		end = (unsigned long)(state->stack + nslots);
+		if (nslots && addr >= start && addr < end) {
+			spi = ((const char *)reg - (const char *)state->stack) /
+			      sizeof(*state->stack);
+			*target = diag_stack_slot_target(state->diag_frame_id, state->frameno, spi);
+			return true;
+		}
+	}
+	return false;
+}
+
+void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
+			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason)
+{
+	struct bpf_diag *diag = env->diag;
+
+	if (!diag)
+		return;
+	diag->mod.active = reg_to_target(env, reg, &diag->mod.target);
+	if (!diag->mod.active)
+		return;
+	diag->mod.target_reg_snapshot = *reg;
+	diag->mod.insn_idx = env->insn_idx;
+	diag->mod.reason = reason;
+	diag->mod.origin_valid = origin && reg_to_target(env, origin, &diag->mod.origin);
+}
+
+void bpf_diag_mod_end(struct bpf_verifier_env *env)
+{
+	struct bpf_diag *diag = env->diag;
+	const struct bpf_reg_state *new_reg;
+
+	if (!diag || !diag->mod.active)
+		return;
+	diag->mod.active = false;
+	/*
+	 * Resolve the target again because the enclosing function state's stack
+	 * may have been reallocated while the modification was in progress.
+	 */
+	new_reg = target_to_reg(env, &diag->mod.target);
+	if (!new_reg)
+		return;
+	diag_record_mod(env, diag->mod.insn_idx, diag->mod.target, diag->mod.reason,
+			&diag->mod.target_reg_snapshot, new_reg,
+			diag->mod.origin_valid ? &diag->mod.origin : NULL);
+}
+
+void bpf_diag_record_scrub(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
+			   enum bpf_diag_mod_reason reason)
+{
+	struct bpf_diag_mod_target target;
+
+	if (!env->diag || reg->type == NOT_INIT || !reg_to_target(env, reg, &target))
+		return;
+	diag_record_mod(env, env->insn_idx, target, reason, reg, NULL, NULL);
+}
+
+void bpf_diag_record_scrub_stack(struct bpf_verifier_env *env,
+				 const struct bpf_func_state *state, s16 min_off, s16 max_off,
+				 enum bpf_diag_mod_reason reason)
+{
+	diag_record_mod(env, env->insn_idx,
+			diag_stack_range_target(state->diag_frame_id, state->frameno, min_off, max_off),
+			reason, NULL, NULL, NULL);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index 6eda2fd65ee1..c4e44b86e89d 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -8,17 +8,40 @@
 #include <linux/stdarg.h>
 #include <linux/types.h>
 
+struct bpf_func_state;
+struct bpf_reg_state;
 struct bpf_verifier_env;
+struct btf;
+
+enum bpf_diag_mod_reason {
+	BPF_DIAG_MOD_WRITE,
+	BPF_DIAG_MOD_SPILL,
+	BPF_DIAG_MOD_VAR_WRITE,
+	BPF_DIAG_MOD_REF_RELEASE,
+	BPF_DIAG_MOD_PKT_DATA_CHANGE,
+	BPF_DIAG_MOD_NON_OWN_REF,
+	BPF_DIAG_MOD_CALLER_SAVED,
+};
 
 bool bpf_diag_enabled(const struct bpf_verifier_env *env);
 int bpf_diag_init(struct bpf_verifier_env *env);
+void bpf_diag_init_frame(struct bpf_verifier_env *env, struct bpf_func_state *state);
 char *bpf_diag_fmt_buf(struct bpf_verifier_env *env, size_t size);
 const char *bpf_diag_vfmt(struct bpf_verifier_env *env, const char *fmt, va_list args)
 	__printf(2, 0);
 const char *bpf_diag_fmt(struct bpf_verifier_env *env, const char *fmt, ...) __printf(2, 3);
+const char *bpf_diag_fmt_btf_type(struct bpf_verifier_env *env, const struct btf *btf, u32 type_id);
 u64 bpf_diag_event_log_save(struct bpf_verifier_env *env);
 void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos);
 void bpf_diag_free(struct bpf_verifier_env *env);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
+void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
+			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
+void bpf_diag_mod_end(struct bpf_verifier_env *env);
+void bpf_diag_record_scrub(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
+			   enum bpf_diag_mod_reason reason);
+void bpf_diag_record_scrub_stack(struct bpf_verifier_env *env,
+				 const struct bpf_func_state *state, s16 min_off, s16 max_off,
+				 enum bpf_diag_mod_reason reason);
 
 #endif /* __BPF_DIAGNOSTICS_H */
diff --git a/kernel/bpf/log.c b/kernel/bpf/log.c
index b740fa73ee26..589770ca3d3a 100644
--- a/kernel/bpf/log.c
+++ b/kernel/bpf/log.c
@@ -615,17 +615,6 @@ static void print_scalar_ranges(struct bpf_verifier_env *env,
 	}
 }
 
-static bool type_is_map_ptr(enum bpf_reg_type t) {
-	switch (base_type(t)) {
-	case CONST_PTR_TO_MAP:
-	case PTR_TO_MAP_KEY:
-	case PTR_TO_MAP_VALUE:
-		return true;
-	default:
-		return false;
-	}
-}
-
 /*
  * _a stands for append, was shortened to avoid multiline statements below.
  * This macro is used to output a comma separated list of attributes.
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index db644690ac4b..a5929e40f18d 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1792,6 +1792,17 @@ static const int caller_saved[CALLER_SAVED_REGS] = {
 	BPF_REG_0, BPF_REG_1, BPF_REG_2, BPF_REG_3, BPF_REG_4, BPF_REG_5
 };
 
+static void bpf_diag_record_caller_saved(struct bpf_verifier_env *env,
+					 struct bpf_reg_state *regs)
+{
+	int i;
+
+	for (i = 1; i < CALLER_SAVED_REGS; i++) {
+		bpf_diag_record_scrub(env, &regs[caller_saved[i]],
+				      BPF_DIAG_MOD_CALLER_SAVED);
+	}
+}
+
 /* This helper doesn't clear reg->id */
 static void ___mark_reg_known(struct bpf_reg_state *reg, u64 imm)
 {
@@ -2245,6 +2256,7 @@ static void init_func_state(struct bpf_verifier_env *env,
 {
 	state->callsite = callsite;
 	state->frameno = frameno;
+	bpf_diag_init_frame(env, state);
 	state->subprogno = subprogno;
 	state->callback_ret_range = retval_range(0, 0);
 	init_reg_state(env, state);
@@ -3362,6 +3374,7 @@ static void save_register_state(struct bpf_verifier_env *env,
 {
 	int i;
 
+	bpf_diag_mod_begin(env, &state->stack[spi].spilled_ptr, reg, BPF_DIAG_MOD_SPILL);
 	state->stack[spi].spilled_ptr = *reg;
 
 	for (i = BPF_REG_SIZE; i > BPF_REG_SIZE - size; i--)
@@ -3370,6 +3383,8 @@ static void save_register_state(struct bpf_verifier_env *env,
 	/* size < 8 bytes spill */
 	for (; i; i--)
 		mark_stack_slot_misc(env, &state->stack[spi].slot_type[i - 1]);
+
+	bpf_diag_mod_end(env);
 }
 
 static bool is_bpf_st_mem(struct bpf_insn *insn)
@@ -3506,6 +3521,9 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 	} else {
 		u8 type = STACK_MISC;
 
+		if (bpf_is_spilled_reg(&state->stack[spi]))
+			bpf_diag_record_scrub(env, &state->stack[spi].spilled_ptr,
+					      BPF_DIAG_MOD_WRITE);
 		scrub_special_slot(state, spi);
 
 		/* when we zero initialize stack slots mark them as such */
@@ -3666,6 +3684,8 @@ static int check_stack_write_var_off(struct bpf_verifier_env *env,
 		if (err)
 			return err;
 	}
+	bpf_diag_record_scrub_stack(env, state, min_off, max_off,
+				    BPF_DIAG_MOD_VAR_WRITE);
 	return 0;
 }
 
@@ -3758,6 +3778,12 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
 	mark_stack_slot_scratched(env, spi);
 	check_fastcall_stack_contract(env, state, env->insn_idx, off);
 
+	/*
+	 * Refine the in-progress load record's origin to the source stack slot.
+	 */
+	if (dst_regno >= 0)
+		bpf_diag_mod_begin(env, &state->regs[dst_regno], reg, BPF_DIAG_MOD_WRITE);
+
 	if (bpf_is_spilled_reg(&reg_state->stack[spi])) {
 		u8 spill_size = 1;
 
@@ -4051,14 +4077,17 @@ static int check_stack_arg_write(struct bpf_verifier_env *env, struct bpf_func_s
 	if (spi + 1 > subprog->max_out_stack_arg_cnt)
 		subprog->max_out_stack_arg_cnt = spi + 1;
 
+	arg = &state->stack_arg_regs[spi];
+	bpf_diag_mod_begin(env, arg, value_reg, BPF_DIAG_MOD_WRITE);
+
 	if (value_reg) {
 		state->stack_arg_regs[spi] = *value_reg;
 	} else {
 		/* BPF_ST: store immediate, treat as scalar */
-		arg = &state->stack_arg_regs[spi];
 		arg->type = SCALAR_VALUE;
 		__mark_reg_known(arg, env->prog->insnsi[env->insn_idx].imm);
 	}
+	bpf_diag_mod_end(env);
 	state->no_stack_arg_load = true;
 	return bpf_push_jmp_history(env, env->cur_state,
 				    INSN_F_STACK_ARG_ACCESS, spi, 0, 0);
@@ -4091,7 +4120,9 @@ static int check_stack_arg_read(struct bpf_verifier_env *env, struct bpf_func_st
 	caller = vstate->frame[vstate->curframe - 1];
 	arg = &caller->stack_arg_regs[spi];
 	cur = vstate->frame[vstate->curframe];
+	bpf_diag_mod_begin(env, &cur->regs[dst_regno], arg, BPF_DIAG_MOD_WRITE);
 	cur->regs[dst_regno] = *arg;
+	bpf_diag_mod_end(env);
 	return bpf_push_jmp_history(env, env->cur_state,
 				    INSN_F_STACK_ARG_ACCESS, spi, 0, 0);
 }
@@ -6426,15 +6457,19 @@ static int check_load_mem(struct bpf_verifier_env *env, struct bpf_insn *insn,
 
 	src_reg_type = regs[insn->src_reg].type;
 
-	/* Check if (src_reg + off) is readable. The state of dst_reg will be
-	 * updated by this call.
+	/*
+	 * check_stack_read_fixed_off() may refine the modification's origin to
+	 * the source stack slot.
 	 */
+	bpf_diag_mod_begin(env, &regs[insn->dst_reg], NULL, BPF_DIAG_MOD_WRITE);
 	err = check_mem_access(env, env->insn_idx, regs + insn->src_reg, argno_from_reg(insn->src_reg), insn->off,
 			       BPF_SIZE(insn->code), BPF_READ, insn->dst_reg,
 			       strict_alignment_once, is_ldsx);
 	err = err ?: save_aux_ptr_type(env, src_reg_type,
 				       allow_trust_mismatch);
 	err = err ?: reg_bounds_sanity_check(env, &regs[insn->dst_reg], ctx);
+	if (!err)
+		bpf_diag_mod_end(env);
 
 	return err;
 }
@@ -6540,10 +6575,14 @@ static int check_atomic_rmw(struct bpf_verifier_env *env,
 	 */
 	err = check_mem_access(env, env->insn_idx, dst_reg, argno_from_reg(insn->dst_reg), insn->off,
 			       BPF_SIZE(insn->code), BPF_READ, -1, true, false);
-	if (!err && load_reg >= 0)
+	if (!err && load_reg >= 0) {
+		bpf_diag_mod_begin(env, cur_regs(env) + load_reg, NULL, BPF_DIAG_MOD_WRITE);
 		err = check_mem_access(env, env->insn_idx, dst_reg, argno_from_reg(insn->dst_reg),
 				       insn->off, BPF_SIZE(insn->code),
 				       BPF_READ, load_reg, true, false);
+		if (!err)
+			bpf_diag_mod_end(env);
+	}
 	if (err)
 		return err;
 
@@ -8945,8 +8984,10 @@ static void clear_all_pkt_pointers(struct bpf_verifier_env *env)
 	struct bpf_reg_state *reg;
 
 	bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
-		if (reg_is_pkt_pointer_any(reg) || reg_is_dynptr_slice_pkt(reg))
+		if (reg_is_pkt_pointer_any(reg) || reg_is_dynptr_slice_pkt(reg)) {
+			bpf_diag_record_scrub(env, reg, BPF_DIAG_MOD_PKT_DATA_CHANGE);
 			mark_reg_invalid(env, reg);
+		}
 	}));
 }
 
@@ -9062,10 +9103,25 @@ static int release_reference(struct bpf_verifier_env *env, int id)
 					return err;
 			}
 
+			/*
+			 * A dynptr occupies two stack slots that invalidate_dynptr()
+			 * clears together. Record both scrubs before invalidating it.
+			 */
+			if (stack && stack->slot_type[BPF_REG_SIZE - 1] == STACK_DYNPTR) {
+				struct bpf_stack_state *dyn_stack = stack;
+
+				if (reg->dynptr.first_slot)
+					dyn_stack--;
+				bpf_diag_record_scrub(env, &dyn_stack[0].spilled_ptr,
+						      BPF_DIAG_MOD_REF_RELEASE);
+				bpf_diag_record_scrub(env, &dyn_stack[1].spilled_ptr,
+						      BPF_DIAG_MOD_REF_RELEASE);
+				invalidate_dynptr(env, dyn_stack);
+				continue;
+			}
+			bpf_diag_record_scrub(env, reg, BPF_DIAG_MOD_REF_RELEASE);
 			if (!stack || stack->slot_type[BPF_REG_SIZE - 1] == STACK_SPILL)
 				mark_reg_invalid(env, reg);
-			else if (stack->slot_type[BPF_REG_SIZE - 1] == STACK_DYNPTR)
-				invalidate_dynptr(env, stack);
 		}));
 	}
 
@@ -9078,8 +9134,10 @@ static void invalidate_non_owning_refs(struct bpf_verifier_env *env)
 	struct bpf_reg_state *reg;
 
 	bpf_for_each_reg_in_vstate(env->cur_state, unused, reg, ({
-		if (type_is_non_owning_ref(reg->type))
+		if (type_is_non_owning_ref(reg->type)) {
+			bpf_diag_record_scrub(env, reg, BPF_DIAG_MOD_NON_OWN_REF);
 			mark_reg_invalid(env, reg);
+		}
 	}));
 }
 
@@ -9092,8 +9150,10 @@ static void invalidate_rcu_protected_refs(struct bpf_verifier_env *env)
 
 	bpf_for_each_reg_in_vstate_mask(env->cur_state, state, reg, stack, clear_mask, ({
 		if (reg->type & MEM_RCU) {
+			bpf_diag_mod_begin(env, reg, NULL, BPF_DIAG_MOD_WRITE);
 			reg->type &= ~(MEM_RCU | PTR_MAYBE_NULL);
 			reg->type |= PTR_UNTRUSTED;
+			bpf_diag_mod_end(env);
 		}
 	}));
 }
@@ -9110,9 +9170,11 @@ static int ref_convert_alloc_rcu_protected(struct bpf_verifier_env *env, u32 id)
 		if (reg->id != id)
 			continue;
 		if ((reg->type & MEM_ALLOC) && (reg->type & MEM_PERCPU)) {
+			bpf_diag_mod_begin(env, reg, NULL, BPF_DIAG_MOD_WRITE);
 			reg->id = 0;
 			reg->type &= ~MEM_ALLOC;
 			reg->type |= MEM_RCU;
+			bpf_diag_mod_end(env);
 		}
 	}));
 
@@ -9124,6 +9186,8 @@ static void clear_caller_saved_regs(struct bpf_verifier_env *env,
 {
 	int i;
 
+	bpf_diag_record_caller_saved(env, regs);
+
 	/* after the call registers r0 - r5 were scratched */
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		bpf_mark_reg_not_init(env, &regs[caller_saved[i]]);
@@ -9131,13 +9195,15 @@ static void clear_caller_saved_regs(struct bpf_verifier_env *env,
 	}
 }
 
-static void invalidate_outgoing_stack_args(const struct bpf_verifier_env *env,
+static void invalidate_outgoing_stack_args(struct bpf_verifier_env *env,
 					   struct bpf_func_state *state)
 {
 	int i, nslots = state->out_stack_arg_cnt;
 
-	for (i = 0; i < nslots; i++)
+	for (i = 0; i < nslots; i++) {
+		bpf_diag_record_scrub(env, &state->stack_arg_regs[i], BPF_DIAG_MOD_CALLER_SAVED);
 		bpf_mark_reg_not_init(env, &state->stack_arg_regs[i]);
+	}
 }
 
 typedef int (*set_callee_state_fn)(struct bpf_verifier_env *env,
@@ -9436,6 +9502,7 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		return err;
 	if (bpf_subprog_is_global(env, subprog)) {
 		const char *sub_name = bpf_subprog_name(env, subprog);
+		bool returns_void;
 
 		if (env->cur_state->active_locks) {
 			verbose(env, "global function calls are not allowed while holding a lock,\n"
@@ -9458,16 +9525,22 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		if (env->log.level & BPF_LOG_LEVEL)
 			verbose(env, "Func#%d ('%s') is global and assumed valid.\n",
 				subprog, sub_name);
+		returns_void = subprog_returns_void(env, subprog);
 		if (env->subprog_info[subprog].changes_pkt_data)
 			clear_all_pkt_pointers(env);
 		/* mark global subprog for verifying after main prog */
 		subprog_aux(env, subprog)->called = true;
+		if (returns_void)
+			bpf_diag_record_scrub(env, &caller->regs[BPF_REG_0], BPF_DIAG_MOD_CALLER_SAVED);
+		else
+			bpf_diag_mod_begin(env, &caller->regs[BPF_REG_0], NULL, BPF_DIAG_MOD_WRITE);
 		clear_caller_saved_regs(env, caller->regs);
 		invalidate_outgoing_stack_args(env, cur_func(env));
 
 		/* All non-void global functions return a 64-bit SCALAR_VALUE. */
-		if (!subprog_returns_void(env, subprog)) {
+		if (!returns_void) {
 			mark_reg_unknown(env, caller->regs, BPF_REG_0);
+			bpf_diag_mod_end(env);
 		}
 
 		if (env->subprog_info[subprog].might_throw) {
@@ -9502,6 +9575,7 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	if (err)
 		return err;
 
+	bpf_diag_record_scrub(env, &caller->regs[BPF_REG_0], BPF_DIAG_MOD_CALLER_SAVED);
 	clear_caller_saved_regs(env, caller->regs);
 
 	/* and go analyze first insn of the callee */
@@ -9865,7 +9939,9 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx)
 		}
 	} else {
 		/* return to the caller whatever r0 had in the callee */
+		bpf_diag_mod_begin(env, &caller->regs[BPF_REG_0], r0, BPF_DIAG_MOD_WRITE);
 		caller->regs[BPF_REG_0] = *r0;
+		bpf_diag_mod_end(env);
 	}
 
 	/* for callbacks like bpf_loop or bpf_for_each_map_elem go back to callsite,
@@ -10518,12 +10594,14 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		return err;
 
 	/* reset caller saved regs */
+	bpf_diag_record_caller_saved(env, regs);
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		bpf_mark_reg_not_init(env, &regs[caller_saved[i]]);
 		check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
 	}
 	invalidate_outgoing_stack_args(env, cur_func(env));
 
+	bpf_diag_mod_begin(env, &regs[BPF_REG_0], NULL, BPF_DIAG_MOD_WRITE);
 	/* update return register (already marked as written above) */
 	ret_type = fn->ret_type;
 	ret_flag = type_flag(ret_type);
@@ -10672,6 +10750,8 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		if (err)
 			return err;
 
+		bpf_diag_mod_end(env);
+
 		/*
 		 * In order for a release of any of the original or cast pointers
 		 * to invalidate all other pointers, reuse the same reference id for
@@ -10688,6 +10768,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 		__mark_reg_known_zero(r0);
 		r0->type = SCALAR_VALUE;
 
+		bpf_diag_mod_begin(env, &regs[BPF_REG_0], NULL, BPF_DIAG_MOD_WRITE);
 		regs[BPF_REG_0].type &= ~PTR_MAYBE_NULL;
 		regs[BPF_REG_0].id = meta.ref_obj.id;
 	} else if (is_acquire_function(func_id, meta.map.ptr)) {
@@ -10706,6 +10787,8 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	if (err)
 		return err;
 
+	bpf_diag_mod_end(env);
+
 	err = check_map_func_compatibility(env, meta.map.ptr, func_id);
 	if (err)
 		return err;
@@ -13211,6 +13294,8 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		}
 	}
 
+	bpf_diag_record_caller_saved(env, regs);
+	bpf_diag_mod_begin(env, &regs[BPF_REG_0], NULL, BPF_DIAG_MOD_WRITE);
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		u32 regno = caller_saved[i];
 
@@ -13362,6 +13447,12 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 			caller_info->stack_arg_cnt = stack_arg_cnt;
 	}
 
+	/*
+	 * Record R0 before process_iter_next_call() snapshots the alternate
+	 * iterator path's diagnostic position.
+	 */
+	bpf_diag_mod_end(env);
+
 	if (bpf_is_iter_next_kfunc(&meta)) {
 		err = process_iter_next_call(env, insn_idx, &meta);
 		if (err)
@@ -15004,6 +15095,8 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	u8 opcode = BPF_OP(insn->code);
 	int err;
 
+	bpf_diag_mod_begin(env, &regs[insn->dst_reg], NULL, BPF_DIAG_MOD_WRITE);
+
 	if (opcode == BPF_END || opcode == BPF_NEG) {
 		/* check src operand */
 		err = check_reg_arg(env, insn->dst_reg, SRC_OP);
@@ -15177,7 +15270,12 @@ static int check_alu_op(struct bpf_verifier_env *env, struct bpf_insn *insn)
 			return err;
 	}
 
-	return reg_bounds_sanity_check(env, &regs[insn->dst_reg], "alu");
+	err = reg_bounds_sanity_check(env, &regs[insn->dst_reg], "alu");
+	if (err)
+		return err;
+
+	bpf_diag_mod_end(env);
+	return 0;
 }
 
 static void find_good_pkt_pointers(struct bpf_verifier_state *vstate,
@@ -16271,11 +16369,13 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		return err;
 
 	dst_reg = &regs[insn->dst_reg];
+	bpf_diag_mod_begin(env, dst_reg, NULL, BPF_DIAG_MOD_WRITE);
 	if (insn->src_reg == 0) {
 		u64 imm = ((u64)(insn + 1)->imm << 32) | (u32)insn->imm;
 
 		dst_reg->type = SCALAR_VALUE;
 		__mark_reg_known(&regs[insn->dst_reg], imm);
+		bpf_diag_mod_end(env);
 		return 0;
 	}
 
@@ -16299,6 +16399,7 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 			verifier_bug(env, "pseudo btf id: unexpected dst reg type");
 			return -EFAULT;
 		}
+		bpf_diag_mod_end(env);
 		return 0;
 	}
 
@@ -16318,6 +16419,7 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 
 		dst_reg->type = PTR_TO_FUNC;
 		dst_reg->subprogno = subprogno;
+		bpf_diag_mod_end(env);
 		return 0;
 	}
 
@@ -16328,6 +16430,7 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		if (map->map_type == BPF_MAP_TYPE_ARENA) {
 			__mark_reg_unknown(env, dst_reg);
 			dst_reg->map_ptr = map;
+			bpf_diag_mod_end(env);
 			return 0;
 		}
 		__mark_reg_known(dst_reg, aux->map_off);
@@ -16345,6 +16448,7 @@ static int check_ld_imm(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		return -EFAULT;
 	}
 
+	bpf_diag_mod_end(env);
 	return 0;
 }
 
@@ -16423,6 +16527,8 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 		return err;
 
 	/* reset caller saved regs to unreadable */
+	bpf_diag_record_caller_saved(env, regs);
+	bpf_diag_mod_begin(env, &regs[BPF_REG_0], NULL, BPF_DIAG_MOD_WRITE);
 	for (i = 0; i < CALLER_SAVED_REGS; i++) {
 		bpf_mark_reg_not_init(env, &regs[caller_saved[i]]);
 		check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
@@ -16433,6 +16539,7 @@ static int check_ld_abs(struct bpf_verifier_env *env, struct bpf_insn *insn)
 	 * Already marked as written above.
 	 */
 	mark_reg_unknown(env, regs, BPF_REG_0);
+	bpf_diag_mod_end(env);
 	/*
 	 * See bpf_gen_ld_abs() which emits a hidden BPF_EXIT with r0=0
 	 * which must be explored by the verifier when in a subprog.

From 9ecd70304e28985af297726cd961a33a6fec5f67 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:01 +0200
Subject: [PATCH 06/14] bpf: Track verifier reference diagnostic events

Add reference acquire and release events to diagnostic history so Resource
Lifetime Safety reports can show the lifetime of a specific reference id along
the path.

Record acquisitions after the verifier assigns the reference id. Record
releases only after release_reference_nomark() succeeds, including the
kptr_xchg RCU conversion path and owning-to-non-owning conversion path that
consume an owning reference.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-7-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c | 28 ++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h |  2 ++
 kernel/bpf/verifier.c    | 32 +++++++++++++++++++++++++-------
 3 files changed, 55 insertions(+), 7 deletions(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 2e8e75815581..ddeaff1e90b7 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -102,6 +102,8 @@ struct bpf_diag_reg_snapshot {
 enum bpf_diag_history_kind {
 	BPF_DIAG_HISTORY_BRANCH,
 	BPF_DIAG_HISTORY_MOD,
+	BPF_DIAG_HISTORY_REF_ACQUIRE,
+	BPF_DIAG_HISTORY_REF_RELEASE,
 };
 
 struct bpf_diag_history_event {
@@ -119,6 +121,9 @@ struct bpf_diag_history_event {
 			u8 reason;
 			bool origin_valid;
 		} mod;
+		struct {
+			u32 ref_id;
+		} ref;
 	};
 };
 
@@ -1021,3 +1026,26 @@ void bpf_diag_record_scrub_stack(struct bpf_verifier_env *env,
 			diag_stack_range_target(state->diag_frame_id, state->frameno, min_off, max_off),
 			reason, NULL, NULL, NULL);
 }
+
+static void diag_record_ref(struct bpf_verifier_env *env, u32 insn_idx, u8 kind, u32 ref_id)
+{
+	struct bpf_diag_history_event event = {
+		.insn_idx = insn_idx,
+		.kind = kind,
+		.ref = {
+			.ref_id = ref_id,
+		},
+	};
+
+	diag_append_history(env, &event);
+}
+
+void bpf_diag_record_ref_acquire(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id)
+{
+	diag_record_ref(env, insn_idx, BPF_DIAG_HISTORY_REF_ACQUIRE, ref_id);
+}
+
+void bpf_diag_record_ref_release(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id)
+{
+	diag_record_ref(env, insn_idx, BPF_DIAG_HISTORY_REF_RELEASE, ref_id);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index c4e44b86e89d..d17b498a3f66 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -43,5 +43,7 @@ void bpf_diag_record_scrub(struct bpf_verifier_env *env, const struct bpf_reg_st
 void bpf_diag_record_scrub_stack(struct bpf_verifier_env *env,
 				 const struct bpf_func_state *state, s16 min_off, s16 max_off,
 				 enum bpf_diag_mod_reason reason);
+void bpf_diag_record_ref_acquire(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id);
+void bpf_diag_record_ref_release(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id);
 
 #endif /* __BPF_DIAGNOSTICS_H */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index a5929e40f18d..8e32fa5fa30a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -205,7 +205,8 @@ struct bpf_verifier_stack_elem {
 #define BPF_PRIV_STACK_MIN_SIZE		64
 
 static int acquire_reference(struct bpf_verifier_env *env, int insn_idx, int parent_id);
-static int release_reference_nomark(struct bpf_verifier_state *state, int id);
+static int __release_reference_nomark(struct bpf_verifier_state *state, int id);
+static int release_reference_nomark(struct bpf_verifier_env *env, int id);
 static int release_reference(struct bpf_verifier_env *env, int id);
 static void invalidate_non_owning_refs(struct bpf_verifier_env *env);
 static void invalidate_rcu_protected_refs(struct bpf_verifier_env *env);
@@ -1418,6 +1419,7 @@ static int acquire_reference(struct bpf_verifier_env *env, int insn_idx, int par
 	s->type = REF_TYPE_PTR;
 	s->id = ++env->id_gen;
 	s->parent_id = parent_id;
+	bpf_diag_record_ref_acquire(env, insn_idx, s->id);
 	return s->id;
 }
 
@@ -9017,7 +9019,7 @@ static void mark_pkt_end(struct bpf_verifier_state *vstate, int regn, bool range
 		reg->range = AT_PKT_END;
 }
 
-static int release_reference_nomark(struct bpf_verifier_state *state, int id)
+static int __release_reference_nomark(struct bpf_verifier_state *state, int id)
 {
 	int i;
 
@@ -9032,6 +9034,16 @@ static int release_reference_nomark(struct bpf_verifier_state *state, int id)
 	return -EINVAL;
 }
 
+static int release_reference_nomark(struct bpf_verifier_env *env, int id)
+{
+	int err;
+
+	err = __release_reference_nomark(env->cur_state, id);
+	if (!err)
+		bpf_diag_record_ref_release(env, env->insn_idx, id);
+	return err;
+}
+
 static int idstack_push(struct bpf_idmap *idmap, u32 id)
 {
 	int i;
@@ -9074,8 +9086,10 @@ static int release_reference(struct bpf_verifier_env *env, int id)
 	if (err)
 		return err;
 
-	if (find_reference_state(vstate, id))
-		WARN_ON_ONCE(release_reference_nomark(vstate, id));
+	if (find_reference_state(vstate, id)) {
+		err = release_reference_nomark(env, id);
+		WARN_ON_ONCE(err);
+	}
 
 	while ((id = idstack_pop(idstack))) {
 		/*
@@ -9164,7 +9178,9 @@ static int ref_convert_alloc_rcu_protected(struct bpf_verifier_env *env, u32 id)
 	struct bpf_reg_state *reg;
 	int err;
 
-	err = release_reference_nomark(env->cur_state, id);
+	err = release_reference_nomark(env, id);
+	if (err)
+		return err;
 
 	bpf_for_each_reg_in_vstate(env->cur_state, state, reg, ({
 		if (reg->id != id)
@@ -11757,8 +11773,10 @@ static void ref_convert_owning_non_owning(struct bpf_verifier_env *env, u32 id)
 {
 	struct bpf_func_state *unused;
 	struct bpf_reg_state *reg;
+	int err;
 
-	WARN_ON_ONCE(release_reference_nomark(env->cur_state, id));
+	err = release_reference_nomark(env, id);
+	WARN_ON_ONCE(err);
 
 	bpf_for_each_reg_in_vstate(env->cur_state, unused, reg, ({
 		if (reg->id == id) {
@@ -15890,7 +15908,7 @@ static void mark_ptr_or_null_regs(struct bpf_verifier_state *vstate, u32 regno,
 		 * No one could have freed the reference state before
 		 * doing the NULL check.
 		 */
-		WARN_ON_ONCE(release_reference_nomark(vstate, id));
+		WARN_ON_ONCE(__release_reference_nomark(vstate, id));
 
 	bpf_for_each_reg_in_vstate(vstate, state, reg, ({
 		mark_ptr_or_null_reg(state, reg, id, is_null);

From 956a66e5c33fb53003ca2bc043a90ff0b671b3a5 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:02 +0200
Subject: [PATCH 07/14] bpf: Track verifier context diagnostic events

Record verifier context transitions in the diagnostic history so later reports
can anchor causal paths to the critical section that made an operation invalid.

This covers lock, IRQ, RCU, and preempt regions without adding any new
verifier error reports. Category-specific commits decide where those recorded
events should be rendered.

Use context depth when selecting scoped history so nested regions anchor at the
outer active region, and fall back to the earliest retained event when the
matching entry was pruned.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-8-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c | 39 +++++++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h | 12 ++++++++++++
 kernel/bpf/verifier.c    | 28 +++++++++++++++++++++++-----
 3 files changed, 74 insertions(+), 5 deletions(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index ddeaff1e90b7..15bca8a02a48 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -104,6 +104,7 @@ enum bpf_diag_history_kind {
 	BPF_DIAG_HISTORY_MOD,
 	BPF_DIAG_HISTORY_REF_ACQUIRE,
 	BPF_DIAG_HISTORY_REF_RELEASE,
+	BPF_DIAG_HISTORY_CONTEXT,
 };
 
 struct bpf_diag_history_event {
@@ -124,6 +125,11 @@ struct bpf_diag_history_event {
 		struct {
 			u32 ref_id;
 		} ref;
+		struct {
+			u32 depth;
+			u8 kind;
+			bool enter;
+		} ctx;
 	};
 };
 
@@ -388,6 +394,19 @@ void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos)
 	log->cnt = log_pos - log->first_seq;
 }
 
+u32 bpf_diag_irq_depth(const struct bpf_verifier_state *state)
+{
+	u32 depth = 0;
+	int i;
+
+	for (i = 0; i < state->acquired_refs; i++) {
+		if (state->refs[i].type == REF_TYPE_IRQ)
+			depth++;
+	}
+
+	return depth;
+}
+
 static void diag_append_history(struct bpf_verifier_env *env,
 				const struct bpf_diag_history_event *event)
 {
@@ -1049,3 +1068,23 @@ void bpf_diag_record_ref_release(struct bpf_verifier_env *env, u32 insn_idx, u32
 {
 	diag_record_ref(env, insn_idx, BPF_DIAG_HISTORY_REF_RELEASE, ref_id);
 }
+
+void bpf_diag_record_context(struct bpf_verifier_env *env, u32 insn_idx,
+			     enum bpf_diag_context_kind ctx_kind, bool enter, u32 depth)
+{
+	/*
+	 * Keep leave events so context rendering can stop at a depth-zero exit
+	 * and show nested-region depth accurately for the active path.
+	 */
+	struct bpf_diag_history_event event = {
+		.insn_idx = insn_idx,
+		.kind = BPF_DIAG_HISTORY_CONTEXT,
+		.ctx = {
+			.kind = ctx_kind,
+			.enter = enter,
+			.depth = depth,
+		},
+	};
+
+	diag_append_history(env, &event);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index d17b498a3f66..ed64776736c6 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -11,6 +11,7 @@
 struct bpf_func_state;
 struct bpf_reg_state;
 struct bpf_verifier_env;
+struct bpf_verifier_state;
 struct btf;
 
 enum bpf_diag_mod_reason {
@@ -23,6 +24,14 @@ enum bpf_diag_mod_reason {
 	BPF_DIAG_MOD_CALLER_SAVED,
 };
 
+enum bpf_diag_context_kind {
+	BPF_DIAG_CONTEXT_NONE,
+	BPF_DIAG_CONTEXT_RCU,
+	BPF_DIAG_CONTEXT_PREEMPT,
+	BPF_DIAG_CONTEXT_IRQ,
+	BPF_DIAG_CONTEXT_LOCK,
+};
+
 bool bpf_diag_enabled(const struct bpf_verifier_env *env);
 int bpf_diag_init(struct bpf_verifier_env *env);
 void bpf_diag_init_frame(struct bpf_verifier_env *env, struct bpf_func_state *state);
@@ -33,6 +42,7 @@ const char *bpf_diag_fmt(struct bpf_verifier_env *env, const char *fmt, ...) __p
 const char *bpf_diag_fmt_btf_type(struct bpf_verifier_env *env, const struct btf *btf, u32 type_id);
 u64 bpf_diag_event_log_save(struct bpf_verifier_env *env);
 void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos);
+u32 bpf_diag_irq_depth(const struct bpf_verifier_state *state);
 void bpf_diag_free(struct bpf_verifier_env *env);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
@@ -45,5 +55,7 @@ void bpf_diag_record_scrub_stack(struct bpf_verifier_env *env,
 				 enum bpf_diag_mod_reason reason);
 void bpf_diag_record_ref_acquire(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id);
 void bpf_diag_record_ref_release(struct bpf_verifier_env *env, u32 insn_idx, u32 ref_id);
+void bpf_diag_record_context(struct bpf_verifier_env *env, u32 insn_idx,
+			     enum bpf_diag_context_kind ctx_kind, bool enter, u32 depth);
 
 #endif /* __BPF_DIAGNOSTICS_H */
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 8e32fa5fa30a..1f2a7f480ce3 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -1045,7 +1045,7 @@ static int is_iter_reg_valid_init(struct bpf_verifier_env *env, struct bpf_reg_s
 }
 
 static int acquire_irq_state(struct bpf_verifier_env *env, int insn_idx);
-static int release_irq_state(struct bpf_verifier_state *state, int id);
+static int release_irq_state(struct bpf_verifier_env *env, int id);
 
 static int mark_stack_slot_irq_flag(struct bpf_verifier_env *env,
 				     struct bpf_call_arg_meta *meta,
@@ -1104,7 +1104,7 @@ static int unmark_stack_slot_irq_flag(struct bpf_verifier_env *env, struct bpf_r
 		return -EINVAL;
 	}
 
-	err = release_irq_state(env->cur_state, st->id);
+	err = release_irq_state(env, st->id);
 	WARN_ON_ONCE(err && err != -EACCES);
 	if (err) {
 		int insn_idx = 0;
@@ -1439,6 +1439,8 @@ static int acquire_lock_state(struct bpf_verifier_env *env, int insn_idx, enum r
 	state->active_locks++;
 	state->active_lock_id = id;
 	state->active_lock_ptr = ptr;
+	bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_LOCK, true,
+				state->active_locks);
 	return 0;
 }
 
@@ -1454,6 +1456,8 @@ static int acquire_irq_state(struct bpf_verifier_env *env, int insn_idx)
 	s->id = ++env->id_gen;
 
 	state->active_irq_id = s->id;
+	bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_IRQ, true,
+				bpf_diag_irq_depth(state));
 	return s->id;
 }
 
@@ -1495,8 +1499,9 @@ static bool reg_is_referenced(struct bpf_verifier_env *env, const struct bpf_reg
 	return find_reference_state(env->cur_state, reg->id);
 }
 
-static int release_lock_state(struct bpf_verifier_state *state, int type, int id, void *ptr)
+static int release_lock_state(struct bpf_verifier_env *env, int type, int id, void *ptr)
 {
+	struct bpf_verifier_state *state = env->cur_state;
 	void *prev_ptr = NULL;
 	u32 prev_id = 0;
 	int i;
@@ -1509,6 +1514,8 @@ static int release_lock_state(struct bpf_verifier_state *state, int type, int id
 			/* Reassign active lock (id, ptr). */
 			state->active_lock_id = prev_id;
 			state->active_lock_ptr = prev_ptr;
+			bpf_diag_record_context(env, env->insn_idx, BPF_DIAG_CONTEXT_LOCK,
+						false, state->active_locks);
 			return 0;
 		}
 		if (state->refs[i].type & REF_TYPE_LOCK_MASK) {
@@ -1519,8 +1526,9 @@ static int release_lock_state(struct bpf_verifier_state *state, int type, int id
 	return -EINVAL;
 }
 
-static int release_irq_state(struct bpf_verifier_state *state, int id)
+static int release_irq_state(struct bpf_verifier_env *env, int id)
 {
+	struct bpf_verifier_state *state = env->cur_state;
 	u32 prev_id = 0;
 	int i;
 
@@ -1533,6 +1541,8 @@ static int release_irq_state(struct bpf_verifier_state *state, int id)
 		if (state->refs[i].id == id) {
 			release_reference_state(state, i);
 			state->active_irq_id = prev_id;
+			bpf_diag_record_context(env, env->insn_idx, BPF_DIAG_CONTEXT_IRQ,
+						false, bpf_diag_irq_depth(state));
 			return 0;
 		} else {
 			prev_id = state->refs[i].id;
@@ -7181,7 +7191,7 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state
 			verbose(env, "%s_unlock cannot be out of order\n", lock_str);
 			return -EINVAL;
 		}
-		if (release_lock_state(cur, type, reg->id, ptr)) {
+		if (release_lock_state(env, type, reg->id, ptr)) {
 			verbose(env, "%s_unlock of different lock\n", lock_str);
 			return -EINVAL;
 		}
@@ -13242,22 +13252,30 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 
 	if (rcu_lock) {
 		env->cur_state->active_rcu_locks++;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_RCU, true,
+					env->cur_state->active_rcu_locks);
 	} else if (rcu_unlock) {
 		if (env->cur_state->active_rcu_locks == 0) {
 			verbose(env, "unmatched rcu read unlock (kernel function %s)\n", func_name);
 			return -EINVAL;
 		}
 		env->cur_state->active_rcu_locks--;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_RCU, false,
+					env->cur_state->active_rcu_locks);
 		if (!in_rcu_cs(env))
 			invalidate_rcu_protected_refs(env);
 	} else if (preempt_disable) {
 		env->cur_state->active_preempt_locks++;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_PREEMPT, true,
+					env->cur_state->active_preempt_locks);
 	} else if (preempt_enable) {
 		if (env->cur_state->active_preempt_locks == 0) {
 			verbose(env, "unmatched attempt to enable preemption (kernel function %s)\n", func_name);
 			return -EINVAL;
 		}
 		env->cur_state->active_preempt_locks--;
+		bpf_diag_record_context(env, insn_idx, BPF_DIAG_CONTEXT_PREEMPT, false,
+					env->cur_state->active_preempt_locks);
 		if (!in_rcu_cs(env))
 			invalidate_rcu_protected_refs(env);
 	}

From d63284e62b3185cafe40d5fab17245ee60b6cffe Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:03 +0200
Subject: [PATCH 08/14] bpf: Report Register Type Safety errors

Augment selected register-state verifier failures with Register Type Safety
reports. The existing verbose verifier messages remain in place; the new
reports add reason, source context, causal path, and suggestions.

Cover invalid pointer dereferences, unreadable registers, missing outgoing
stack arguments for bpf2bpf and kfunc calls, and rejected pointer arithmetic.
Use scoped diagnostic history so reports start from the latest relevant value
change and then show later branch outcomes.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-9-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c                      | 854 ++++++++++++++++++
 kernel/bpf/diagnostics.h                      |  18 +
 kernel/bpf/verifier.c                         | 128 ++-
 .../selftests/bpf/progs/verifier_uninit.c     |   1 +
 4 files changed, 986 insertions(+), 15 deletions(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 15bca8a02a48..02399cad2fb0 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -15,9 +15,13 @@
 #include "disasm.h"
 #include "diagnostics.h"
 
+#define REGISTER_TYPE_SAFETY "Register Type Safety"
+
 #define BPF_DIAG_TEXT_WIDTH 100
+#define BPF_DIAG_TEXT_INDENT "  "
 #define BPF_DIAG_CONTEXT 2
 #define BPF_DIAG_CONTEXT_CNT (1 + BPF_DIAG_CONTEXT * 2)
+#define BPF_DIAG_HISTORY_RENDER_MAX 64
 #define BPF_DIAG_SOURCE_LANE_WIDTH 88
 #define BPF_DIAG_TAB_WIDTH 8
 #define BPF_DIAG_FMT_CHUNK_SIZE (PAGE_SIZE - sizeof(struct diag_fmt_chunk))
@@ -133,6 +137,28 @@ struct bpf_diag_history_event {
 	};
 };
 
+enum bpf_diag_history_scope {
+	BPF_DIAG_HISTORY_SCOPE_REG,
+	BPF_DIAG_HISTORY_SCOPE_STACK_ARG,
+	BPF_DIAG_HISTORY_SCOPE_REF,
+	BPF_DIAG_HISTORY_SCOPE_CONTEXT,
+};
+
+struct bpf_diag_history_opts {
+	enum bpf_diag_history_scope scope;
+	u32 frame_id;
+	u32 frameno;
+	int regno;
+	int stack_arg_slot;
+	u32 ref_id;
+	enum bpf_diag_context_kind ctx_kind;
+	u32 ctx_depth;
+};
+
+static void diag_print_history(struct bpf_verifier_env *env,
+			       const struct bpf_diag_history_opts *opts);
+static bool diag_target_matches(const struct bpf_diag_mod_target *event_target,
+				const struct bpf_diag_mod_target *target);
 struct disasm_line {
 	char text[DISASM_LINE_LEN];
 	int idx;
@@ -505,6 +531,26 @@ const char *bpf_diag_fmt_btf_type(struct bpf_verifier_env *env, const struct btf
 	return buf;
 }
 
+static void diag_vprint_indented(struct bpf_verifier_env *env, const char *fmt, va_list args)
+	__printf(2, 0);
+
+static void diag_vprint_indented(struct bpf_verifier_env *env, const char *fmt, va_list args)
+{
+	char *buf;
+
+	if (!bpf_diag_enabled(env))
+		return;
+
+	buf = kvasprintf(GFP_KERNEL_ACCOUNT, fmt, args);
+	if (!buf) {
+		diag_write(env, "%s<failed to allocate diagnostic text>\n", BPF_DIAG_TEXT_INDENT);
+		return;
+	}
+
+	diag_print_wrapped_prefixed(env, BPF_DIAG_TEXT_INDENT, BPF_DIAG_TEXT_INDENT, buf);
+	kfree(buf);
+}
+
 static int diag_line_width(unsigned int line)
 {
 	int width = 1;
@@ -663,6 +709,47 @@ static void bpf_diag_header(struct bpf_verifier_env *env, const char *category,
 	diag_write(env, "\nVerification failed: %s: %c%s\n", category, first, problem + 1);
 }
 
+static void diag_reason(struct bpf_verifier_env *env, const char *fmt, ...) __printf(2, 3);
+static void diag_suggestion(struct bpf_verifier_env *env, const char *fmt, ...)
+	__printf(2, 3);
+
+static void diag_section(struct bpf_verifier_env *env, const char *title)
+{
+	if (!bpf_diag_enabled(env))
+		return;
+
+	diag_write(env, "\n%s:\n", title);
+}
+
+static void diag_reason(struct bpf_verifier_env *env, const char *fmt, ...)
+{
+	va_list args;
+
+	if (!bpf_diag_enabled(env))
+		return;
+
+	diag_section(env, "Reason");
+
+	va_start(args, fmt);
+	diag_vprint_indented(env, fmt, args);
+	va_end(args);
+}
+
+static void diag_suggestion(struct bpf_verifier_env *env, const char *fmt, ...)
+{
+	va_list args;
+
+	if (!bpf_diag_enabled(env))
+		return;
+
+	diag_section(env, "Suggestion");
+
+	va_start(args, fmt);
+	diag_vprint_indented(env, fmt, args);
+	va_end(args);
+	diag_write(env, "\n");
+}
+
 static void diag_print_source_annotation(struct bpf_verifier_env *env, int line_width, int indent,
 					 const char *label, const char *msg)
 {
@@ -799,6 +886,284 @@ static void bpf_diag_source(struct bpf_verifier_env *env, u32 insn_idx, const ch
 	diag_fmt_restore(env, mark);
 }
 
+static const struct bpf_func_state *diag_current_frame(const struct bpf_verifier_env *env)
+{
+	return env->cur_state->frame[env->cur_state->curframe];
+}
+
+void bpf_diag_register_type(struct bpf_verifier_env *env, u32 insn_idx, int regno,
+			    const char *problem, const char *reason, const char *suggestion)
+{
+	const struct bpf_func_state *frame = diag_current_frame(env);
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_REG,
+		.frame_id = frame->diag_frame_id,
+		.frameno = frame->frameno,
+		.regno = regno,
+	};
+
+	bpf_diag_header(env, REGISTER_TYPE_SAFETY, problem);
+	diag_reason(env, "%s", reason);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s", problem);
+
+	if (regno >= 0)
+		diag_print_history(env, &opts);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
+const char *bpf_diag_reg_type_plain(struct bpf_verifier_env *env, enum bpf_reg_type type)
+{
+	switch (base_type(type)) {
+	case NOT_INIT:
+		return "an uninitialized value";
+	case SCALAR_VALUE:
+		return "an integer scalar";
+	case PTR_TO_CTX:
+		return "a context pointer";
+	case PTR_TO_STACK:
+		return "a stack pointer";
+	case PTR_TO_MAP_VALUE:
+		if (type_may_be_null(type))
+			return "a nullable map value pointer";
+		return "a map value pointer";
+	case PTR_TO_MEM:
+		if (type_may_be_null(type))
+			return "a nullable memory pointer";
+		return "a memory pointer";
+	case PTR_TO_BTF_ID:
+		if (type_may_be_null(type))
+			return "a nullable kernel object pointer";
+		if (type_is_non_owning_ref(type))
+			return "a borrowed allocated object pointer";
+		if (type_is_ptr_alloc_obj(type))
+			return "an owned allocated object pointer";
+		if (type_flag(type) & PTR_UNTRUSTED)
+			return "an untrusted kernel object pointer";
+		return "a kernel object pointer";
+	default:
+		return reg_type_str(env, type);
+	}
+}
+
+static const char *diag_arg_ordinal(int argno)
+{
+	switch (argno) {
+	case 1:
+		return "first";
+	case 2:
+		return "second";
+	case 3:
+		return "third";
+	case 4:
+		return "fourth";
+	case 5:
+		return "fifth";
+	case 6:
+		return "sixth";
+	case 7:
+		return "seventh";
+	case 8:
+		return "eighth";
+	case 9:
+		return "ninth";
+	case 10:
+		return "tenth";
+	case 11:
+		return "eleventh";
+	case 12:
+		return "twelfth";
+	default:
+		return NULL;
+	}
+}
+
+void bpf_diag_invalid_deref(struct bpf_verifier_env *env, u32 insn_idx, int regno,
+			    const char *reg_name, const struct bpf_reg_state *reg,
+			    enum bpf_diag_invalid_deref_kind kind, s64 offset)
+{
+	const struct bpf_func_state *frame = diag_current_frame(env);
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_REG,
+		.frame_id = frame->diag_frame_id,
+		.frameno = frame->frameno,
+		.regno = regno,
+	};
+	const char *type_name = bpf_diag_reg_type_plain(env, reg->type);
+
+	bpf_diag_header(env, REGISTER_TYPE_SAFETY, "invalid dereference");
+
+	switch (kind) {
+	case BPF_DIAG_DEREF_SCALAR:
+		diag_reason(env, "%s is an integer scalar here, not a pointer to memory.",
+			    reg_name);
+		break;
+	case BPF_DIAG_DEREF_NULLABLE_PTR:
+		diag_reason(
+			env, "%s may be NULL here (%s). The program could dereference NULL on this path, so the verifier cannot prove this access is safe.",
+			reg_name, type_name);
+		break;
+	case BPF_DIAG_DEREF_MODIFIED_PTR:
+		diag_reason(
+			env, "%s has offset %lld here, but this pointer type must be dereferenced in its original form.",
+			reg_name, offset);
+		break;
+	case BPF_DIAG_DEREF_INVALID_PTR:
+	default:
+		diag_reason(
+			env, "%s has type %s here, which is not valid for this memory access.",
+			reg_name, type_name);
+		break;
+	}
+
+	diag_section(env, "At");
+	if (kind == BPF_DIAG_DEREF_MODIFIED_PTR)
+		bpf_diag_source(env, insn_idx, "error",
+				"dereference requires the original %s pointer", type_name);
+	else
+		bpf_diag_source(env, insn_idx, "error", "invalid dereference of %s (%s)",
+				reg_name, type_name);
+
+	if (regno >= 0)
+		diag_print_history(env, &opts);
+
+	switch (kind) {
+	case BPF_DIAG_DEREF_NULLABLE_PTR:
+		diag_suggestion(
+			env, "Add a NULL check before the access and dereference the pointer only on the non-NULL path.");
+		break;
+	case BPF_DIAG_DEREF_MODIFIED_PTR:
+		diag_suggestion(
+			env, "Preserve the original pointer in another register, or use only offsets this pointer type permits before dereferencing it.");
+		break;
+	case BPF_DIAG_DEREF_SCALAR:
+	case BPF_DIAG_DEREF_INVALID_PTR:
+	default:
+		diag_suggestion(
+			env, "Preserve a pointer-valued register where needed, or reload and revalidate the pointer after scalar arithmetic, helper calls, or other operations that can invalidate it.");
+		break;
+	}
+}
+
+void bpf_diag_unreadable_reg(struct bpf_verifier_env *env, u32 insn_idx, int regno)
+{
+	const struct bpf_func_state *frame = diag_current_frame(env);
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_REG,
+		.frame_id = frame->diag_frame_id,
+		.frameno = frame->frameno,
+		.regno = regno,
+	};
+	const struct bpf_diag_log *log = env->diag ? &env->diag->log : NULL;
+	struct bpf_diag_mod_target target;
+	bool invalidated = false;
+	int i;
+
+	target = diag_reg_target(opts.frame_id, opts.frameno, regno);
+	for (i = log ? log->cnt : 0; i > 0; i--) {
+		const struct bpf_diag_history_event *event;
+
+		event = &log->events[log_pos(log, i - 1)];
+
+		if (event->kind != BPF_DIAG_HISTORY_MOD ||
+		    !diag_target_matches(&event->mod.target, &target))
+			continue;
+		invalidated = event->mod.new.type == NOT_INIT;
+		break;
+	}
+
+	bpf_diag_header(env, REGISTER_TYPE_SAFETY, "unreadable register");
+	if (invalidated)
+		diag_reason(
+			env, "R%d is not readable here. A previous operation invalidated this register, so the verifier cannot use it as an input.",
+			regno);
+	else if (log && !log->first_seq)
+		diag_reason(env,
+			    "R%d has never been initialized on this path, so the verifier cannot use it as an input.",
+			    regno);
+	else
+		diag_reason(
+			env, "R%d is not readable here. It may never have been initialized, or an earlier operation may have invalidated it.",
+			regno);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "R%d is not readable", regno);
+
+	if (regno >= 0)
+		diag_print_history(env, &opts);
+
+	if (invalidated)
+		diag_suggestion(
+			env, "Avoid using the register after it is invalidated, or initialize it again before this instruction.");
+	else if (log && !log->first_seq)
+		diag_suggestion(env, "Initialize R%d on every path before this instruction.", regno);
+	else
+		diag_suggestion(
+			env, "Initialize the register on every path, or initialize it again after any operation that invalidates it.");
+}
+
+static int diag_stack_argno(u8 slot)
+{
+	return MAX_BPF_FUNC_REG_ARGS + slot + 1;
+}
+
+static void diag_format_stack_arg(char *buf, size_t size, u8 slot, const char *arg_name)
+{
+	int argno = diag_stack_argno(slot);
+	const char *ordinal = diag_arg_ordinal(argno);
+
+	if (ordinal && arg_name)
+		scnprintf(buf, size, "outgoing stack argument %u (%s argument, %s)", slot + 1,
+			  ordinal, arg_name);
+	else if (ordinal)
+		scnprintf(buf, size, "outgoing stack argument %u (%s argument)", slot + 1, ordinal);
+	else if (arg_name)
+		scnprintf(buf, size, "outgoing stack argument %u (%s)", slot + 1, arg_name);
+	else
+		scnprintf(buf, size, "outgoing stack argument %u", slot + 1);
+}
+
+void bpf_diag_stack_arg_uninit(struct bpf_verifier_env *env, u32 insn_idx, int nargs,
+			       int stack_arg_slot, const char *callee_name,
+			       const char *arg_name)
+{
+	const struct bpf_func_state *frame = diag_current_frame(env);
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_STACK_ARG,
+		.frame_id = frame->diag_frame_id,
+		.frameno = frame->frameno,
+		.stack_arg_slot = stack_arg_slot,
+	};
+	const char *arg_buf;
+
+	arg_buf = bpf_diag_fmt_buf(env, BPF_DIAG_FMT_BUF_SIZE);
+	if (arg_buf)
+		diag_format_stack_arg((char *)arg_buf, BPF_DIAG_FMT_BUF_SIZE, stack_arg_slot,
+				      arg_name);
+	else
+		arg_buf = "";
+	bpf_diag_header(env, REGISTER_TYPE_SAFETY, "missing stack argument");
+	if (callee_name && *callee_name)
+		diag_reason(
+			env, "Function %s expects %d arguments, but %s is not initialized at this call.",
+			callee_name, nargs, arg_buf);
+	else
+		diag_reason(
+			env, "The callee expects %d arguments, but %s is not initialized at this call.",
+			nargs, arg_buf);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s is not initialized", arg_buf);
+
+	if (stack_arg_slot >= 0)
+		diag_print_history(env, &opts);
+
+	diag_suggestion(
+		env, "Write the outgoing stack argument after any operation that may invalidate stored pointer values, and before making this call.");
+}
+
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true)
 {
 	struct bpf_diag_history_event event = {
@@ -1088,3 +1453,492 @@ void bpf_diag_record_context(struct bpf_verifier_env *env, u32 insn_idx,
 
 	diag_append_history(env, &event);
 }
+
+static int diag_history_context_start_idx(const struct bpf_diag_log *log,
+					  const struct bpf_diag_history_opts *opts)
+{
+	int i;
+
+	if (!opts->ctx_depth)
+		return 0;
+
+	/* Find the most recent outermost entry, or a depth-zero exit. */
+	for (i = log->cnt; i > 0; i--) {
+		const struct bpf_diag_history_event *event;
+
+		event = &log->events[log_pos(log, i - 1)];
+
+		if (event->kind != BPF_DIAG_HISTORY_CONTEXT || event->ctx.kind != opts->ctx_kind)
+			continue;
+
+		if (event->ctx.enter && event->ctx.depth == 1)
+			return i - 1;
+		if (!event->ctx.enter && event->ctx.depth == 0)
+			return 0;
+	}
+
+	return 0;
+}
+
+struct bpf_diag_history_filter {
+	const struct bpf_diag_history_opts *opts;
+	u32 lineage_start;
+	bool lineage_valid;
+};
+
+static bool diag_target_matches(const struct bpf_diag_mod_target *event_target,
+				const struct bpf_diag_mod_target *target)
+{
+	int slot_off;
+
+	if (event_target->frame_id != target->frame_id || event_target->frameno != target->frameno)
+		return false;
+
+	if (event_target->kind == BPF_DIAG_MOD_TARGET_STACK_RANGE &&
+	    target->kind == BPF_DIAG_MOD_TARGET_STACK_SLOT) {
+		slot_off = -(target->spi + 1) * BPF_REG_SIZE;
+		return event_target->range.min_off < slot_off + BPF_REG_SIZE &&
+		       event_target->range.max_off > slot_off;
+	}
+
+	if (event_target->kind != target->kind)
+		return false;
+
+	switch (target->kind) {
+	case BPF_DIAG_MOD_TARGET_REG:
+		return event_target->regno == target->regno;
+	case BPF_DIAG_MOD_TARGET_STACK_ARG:
+		return event_target->stack_arg == target->stack_arg;
+	case BPF_DIAG_MOD_TARGET_STACK_SLOT:
+		return event_target->spi == target->spi;
+	default:
+		return false;
+	}
+}
+
+static void diag_build_lineage(struct bpf_verifier_env *env, struct bpf_diag_log *log,
+			       struct bpf_diag_history_filter *filter)
+{
+	const struct bpf_diag_history_opts *opts = filter->opts;
+	struct bpf_diag_mod_target target;
+	int i;
+
+	for (i = 0; i < log->cnt; i++)
+		log->events[log_pos(log, i)].in_lineage = false;
+
+	if (opts->scope == BPF_DIAG_HISTORY_SCOPE_REG)
+		target = diag_reg_target(opts->frame_id, opts->frameno, opts->regno);
+	else if (opts->scope == BPF_DIAG_HISTORY_SCOPE_STACK_ARG)
+		target = diag_stack_arg_target(opts->frame_id, opts->frameno,
+					       opts->stack_arg_slot);
+	else
+		return;
+
+	/*
+	 * Find the nearest mutation of the active target. A fill or spill changes
+	 * the target to its origin, so the same walk follows register/stack
+	 * lineage recursively until it reaches the write that created the value.
+	 */
+	for (i = log->cnt; i > 0; i--) {
+		struct bpf_diag_history_event *event;
+
+		event = &log->events[log_pos(log, i - 1)];
+		if (event->kind != BPF_DIAG_HISTORY_MOD ||
+		    !diag_target_matches(&event->mod.target, &target))
+			continue;
+
+		event->in_lineage = true;
+		filter->lineage_start = i - 1;
+		filter->lineage_valid = true;
+
+		if (event->mod.origin_valid) {
+			target = event->mod.origin;
+			continue;
+		}
+		if (event->mod.reason != BPF_DIAG_MOD_WRITE &&
+		    event->mod.reason != BPF_DIAG_MOD_SPILL)
+			continue;
+		if (diag_mod_keeps_lineage(env, event))
+			continue;
+		break;
+	}
+}
+
+static int diag_history_start_idx(const struct bpf_diag_log *log,
+				  const struct bpf_diag_history_filter *filter)
+{
+	const struct bpf_diag_history_opts *opts = filter->opts;
+	int i;
+
+	if (opts->scope == BPF_DIAG_HISTORY_SCOPE_CONTEXT)
+		return diag_history_context_start_idx(log, opts);
+	if (filter->lineage_valid)
+		return filter->lineage_start;
+	if (opts->scope != BPF_DIAG_HISTORY_SCOPE_REF)
+		return 0;
+
+	for (i = log->cnt; i > 0; i--) {
+		const struct bpf_diag_history_event *event;
+
+		event = &log->events[log_pos(log, i - 1)];
+		if (event->kind == BPF_DIAG_HISTORY_REF_ACQUIRE &&
+		    event->ref.ref_id == opts->ref_id)
+			return i - 1;
+	}
+
+	return 0;
+}
+
+static bool diag_history_event_visible(const struct bpf_diag_history_event *event,
+				       const struct bpf_diag_history_filter *filter)
+{
+	const struct bpf_diag_history_opts *opts = filter->opts;
+
+	switch (event->kind) {
+	case BPF_DIAG_HISTORY_BRANCH:
+		return true;
+	case BPF_DIAG_HISTORY_MOD:
+		return filter->lineage_valid && event->in_lineage;
+	case BPF_DIAG_HISTORY_REF_ACQUIRE:
+	case BPF_DIAG_HISTORY_REF_RELEASE:
+		return opts->scope == BPF_DIAG_HISTORY_SCOPE_REF &&
+		       event->ref.ref_id == opts->ref_id;
+	case BPF_DIAG_HISTORY_CONTEXT:
+		return opts->scope == BPF_DIAG_HISTORY_SCOPE_CONTEXT &&
+		       event->ctx.kind == opts->ctx_kind;
+	default:
+		return false;
+	}
+}
+
+static const char *diag_s64_bound_name(s64 value)
+{
+	if (value == S64_MIN)
+		return "S64_MIN";
+	if (value == S64_MAX)
+		return "S64_MAX";
+	return NULL;
+}
+
+static const char *diag_u64_bound_name(u64 value)
+{
+	if (value == U64_MAX)
+		return "U64_MAX";
+	return NULL;
+}
+
+static const char *diag_s64_str(struct bpf_verifier_env *env, s64 value)
+{
+	return diag_s64_bound_name(value) ?: bpf_diag_fmt(env, "%lld", value);
+}
+
+static const char *diag_u64_str(struct bpf_verifier_env *env, u64 value)
+{
+	return diag_u64_bound_name(value) ?: bpf_diag_fmt(env, "%llu", value);
+}
+
+static bool diag_cnum64_unknown(struct cnum64 range)
+{
+	return cnum64_smin(range) == S64_MIN && cnum64_smax(range) == S64_MAX &&
+	       cnum64_umin(range) == 0 && cnum64_umax(range) == U64_MAX;
+}
+
+static bool diag_snapshot_unknown(const struct bpf_diag_reg_snapshot *snapshot)
+{
+	return tnum_is_unknown(snapshot->var_off) && diag_cnum64_unknown(snapshot->r64);
+}
+
+static const char *diag_scalar_range(struct bpf_verifier_env *env, struct cnum64 range)
+{
+	return bpf_diag_fmt(env, "signed range [%s, %s], unsigned range [%s, %s]",
+			    diag_s64_str(env, cnum64_smin(range)),
+			    diag_s64_str(env, cnum64_smax(range)),
+			    diag_u64_str(env, cnum64_umin(range)),
+			    diag_u64_str(env, cnum64_umax(range)));
+}
+
+static const char *diag_var_offset(struct bpf_verifier_env *env,
+				   const struct bpf_diag_reg_snapshot *snapshot)
+{
+	if (tnum_is_const(snapshot->var_off))
+		return bpf_diag_fmt(env, "at offset %lld", (s64)snapshot->var_off.value);
+
+	if (diag_snapshot_unknown(snapshot))
+		return bpf_diag_fmt(env, "with unknown offset");
+
+	return bpf_diag_fmt(env,
+			    "with variable offset: known bits %#llx, unknown mask %#llx, %s",
+			    snapshot->var_off.value, snapshot->var_off.mask,
+			    diag_scalar_range(env, snapshot->r64));
+}
+
+static const char *diag_reg_map_name(const struct bpf_map *map)
+{
+	if (!map || !map->name[0])
+		return NULL;
+
+	return map->name;
+}
+
+static const char *diag_reg_snapshot(struct bpf_verifier_env *env,
+				     const struct bpf_diag_reg_snapshot *snapshot)
+{
+	const char *type_name = reg_type_str(env, snapshot->type);
+	const char *offset = diag_var_offset(env, snapshot);
+	const char *btf = snapshot->btf && snapshot->btf_id ?
+			  bpf_diag_fmt_btf_type(env, snapshot->btf, snapshot->btf_id) : NULL;
+	const char *map_name;
+
+	if (snapshot->type == SCALAR_VALUE) {
+		if (tnum_is_const(snapshot->var_off))
+			return bpf_diag_fmt(env, "integer scalar value %lld",
+					    (s64)snapshot->var_off.value);
+		if (diag_snapshot_unknown(snapshot))
+			return bpf_diag_fmt(env, "integer scalar with unknown value");
+		if (cnum64_is_const(snapshot->r64))
+			return bpf_diag_fmt(env, "integer scalar value %lld",
+					    cnum64_smin(snapshot->r64));
+		return bpf_diag_fmt(env, "integer scalar with %s",
+				    diag_scalar_range(env, snapshot->r64));
+	}
+
+	if (snapshot->type == NOT_INIT)
+		return bpf_diag_fmt(env, "uninitialized value");
+
+	if (base_type(snapshot->type) == PTR_TO_CTX)
+		return bpf_diag_fmt(env, "context pointer %s", offset);
+
+	if (base_type(snapshot->type) == PTR_TO_STACK)
+		return bpf_diag_fmt(env, "stack pointer %s", offset);
+
+	if (base_type(snapshot->type) == PTR_TO_MAP_VALUE) {
+		const char *kind = type_may_be_null(snapshot->type) ? "nullable map value" :
+								      "map value";
+
+		map_name = diag_reg_map_name(snapshot->map_ptr);
+		if (map_name)
+			return bpf_diag_fmt(env, "%s from %s %s", kind, map_name, offset);
+		return bpf_diag_fmt(env, "%s %s", kind, offset);
+	}
+
+	if (base_type(snapshot->type) == CONST_PTR_TO_MAP) {
+		map_name = diag_reg_map_name(snapshot->map_ptr);
+		if (map_name)
+			return bpf_diag_fmt(env, "map pointer for map %s", map_name);
+		return bpf_diag_fmt(env, "map pointer");
+	}
+
+	if (type_is_non_owning_ref(snapshot->type)) {
+		if (btf)
+			return bpf_diag_fmt(env, "borrowed allocated object pointer type=%s", btf);
+		return bpf_diag_fmt(env, "borrowed allocated object pointer");
+	}
+
+	if (type_is_ptr_alloc_obj(snapshot->type)) {
+		if (btf)
+			return bpf_diag_fmt(env, "owned allocated object pointer type=%s", btf);
+		return bpf_diag_fmt(env, "owned allocated object pointer");
+	}
+
+	if (base_type(snapshot->type) == PTR_TO_BTF_ID && btf)
+		return bpf_diag_fmt(env, "%s type=%s %s", type_name, btf, offset);
+
+	return bpf_diag_fmt(env, "%s %s", type_name, offset);
+}
+
+static const char *diag_mod_target_desc(struct bpf_verifier_env *env,
+					const struct bpf_diag_mod_target *target)
+{
+	switch (target->kind) {
+	case BPF_DIAG_MOD_TARGET_REG:
+		return bpf_diag_fmt(env, "R%u", target->regno);
+	case BPF_DIAG_MOD_TARGET_STACK_ARG:
+		return bpf_diag_fmt(env, "stack arg%d", diag_stack_argno(target->stack_arg));
+	case BPF_DIAG_MOD_TARGET_STACK_SLOT:
+		return bpf_diag_fmt(env, "stack slot fp%d", -(target->spi + 1) * BPF_REG_SIZE);
+	default:
+		return "value";
+	}
+}
+
+static void diag_print_mod(struct bpf_verifier_env *env, const struct bpf_diag_history_event *event)
+{
+	const struct bpf_diag_mod_target *target = &event->mod.target;
+	const char *target_desc, *reason = NULL, *old, *new;
+	const char *label = "update";
+
+	if (target->kind == BPF_DIAG_MOD_TARGET_STACK_RANGE) {
+		bpf_diag_source(
+			env, event->insn_idx, "invalidated",
+			"variable-offset stack write may affect bytes fp%d through fp%d",
+			target->range.min_off, target->range.max_off - 1);
+		return;
+	}
+
+	old = diag_reg_snapshot(env, &event->mod.old);
+	new = diag_reg_snapshot(env, &event->mod.new);
+	target_desc = diag_mod_target_desc(env, target);
+
+	switch (event->mod.reason) {
+	case BPF_DIAG_MOD_REF_RELEASE:
+		reason = target->kind == BPF_DIAG_MOD_TARGET_REG ? "resource release invalidated "
+								   "this pointer" :
+								   "resource release invalidated "
+								   "this value";
+		break;
+	case BPF_DIAG_MOD_PKT_DATA_CHANGE:
+		reason = "packet data may have moved";
+		break;
+	case BPF_DIAG_MOD_NON_OWN_REF:
+		reason = "leaving the protected region invalidated this borrowed pointer";
+		break;
+	case BPF_DIAG_MOD_CALLER_SAVED:
+		reason = target->kind == BPF_DIAG_MOD_TARGET_STACK_ARG ?
+			 "call invalidated this outgoing stack argument" :
+			 "call invalidated this caller-saved register";
+		break;
+	case BPF_DIAG_MOD_WRITE:
+		if (target->kind == BPF_DIAG_MOD_TARGET_STACK_SLOT)
+			reason = "a later stack write overwrote this spilled value";
+		break;
+	case BPF_DIAG_MOD_SPILL:
+		label = "spilled";
+		break;
+	case BPF_DIAG_MOD_VAR_WRITE:
+	default:
+		break;
+	}
+
+	if (reason) {
+		bpf_diag_source(env, event->insn_idx, "invalidated",
+				"%s: %s; previous value was %s", target_desc, reason, old);
+		return;
+	}
+
+	bpf_diag_source(env, event->insn_idx, label, "%s changed from %s to %s", target_desc,
+			old, new);
+}
+
+static void diag_print_ref_event(struct bpf_verifier_env *env,
+				 const struct bpf_diag_history_event *event)
+{
+	const char *label;
+
+	label = event->kind == BPF_DIAG_HISTORY_REF_ACQUIRE ? "acquired" : "released";
+	bpf_diag_source(env, event->insn_idx, label, "owned resource (id=%u)",
+			event->ref.ref_id);
+}
+
+static const char *diag_context_name(enum bpf_diag_context_kind kind)
+{
+	switch (kind) {
+	case BPF_DIAG_CONTEXT_RCU:
+		return "RCU read lock region";
+	case BPF_DIAG_CONTEXT_PREEMPT:
+		return "non-preemptible region";
+	case BPF_DIAG_CONTEXT_IRQ:
+		return "IRQ-disabled region";
+	case BPF_DIAG_CONTEXT_LOCK:
+		return "lock region";
+	case BPF_DIAG_CONTEXT_NONE:
+	default:
+		return "context";
+	}
+}
+
+static void diag_print_context_event(struct bpf_verifier_env *env,
+				     const struct bpf_diag_history_event *event)
+{
+	bpf_diag_source(env, event->insn_idx, "context", "%s %s; depth is now %u",
+			event->ctx.enter ? "entered" : "left",
+			diag_context_name(event->ctx.kind), event->ctx.depth);
+}
+
+static void diag_print_history(struct bpf_verifier_env *env,
+			       const struct bpf_diag_history_opts *opts)
+{
+	const struct bpf_diag_history_event *event;
+	struct bpf_diag_history_filter filter = {
+		.opts = opts,
+	};
+	struct bpf_diag_log *log;
+	struct diag_fmt_mark mark;
+	bool first = true;
+	int start_idx;
+	u32 i, visible_cnt = 0, visible_idx = 0;
+
+	if (!bpf_diag_enabled(env))
+		return;
+
+	if (!env->diag)
+		return;
+	log = &env->diag->log;
+
+	diag_build_lineage(env, log, &filter);
+
+	start_idx = diag_history_start_idx(log, &filter);
+	for (i = start_idx; i < log->cnt; i++) {
+		event = &log->events[log_pos(log, i)];
+		if (diag_history_event_visible(event, &filter))
+			visible_cnt++;
+	}
+
+	if (!visible_cnt && !log->first_seq && opts->scope == BPF_DIAG_HISTORY_SCOPE_STACK_ARG)
+		return;
+
+	diag_section(env, "Causal path");
+	mark = diag_fmt_save(env);
+	for (i = start_idx; i < log->cnt; i++) {
+		event = &log->events[log_pos(log, i)];
+		if (!diag_history_event_visible(event, &filter))
+			continue;
+
+		diag_fmt_restore(env, mark);
+		if (visible_cnt > BPF_DIAG_HISTORY_RENDER_MAX &&
+		    visible_idx >= BPF_DIAG_HISTORY_RENDER_MAX / 2 &&
+		    visible_idx < visible_cnt - BPF_DIAG_HISTORY_RENDER_MAX / 2) {
+			if (visible_idx++ != BPF_DIAG_HISTORY_RENDER_MAX / 2)
+				continue;
+			if (!first)
+				diag_write(env, "\n");
+			first = false;
+			diag_write(env, "  %u intermediate causal-history events omitted\n",
+				   visible_cnt - BPF_DIAG_HISTORY_RENDER_MAX);
+			continue;
+		}
+		visible_idx++;
+
+		if (!first)
+			diag_write(env, "\n");
+		first = false;
+
+		switch (event->kind) {
+		case BPF_DIAG_HISTORY_BRANCH:
+			bpf_diag_source(env, event->insn_idx, "branch",
+					"took the %s branch of this conditional, goto %s",
+					event->branch.cond_true ? "true" : "false",
+					event->branch.cond_true ? "followed" : "not followed");
+			break;
+		case BPF_DIAG_HISTORY_MOD:
+			diag_print_mod(env, event);
+			break;
+		case BPF_DIAG_HISTORY_REF_ACQUIRE:
+		case BPF_DIAG_HISTORY_REF_RELEASE:
+			diag_print_ref_event(env, event);
+			break;
+		case BPF_DIAG_HISTORY_CONTEXT:
+			diag_print_context_event(env, event);
+			break;
+		default:
+			break;
+		}
+	}
+
+	if (!visible_cnt)
+		diag_write(env, "  no retained diagnostic events on this path\n");
+	if (log->first_seq)
+		diag_write(env, "  %llu older causal-history event%s not retained because diagnostic "
+			   "event storage reached capacity\n",
+			   log->first_seq, log->first_seq == 1 ? "" : "s");
+	diag_fmt_restore(env, mark);
+}
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index ed64776736c6..d2355c46dad1 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -4,6 +4,7 @@
 #ifndef __BPF_DIAGNOSTICS_H
 #define __BPF_DIAGNOSTICS_H
 
+#include <linux/bpf.h>
 #include <linux/compiler_attributes.h>
 #include <linux/stdarg.h>
 #include <linux/types.h>
@@ -32,6 +33,13 @@ enum bpf_diag_context_kind {
 	BPF_DIAG_CONTEXT_LOCK,
 };
 
+enum bpf_diag_invalid_deref_kind {
+	BPF_DIAG_DEREF_SCALAR,
+	BPF_DIAG_DEREF_NULLABLE_PTR,
+	BPF_DIAG_DEREF_MODIFIED_PTR,
+	BPF_DIAG_DEREF_INVALID_PTR,
+};
+
 bool bpf_diag_enabled(const struct bpf_verifier_env *env);
 int bpf_diag_init(struct bpf_verifier_env *env);
 void bpf_diag_init_frame(struct bpf_verifier_env *env, struct bpf_func_state *state);
@@ -40,10 +48,20 @@ const char *bpf_diag_vfmt(struct bpf_verifier_env *env, const char *fmt, va_list
 	__printf(2, 0);
 const char *bpf_diag_fmt(struct bpf_verifier_env *env, const char *fmt, ...) __printf(2, 3);
 const char *bpf_diag_fmt_btf_type(struct bpf_verifier_env *env, const struct btf *btf, u32 type_id);
+const char *bpf_diag_reg_type_plain(struct bpf_verifier_env *env, enum bpf_reg_type type);
 u64 bpf_diag_event_log_save(struct bpf_verifier_env *env);
 void bpf_diag_event_log_restore(struct bpf_verifier_env *env, u64 log_pos);
 u32 bpf_diag_irq_depth(const struct bpf_verifier_state *state);
 void bpf_diag_free(struct bpf_verifier_env *env);
+void bpf_diag_register_type(struct bpf_verifier_env *env, u32 insn_idx, int regno,
+			    const char *problem, const char *reason, const char *suggestion);
+void bpf_diag_invalid_deref(struct bpf_verifier_env *env, u32 insn_idx, int regno,
+			    const char *reg_name, const struct bpf_reg_state *reg,
+			    enum bpf_diag_invalid_deref_kind kind, s64 offset);
+void bpf_diag_unreadable_reg(struct bpf_verifier_env *env, u32 insn_idx, int regno);
+void bpf_diag_stack_arg_uninit(struct bpf_verifier_env *env, u32 insn_idx, int nargs,
+			       int stack_arg_slot, const char *callee_name,
+			       const char *arg_name);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
 			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 1f2a7f480ce3..962eb7b37e6b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3130,6 +3130,7 @@ static int __check_reg_arg(struct bpf_verifier_env *env, struct bpf_reg_state *r
 		/* check whether register used as source operand can be read */
 		if (reg->type == NOT_INIT) {
 			verbose(env, "R%d !read_ok\n", regno);
+			bpf_diag_unreadable_reg(env, env->insn_idx, regno);
 			return -EACCES;
 		}
 		/* We don't need to worry about FP liveness because it's read-only */
@@ -4149,7 +4150,8 @@ static int mark_stack_arg_precision(struct bpf_verifier_env *env, int arg_idx)
 }
 
 static int check_outgoing_stack_args(struct bpf_verifier_env *env, struct bpf_func_state *caller,
-				     int nargs)
+				     int nargs, const char *callee_name, const struct btf *btf,
+				     const struct btf_param *args)
 {
 	int i, spi;
 
@@ -4157,8 +4159,14 @@ static int check_outgoing_stack_args(struct bpf_verifier_env *env, struct bpf_fu
 		spi = i - MAX_BPF_FUNC_REG_ARGS;
 		if (spi >= caller->out_stack_arg_cnt ||
 		    caller->stack_arg_regs[spi].type == NOT_INIT) {
+			const char *arg_name = NULL;
+
+			if (args && args[i].name_off)
+				arg_name = btf_name_by_offset(btf, args[i].name_off);
 			verbose(env, "callee expects %d args, stack arg%d is not initialized\n",
 				nargs, spi + 1);
+			bpf_diag_stack_arg_uninit(env, env->insn_idx, nargs, spi,
+						  callee_name, arg_name);
 			return -EFAULT;
 		}
 	}
@@ -4313,6 +4321,9 @@ static int __check_ptr_off_reg(struct bpf_verifier_env *env,
 	if (!fixed_off_ok && reg->var_off.value != 0) {
 		verbose(env, "dereference of modified %s ptr %s off=%lld disallowed\n",
 			reg_type_str(env, reg->type), reg_arg_name(env, argno), reg->var_off.value);
+		bpf_diag_invalid_deref(env, env->insn_idx, reg_from_argno(argno),
+				       reg_arg_name(env, argno), reg,
+					      BPF_DIAG_DEREF_MODIFIED_PTR, reg->var_off.value);
 		return -EACCES;
 	}
 
@@ -6258,6 +6269,9 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, struct b
 		if (type_may_be_null(reg->type)) {
 			verbose(env, "%s invalid mem access '%s'\n", reg_arg_name(env, argno),
 				reg_type_str(env, reg->type));
+			bpf_diag_invalid_deref(env, insn_idx, reg_from_argno(argno),
+					       reg_arg_name(env, argno), reg,
+						      BPF_DIAG_DEREF_NULLABLE_PTR, 0);
 			return -EACCES;
 		}
 
@@ -6408,8 +6422,16 @@ static int check_mem_access(struct bpf_verifier_env *env, int insn_idx, struct b
 		if (t == BPF_READ && value_regno >= 0)
 			mark_reg_unknown(env, regs, value_regno);
 	} else {
+		enum bpf_diag_invalid_deref_kind kind = BPF_DIAG_DEREF_INVALID_PTR;
+
 		verbose(env, "%s invalid mem access '%s'\n", reg_arg_name(env, argno),
 			reg_type_str(env, reg->type));
+		if (reg->type == SCALAR_VALUE)
+			kind = BPF_DIAG_DEREF_SCALAR;
+		else if (type_may_be_null(reg->type))
+			kind = BPF_DIAG_DEREF_NULLABLE_PTR;
+		bpf_diag_invalid_deref(env, insn_idx, reg_from_argno(argno),
+				       reg_arg_name(env, argno), reg, kind, 0);
 		return -EACCES;
 	}
 
@@ -9297,20 +9319,28 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 	struct bpf_func_state *caller = cur_func(env);
 	struct bpf_verifier_log *log = &env->log;
 	struct ref_obj_desc ref_obj = {};
+	const struct btf_param *args;
+	const struct btf_type *func, *func_proto;
 	u32 i;
 	int ret, err;
 
 	ret = btf_prepare_func_args(env, subprog);
 	if (ret) {
 		if (bpf_in_stack_arg_cnt(sub) > 0) {
-			err = check_outgoing_stack_args(env, caller, sub->arg_cnt);
+			err = check_outgoing_stack_args(env, caller, sub->arg_cnt,
+							bpf_subprog_name(env, subprog),
+							NULL, NULL);
 			if (err)
 				return err;
 		}
 		return ret;
 	}
 
-	ret = check_outgoing_stack_args(env, caller, sub->arg_cnt);
+	func = btf_type_by_id(btf, env->prog->aux->func_info[subprog].type_id);
+	func_proto = btf_type_by_id(btf, func->type);
+	args = btf_params(func_proto);
+	ret = check_outgoing_stack_args(env, caller, sub->arg_cnt,
+					bpf_subprog_name(env, subprog), btf, args);
 	if (ret)
 		return ret;
 
@@ -12191,7 +12221,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 	args = (const struct btf_param *)(meta->func_proto + 1);
 	nargs = btf_type_vlen(meta->func_proto);
 
-	ret = check_outgoing_stack_args(env, caller, nargs);
+	ret = check_outgoing_stack_args(env, caller, nargs, func_name, btf, args);
 	if (ret)
 		return ret;
 
@@ -13872,9 +13902,8 @@ static int sanitize_check_bounds(struct bpf_verifier_env *env,
  * If we return -EACCES, caller may want to try again treating pointer as a
  * scalar.  So we only emit a diagnostic if !env->allow_ptr_leaks.
  */
-static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
-				   struct bpf_insn *insn,
-				   const struct bpf_reg_state *ptr_reg,
+static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env, struct bpf_insn *insn,
+				   u32 ptr_regno, const struct bpf_reg_state *ptr_reg,
 				   const struct bpf_reg_state *off_reg)
 {
 	struct bpf_verifier_state *vstate = env->cur_state;
@@ -13886,6 +13915,7 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 	struct bpf_sanitize_info info = {};
 	u8 opcode = BPF_OP(insn->code);
 	u32 dst = insn->dst_reg;
+	const char *reason;
 	int ret, bounds_ret;
 
 	dst_reg = &regs[dst];
@@ -13909,12 +13939,24 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		verbose(env,
 			"R%d 32-bit pointer arithmetic prohibited\n",
 			dst);
+		reason = bpf_diag_fmt(
+			env, "R%d holds %s. 32-bit ALU operations on pointers discard pointer tracking, so the verifier cannot keep the result as a safe pointer.",
+			ptr_regno, bpf_diag_reg_type_plain(env, ptr_reg->type));
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "32-bit pointer arithmetic", reason,
+			"Use a 64-bit ALU instruction with an allowed, bounded scalar offset.");
 		return -EACCES;
 	}
 
 	if (ptr_reg->type & PTR_MAYBE_NULL) {
 		verbose(env, "R%d pointer arithmetic on %s prohibited, null-check it first\n",
 			dst, reg_type_str(env, ptr_reg->type));
+		reason = bpf_diag_fmt(
+			env, "R%d may be NULL (%s). Pointer arithmetic is allowed only after the program proves the pointer is non-NULL on this path.",
+			ptr_regno, reg_type_str(env, ptr_reg->type));
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "pointer arithmetic before NULL check", reason,
+			"Make sure that a NULL check precedes any arithmetic performed on the pointer.");
 		return -EACCES;
 	}
 
@@ -13944,6 +13986,12 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 	default:
 		verbose(env, "R%d pointer arithmetic on %s prohibited\n",
 			dst, reg_type_str(env, ptr_reg->type));
+		reason = bpf_diag_fmt(
+			env, "R%d holds %s. This pointer kind does not allow offset arithmetic.",
+			ptr_regno, bpf_diag_reg_type_plain(env, ptr_reg->type));
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "pointer arithmetic is not allowed", reason,
+			"Do not change this pointer's offset; use it only in operations accepted for its kind.");
 		return -EACCES;
 	}
 
@@ -13961,9 +14009,25 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 	if (base_type(ptr_reg->type) == PTR_TO_MEM && (ptr_reg->type & PTR_UNTRUSTED))
 		return 0;
 
-	if (!check_reg_sane_offset_scalar(env, off_reg, ptr_reg->type) ||
-	    !check_reg_sane_offset_ptr(env, ptr_reg, ptr_reg->type))
+	if (!check_reg_sane_offset_scalar(env, off_reg, ptr_reg->type)) {
+		reason = bpf_diag_fmt(
+			env, "The scalar offset used with R%d is unbounded or outside the verifier's safe pointer-offset range [-%u, %u].",
+			ptr_regno, BPF_MAX_VAR_OFF, BPF_MAX_VAR_OFF);
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "pointer offset is not safe", reason,
+			"Clamp or bounds-check the scalar offset before applying it to the pointer.");
 		return -EINVAL;
+	}
+	if (!check_reg_sane_offset_ptr(env, ptr_reg, ptr_reg->type)) {
+		reason = bpf_diag_fmt(
+			env, "R%d already has an offset outside the verifier's safe range [-%u, %u] for %s.",
+			ptr_regno, BPF_MAX_VAR_OFF, BPF_MAX_VAR_OFF,
+			bpf_diag_reg_type_plain(env, ptr_reg->type));
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "pointer offset is not safe", reason,
+			"Keep the base pointer within the verifier's allowed offset range before applying more arithmetic.");
+		return -EINVAL;
+	}
 
 	/* pointer types do not carry 32-bit bounds at the moment. */
 	__mark_reg32_unbounded(dst_reg);
@@ -14006,6 +14070,13 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 			/* scalar -= pointer.  Creates an unknown scalar */
 			verbose(env, "R%d tried to subtract pointer from scalar\n",
 				dst);
+			reason = bpf_diag_fmt(
+				env, "This operation subtracts pointer register R%d from scalar register R%d. "
+				"The verifier only tracks pointer-minus-scalar arithmetic for allowed pointer types.",
+				ptr_regno, dst);
+			bpf_diag_register_type(
+				env, env->insn_idx, ptr_regno, "pointer subtracted from scalar", reason,
+				"Keep the pointer as the base; only add or subtract bounded scalars when permitted.");
 			return -EACCES;
 		}
 		/* We don't allow subtraction from FP, because (according to
@@ -14015,6 +14086,12 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		if (ptr_reg->type == PTR_TO_STACK) {
 			verbose(env, "R%d subtraction from stack pointer prohibited\n",
 				dst);
+			reason = bpf_diag_fmt(
+				env, "R%d is a stack pointer. The verifier does not allow BPF_SUB to move stack pointers.",
+				ptr_regno);
+			bpf_diag_register_type(
+				env, env->insn_idx, ptr_regno, "subtraction from stack pointer", reason,
+				"Use addition from R10 to form stack addresses within the tracked stack frame.");
 			return -EACCES;
 		}
 		dst_reg->r64 = cnum64_add(ptr_reg->r64, cnum64_negate(off_reg->r64));
@@ -14040,16 +14117,38 @@ static int adjust_ptr_min_max_vals(struct bpf_verifier_env *env,
 		/* bitwise ops on pointers are troublesome, prohibit. */
 		verbose(env, "R%d bitwise operator %s on pointer prohibited\n",
 			dst, bpf_alu_string[opcode >> 4]);
+		reason = bpf_diag_fmt(
+			env, "R%d holds %s. Bitwise operator %s would destroy the pointer value the verifier is tracking.",
+			ptr_regno, bpf_diag_reg_type_plain(env, ptr_reg->type),
+			bpf_alu_string[opcode >> 4]);
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "bitwise operation on pointer", reason,
+			"Do bitwise operations on scalar values, not on pointer-valued registers.");
 		return -EACCES;
 	default:
 		/* other operators (e.g. MUL,LSH) produce non-pointer results */
 		verbose(env, "R%d pointer arithmetic with %s operator prohibited\n",
 			dst, bpf_alu_string[opcode >> 4]);
+		reason = bpf_diag_fmt(
+			env, "R%d holds %s. Operator %s is not one of the limited pointer arithmetic operations the verifier can track.",
+			ptr_regno, bpf_diag_reg_type_plain(env, ptr_reg->type),
+			bpf_alu_string[opcode >> 4]);
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "invalid pointer arithmetic operator", reason,
+			"Use only verifier-supported addition or subtraction with a bounded scalar offset, or perform this operation on a scalar value.");
 		return -EACCES;
 	}
 
-	if (!check_reg_sane_offset_ptr(env, dst_reg, ptr_reg->type))
+	if (!check_reg_sane_offset_ptr(env, dst_reg, ptr_reg->type)) {
+		reason = bpf_diag_fmt(
+			env, "After this arithmetic, R%d would be outside the verifier's safe offset range [-%u, %u] for %s.",
+			dst, BPF_MAX_VAR_OFF, BPF_MAX_VAR_OFF,
+			bpf_diag_reg_type_plain(env, ptr_reg->type));
+		bpf_diag_register_type(
+			env, env->insn_idx, ptr_regno, "pointer offset is not safe", reason,
+			"Tighten the scalar bounds before the arithmetic so the resulting pointer remains within the allowed range.");
 		return -EINVAL;
+	}
 	reg_bounds_sync(dst_reg);
 	bounds_ret = sanitize_check_bounds(env, insn, dst_reg);
 	if (bounds_ret == -EACCES)
@@ -15021,15 +15120,15 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 				if (err)
 					return err;
 				off_reg = *dst_reg;
-				return adjust_ptr_min_max_vals(env, insn, src_reg, &off_reg);
+				return adjust_ptr_min_max_vals(env, insn, insn->src_reg, src_reg,
+							       &off_reg);
 			}
 		} else if (ptr_reg) {
 			/* pointer += scalar */
 			err = mark_chain_precision(env, insn->src_reg);
 			if (err)
 				return err;
-			return adjust_ptr_min_max_vals(env, insn,
-						       dst_reg, src_reg);
+			return adjust_ptr_min_max_vals(env, insn, insn->dst_reg, dst_reg, src_reg);
 		} else if (dst_reg->precise) {
 			/* if dst_reg is precise, src_reg should be precise as well */
 			err = mark_chain_precision(env, insn->src_reg);
@@ -15044,8 +15143,7 @@ static int adjust_reg_min_max_vals(struct bpf_verifier_env *env,
 		__mark_reg_known(&off_reg, insn->imm);
 		src_reg = &off_reg;
 		if (ptr_reg) /* pointer += K */
-			return adjust_ptr_min_max_vals(env, insn,
-						       ptr_reg, src_reg);
+			return adjust_ptr_min_max_vals(env, insn, insn->dst_reg, ptr_reg, src_reg);
 	}
 
 	/* Got here implies adding two SCALAR_VALUEs */
diff --git a/tools/testing/selftests/bpf/progs/verifier_uninit.c b/tools/testing/selftests/bpf/progs/verifier_uninit.c
index 7718cd7d19ce..691018a46049 100644
--- a/tools/testing/selftests/bpf/progs/verifier_uninit.c
+++ b/tools/testing/selftests/bpf/progs/verifier_uninit.c
@@ -9,6 +9,7 @@
 SEC("socket")
 __description("read uninitialized register")
 __failure __msg("R2 !read_ok")
+__msg("R2 has never been initialized on this path")
 __failure_unpriv
 __naked void read_uninitialized_register(void)
 {

From 2bdc90f5319451d825466375b4c0d7fc1e52c501 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:04 +0200
Subject: [PATCH 09/14] bpf: Report Memory Safety bounds errors

Augment selected memory-range verifier failures with Memory Safety reports
while preserving the existing terse verifier messages for compatibility.

Cover stack spill corruption, uninitialized stack reads, variable stack helper
accesses, and check_mem_region_access() range-proof failures. The bounds report
spells out the required offset + access_size <= object_size proof with concrete
values and uses scoped diagnostic history for causal context.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-10-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c | 78 ++++++++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h |  6 ++++
 kernel/bpf/verifier.c    | 78 +++++++++++++++++++++++++++++++++++++---
 3 files changed, 158 insertions(+), 4 deletions(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 02399cad2fb0..058574a1411e 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -8,6 +8,7 @@
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/seq_buf.h>
+#include <linux/overflow.h>
 #include <linux/slab.h>
 #include <linux/stdarg.h>
 #include <linux/string.h>
@@ -16,6 +17,7 @@
 #include "diagnostics.h"
 
 #define REGISTER_TYPE_SAFETY "Register Type Safety"
+#define MEMORY_SAFETY "Memory Safety"
 
 #define BPF_DIAG_TEXT_WIDTH 100
 #define BPF_DIAG_TEXT_INDENT "  "
@@ -1164,6 +1166,18 @@ void bpf_diag_stack_arg_uninit(struct bpf_verifier_env *env, u32 insn_idx, int n
 		env, "Write the outgoing stack argument after any operation that may invalidate stored pointer values, and before making this call.");
 }
 
+void bpf_diag_memory(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		     const char *reason, const char *suggestion)
+{
+	bpf_diag_header(env, MEMORY_SAFETY, problem);
+	diag_reason(env, "%s", reason);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s", problem);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true)
 {
 	struct bpf_diag_history_event event = {
@@ -1657,6 +1671,70 @@ static const char *diag_scalar_range(struct bpf_verifier_env *env, struct cnum64
 			    diag_u64_str(env, cnum64_umax(range)));
 }
 
+const char *bpf_diag_fmt_s64_sum(struct bpf_verifier_env *env, s64 value, int addend)
+{
+	s64 sum;
+
+	if (check_add_overflow(value, (s64)addend, &sum))
+		return bpf_diag_fmt(env, "%lld plus %d (%s)", value, addend,
+				    addend < 0 ? "below S64_MIN" : "above S64_MAX");
+
+	return bpf_diag_fmt(env, "%lld", sum);
+}
+
+static const char *diag_access_offset(struct bpf_verifier_env *env, int off,
+				      const struct bpf_reg_state *reg)
+{
+	if (tnum_is_const(reg->var_off))
+		return bpf_diag_fmt(env, "constant %s",
+				    bpf_diag_fmt_s64_sum(env, (s64)reg->var_off.value, off));
+
+	if (tnum_is_unknown(reg->var_off) && diag_cnum64_unknown(reg->r64))
+		return bpf_diag_fmt(env, "unbounded");
+
+	if (off)
+		return bpf_diag_fmt(env,
+			"variable: known bits %#llx, unknown mask %#llx, plus fixed offset %d; %s",
+			(u64)reg->var_off.value, reg->var_off.mask, off,
+			diag_scalar_range(env, reg->r64));
+	return bpf_diag_fmt(env, "variable: known bits %#llx, unknown mask %#llx; %s",
+			    (u64)reg->var_off.value, reg->var_off.mask,
+			    diag_scalar_range(env, reg->r64));
+}
+
+void bpf_diag_mem_bounds(struct bpf_verifier_env *env, u32 insn_idx, int regno,
+			 const char *reg_name, const char *type_name, const char *proof,
+			 int off, int size, u32 mem_size, const struct bpf_reg_state *reg)
+{
+	const struct bpf_func_state *frame = diag_current_frame(env);
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_REG,
+		.frame_id = frame->diag_frame_id,
+		.frameno = frame->frameno,
+		.regno = regno,
+	};
+	const char *offset_desc;
+
+	if (!bpf_diag_enabled(env))
+		return;
+
+	offset_desc = diag_access_offset(env, off, reg);
+
+	bpf_diag_header(env, MEMORY_SAFETY, "access outside bounds");
+	diag_reason(
+		env, "The verifier cannot prove offset + access_size <= object_size. Here, %s. %s is %s; offset is %s; access_size is %d; object_size is %u.",
+		proof, reg_name, type_name, offset_desc, size, mem_size);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "access may be outside object bounds");
+
+	if (regno >= 0)
+		diag_print_history(env, &opts);
+
+	diag_suggestion(
+		env, "Add or adjust a bounds check that proves offset + access_size stays within the object.");
+}
+
 static const char *diag_var_offset(struct bpf_verifier_env *env,
 				   const struct bpf_diag_reg_snapshot *snapshot)
 {
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index d2355c46dad1..b5feda71de3e 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -15,6 +15,7 @@ struct bpf_verifier_env;
 struct bpf_verifier_state;
 struct btf;
 
+const char *bpf_diag_fmt_s64_sum(struct bpf_verifier_env *env, s64 value, int addend);
 enum bpf_diag_mod_reason {
 	BPF_DIAG_MOD_WRITE,
 	BPF_DIAG_MOD_SPILL,
@@ -62,6 +63,11 @@ void bpf_diag_unreadable_reg(struct bpf_verifier_env *env, u32 insn_idx, int reg
 void bpf_diag_stack_arg_uninit(struct bpf_verifier_env *env, u32 insn_idx, int nargs,
 			       int stack_arg_slot, const char *callee_name,
 			       const char *arg_name);
+void bpf_diag_memory(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		     const char *reason, const char *suggestion);
+void bpf_diag_mem_bounds(struct bpf_verifier_env *env, u32 insn_idx, int regno,
+			 const char *reg_name, const char *type_name, const char *proof,
+			 int off, int size, u32 mem_size, const struct bpf_reg_state *reg);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
 			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 962eb7b37e6b..86c4212de5aa 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3470,7 +3470,16 @@ static int check_stack_write_fixed_off(struct bpf_verifier_env *env,
 	    bpf_is_spilled_reg(&state->stack[spi]) &&
 	    !bpf_is_spilled_scalar_reg(&state->stack[spi]) &&
 	    size != BPF_REG_SIZE) {
+		const char *reason;
+
 		verbose(env, "attempt to corrupt spilled pointer on stack\n");
+		reason = bpf_diag_fmt(env,
+				      "This store writes %d bytes at stack offset %d into a stack slot that currently holds a spilled pointer. "
+			"Partial writes to spilled pointers are rejected because they can corrupt pointer metadata and leak kernel pointers.",
+			size, off);
+		bpf_diag_memory(
+			env, insn_idx, "stack spill corruption", reason,
+			"Write the full 8-byte spilled pointer slot, or use a separate stack slot for scalar data before overwriting only part of it.");
 		return -EACCES;
 	}
 
@@ -3762,6 +3771,21 @@ static int mark_reg_stack_read(struct bpf_verifier_env *env,
 	return 0;
 }
 
+static void bpf_diag_stack_read_uninit(struct bpf_verifier_env *env, int off, int i,
+				       int size)
+{
+	const char *reason;
+
+	reason = bpf_diag_fmt(env,
+			      "This rejected read uses %d bytes at stack offset %d, but byte %d in that range is uninitialized on this path. "
+		"Programs loaded with CAP_PERFMON can be allowed to read uninitialized stack bytes, but this program is being rejected without that allowance.",
+		size, off, i);
+	bpf_diag_memory(
+		env, env->insn_idx, "uninitialized stack read", reason,
+		"Initialize every byte in the stack range before reading it, adjust the offset and size so the read covers only initialized bytes, "
+		"or load with CAP_PERFMON if uninitialized stack reads are intended.");
+}
+
 /* Read the stack at 'off' and put the results into the register indicated by
  * 'dst_regno'. It handles reg filling if the addressed stack slot is a
  * spilled reg.
@@ -3851,6 +3875,7 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
 					} else {
 						verbose(env, "invalid read from stack off %d+%d size %d\n",
 							off, i, size);
+						bpf_diag_stack_read_uninit(env, off, i, size);
 					}
 					return -EACCES;
 				}
@@ -3909,6 +3934,7 @@ static int check_stack_read_fixed_off(struct bpf_verifier_env *env,
 			} else {
 				verbose(env, "invalid read from stack off %d+%d size %d\n",
 					off, i, size);
+				bpf_diag_stack_read_uninit(env, off, i, size);
 			}
 			return -EACCES;
 		}
@@ -4001,11 +4027,19 @@ static int check_stack_read(struct bpf_verifier_env *env,
 	 * check_stack_read_fixed_off).
 	 */
 	if (dst_regno < 0 && var_off) {
+		const char *reason;
 		char tn_buf[48];
 
 		tnum_strn(tn_buf, sizeof(tn_buf), reg->var_off);
 		verbose(env, "variable offset stack pointer cannot be passed into helper function; var_off=%s off=%d size=%d\n",
 			tn_buf, off, size);
+		reason = bpf_diag_fmt(env,
+				      "The helper would access the stack through variable offset %s plus fixed offset %d and size %d. "
+			"Helper stack memory arguments require a constant stack offset and a precise initialized range.",
+			tn_buf, off, size);
+		bpf_diag_memory(
+			env, env->insn_idx, "variable stack access", reason,
+			"Use a fixed stack offset for helper memory arguments, or copy the needed bytes into a fixed stack slot first.");
 		return -EACCES;
 	}
 	/* Variable offset is prohibited for unprivileged mode for simplicity
@@ -4247,6 +4281,9 @@ static int check_mem_region_access(struct bpf_verifier_env *env, struct bpf_reg_
 				   int off, int size, u32 mem_size,
 				   bool zero_size_allowed)
 {
+	const char *proof = "";
+	const char *start;
+	s64 max_start, max_end;
 	int err;
 
 	/* We may have adjusted the register pointing to memory region, so we
@@ -4265,14 +4302,28 @@ static int check_mem_region_access(struct bpf_verifier_env *env, struct bpf_reg_
 	      reg_smin(reg) + off < 0)) {
 		verbose(env, "%s min value is negative, either use unsigned index or do a if (index >=0) check.\n",
 			reg_arg_name(env, argno));
-		return -EACCES;
+		err = -EACCES;
+		if (bpf_diag_enabled(env)) {
+			start = bpf_diag_fmt_s64_sum(env, reg_smin(reg), off);
+			proof = bpf_diag_fmt(
+				env, "the minimal bound for a memory access is a negative value: %s",
+				start);
+		}
+		goto report_error;
 	}
+
 	err = __check_mem_access(env, reg, argno, reg_smin(reg) + off, size,
 				 mem_size, zero_size_allowed);
 	if (err) {
 		verbose(env, "%s min value is outside of the allowed memory range\n",
 			reg_arg_name(env, argno));
-		return err;
+		if (bpf_diag_enabled(env)) {
+			start = bpf_diag_fmt_s64_sum(env, reg_smin(reg), off);
+			proof = bpf_diag_fmt(
+				env, "the minimal bound for a memory access is %s and is outside of the object of size %u",
+				start, mem_size);
+		}
+		goto report_error;
 	}
 
 	/* If we haven't set a max value then we need to bail since we can't be
@@ -4282,17 +4333,36 @@ static int check_mem_region_access(struct bpf_verifier_env *env, struct bpf_reg_
 	if (reg_umax(reg) >= BPF_MAX_VAR_OFF) {
 		verbose(env, "%s unbounded memory access, make sure to bounds check any such access\n",
 			reg_arg_name(env, argno));
-		return -EACCES;
+		err = -EACCES;
+		if (bpf_diag_enabled(env))
+			proof = bpf_diag_fmt(
+				env, "the maximal bound for a memory access is %llu and exceeds maximum allowed offset of %u",
+				reg_umax(reg), BPF_MAX_VAR_OFF);
+		goto report_error;
 	}
+
 	err = __check_mem_access(env, reg, argno, reg_umax(reg) + off, size,
 				 mem_size, zero_size_allowed);
 	if (err) {
 		verbose(env, "%s max value is outside of the allowed memory range\n",
 			reg_arg_name(env, argno));
-		return err;
+		if (bpf_diag_enabled(env)) {
+			max_start = (s64)reg_umax(reg) + off;
+			max_end = max_start + size;
+			proof = bpf_diag_fmt(
+				env, "the maximal bound for a memory access is %lld: start %lld + access_size %d, beyond object_size %u",
+				max_end, max_start, size, mem_size);
+		}
+		goto report_error;
 	}
 
 	return 0;
+
+report_error:
+	bpf_diag_mem_bounds(env, env->insn_idx, reg_from_argno(argno),
+			    reg_arg_name(env, argno), reg_type_str(env, reg->type), proof,
+			    off, size, mem_size, reg);
+	return err;
 }
 
 static int __check_ptr_off_reg(struct bpf_verifier_env *env,

From 5d5764627555f6beda39bc03af56428dec0c4582 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:05 +0200
Subject: [PATCH 10/14] bpf: Report Resource Lifetime reference leaks

Augment selected Resource Lifetime Safety failures with structured diagnostics
while preserving the existing verifier messages.

Report unreleased references from check_reference_leak() using
reference-scoped diagnostic history, and add state reports for dynptr,
iterator, lock, and IRQ-flag lifetime misuse.

IRQ restore mismatch and out-of-order diagnostics use IRQ context-scoped
history when an IRQ-disabled region is active, so retained save/restore context
is still visible after per-state history removal.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-11-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c |  91 ++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.h |   9 ++++
 kernel/bpf/verifier.c    | 103 ++++++++++++++++++++++++++++++++++++---
 3 files changed, 195 insertions(+), 8 deletions(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 058574a1411e..5d20ea9e470e 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -18,6 +18,7 @@
 
 #define REGISTER_TYPE_SAFETY "Register Type Safety"
 #define MEMORY_SAFETY "Memory Safety"
+#define RESOURCE_LIFETIME_SAFETY "Resource Lifetime Safety"
 
 #define BPF_DIAG_TEXT_WIDTH 100
 #define BPF_DIAG_TEXT_INDENT "  "
@@ -1735,6 +1736,96 @@ void bpf_diag_mem_bounds(struct bpf_verifier_env *env, u32 insn_idx, int regno,
 		env, "Add or adjust a bounds check that proves offset + access_size stays within the object.");
 }
 
+static const char *diag_lock_name(const struct bpf_reference_state *lock)
+{
+	switch (lock->type) {
+	case REF_TYPE_LOCK:
+		return "bpf_spin_lock";
+	case REF_TYPE_RES_LOCK:
+		return "resource spin lock";
+	case REF_TYPE_RES_LOCK_IRQ:
+		return "IRQ-saving resource spin lock";
+	default:
+		return "lock";
+	}
+}
+
+static void diag_res_report(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+			    const char *reason)
+{
+	bpf_diag_header(env, RESOURCE_LIFETIME_SAFETY, problem);
+	diag_reason(env, "%s", reason);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s", problem);
+}
+
+void bpf_diag_res(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		  const char *reason, const char *suggestion)
+{
+	diag_res_report(env, insn_idx, problem, reason);
+	diag_suggestion(env, "%s", suggestion);
+}
+
+void bpf_diag_lock(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		   const char *reason, const char *suggestion,
+		   const struct bpf_reference_state *active_lock)
+{
+	diag_res_report(env, insn_idx, problem, reason);
+
+	if (active_lock) {
+		diag_section(env, "Active lock");
+		bpf_diag_source(env, active_lock->insn_idx, "acquired",
+				"active %s has verifier identity %d",
+				diag_lock_name(active_lock), active_lock->id);
+	}
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
+void bpf_diag_irq(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		  const char *reason, const char *suggestion, u32 depth)
+{
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_CONTEXT,
+		.ctx_kind = BPF_DIAG_CONTEXT_IRQ,
+		.ctx_depth = depth,
+	};
+
+	bpf_diag_header(env, RESOURCE_LIFETIME_SAFETY, problem);
+	diag_reason(env, "%s", reason);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s", problem);
+
+	if (depth)
+		diag_print_history(env, &opts);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
+void bpf_diag_leak(struct bpf_verifier_env *env, u32 ref_id, u32 alloc_insn, u32 fail_insn)
+{
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_REF,
+		.ref_id = ref_id,
+	};
+
+	bpf_diag_header(env, RESOURCE_LIFETIME_SAFETY, "unreleased resource");
+	diag_reason(
+		env, "Owned resource (id=%u) was acquired at instruction %u and still needs to be released before this exit path.",
+		ref_id, alloc_insn);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, fail_insn, "error",
+			"owned resource (id=%u) still needs release", ref_id);
+
+	diag_print_history(env, &opts);
+
+	diag_suggestion(
+		env, "Release or transfer ownership of the acquired resource on every path before the program exits.");
+}
+
 static const char *diag_var_offset(struct bpf_verifier_env *env,
 				   const struct bpf_diag_reg_snapshot *snapshot)
 {
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index b5feda71de3e..66dd2bb655b7 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -9,6 +9,7 @@
 #include <linux/stdarg.h>
 #include <linux/types.h>
 
+struct bpf_reference_state;
 struct bpf_func_state;
 struct bpf_reg_state;
 struct bpf_verifier_env;
@@ -68,6 +69,14 @@ void bpf_diag_memory(struct bpf_verifier_env *env, u32 insn_idx, const char *pro
 void bpf_diag_mem_bounds(struct bpf_verifier_env *env, u32 insn_idx, int regno,
 			 const char *reg_name, const char *type_name, const char *proof,
 			 int off, int size, u32 mem_size, const struct bpf_reg_state *reg);
+void bpf_diag_res(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		  const char *reason, const char *suggestion);
+void bpf_diag_lock(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		   const char *reason, const char *suggestion,
+		   const struct bpf_reference_state *active_lock);
+void bpf_diag_irq(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
+		  const char *reason, const char *suggestion, u32 depth);
+void bpf_diag_leak(struct bpf_verifier_env *env, u32 ref_id, u32 alloc_insn, u32 fail_insn);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
 			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 86c4212de5aa..186176973c3c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -816,6 +816,10 @@ static int destroy_if_dynptr_stack_slot(struct bpf_verifier_env *env,
 	if (dynptr_type_referenced(state->stack[spi].spilled_ptr.dynptr.type) &&
 	    dynptr_ref_cnt(env, state->stack[spi].spilled_ptr.parent_id) <= 1) {
 		verbose(env, "cannot overwrite referenced dynptr\n");
+		bpf_diag_res(
+			env, env->insn_idx, "referenced dynptr overwrite",
+			"This stack slot contains a dynptr that owns or protects a referenced resource. Overwriting the last dynptr for that resource would lose the verifier-tracked release path.",
+			"Release or clone the dynptr so another live dynptr still tracks the referenced resource before overwriting this stack slot.");
 		return -EINVAL;
 	}
 
@@ -1098,9 +1102,19 @@ static int unmark_stack_slot_irq_flag(struct bpf_verifier_env *env, struct bpf_r
 	if (st->irq.kfunc_class != kfunc_class) {
 		const char *flag_kfunc = st->irq.kfunc_class == IRQ_NATIVE_KFUNC ? "native" : "lock";
 		const char *used_kfunc = kfunc_class == IRQ_NATIVE_KFUNC ? "native" : "lock";
+		const char *reason;
 
 		verbose(env, "irq flag acquired by %s kfuncs cannot be restored with %s kfuncs\n",
 			flag_kfunc, used_kfunc);
+		reason = bpf_diag_fmt(env,
+				      "This IRQ flag was saved by %s IRQ kfuncs, but the restore call "
+			"belongs to the %s IRQ kfunc family. Save and restore operations "
+			"must use the same family.",
+			flag_kfunc, used_kfunc);
+		bpf_diag_irq(env, env->insn_idx, "IRQ flag restore mismatch", reason,
+			     "Restore the flag with the matching IRQ restore kfunc for the save "
+			     "operation that created it.",
+			     bpf_diag_irq_depth(env->cur_state));
 		return -EINVAL;
 	}
 
@@ -1118,6 +1132,11 @@ static int unmark_stack_slot_irq_flag(struct bpf_verifier_env *env, struct bpf_r
 
 		verbose(env, "cannot restore irq state out of order, expected id=%d acquired at insn_idx=%d\n",
 			env->cur_state->active_irq_id, insn_idx);
+		bpf_diag_irq(env, env->insn_idx, "IRQ flag restore out of order",
+			     "IRQ-disabled regions must be restored in last-in, first-out order, "
+			     "but this restore does not match the currently active IRQ flag.",
+			     "Restore nested IRQ flags in the reverse order they were saved.",
+			     bpf_diag_irq_depth(env->cur_state));
 		return err;
 	}
 
@@ -7183,6 +7202,7 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state
 	bool is_lock = flags & PROCESS_SPIN_LOCK, is_res_lock = flags & PROCESS_RES_LOCK;
 	const char *lock_str = is_res_lock ? "bpf_res_spin" : "bpf_spin";
 	struct bpf_verifier_state *cur = env->cur_state;
+	struct bpf_reference_state *lock;
 	bool is_const = tnum_is_const(reg->var_off);
 	bool is_irq = flags & PROCESS_LOCK_IRQ;
 	u64 val = reg->var_off.value;
@@ -7232,14 +7252,25 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state
 			ptr = btf;
 
 		if (!is_res_lock && cur->active_locks) {
-			if (find_lock_state(env->cur_state, REF_TYPE_LOCK, 0, NULL)) {
+			lock = find_lock_state(cur, REF_TYPE_LOCK, 0, NULL);
+			if (lock) {
 				verbose(env,
 					"Locking two bpf_spin_locks are not allowed\n");
+				bpf_diag_lock(
+					env, env->insn_idx, "nested spin lock",
+					"This path already holds a bpf_spin_lock. The verifier allows only one regular BPF spin lock at a time.",
+					"Unlock the current bpf_spin_lock before taking another one.", lock);
 				return -EINVAL;
 			}
 		} else if (is_res_lock && cur->active_locks) {
-			if (find_lock_state(env->cur_state, REF_TYPE_RES_LOCK | REF_TYPE_RES_LOCK_IRQ, reg->id, ptr)) {
+			lock = find_lock_state(cur, REF_TYPE_RES_LOCK | REF_TYPE_RES_LOCK_IRQ,
+					       reg->id, ptr);
+			if (lock) {
 				verbose(env, "Acquiring the same lock again, AA deadlock detected\n");
+				bpf_diag_lock(
+					env, env->insn_idx, "recursive resource spin lock",
+					"This path already holds the same resource spin lock. Taking it again would deadlock.",
+					"Avoid reacquiring the same resource spin lock before it is unlocked.", lock);
 				return -EINVAL;
 			}
 		}
@@ -7266,6 +7297,10 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state
 
 		if (!cur->active_locks) {
 			verbose(env, "%s_unlock without taking a lock\n", lock_str);
+			bpf_diag_res(
+				env, env->insn_idx, "unlock without lock",
+				"This unlock operation has no matching active lock on the current path.",
+				"Take the matching lock before this unlock, or remove the unmatched unlock path.");
 			return -EINVAL;
 		}
 
@@ -7275,16 +7310,35 @@ static int process_spin_lock(struct bpf_verifier_env *env, struct bpf_reg_state
 			type = REF_TYPE_RES_LOCK;
 		else
 			type = REF_TYPE_LOCK;
-		if (!find_lock_state(cur, type, reg->id, ptr)) {
+
+		lock = find_lock_state(cur, type, reg->id, ptr);
+		if (!lock) {
 			verbose(env, "%s_unlock of different lock\n", lock_str);
+			lock = find_lock_state(cur, REF_TYPE_LOCK_MASK, cur->active_lock_id,
+					       cur->active_lock_ptr);
+			bpf_diag_lock(
+				env, env->insn_idx, "unlock of a different lock",
+				"This unlock does not match any active lock with the same tracked identity on the current path.",
+				"Unlock the same lock object that was most recently acquired.", lock);
 			return -EINVAL;
 		}
 		if (reg->id != cur->active_lock_id || ptr != cur->active_lock_ptr) {
 			verbose(env, "%s_unlock cannot be out of order\n", lock_str);
+			lock = find_lock_state(cur, REF_TYPE_LOCK_MASK, cur->active_lock_id,
+					       cur->active_lock_ptr);
+			bpf_diag_lock(
+				env, env->insn_idx, "unlock out of order",
+				"Locks must be released in last-in, first-out order, but this unlock does not match the currently active lock.",
+				"Release nested locks in the reverse order they were acquired.", lock);
 			return -EINVAL;
 		}
 		if (release_lock_state(env, type, reg->id, ptr)) {
 			verbose(env, "%s_unlock of different lock\n", lock_str);
+			bpf_diag_lock(
+				env, env->insn_idx, "unlock of a different lock",
+				"The verifier could not release a lock state matching this unlock operation.",
+				"Pass the same lock object and lock kind that were used for the matching lock operation.",
+				lock);
 			return -EINVAL;
 		}
 		if (!in_rcu_cs(env))
@@ -7462,6 +7516,10 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat
 
 		if (!is_dynptr_reg_valid_uninit(env, reg)) {
 			verbose(env, "Dynptr has to be an uninitialized dynptr\n");
+			bpf_diag_res(
+				env, insn_idx, "dynptr is already initialized",
+				"This kfunc constructs a dynptr and requires an uninitialized dynptr stack slot, but the selected slot already holds dynptr state.",
+				"Use a fresh stack dynptr slot, or release/destroy the existing dynptr before reusing the slot.");
 			return -EINVAL;
 		}
 
@@ -7478,21 +7536,29 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat
 		/* For the reg->type == PTR_TO_STACK case, bpf_dynptr is never const */
 		if (reg->type == CONST_PTR_TO_DYNPTR && (arg_type & OBJ_RELEASE)) {
 			verbose(env, "CONST_PTR_TO_DYNPTR cannot be released\n");
+			bpf_diag_res(
+				env, insn_idx, "const dynptr release",
+				"This release operation was given a const dynptr. Const dynptr values are verifier-provided views and cannot be released by the program.",
+				"Release only mutable dynptrs that the program initialized or reserved.");
 			return -EINVAL;
 		}
 
 		if (!is_dynptr_reg_valid_init(env, reg)) {
 			verbose(env, "Expected an initialized dynptr as %s\n",
 				reg_arg_name(env, argno));
+			bpf_diag_res(
+				env, insn_idx, "uninitialized dynptr use",
+				"This operation requires an initialized dynptr, but the stack slot does not currently hold a valid dynptr on this path.",
+				"Initialize the dynptr on every path before this call, and avoid overwriting or releasing it before this use.");
 			return -EINVAL;
 		}
 
 		/* Fold modifiers (in this case, OBJ_RELEASE) when checking expected type */
 		if (!is_dynptr_type_expected(env, reg, arg_type & ~OBJ_RELEASE)) {
-			verbose(env,
-				"Expected a dynptr of type %s as %s\n",
-				dynptr_type_str(arg_to_dynptr_type(arg_type)),
-				reg_arg_name(env, argno));
+			enum bpf_dynptr_type expected_type = arg_to_dynptr_type(arg_type);
+
+			verbose(env, "Expected a dynptr of type %s as %s\n",
+				dynptr_type_str(expected_type), reg_arg_name(env, argno));
 			return -EINVAL;
 		}
 
@@ -7579,6 +7645,10 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *
 		if (!is_iter_reg_valid_uninit(env, reg, nr_slots)) {
 			verbose(env, "expected uninitialized iter_%s as %s\n",
 				iter_type_str(meta->btf, btf_id), reg_arg_name(env, argno));
+			bpf_diag_res(
+				env, insn_idx, "iterator is already initialized",
+				"Iterator creation requires an uninitialized iterator stack object, but this stack range already contains iterator state.",
+				"Use a fresh iterator stack slot, or destroy the existing iterator before reusing the slot.");
 			return -EINVAL;
 		}
 
@@ -7603,6 +7673,10 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *
 		case -EINVAL:
 			verbose(env, "expected an initialized iter_%s as %s\n",
 				iter_type_str(meta->btf, btf_id), reg_arg_name(env, argno));
+			bpf_diag_res(
+				env, insn_idx, "uninitialized iterator use",
+				"This iterator operation requires an initialized iterator state object, but the stack range does not contain a live iterator on this path.",
+				"Call the matching iterator new kfunc on every path before calling next or destroy, and do not destroy the iterator before this use.");
 			return err;
 		case -EPROTO:
 			verbose(env, "expected an RCU CS when using %s\n", meta->func_name);
@@ -9475,7 +9549,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 			if (ret)
 				return ret;
 
-			ret = process_dynptr_func(env, reg, argno, -1, arg->arg_type, &ref_obj, NULL);
+			ret = process_dynptr_func(env, reg, argno, env->insn_idx, arg->arg_type,
+						  &ref_obj, NULL);
 			if (ret)
 				return ret;
 		} else if (base_type(arg->arg_type) == ARG_PTR_TO_BTF_ID) {
@@ -10273,6 +10348,7 @@ static int check_reference_leak(struct bpf_verifier_env *env, bool exception_exi
 			continue;
 		verbose(env, "Unreleased reference id=%d alloc_insn=%d\n",
 			state->refs[i].id, state->refs[i].insn_idx);
+		bpf_diag_leak(env, state->refs[i].id, state->refs[i].insn_idx, env->insn_idx);
 		refs_lingering = true;
 	}
 	return refs_lingering ? -EINVAL : 0;
@@ -11823,6 +11899,12 @@ static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state *
 		if (!is_irq_flag_reg_valid_uninit(env, reg)) {
 			verbose(env, "expected uninitialized irq flag as %s\n",
 				reg_arg_name(env, argno));
+			bpf_diag_res(env, env->insn_idx, "IRQ flag is already initialized",
+				     "Saving IRQ state requires an uninitialized stack slot for "
+				     "the IRQ flag, but this slot already contains tracked IRQ "
+				     "flag state.",
+				     "Use a fresh stack slot for this save operation, or restore "
+				     "the existing IRQ flag before reusing the slot.");
 			return -EINVAL;
 		}
 
@@ -11839,6 +11921,11 @@ static int process_irq_flag(struct bpf_verifier_env *env, struct bpf_reg_state *
 		if (err) {
 			verbose(env, "expected an initialized irq flag as %s\n",
 				reg_arg_name(env, argno));
+			bpf_diag_res(env, env->insn_idx, "uninitialized IRQ flag restore",
+				     "Restoring IRQ state requires a stack slot that was "
+				     "initialized by a matching IRQ save operation on this path.",
+				     "Pass the same stack slot that was previously initialized by "
+				     "the matching IRQ save kfunc.");
 			return err;
 		}
 

From 66e2727395dd994e26ace31d331013acc9ce8f2e Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:06 +0200
Subject: [PATCH 11/14] bpf: Report Call Type Safety argument errors

Augment selected helper and kfunc argument-contract failures with Call Type
Safety reports. Keep the existing terse verifier messages and add reason,
source context, causal register or stack-argument history, and targeted
suggestions.

Cover helper register-type mismatch, helper and kfunc non-NULL pointer
requirements, release-helper ownership requirements, scalar and constant kfunc
arguments, trusted and RCU pointer contracts, kfunc memory arguments,
memory/length pairs, refcounted kptrs, constant strings, and IRQ flag stack
arguments.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-12-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c                      |  46 ++
 kernel/bpf/diagnostics.h                      |   3 +
 kernel/bpf/verifier.c                         | 414 +++++++++++++++---
 .../selftests/bpf/progs/verifier_map_in_map.c |   1 +
 4 files changed, 398 insertions(+), 66 deletions(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 5d20ea9e470e..99784d465881 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -19,6 +19,7 @@
 #define REGISTER_TYPE_SAFETY "Register Type Safety"
 #define MEMORY_SAFETY "Memory Safety"
 #define RESOURCE_LIFETIME_SAFETY "Resource Lifetime Safety"
+#define CALL_TYPE_SAFETY "Call Type Safety"
 
 #define BPF_DIAG_TEXT_WIDTH 100
 #define BPF_DIAG_TEXT_INDENT "  "
@@ -983,6 +984,51 @@ static const char *diag_arg_ordinal(int argno)
 	}
 }
 
+void bpf_diag_call_type(struct bpf_verifier_env *env, u32 insn_idx, int argno, int regno,
+			int stack_arg_slot, const char *call_name, const char *arg_name,
+			const char *reason, const char *suggestion)
+{
+	const struct bpf_func_state *frame = diag_current_frame(env);
+	struct bpf_diag_history_opts opts = {
+		.frame_id = frame->diag_frame_id,
+		.frameno = frame->frameno,
+	};
+	const char *ordinal = diag_arg_ordinal(argno);
+	const char *arg_desc;
+	bool print_history = true;
+
+	if (regno >= 0) {
+		opts.scope = BPF_DIAG_HISTORY_SCOPE_REG;
+		opts.regno = regno;
+	} else if (stack_arg_slot >= 0) {
+		opts.scope = BPF_DIAG_HISTORY_SCOPE_STACK_ARG;
+		opts.stack_arg_slot = stack_arg_slot;
+	} else {
+		print_history = false;
+	}
+
+	if (ordinal && arg_name)
+		arg_desc = bpf_diag_fmt(env, "%s argument (%s)", ordinal, arg_name);
+	else if (ordinal)
+		arg_desc = bpf_diag_fmt(env, "%s argument", ordinal);
+	else if (arg_name)
+		arg_desc = bpf_diag_fmt(env, "argument %s", arg_name);
+	else
+		arg_desc = "argument";
+
+	bpf_diag_header(env, CALL_TYPE_SAFETY, "invalid call argument");
+	diag_reason(env, "The %s to %s does not satisfy the verifier contract: %s.",
+		    arg_desc, call_name, reason);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "invalid %s for %s", arg_desc, call_name);
+
+	if (print_history)
+		diag_print_history(env, &opts);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
 void bpf_diag_invalid_deref(struct bpf_verifier_env *env, u32 insn_idx, int regno,
 			    const char *reg_name, const struct bpf_reg_state *reg,
 			    enum bpf_diag_invalid_deref_kind kind, s64 offset)
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index 66dd2bb655b7..4b85a7ad2019 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -77,6 +77,9 @@ void bpf_diag_lock(struct bpf_verifier_env *env, u32 insn_idx, const char *probl
 void bpf_diag_irq(struct bpf_verifier_env *env, u32 insn_idx, const char *problem,
 		  const char *reason, const char *suggestion, u32 depth);
 void bpf_diag_leak(struct bpf_verifier_env *env, u32 ref_id, u32 alloc_insn, u32 fail_insn);
+void bpf_diag_call_type(struct bpf_verifier_env *env, u32 insn_idx, int argno, int regno,
+			int stack_arg_slot, const char *call_name, const char *arg_name,
+			const char *reason, const char *suggestion);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
 			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 186176973c3c..30e48d4b02f9 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -890,26 +890,29 @@ static bool is_dynptr_reg_valid_init(struct bpf_verifier_env *env, struct bpf_re
 	return true;
 }
 
+static enum bpf_dynptr_type dynptr_reg_type(struct bpf_verifier_env *env, struct bpf_reg_state *reg)
+{
+	struct bpf_func_state *state;
+	int spi;
+
+	if (reg->type == CONST_PTR_TO_DYNPTR)
+		return reg->dynptr.type;
+
+	spi = dynptr_get_spi(env, reg);
+	if (spi < 0)
+		return BPF_DYNPTR_TYPE_INVALID;
+	state = bpf_func(env, reg);
+	return state->stack[spi].spilled_ptr.dynptr.type;
+}
+
 static bool is_dynptr_type_expected(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 				    enum bpf_arg_type arg_type)
 {
-	struct bpf_func_state *state = bpf_func(env, reg);
-	enum bpf_dynptr_type dynptr_type;
-	int spi;
-
 	/* ARG_PTR_TO_DYNPTR takes any type of dynptr */
 	if (arg_type == ARG_PTR_TO_DYNPTR)
 		return true;
 
-	dynptr_type = arg_to_dynptr_type(arg_type);
-	if (reg->type == CONST_PTR_TO_DYNPTR) {
-		return reg->dynptr.type == dynptr_type;
-	} else {
-		spi = dynptr_get_spi(env, reg);
-		if (spi < 0)
-			return false;
-		return state->stack[spi].spilled_ptr.dynptr.type == dynptr_type;
-	}
+	return dynptr_reg_type(env, reg) == arg_to_dynptr_type(arg_type);
 }
 
 static void __mark_reg_known_zero(struct bpf_reg_state *reg);
@@ -6923,14 +6926,17 @@ static int check_stack_range_initialized(
 	return 0;
 }
 
-static int check_helper_mem_access(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno,
-				   int access_size, enum bpf_access_type access_type,
-				   bool zero_size_allowed,
-				   struct bpf_call_arg_meta *meta)
+static int check_helper_mem_access(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
+				   argno_t argno, int access_size,
+				   enum bpf_access_type access_type, bool zero_size_allowed,
+				   struct bpf_call_arg_meta *meta, bool *known_memory)
 {
 	struct bpf_reg_state *regs = cur_regs(env);
 	u32 *max_access;
 
+	if (known_memory)
+		*known_memory = true;
+
 	switch (base_type(reg->type)) {
 	case PTR_TO_PACKET:
 	case PTR_TO_PACKET_META:
@@ -7000,6 +7006,8 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, struct bpf_reg_
 		if (zero_size_allowed && access_size == 0 &&
 		    bpf_register_is_null(reg))
 			return 0;
+		if (known_memory && base_type(reg->type) != PTR_TO_CTX)
+			*known_memory = false;
 
 		verbose(env, "%s type=%s ", reg_arg_name(env, argno),
 			reg_type_str(env, reg->type));
@@ -7008,6 +7016,12 @@ static int check_helper_mem_access(struct bpf_verifier_env *env, struct bpf_reg_
 	}
 }
 
+enum bpf_mem_size_failure {
+	BPF_MEM_SIZE_FAIL_NONE,
+	BPF_MEM_SIZE_FAIL_MEMORY,
+	BPF_MEM_SIZE_FAIL_SIZE,
+};
+
 /* verify arguments to helpers or kfuncs consisting of a pointer and an access
  * size.
  *
@@ -7018,10 +7032,14 @@ static int check_mem_size_reg(struct bpf_verifier_env *env,
 			      struct bpf_reg_state *size_reg, argno_t mem_argno,
 			      argno_t size_argno, u32 access_type,
 			      bool zero_size_allowed,
-			      struct bpf_call_arg_meta *meta)
+			      struct bpf_call_arg_meta *meta,
+			      enum bpf_mem_size_failure *failure)
 {
 	int err = 0;
 
+	if (failure)
+		*failure = BPF_MEM_SIZE_FAIL_NONE;
+
 	/* This is used to refine r0 return value bounds for helpers
 	 * that enforce this value as an upper bound on return values.
 	 * See do_refine_retval_range() for helpers that can refine
@@ -7043,27 +7061,32 @@ static int check_mem_size_reg(struct bpf_verifier_env *env,
 	if (reg_smin(size_reg) < 0) {
 		verbose(env, "%s min value is negative, either use unsigned or 'var &= const'\n",
 			reg_arg_name(env, size_argno));
-		return -EACCES;
+		err = -EACCES;
+		goto size_error;
 	}
 
 	if (reg_umin(size_reg) == 0 && !zero_size_allowed) {
 		verbose(env, "%s invalid zero-sized read: u64=[%lld,%lld]\n",
 			reg_arg_name(env, size_argno), reg_umin(size_reg), reg_umax(size_reg));
-		return -EACCES;
+		err = -EACCES;
+		goto size_error;
 	}
 
 	if (reg_umax(size_reg) >= BPF_MAX_VAR_SIZ) {
 		verbose(env, "%s unbounded memory access, use 'var &= const' or 'if (var < const)'\n",
 			reg_arg_name(env, size_argno));
-		return -EACCES;
+		err = -EACCES;
+		goto size_error;
 	}
 
 	if (access_type & BPF_READ)
 		err = check_helper_mem_access(env, mem_reg, mem_argno, reg_umax(size_reg),
-					      BPF_READ, zero_size_allowed, meta);
+					      BPF_READ, zero_size_allowed, meta, NULL);
 	if (!err && access_type & BPF_WRITE)
 		err = check_helper_mem_access(env, mem_reg, mem_argno, reg_umax(size_reg),
-					      BPF_WRITE, zero_size_allowed, meta);
+					      BPF_WRITE, zero_size_allowed, meta, NULL);
+	if (err && failure)
+		*failure = BPF_MEM_SIZE_FAIL_MEMORY;
 
 	if (!err) {
 		int regno = reg_from_argno(size_argno);
@@ -7075,16 +7098,23 @@ static int check_mem_size_reg(struct bpf_verifier_env *env,
 	}
 
 	return err;
+
+size_error:
+	if (failure)
+		*failure = BPF_MEM_SIZE_FAIL_SIZE;
+	return err;
 }
 
 static int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
 			 argno_t argno, u32 mem_size, enum bpf_access_type access_type,
-			 struct bpf_call_arg_meta *meta)
+			 struct bpf_call_arg_meta *meta, bool *known_memory)
 {
 	int size, err = 0;
 
 	if (bpf_register_is_null(reg))
 		return 0;
+	if (known_memory)
+		*known_memory = true;
 
 	if (mem_size > S32_MAX) {
 		verbose(env, "%s memory size %u is too large\n",
@@ -7099,9 +7129,11 @@ static int check_mem_reg(struct bpf_verifier_env *env, struct bpf_reg_state *reg
 	size = (!meta && base_type(reg->type) == PTR_TO_STACK) ? -(int)mem_size : mem_size;
 
 	if (access_type & BPF_READ)
-		err = check_helper_mem_access(env, reg, argno, size, BPF_READ, true, meta);
+		err = check_helper_mem_access(env, reg, argno, size, BPF_READ, true, meta,
+					      known_memory);
 	if (!err && (access_type & BPF_WRITE))
-		err = check_helper_mem_access(env, reg, argno, size, BPF_WRITE, true, meta);
+		err = check_helper_mem_access(env, reg, argno, size, BPF_WRITE, true, meta,
+					      known_memory);
 
 	return err;
 }
@@ -7461,6 +7493,12 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
 	return 0;
 }
 
+static void bpf_diag_call_arg(struct bpf_verifier_env *env, u32 insn_idx, argno_t argno,
+			      const char *call_name, const char *reason, const char *suggestion);
+__printf(6, 7) static void bpf_diag_call_arg_fmt(struct bpf_verifier_env *env, u32 insn_idx,
+						 argno_t argno, const char *call_name,
+						 const char *suggestion, const char *fmt, ...);
+
 /*
  * Validate dynptr arguments for helper, kfunc and subprog.
  *
@@ -7485,7 +7523,8 @@ static int process_kptr_func(struct bpf_verifier_env *env, int regno,
  * and checked dynamically during runtime.
  */
 static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_state *reg,
-			       argno_t argno, int insn_idx, enum bpf_arg_type arg_type,
+			       argno_t argno, int insn_idx, const char *call_name,
+			       enum bpf_arg_type arg_type,
 			       struct ref_obj_desc *ref_obj, struct bpf_dynptr_desc *dynptr)
 {
 	int spi, err = 0;
@@ -7494,6 +7533,11 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat
 		verbose(env,
 			"%s expected pointer to stack or const struct bpf_dynptr\n",
 			reg_arg_name(env, argno));
+		bpf_diag_call_arg_fmt(
+			env, insn_idx, argno, call_name,
+			"Pass the address of a stack dynptr object, or use a const dynptr pointer returned by the verifier-supported path.",
+			"a dynptr argument must be a pointer to a dynptr stack slot or a verifier-provided const struct bpf_dynptr, but %s is %s",
+			reg_arg_name(env, argno), bpf_diag_reg_type_plain(env, reg->type));
 		return -EINVAL;
 	}
 
@@ -7556,9 +7600,15 @@ static int process_dynptr_func(struct bpf_verifier_env *env, struct bpf_reg_stat
 		/* Fold modifiers (in this case, OBJ_RELEASE) when checking expected type */
 		if (!is_dynptr_type_expected(env, reg, arg_type & ~OBJ_RELEASE)) {
 			enum bpf_dynptr_type expected_type = arg_to_dynptr_type(arg_type);
+			enum bpf_dynptr_type actual_type = dynptr_reg_type(env, reg);
 
 			verbose(env, "Expected a dynptr of type %s as %s\n",
 				dynptr_type_str(expected_type), reg_arg_name(env, argno));
+			bpf_diag_call_arg_fmt(
+				env, insn_idx, argno, call_name,
+				"Use a dynptr constructor that matches this operation, or call an operation that accepts the dynptr's current type.",
+				"the dynptr is initialized with backing object type %s, but this operation expects dynptr type %s",
+				dynptr_type_str(actual_type), dynptr_type_str(expected_type));
 			return -EINVAL;
 		}
 
@@ -7622,6 +7672,11 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *
 	if (reg->type != PTR_TO_STACK) {
 		verbose(env, "%s expected pointer to an iterator on stack\n",
 			reg_arg_name(env, argno));
+		bpf_diag_call_arg_fmt(
+			env, insn_idx, argno, meta->func_name,
+			"Pass the address of a stack iterator object for iterator new, next, and destroy calls.",
+			"iterator state must live in verifier-tracked stack memory, but %s is %s",
+			reg_arg_name(env, argno), bpf_diag_reg_type_plain(env, reg->type));
 		return -EINVAL;
 	}
 
@@ -7635,6 +7690,10 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *
 	if (btf_id < 0) {
 		verbose(env, "expected valid iter pointer as %s\n",
 			reg_arg_name(env, argno));
+		bpf_diag_call_arg(
+			env, insn_idx, argno, meta->func_name,
+			"the kfunc expects a recognized iterator state pointer, but this argument does not match a valid iterator type",
+			"Pass the exact iterator state type expected by this kfunc.");
 		return -EINVAL;
 	}
 	t = btf_type_by_id(meta->btf, btf_id);
@@ -8099,13 +8158,70 @@ static const struct bpf_reg_types *compatible_reg_types[__BPF_ARG_TYPE_MAX] = {
 	[ARG_PTR_TO_DYNPTR]		= &dynptr_types,
 };
 
+static void bpf_diag_call_arg(struct bpf_verifier_env *env, u32 insn_idx, argno_t argno,
+			      const char *call_name, const char *reason,
+			      const char *suggestion)
+{
+	int arg = arg_from_argno(argno);
+	int regno = reg_from_argno(argno);
+	int stack_slot = -1;
+
+	if (arg < 0 && regno >= BPF_REG_1 && regno <= BPF_REG_5)
+		arg = regno;
+	if (arg > MAX_BPF_FUNC_REG_ARGS)
+		stack_slot = arg - MAX_BPF_FUNC_REG_ARGS - 1;
+
+	bpf_diag_call_type(env, insn_idx, arg, regno, stack_slot,
+			   call_name && *call_name ? call_name : "call",
+			   reg_arg_name(env, argno), reason, suggestion);
+}
+
+static const char *bpf_diag_arg_name(struct bpf_verifier_env *env, argno_t argno)
+{
+	return bpf_diag_fmt(env, "%s", reg_arg_name(env, argno));
+}
+
+__printf(6, 7) static void bpf_diag_call_arg_fmt(struct bpf_verifier_env *env, u32 insn_idx,
+						 argno_t argno, const char *call_name,
+						 const char *suggestion, const char *fmt, ...)
+{
+	const char *reason;
+	va_list args;
+
+	va_start(args, fmt);
+	reason = bpf_diag_vfmt(env, fmt, args);
+	va_end(args);
+
+	bpf_diag_call_arg(env, insn_idx, argno, call_name, reason, suggestion);
+}
+
+static const char *bpf_diag_expected_reg_types(struct bpf_verifier_env *env,
+					       const enum bpf_reg_type *types, int count)
+{
+	size_t len = 0, size = 1;
+	char *buf;
+	int i;
+
+	for (i = 0; i < count; i++)
+		size += strlen(reg_type_str(env, types[i])) + (i ? 2 : 0);
+
+	buf = bpf_diag_fmt_buf(env, size);
+	if (!buf)
+		return "";
+
+	for (i = 0; i < count; i++)
+		len += scnprintf(buf + len, size - len, "%s%s", i ? ", " : "",
+				 reg_type_str(env, types[i]));
+	return buf;
+}
+
 static int check_reg_type(struct bpf_verifier_env *env, struct bpf_reg_state *reg, argno_t argno,
-			  enum bpf_arg_type arg_type,
-			  const u32 *arg_btf_id,
-			  struct bpf_call_arg_meta *meta)
+			  enum bpf_arg_type arg_type, const u32 *arg_btf_id,
+			  struct bpf_call_arg_meta *meta, const char *call_name)
 {
 	enum bpf_reg_type expected, type = reg->type;
 	const struct bpf_reg_types *compatible;
+	const char *actual, *accepted;
 	int i, j, err;
 
 	compatible = compatible_reg_types[base_type(arg_type)];
@@ -8152,6 +8268,12 @@ static int check_reg_type(struct bpf_verifier_env *env, struct bpf_reg_state *re
 	for (j = 0; j + 1 < i; j++)
 		verbose(env, "%s, ", reg_type_str(env, compatible->types[j]));
 	verbose(env, "%s\n", reg_type_str(env, compatible->types[j]));
+	actual = bpf_diag_fmt(env, "%s", reg_type_str(env, reg->type));
+	accepted = bpf_diag_expected_reg_types(env, compatible->types, i);
+	bpf_diag_call_arg_fmt(env, env->insn_idx, argno, call_name,
+			      "Pass a value with one of the accepted pointer or scalar types for this call.",
+			      "it has type %s, but this argument accepts %s",
+			      actual, accepted);
 	return -EACCES;
 
 found:
@@ -8188,6 +8310,10 @@ static int check_reg_type(struct bpf_verifier_env *env, struct bpf_reg_state *re
 		    (!type_may_be_null(arg_type) || arg_type_is_release(arg_type))) {
 			verbose(env, "Possibly NULL pointer passed to helper %s\n",
 				reg_arg_name(env, argno));
+			bpf_diag_call_arg(
+				env, env->insn_idx, argno, call_name,
+				"the pointer may be NULL, but this call requires a non-NULL pointer",
+				"Add a NULL check and make the call only on the non-NULL path.");
 			return -EACCES;
 		}
 
@@ -8574,7 +8700,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	    base_type(arg_type) == ARG_PTR_TO_SPIN_LOCK)
 		arg_btf_id = fn->arg_btf_id[arg];
 
-	err = check_reg_type(env, reg, argno, arg_type, arg_btf_id, meta);
+	err = check_reg_type(env, reg, argno, arg_type, arg_btf_id, meta,
+			     func_id_name(meta->func_id));
 	if (err)
 		return err;
 
@@ -8587,6 +8714,10 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 	    !reg_is_referenced(env, reg) && !bpf_register_is_null(reg)) {
 		verbose(env, "release helper %s expects referenced PTR_TO_BTF_ID passed to %s\n",
 			func_id_name(meta->func_id), reg_arg_name(env, argno));
+		bpf_diag_call_arg(
+			env, insn_idx, argno, func_id_name(meta->func_id),
+			"release helpers require a value that owns a live resource returned by a matching acquire helper",
+			"Pass the resource-owning pointer returned by the matching acquire helper, and avoid calling the release helper after ownership has already been transferred or released.");
 		return -EINVAL;
 	}
 
@@ -8615,7 +8746,8 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 			return -EFAULT;
 		}
 		key_size = meta->map.ptr->key_size;
-		err = check_helper_mem_access(env, reg, argno, key_size, BPF_READ, false, NULL);
+		err = check_helper_mem_access(env, reg, argno, key_size, BPF_READ, false, NULL,
+					      NULL);
 		if (err)
 			return err;
 		if (can_elide_value_nullness(meta->map.ptr)) {
@@ -8652,7 +8784,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 
 		err = check_helper_mem_access(env, reg, argno, meta->map.ptr->value_size,
 					      arg_type & MEM_WRITE ? BPF_WRITE : BPF_READ,
-					      false, meta);
+					      false, meta, NULL);
 		break;
 	case ARG_PTR_TO_PERCPU_BTF_ID:
 		if (!reg->btf_id) {
@@ -8694,7 +8826,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		 */
 		if (arg_type & MEM_FIXED_SIZE) {
 			err = check_mem_reg(env, reg, argno_from_reg(regno), fn->arg_size[arg],
-					    arg_type & MEM_WRITE ? BPF_WRITE : BPF_READ, meta);
+					    arg_type & MEM_WRITE ? BPF_WRITE : BPF_READ, meta, NULL);
 			if (err)
 				return err;
 			if (arg_type & MEM_ALIGNED)
@@ -8705,17 +8837,17 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg,
 		err = check_mem_size_reg(env, reg_state(env, regno - 1), reg,
 					 argno_from_reg(regno - 1), argno,
 					 fn->arg_type[arg - 1] & MEM_WRITE ? BPF_WRITE : BPF_READ,
-					 false, meta);
+					 false, meta, NULL);
 		break;
 	case ARG_MEM_SIZE_OR_ZERO:
 		err = check_mem_size_reg(env, reg_state(env, regno - 1), reg,
 					 argno_from_reg(regno - 1), argno,
 					 fn->arg_type[arg - 1] & MEM_WRITE ? BPF_WRITE : BPF_READ,
-					 true, meta);
+					 true, meta, NULL);
 		break;
 	case ARG_PTR_TO_DYNPTR:
-		err = process_dynptr_func(env, reg, argno, insn_idx, arg_type, &meta->ref_obj,
-					  &meta->dynptr);
+		err = process_dynptr_func(env, reg, argno, insn_idx, func_id_name(meta->func_id),
+					  arg_type, &meta->ref_obj, &meta->dynptr);
 		if (err)
 			return err;
 		break;
@@ -9523,7 +9655,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 			ret = check_func_arg_reg_off(env, reg, argno, ARG_DONTCARE);
 			if (ret < 0)
 				return ret;
-			if (check_mem_reg(env, reg, argno, arg->mem_size, BPF_READ | BPF_WRITE, NULL))
+			if (check_mem_reg(env, reg, argno, arg->mem_size, BPF_READ | BPF_WRITE, NULL,
+					  NULL))
 				return -EINVAL;
 			if (!(arg->arg_type & PTR_MAYBE_NULL) &&
 			    (type_may_be_null(reg->type) || bpf_register_is_null(reg))) {
@@ -9549,7 +9682,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 			if (ret)
 				return ret;
 
-			ret = process_dynptr_func(env, reg, argno, env->insn_idx, arg->arg_type,
+			ret = process_dynptr_func(env, reg, argno, env->insn_idx,
+						  bpf_subprog_name(env, subprog), arg->arg_type,
 						  &ref_obj, NULL);
 			if (ret)
 				return ret;
@@ -9561,7 +9695,8 @@ static int btf_check_func_arg_match(struct bpf_verifier_env *env, int subprog,
 				continue;
 
 			memset(&meta, 0, sizeof(meta)); /* leave func_id as zero */
-			err = check_reg_type(env, reg, argno, arg->arg_type, &arg->btf_id, &meta);
+			err = check_reg_type(env, reg, argno, arg->arg_type, &arg->btf_id, &meta,
+					     bpf_subprog_name(env, subprog));
 			err = err ?: check_func_arg_reg_off(env, reg, argno, arg->arg_type);
 			if (err)
 				return err;
@@ -12392,7 +12527,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 		argno_t argno = argno_from_arg(i + 1);
 		int regno = reg_from_argno(argno);
 		bool btf_id_fixed_off_ok = true;
-		u32 ref_id, type_size;
+		u32 ref_id = args[i].type, type_size;
 		int kf_arg_type = meta->fn->arg_type[i];
 
 		if (is_kfunc_arg_prog_aux(btf, &args[i])) {
@@ -12416,28 +12551,42 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 
 		t = btf_type_skip_modifiers(btf, args[i].type, NULL);
 
-		if (btf_type_is_ptr(t) && (bpf_register_is_null(reg) || type_may_be_null(reg->type)) &&
-		    !type_may_be_null(kf_arg_type)) {
-			verbose(env, "Possibly NULL pointer passed to trusted %s\n",
-				reg_arg_name(env, argno));
-			return -EACCES;
-		}
-
-		if (regno == meta->release_regno && !is_kfunc_arg_dynptr(meta->btf, &args[i]) &&
-		    !reg_is_referenced(env, reg) && !bpf_register_is_null(reg)) {
-			verbose(env, "release kfunc %s expects referenced PTR_TO_BTF_ID passed to %s\n",
-				func_name, reg_arg_name(env, argno));
-			return -EINVAL;
-		}
-
-		if (reg_is_referenced(env, reg))
-			update_ref_obj(&meta->ref_obj, reg);
-
 		if (btf_type_is_ptr(t)) {
 			ref_t = btf_type_skip_modifiers(btf, t->type, &ref_id);
 			ref_tname = btf_name_by_offset(btf, ref_t->name_off);
 		}
 
+		if (btf_type_is_ptr(t) &&
+		    (bpf_register_is_null(reg) || type_may_be_null(reg->type)) &&
+		    !type_may_be_null(kf_arg_type)) {
+			const char *expected_type;
+
+			expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
+			verbose(env, "Possibly NULL pointer passed to trusted %s\n",
+				reg_arg_name(env, argno));
+			bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+					      "Add a NULL check and call the kfunc only on the non-NULL path.",
+					      "the pointer may be NULL, but this kfunc requires a non-NULL pointer to %s",
+					      expected_type);
+			return -EACCES;
+		}
+
+		if (regno == meta->release_regno && !is_kfunc_arg_dynptr(meta->btf, &args[i]) &&
+		    !reg_is_referenced(env, reg) && !bpf_register_is_null(reg)) {
+			const char *expected_type;
+
+			expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
+			verbose(env, "release kfunc %s expects referenced PTR_TO_BTF_ID passed to %s\n",
+				func_name, reg_arg_name(env, argno));
+			bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+					      "Pass the resource-owning pointer returned by the matching acquire kfunc, and avoid calling the release kfunc after ownership has already been transferred or released.",
+					      "release kfuncs require a resource-owning value of type %s returned by a matching acquire kfunc",
+					      expected_type);
+			return -EINVAL;
+		}
+
+		if (reg_is_referenced(env, reg))
+			update_ref_obj(&meta->ref_obj, reg);
 
 		if (bpf_register_is_null(reg) && type_may_be_null(kf_arg_type))
 			continue;
@@ -12498,35 +12647,67 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 		case KF_ARG_CONST:
 			if (reg->type != SCALAR_VALUE) {
 				verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass an integer scalar value for this argument, not a pointer or resource object.",
+						      "the kfunc expects an integer scalar, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 
 			ret = process_const_arg(env, reg, argno, meta);
-			if (ret < 0)
+			if (ret < 0) {
+				if (ret == -EINVAL)
+					bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+							      "Pass a compile-time constant or a value the verifier can prove is constant at this call.",
+							      "the kfunc requires this scalar argument to be a verifier-known constant, but %s is variable on this path",
+							      reg_arg_name(env, argno));
 				return ret;
+			}
 			break;
 		case KF_ARG_ANYTHING:
 			if (reg->type != SCALAR_VALUE) {
 				verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass an integer scalar value for this argument, not a pointer or resource object.",
+						      "the kfunc expects an integer scalar, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 			break;
 		case KF_ARG_CONST_ALLOC_SIZE_OR_ZERO:
 			if (reg->type != SCALAR_VALUE) {
 				verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass an integer scalar value for this argument, not a pointer or resource object.",
+						      "the kfunc expects an integer scalar, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 
 			if (is_kfunc_arg_scalar_with_name(btf, &args[i], "rdonly_buf_size"))
 				meta->r0_rdonly = true;
 			ret = process_const_alloc_mem_size(env, reg, argno, &meta->ret_mem);
-			if (ret < 0)
+			if (ret < 0) {
+				if (ret == -EINVAL)
+					bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+							      "Pass a verifier-known constant size for this kfunc buffer argument.",
+							      "the kfunc uses this argument as a return-buffer size, but %s is invalid or variable on this path",
+							      reg_arg_name(env, argno));
 				return ret;
+			}
 			break;
 		case KF_ARG_PTR_TO_CTX:
 			if (reg->type != PTR_TO_CTX) {
 				verbose(env, "%s expected pointer to ctx, but got %s\n",
 					reg_arg_name(env, argno), reg_type_str(env, reg->type));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass the original program context pointer or preserve it before modifying registers.",
+						      "the kfunc expects a context pointer, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 
@@ -12560,10 +12741,19 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 			} else {
 				verbose(env, "%s expected pointer to allocated object\n",
 					reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass a pointer returned by the matching BPF object allocation path.",
+						      "the kfunc expects an allocated object pointer, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 			if (!reg_is_referenced(env, reg)) {
 				verbose(env, "allocated object must be referenced\n");
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass the owned object pointer before it is released or transferred.",
+						      "the allocated object pointer in %s must still carry verifier-tracked ownership, but this pointer no longer owns a live resource",
+						      reg_arg_name(env, argno));
 				return -EINVAL;
 			}
 			if (meta->btf == btf_vmlinux) {
@@ -12600,8 +12790,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 				dynptr_arg_type |= (unsigned int)get_dynptr_type_flag(parent_type);
 			}
 
-			ret = process_dynptr_func(env, reg, argno, insn_idx, dynptr_arg_type,
-						  &meta->ref_obj, &meta->dynptr);
+			ret = process_dynptr_func(env, reg, argno, insn_idx, func_name,
+						  dynptr_arg_type, &meta->ref_obj, &meta->dynptr);
 			if (ret < 0)
 				return ret;
 			break;
@@ -12716,13 +12906,31 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 				if (!is_trusted_reg(env, reg) ||
 				    bpf_type_has_unsafe_modifiers(reg->type)) {
 					if (!is_kfunc_rcu(meta)) {
+						const char *expected_type;
+
+						expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
 						verbose(env, "%s must be referenced or trusted\n",
 							reg_arg_name(env, argno));
+						bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+								      "Pass a pointer acquired from a verifier-tracked source, or call this kfunc only inside the required protection if it accepts RCU pointers.",
+								      "the kfunc requires a trusted or resource-owning pointer to %s, but %s is %s",
+								      expected_type,
+								      reg_arg_name(env, argno),
+								      bpf_diag_reg_type_plain(env, reg->type));
 						return -EINVAL;
 					}
 					if (!is_rcu_reg(reg)) {
+						const char *expected_type;
+
+						expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
 						verbose(env, "%s must be a rcu pointer\n",
 							reg_arg_name(env, argno));
+						bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+								      "Use this kfunc with a pointer that is valid in an RCU read lock region.",
+								      "the kfunc requires an RCU-protected pointer to %s, but %s is %s",
+								      expected_type,
+								      reg_arg_name(env, argno),
+								      bpf_diag_reg_type_plain(env, reg->type));
 						return -EINVAL;
 					}
 				}
@@ -12735,6 +12943,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 
 			if (!__btf_type_is_scalar_struct(env, meta->btf, ref_t, 0)) {
 				enum bpf_reg_type reg2btf_type = lookup_reg2btf_ids(ref_id);
+				const char *expected_type;
 
 				verbose(env, "%s is %s expected %s %s",
 					reg_arg_name(env, argno), reg_type_str(env, reg->type),
@@ -12742,6 +12951,12 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 				if (reg2btf_type != NOT_INIT)
 					verbose(env, " or %s", reg_type_str(env, reg2btf_type));
 				verbose(env, "\n");
+				expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass a verifier-tracked pointer to the expected kernel object type, not a pointer to stack storage or another memory buffer.",
+						      "the kfunc expects a pointer to %s, but this argument is %s and cannot be used as that kernel object pointer",
+						      expected_type,
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 
@@ -12753,6 +12968,8 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 			fallthrough;
 		case KF_ARG_PTR_TO_MEM:
 			if (kf_arg_type & MEM_FIXED_SIZE) {
+				bool known_memory;
+
 				resolve_ret = btf_resolve_size(btf, ref_t, &type_size);
 				if (IS_ERR(resolve_ret)) {
 					verbose(env, "%s reference type('%s %s') size cannot be determined: %ld\n",
@@ -12760,9 +12977,28 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 						ref_tname, PTR_ERR(resolve_ret));
 					return -EINVAL;
 				}
-				ret = check_mem_reg(env, reg, argno, type_size, BPF_READ | BPF_WRITE, meta);
-				if (ret < 0)
+				ret = check_mem_reg(env, reg, argno, type_size, BPF_READ | BPF_WRITE,
+						    meta, &known_memory);
+				if (ret < 0) {
+					const char *expected_type;
+
+					expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
+					if (known_memory)
+						bpf_diag_call_arg_fmt(
+							env, insn_idx, argno, func_name,
+							"Pass memory with at least the required number of accessible bytes and suitable read and write access.",
+							"the kfunc expects %u bytes of memory for %s, but the verifier cannot prove that %s provides a readable and writable range of that size",
+							type_size, expected_type,
+							bpf_diag_reg_type_plain(env, reg->type));
+					else
+						bpf_diag_call_arg_fmt(
+							env, insn_idx, argno, func_name,
+							"Pass stack, map, context, or other verifier-known memory of the expected type and size, not an integer cast to a pointer.",
+							"the kfunc expects %u bytes of memory for %s, but it is %s and not verifier-known memory",
+							type_size, expected_type,
+							bpf_diag_reg_type_plain(env, reg->type));
 					return ret;
+				}
 			}
 			break;
 		case KF_ARG_CONST_MEM_SIZE:
@@ -12775,9 +13011,15 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 			struct bpf_reg_state *buff_reg = get_func_arg_reg(caller, regs, i - 1);
 			struct bpf_reg_state *size_reg = reg;
 			argno_t buff_argno = argno_from_arg(i);
+			enum bpf_mem_size_failure failure;
 
 			if (reg->type != SCALAR_VALUE) {
 				verbose(env, "%s is not a scalar\n", reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass an integer scalar length for this memory argument.",
+						      "the kfunc expects a scalar memory size, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 
@@ -12785,11 +13027,34 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 				break;
 
 			ret = check_mem_size_reg(env, buff_reg, size_reg, buff_argno, argno,
-						 BPF_READ | BPF_WRITE, true, meta);
+						 BPF_READ | BPF_WRITE, true, meta, &failure);
 			if (ret < 0) {
+				const char *buff_arg, *size_arg;
+
+				buff_arg = bpf_diag_arg_name(env, buff_argno);
+				size_arg = bpf_diag_arg_name(env, argno);
 				verbose(env, "%s and ", reg_arg_name(env, buff_argno));
 				verbose(env, "%s memory, len pair leads to invalid memory access\n",
 					reg_arg_name(env, argno));
+				if (failure == BPF_MEM_SIZE_FAIL_MEMORY) {
+					bpf_diag_call_arg_fmt(env, insn_idx, buff_argno, func_name,
+							      "Pass a stack, map, context, or other verifier-known memory pointer, and keep the paired length within that object.",
+							      "it is the memory pointer in a memory/length pair with %s, but %s does not describe verifier-readable memory for the requested length",
+							      size_arg, buff_arg);
+				} else if (failure == BPF_MEM_SIZE_FAIL_SIZE) {
+					if (reg_smin(size_reg) < 0)
+						bpf_diag_call_arg_fmt(
+							env, insn_idx, argno, func_name,
+							"Constrain the memory size to a non-negative value smaller than BPF_MAX_VAR_SIZ before this call.",
+							"the memory size in %s may be negative because its signed minimum is %lld",
+							size_arg, reg_smin(size_reg));
+					else
+						bpf_diag_call_arg_fmt(
+							env, insn_idx, argno, func_name,
+							"Constrain the memory size to a non-negative value smaller than BPF_MAX_VAR_SIZ before this call.",
+							"the memory size in %s may reach %llu bytes, but variable memory accesses must stay below %u bytes",
+							size_arg, reg_umax(size_reg), BPF_MAX_VAR_SIZ);
+				}
 				return ret;
 			}
 			break;
@@ -12803,8 +13068,15 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 			break;
 		case KF_ARG_PTR_TO_REFCOUNTED_KPTR:
 			if (!type_is_ptr_alloc_obj(reg->type)) {
+				const char *expected_type;
+
+				expected_type = bpf_diag_fmt_btf_type(env, btf, ref_id);
 				verbose(env, "%s is neither owning or non-owning ref\n",
 					reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass a pointer returned by the matching BPF object allocation or lookup operation for this kfunc.",
+						      "the kfunc expects a pointer to BPF-managed refcounted object type %s, but this argument is not such an object pointer",
+						      expected_type);
 				return -EINVAL;
 			}
 			if (!type_is_non_owning_ref(reg->type))
@@ -12829,6 +13101,11 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 			if (reg->type != PTR_TO_MAP_VALUE) {
 				verbose(env, "%s doesn't point to a const string\n",
 					reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass a constant string pointer that the verifier recognizes, such as a string stored in a read-only map value.",
+						      "the kfunc expects a pointer to a constant string stored in verifier-known memory, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 			ret = check_arg_const_str(env, reg, argno);
@@ -12869,6 +13146,11 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me
 			if (reg->type != PTR_TO_STACK) {
 				verbose(env, "%s doesn't point to an irq flag on stack\n",
 					reg_arg_name(env, argno));
+				bpf_diag_call_arg_fmt(env, insn_idx, argno, func_name,
+						      "Pass the same stack slot used by bpf_local_irq_save() or bpf_res_spin_lock_irqsave().",
+						      "the kfunc expects a stack pointer to an IRQ flag slot, but %s is %s",
+						      reg_arg_name(env, argno),
+						      bpf_diag_reg_type_plain(env, reg->type));
 				return -EINVAL;
 			}
 			ret = process_irq_flag(env, reg, argno, meta);
diff --git a/tools/testing/selftests/bpf/progs/verifier_map_in_map.c b/tools/testing/selftests/bpf/progs/verifier_map_in_map.c
index 7918646e5bfc..d3be69a9a755 100644
--- a/tools/testing/selftests/bpf/progs/verifier_map_in_map.c
+++ b/tools/testing/selftests/bpf/progs/verifier_map_in_map.c
@@ -155,6 +155,7 @@ l0_%=:	r0 = 0;						\
 SEC("socket")
 __description("forgot null checking on the inner map pointer")
 __failure __msg("R1 type=map_ptr_or_null expected=map_ptr")
+__msg("map_ptr_or_null, but this argument accepts map_ptr")
 __failure_unpriv
 __naked void on_the_inner_map_pointer(void)
 {

From 99a6a288a82bf00ba0b01e72bf85164e848d1d18 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:07 +0200
Subject: [PATCH 12/14] bpf: Report Execution Context Safety errors

Augment selected sleepability and critical-section failures with Execution
Context Safety reports. Keep the existing verifier messages and add source
context, path history, and suggestions tied to the active context.

Use the context history recorded earlier to anchor causal paths to lock, IRQ,
RCU, and preempt regions instead of unrelated register updates.

Cover global calls while holding a lock, sleepable global function calls,
sleepable helpers, sleepable kfunc calls from disallowed contexts, operations
that exit while a context is still active, and unmatched context exits.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-13-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c | 165 ++++++++++++++++++++++++++++++++++++++-
 kernel/bpf/diagnostics.h |   9 +++
 kernel/bpf/verifier.c    |  44 +++++++++++
 3 files changed, 217 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 99784d465881..c69160f656e9 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -20,6 +20,7 @@
 #define MEMORY_SAFETY "Memory Safety"
 #define RESOURCE_LIFETIME_SAFETY "Resource Lifetime Safety"
 #define CALL_TYPE_SAFETY "Call Type Safety"
+#define EXECUTION_CONTEXT_SAFETY "Execution Context Safety"
 
 #define BPF_DIAG_TEXT_WIDTH 100
 #define BPF_DIAG_TEXT_INDENT "  "
@@ -163,6 +164,7 @@ static void diag_print_history(struct bpf_verifier_env *env,
 			       const struct bpf_diag_history_opts *opts);
 static bool diag_target_matches(const struct bpf_diag_mod_target *event_target,
 				const struct bpf_diag_mod_target *target);
+static const char *diag_context_name(enum bpf_diag_context_kind kind);
 struct disasm_line {
 	char text[DISASM_LINE_LEN];
 	int idx;
@@ -1029,6 +1031,167 @@ void bpf_diag_call_type(struct bpf_verifier_env *env, u32 insn_idx, int argno, i
 	diag_suggestion(env, "%s", suggestion);
 }
 
+static const char *diag_context_constraint(enum bpf_diag_context_kind kind)
+{
+	switch (kind) {
+	case BPF_DIAG_CONTEXT_RCU:
+		return "RCU read-side critical sections cannot call operations that may sleep";
+	case BPF_DIAG_CONTEXT_PREEMPT:
+		return "preemption-disabled code cannot call operations that may sleep";
+	case BPF_DIAG_CONTEXT_IRQ:
+		return "IRQ-disabled code cannot call operations that may sleep";
+	case BPF_DIAG_CONTEXT_LOCK:
+		return "code holding a BPF spin lock cannot call operations that may sleep";
+	case BPF_DIAG_CONTEXT_NONE:
+	default:
+		return NULL;
+	}
+}
+
+static const char *diag_active_context(struct bpf_verifier_env *env, u32 depth,
+				       const char *context)
+{
+	if (depth == 1)
+		return bpf_diag_fmt(env, "an active %s (depth 1)", context);
+	return bpf_diag_fmt(env, "%u active %ss (depth %u)", depth, context, depth);
+}
+
+static u32 diag_context_depth(struct bpf_verifier_env *env, enum bpf_diag_context_kind kind)
+{
+	switch (kind) {
+	case BPF_DIAG_CONTEXT_RCU:
+		return env->cur_state->active_rcu_locks;
+	case BPF_DIAG_CONTEXT_PREEMPT:
+		return env->cur_state->active_preempt_locks;
+	case BPF_DIAG_CONTEXT_IRQ:
+		return bpf_diag_irq_depth(env->cur_state);
+	case BPF_DIAG_CONTEXT_LOCK:
+		return env->cur_state->active_locks;
+	case BPF_DIAG_CONTEXT_NONE:
+	default:
+		return 0;
+	}
+}
+
+void bpf_diag_ctx_forbidden(struct bpf_verifier_env *env, u32 insn_idx,
+			    const char *operation, const char *suggestion)
+{
+	struct bpf_diag_history_opts opts;
+	enum bpf_diag_context_kind ctx_kind;
+	const char *constraint, *context;
+	u32 depth;
+
+	if (env->cur_state->active_rcu_locks)
+		ctx_kind = BPF_DIAG_CONTEXT_RCU;
+	else if (env->cur_state->active_preempt_locks)
+		ctx_kind = BPF_DIAG_CONTEXT_PREEMPT;
+	else if (env->cur_state->active_irq_id)
+		ctx_kind = BPF_DIAG_CONTEXT_IRQ;
+	else if (env->cur_state->active_locks)
+		ctx_kind = BPF_DIAG_CONTEXT_LOCK;
+	else
+		ctx_kind = BPF_DIAG_CONTEXT_NONE;
+
+	depth = diag_context_depth(env, ctx_kind);
+	opts = (struct bpf_diag_history_opts) {
+		.scope = BPF_DIAG_HISTORY_SCOPE_CONTEXT,
+		.ctx_kind = ctx_kind,
+		.ctx_depth = depth,
+	};
+	constraint = diag_context_constraint(ctx_kind);
+	context = diag_context_name(ctx_kind);
+
+	bpf_diag_header(env, EXECUTION_CONTEXT_SAFETY,
+			"operation is not allowed in this context");
+	if (constraint) {
+		if (depth) {
+			diag_reason(
+				env, "The operation %s cannot be used in %s because %s. This path is still inside %s.",
+				operation, context, constraint, diag_active_context(env, depth, context));
+		} else {
+			diag_reason(env, "The operation %s cannot be used in %s because %s.",
+				    operation, context, constraint);
+		}
+	} else {
+		diag_reason(env, "The operation %s cannot be used in %s.", operation,
+			    context);
+	}
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s is not allowed in %s", operation,
+			context);
+
+	if (ctx_kind != BPF_DIAG_CONTEXT_NONE)
+		diag_print_history(env, &opts);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
+void bpf_diag_ctx_active(struct bpf_verifier_env *env, u32 insn_idx, const char *operation,
+			 enum bpf_diag_context_kind ctx_kind, const char *suggestion)
+{
+	u32 depth = diag_context_depth(env, ctx_kind);
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_CONTEXT,
+		.ctx_kind = ctx_kind,
+		.ctx_depth = depth,
+	};
+	const char *context = diag_context_name(ctx_kind);
+
+	bpf_diag_header(env, EXECUTION_CONTEXT_SAFETY,
+			"operation is not allowed in this context");
+	diag_reason(
+		env, "The operation %s cannot be used while this path is still inside %s. Leave the region before this operation.",
+		operation, diag_active_context(env, depth, context));
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s is not allowed before leaving %s",
+			operation, context);
+
+	diag_print_history(env, &opts);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
+void bpf_diag_ctx_required(struct bpf_verifier_env *env, u32 insn_idx, const char *operation,
+			   enum bpf_diag_context_kind ctx_kind, const char *suggestion)
+{
+	const char *context = diag_context_name(ctx_kind);
+
+	bpf_diag_header(env, EXECUTION_CONTEXT_SAFETY, "required context is not active");
+	diag_reason(env, "The operation %s requires an active %s, but this path is outside one.",
+		    operation, context);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s requires %s", operation, context);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
+void bpf_diag_ctx_underflow(struct bpf_verifier_env *env, u32 insn_idx,
+			    const char *operation, enum bpf_diag_context_kind ctx_kind,
+			    const char *suggestion)
+{
+	struct bpf_diag_history_opts opts = {
+		.scope = BPF_DIAG_HISTORY_SCOPE_CONTEXT,
+		.ctx_kind = ctx_kind,
+	};
+	const char *context = diag_context_name(ctx_kind);
+
+	bpf_diag_header(env, EXECUTION_CONTEXT_SAFETY, "unmatched context exit");
+	diag_reason(
+		env, "The operation %s tries to leave %s, but this path has no active %s to leave. The current depth is 0.",
+		operation, context, context);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s has no matching enter on this path",
+			operation);
+
+	diag_print_history(env, &opts);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
 void bpf_diag_invalid_deref(struct bpf_verifier_env *env, u32 insn_idx, int regno,
 			    const char *reg_name, const struct bpf_reg_state *reg,
 			    enum bpf_diag_invalid_deref_kind kind, s64 offset)
@@ -2057,7 +2220,7 @@ static const char *diag_context_name(enum bpf_diag_context_kind kind)
 		return "lock region";
 	case BPF_DIAG_CONTEXT_NONE:
 	default:
-		return "context";
+		return "non-sleepable program";
 	}
 }
 
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index 4b85a7ad2019..95bc654e5b3e 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -80,6 +80,15 @@ void bpf_diag_leak(struct bpf_verifier_env *env, u32 ref_id, u32 alloc_insn, u32
 void bpf_diag_call_type(struct bpf_verifier_env *env, u32 insn_idx, int argno, int regno,
 			int stack_arg_slot, const char *call_name, const char *arg_name,
 			const char *reason, const char *suggestion);
+void bpf_diag_ctx_forbidden(struct bpf_verifier_env *env, u32 insn_idx,
+			    const char *operation, const char *suggestion);
+void bpf_diag_ctx_active(struct bpf_verifier_env *env, u32 insn_idx, const char *operation,
+			 enum bpf_diag_context_kind ctx_kind, const char *suggestion);
+void bpf_diag_ctx_required(struct bpf_verifier_env *env, u32 insn_idx, const char *operation,
+			   enum bpf_diag_context_kind ctx_kind, const char *suggestion);
+void bpf_diag_ctx_underflow(struct bpf_verifier_env *env, u32 insn_idx,
+			    const char *operation, enum bpf_diag_context_kind ctx_kind,
+			    const char *suggestion);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
 			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 30e48d4b02f9..0f126f090a47 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -7739,6 +7739,9 @@ static int process_iter_arg(struct bpf_verifier_env *env, struct bpf_reg_state *
 			return err;
 		case -EPROTO:
 			verbose(env, "expected an RCU CS when using %s\n", meta->func_name);
+			bpf_diag_ctx_required(
+				env, insn_idx, meta->func_name, BPF_DIAG_CONTEXT_RCU,
+				"Wrap iterator use in bpf_rcu_read_lock() and bpf_rcu_read_unlock(), keeping all exit paths balanced.");
 			return err;
 		default:
 			return err;
@@ -9838,17 +9841,24 @@ static int check_func_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		return err;
 	if (bpf_subprog_is_global(env, subprog)) {
 		const char *sub_name = bpf_subprog_name(env, subprog);
+		const char *operation;
 		bool returns_void;
 
 		if (env->cur_state->active_locks) {
 			verbose(env, "global function calls are not allowed while holding a lock,\n"
 				     "use static function instead\n");
+			operation = bpf_diag_fmt(env, "global function %s()", sub_name);
+			bpf_diag_ctx_active(env, *insn_idx, operation, BPF_DIAG_CONTEXT_LOCK,
+					    "Release the lock before calling the global function, or use a static function instead.");
 			return -EINVAL;
 		}
 
 		if (env->subprog_info[subprog].might_sleep && !in_sleepable_context(env)) {
 			verbose(env, "sleepable global function %s() called in %s\n",
 				sub_name, non_sleepable_context_description(env));
+			operation = bpf_diag_fmt(env, "sleepable global function %s()", sub_name);
+			bpf_diag_ctx_forbidden(env, *insn_idx, operation,
+				"Move the call outside the critical section, or use a non-sleepable function.");
 			return -EINVAL;
 		}
 
@@ -10495,6 +10505,8 @@ static int check_resource_leak(struct bpf_verifier_env *env, bool exception_exit
 
 	if (check_lock && env->cur_state->active_locks) {
 		verbose(env, "%s cannot be used inside bpf_spin_lock-ed region\n", prefix);
+		bpf_diag_ctx_active(env, env->insn_idx, prefix, BPF_DIAG_CONTEXT_LOCK,
+				    "Release the BPF spin lock before this operation on every path.");
 		return -EINVAL;
 	}
 
@@ -10506,16 +10518,23 @@ static int check_resource_leak(struct bpf_verifier_env *env, bool exception_exit
 
 	if (check_lock && env->cur_state->active_irq_id) {
 		verbose(env, "%s cannot be used inside bpf_local_irq_save-ed region\n", prefix);
+		bpf_diag_ctx_active(env, env->insn_idx, prefix, BPF_DIAG_CONTEXT_IRQ,
+				    "Restore the saved IRQ state before this operation on every path.");
 		return -EINVAL;
 	}
 
 	if (check_lock && env->cur_state->active_rcu_locks) {
 		verbose(env, "%s cannot be used inside bpf_rcu_read_lock-ed region\n", prefix);
+		bpf_diag_ctx_active(env, env->insn_idx, prefix, BPF_DIAG_CONTEXT_RCU,
+				    "Call bpf_rcu_read_unlock() before this operation on every path.");
 		return -EINVAL;
 	}
 
 	if (check_lock && env->cur_state->active_preempt_locks) {
 		verbose(env, "%s cannot be used inside bpf_preempt_disable-ed region\n", prefix);
+		bpf_diag_ctx_active(
+			env, env->insn_idx, prefix, BPF_DIAG_CONTEXT_PREEMPT,
+			"Call bpf_preempt_enable() before this operation on every path.");
 		return -EINVAL;
 	}
 
@@ -10697,6 +10716,7 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	enum bpf_type_flag ret_flag;
 	struct bpf_reg_state *regs;
 	struct bpf_call_arg_meta meta;
+	const char *operation;
 	int insn_idx = *insn_idx_p;
 	bool changes_data;
 	int i, err, func_id;
@@ -10744,6 +10764,10 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	if (fn->might_sleep && !in_sleepable_context(env)) {
 		verbose(env, "sleepable helper %s#%d in %s\n", func_id_name(func_id), func_id,
 			non_sleepable_context_description(env));
+		operation = bpf_diag_fmt(env, "sleepable helper %s#%d",
+					 func_id_name(func_id), func_id);
+		bpf_diag_ctx_forbidden(env, insn_idx, operation,
+			"Move the helper call outside the critical section, or use a non-sleepable helper.");
 		return -EINVAL;
 	}
 
@@ -13591,6 +13615,7 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	const struct btf_type *t, *ptr_type;
 	struct bpf_call_arg_meta meta;
 	struct bpf_insn_aux_data *insn_aux;
+	const char *operation;
 	int err, insn_idx = *insn_idx_p;
 	u32 i, nargs, ptr_type_id;
 	struct bpf_kfunc_desc *desc;
@@ -13656,6 +13681,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	sleepable = bpf_is_kfunc_sleepable(&meta);
 	if (sleepable && !in_sleepable(env)) {
 		verbose(env, "program must be sleepable to call sleepable kfunc %s\n", func_name);
+		operation = bpf_diag_fmt(env, "sleepable kfunc %s", func_name);
+		bpf_diag_ctx_forbidden(env, insn_idx, operation,
+			"Mark the program sleepable if the program type allows it, or use a non-sleepable kfunc.");
 		return -EACCES;
 	}
 
@@ -13726,6 +13754,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	} else if (rcu_unlock) {
 		if (env->cur_state->active_rcu_locks == 0) {
 			verbose(env, "unmatched rcu read unlock (kernel function %s)\n", func_name);
+			bpf_diag_ctx_underflow(
+				env, insn_idx, func_name, BPF_DIAG_CONTEXT_RCU,
+				"Remove the extra bpf_rcu_read_unlock() call, or ensure this path first enters an RCU read lock region.");
 			return -EINVAL;
 		}
 		env->cur_state->active_rcu_locks--;
@@ -13740,6 +13771,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	} else if (preempt_enable) {
 		if (env->cur_state->active_preempt_locks == 0) {
 			verbose(env, "unmatched attempt to enable preemption (kernel function %s)\n", func_name);
+			bpf_diag_ctx_underflow(
+				env, insn_idx, func_name, BPF_DIAG_CONTEXT_PREEMPT,
+				"Remove the extra bpf_preempt_enable() call, or ensure this path first disables preemption.");
 			return -EINVAL;
 		}
 		env->cur_state->active_preempt_locks--;
@@ -13752,6 +13786,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 	if (sleepable && !in_sleepable_context(env)) {
 		verbose(env, "kernel func %s is sleepable within %s\n",
 			func_name, non_sleepable_context_description(env));
+		operation = bpf_diag_fmt(env, "sleepable kfunc %s", func_name);
+		bpf_diag_ctx_forbidden(env, insn_idx, operation,
+			"Move the kfunc call outside the critical section, or use a non-sleepable kfunc.");
 		return -EACCES;
 	}
 
@@ -13762,6 +13799,9 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 
 	if (is_kfunc_rcu_protected(&meta) && !in_rcu_cs(env)) {
 		verbose(env, "kernel func %s requires RCU critical section protection\n", func_name);
+		bpf_diag_ctx_required(
+			env, insn_idx, func_name, BPF_DIAG_CONTEXT_RCU,
+			"Call this kfunc between bpf_rcu_read_lock() and bpf_rcu_read_unlock(), keeping all exit paths balanced.");
 		return -EACCES;
 	}
 
@@ -18039,6 +18079,10 @@ static int do_check_insn(struct bpf_verifier_env *env, bool *do_print_state)
 				     !kfunc_spin_allowed(env, insn->imm, insn->off))) {
 					verbose(env,
 						"function calls are not allowed while holding a lock\n");
+					bpf_diag_ctx_active(
+						env, env->insn_idx,
+						"function call", BPF_DIAG_CONTEXT_LOCK,
+						"Release the BPF spin lock before making this call, or move the call outside the locked region.");
 					return -EINVAL;
 				}
 			}

From a8f4278353947d019c990a77d574dfd4d1dc9b46 Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:08 +0200
Subject: [PATCH 13/14] bpf: Report Program Structure CFG errors

Augment selected whole-program and subprogram CFG validation failures with
Program Structure reports. These errors are structural rather than
path-dependent, so the reports focus on source and instruction context
instead of causal history.

Cover direct and indirect jumps outside the program or current subprogram,
unprivileged backedges, missing and out-of-range jump tables, targets in the
second half of an ldimm64, unreachable instructions, subprogram fallthrough,
and recursive bpf2bpf call graph edges.

Format long jump-range reasons directly in diagnostics.c, and keep the
fallthrough suggestion aligned with the verifier check by suggesting exit or
explicit jumps.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-14-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/cfg.c         | 35 +++++++++++++++++++++++++++++++++++
 kernel/bpf/diagnostics.c | 19 +++++++++++++++++++
 kernel/bpf/diagnostics.h |  3 +++
 kernel/bpf/verifier.c    | 16 ++++++++++++++++
 4 files changed, 73 insertions(+)

diff --git a/kernel/bpf/cfg.c b/kernel/bpf/cfg.c
index 818f7afac83a..0f13c13f4133 100644
--- a/kernel/bpf/cfg.c
+++ b/kernel/bpf/cfg.c
@@ -5,6 +5,8 @@
 #include <linux/filter.h>
 #include <linux/sort.h>
 
+#include "diagnostics.h"
+
 #define verbose(env, fmt, args...) bpf_verifier_log_write(env, fmt, ##args)
 
 /* non-recursive DFS pseudo code
@@ -112,6 +114,10 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
 	if (w < 0 || w >= env->prog->len) {
 		verbose_linfo(env, t, "%d: ", t);
 		verbose(env, "jump out of range from insn %d to %d\n", t, w);
+		bpf_diag_program_structure(
+			env, t, "jump out of range", "Keep branch targets inside the program.",
+			"Instruction %d jumps to instruction %d, but the program only contains instructions 0 through %d.",
+			t, w, env->prog->len - 1);
 		return -EINVAL;
 	}
 
@@ -135,6 +141,11 @@ static int push_insn(int t, int w, int e, struct bpf_verifier_env *env)
 		verbose_linfo(env, t, "%d: ", t);
 		verbose_linfo(env, w, "%d: ", w);
 		verbose(env, "back-edge from insn %d to %d\n", t, w);
+		bpf_diag_program_structure(
+			env, t, "back-edge is not allowed",
+			"Load with privileges that allow this back-edge, or rewrite the control flow so it does not branch backward.",
+			"Instruction %d branches back to instruction %d. This program is being rejected without the privilege needed for this back-edge.",
+			t, w);
 		return -EINVAL;
 	} else if (insn_state[w] == EXPLORED) {
 		/* forward- or cross-edge */
@@ -315,6 +326,11 @@ static struct bpf_iarray *jt_from_subprog(struct bpf_verifier_env *env,
 
 	if (!jt) {
 		verbose(env, "no jump tables found for subprog starting at %u\n", subprog_start);
+		bpf_diag_program_structure(
+			env, subprog_start, "missing jump table",
+			"Make sure subprograms containing gotox instructions are accompanied by jump tables referencing these subprograms.",
+			"No jump table was found for the subprogram that starts at instruction %u.",
+			subprog_start);
 		return ERR_PTR(-EINVAL);
 	}
 
@@ -342,6 +358,11 @@ create_jt(int t, struct bpf_verifier_env *env)
 		if (jt->items[i] < subprog_start || jt->items[i] >= subprog_end) {
 			verbose(env, "jump table for insn %d points outside of the subprog [%u,%u]\n",
 					t, subprog_start, subprog_end);
+			bpf_diag_program_structure(
+				env, t, "jump table target out of range",
+				"Keep every jump-table target inside the same subprogram.",
+				"The jump table for instruction %d points outside subprogram range [%u,%u).",
+				t, subprog_start, subprog_end);
 			kvfree(jt);
 			return ERR_PTR(-EINVAL);
 		}
@@ -373,6 +394,11 @@ static int visit_gotox_insn(int t, struct bpf_verifier_env *env)
 		w = jt->items[i];
 		if (w < 0 || w >= env->prog->len) {
 			verbose(env, "indirect jump out of range from insn %d to %d\n", t, w);
+			bpf_diag_program_structure(
+				env, t, "indirect jump out of range",
+				"Keep indirect jump targets inside the program.",
+				"Instruction %d can jump indirectly to instruction %d, but the program only contains instructions 0 through %d.",
+				t, w, env->prog->len - 1);
 			return -EINVAL;
 		}
 
@@ -623,12 +649,21 @@ int bpf_check_cfg(struct bpf_verifier_env *env)
 
 		if (insn_state[i] != EXPLORED) {
 			verbose(env, "unreachable insn %d\n", i);
+			bpf_diag_program_structure(
+				env, i, "unreachable instruction",
+				"Remove the unreachable instruction or add valid control flow that reaches it.",
+				"Instruction %d is not reachable from the program entry point.", i);
 			ret = -EINVAL;
 			goto err_free;
 		}
 		if (bpf_is_ldimm64(insn)) {
 			if (insn_state[i + 1] != 0) {
 				verbose(env, "jump into the middle of ldimm64 insn %d\n", i);
+				bpf_diag_program_structure(
+					env, i, "jump into ldimm64 immediate",
+					"Target the first instruction of the ldimm64 pair, or restructure the jump target.",
+					"Control flow reaches the second half of the ldimm64 instruction pair that starts at instruction %d.",
+					i);
 				ret = -EINVAL;
 				goto err_free;
 			}
diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index c69160f656e9..9fc1f8cf7312 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -21,6 +21,7 @@
 #define RESOURCE_LIFETIME_SAFETY "Resource Lifetime Safety"
 #define CALL_TYPE_SAFETY "Call Type Safety"
 #define EXECUTION_CONTEXT_SAFETY "Execution Context Safety"
+#define PROGRAM_STRUCTURE "Program Structure"
 
 #define BPF_DIAG_TEXT_WIDTH 100
 #define BPF_DIAG_TEXT_INDENT "  "
@@ -1192,6 +1193,24 @@ void bpf_diag_ctx_underflow(struct bpf_verifier_env *env, u32 insn_idx,
 	diag_suggestion(env, "%s", suggestion);
 }
 
+void bpf_diag_program_structure(struct bpf_verifier_env *env, u32 insn_idx,
+				const char *problem, const char *suggestion,
+				const char *reason_fmt, ...)
+{
+	va_list args;
+
+	bpf_diag_header(env, PROGRAM_STRUCTURE, problem);
+	diag_section(env, "Reason");
+
+	va_start(args, reason_fmt);
+	diag_vprint_indented(env, reason_fmt, args);
+	va_end(args);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "%s", problem);
+
+	diag_suggestion(env, "%s", suggestion);
+}
 void bpf_diag_invalid_deref(struct bpf_verifier_env *env, u32 insn_idx, int regno,
 			    const char *reg_name, const struct bpf_reg_state *reg,
 			    enum bpf_diag_invalid_deref_kind kind, s64 offset)
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index 95bc654e5b3e..ab082d2d6e37 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -89,6 +89,9 @@ void bpf_diag_ctx_required(struct bpf_verifier_env *env, u32 insn_idx, const cha
 void bpf_diag_ctx_underflow(struct bpf_verifier_env *env, u32 insn_idx,
 			    const char *operation, enum bpf_diag_context_kind ctx_kind,
 			    const char *suggestion);
+void bpf_diag_program_structure(struct bpf_verifier_env *env, u32 insn_idx,
+				const char *problem, const char *suggestion,
+				const char *reason_fmt, ...) __printf(5, 6);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
 			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 0f126f090a47..6a886650cc40 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -3020,6 +3020,12 @@ static int check_subprogs(struct bpf_verifier_env *env)
 		off = i + bpf_jmp_offset(&insn[i]) + 1;
 		if (off < subprog_start || off >= subprog_end) {
 			verbose(env, "jump out of range from insn %d to %d\n", i, off);
+			bpf_diag_program_structure(
+				env, i, "jump out of range",
+				"Keep branch targets within the same subprogram, or use an explicit subprogram call.",
+				"Instruction %d jumps to instruction %d, but subprogram %d only contains instructions %d through %d. "
+				"A branch target must stay inside the same subprogram.",
+				i, off, cur_subprog, subprog_start, subprog_end - 1);
 			return -EINVAL;
 		}
 next:
@@ -3032,6 +3038,11 @@ static int check_subprogs(struct bpf_verifier_env *env)
 			    code != (BPF_JMP32 | BPF_JA) &&
 			    code != (BPF_JMP | BPF_JA)) {
 				verbose(env, "last insn is not an exit or jmp\n");
+				bpf_diag_program_structure(
+					env, i, "subprogram can fall through",
+					"End each subprogram with an exit or an explicit jump that keeps control flow inside the subprogram.",
+					"Subprogram %d reaches its last instruction %d without an exit or jump, so control could continue into the next subprogram.",
+					cur_subprog, i);
 				return -EINVAL;
 			}
 			subprog_start = subprog_end;
@@ -3104,6 +3115,11 @@ static int sort_subprogs_topo(struct bpf_verifier_env *env)
 					verbose(env, "recursive call from %s() to %s()\n",
 						bpf_subprog_name(env, cur),
 						bpf_subprog_name(env, callee));
+					bpf_diag_program_structure(
+						env, idx, "recursive subprogram call",
+						"Rewrite the recursion as an explicit bounded loop, or split the logic so subprogram calls do not form a cycle.",
+						"This bpf2bpf call would make the subprogram call graph recursive. "
+						"The verifier requires a finite, acyclic call graph so it can bound stack depth and analysis.");
 					ret = -EINVAL;
 					goto out;
 				}

From ac545b00ca56368b8acb498107ad4f1d91a5245d Mon Sep 17 00:00:00 2001
From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Date: Sat, 15 Aug 2026 08:46:09 +0200
Subject: [PATCH 14/14] bpf: Report Policy helper and kfunc errors

Augment selected helper and kfunc allowability failures with Policy reports.
These reports explain which requested operation is forbidden and why, without
adding path history for non-path-dependent policy checks.

Cover unprivileged bpf2bpf and kfunc use, helper program-type restrictions,
GPL-only helpers, helper-specific allow callbacks, kfunc allowability, and
destructive kfunc capability checks.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/20260815064612.378577-15-memxor@gmail.com
Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
---
 kernel/bpf/diagnostics.c | 14 ++++++++++++++
 kernel/bpf/diagnostics.h |  2 ++
 kernel/bpf/verifier.c    | 33 ++++++++++++++++++++++++++++++++-
 3 files changed, 48 insertions(+), 1 deletion(-)

diff --git a/kernel/bpf/diagnostics.c b/kernel/bpf/diagnostics.c
index 9fc1f8cf7312..33b7d9e8e2c3 100644
--- a/kernel/bpf/diagnostics.c
+++ b/kernel/bpf/diagnostics.c
@@ -22,6 +22,7 @@
 #define CALL_TYPE_SAFETY "Call Type Safety"
 #define EXECUTION_CONTEXT_SAFETY "Execution Context Safety"
 #define PROGRAM_STRUCTURE "Program Structure"
+#define POLICY "Policy"
 
 #define BPF_DIAG_TEXT_WIDTH 100
 #define BPF_DIAG_TEXT_INDENT "  "
@@ -1211,6 +1212,19 @@ void bpf_diag_program_structure(struct bpf_verifier_env *env, u32 insn_idx,
 
 	diag_suggestion(env, "%s", suggestion);
 }
+
+void bpf_diag_policy(struct bpf_verifier_env *env, u32 insn_idx, const char *operation,
+		     const char *reason, const char *suggestion)
+{
+	bpf_diag_header(env, POLICY, "operation is not allowed");
+	diag_reason(env, "The %s is not allowed: %s.", operation, reason);
+
+	diag_section(env, "At");
+	bpf_diag_source(env, insn_idx, "error", "policy check failed for %s", operation);
+
+	diag_suggestion(env, "%s", suggestion);
+}
+
 void bpf_diag_invalid_deref(struct bpf_verifier_env *env, u32 insn_idx, int regno,
 			    const char *reg_name, const struct bpf_reg_state *reg,
 			    enum bpf_diag_invalid_deref_kind kind, s64 offset)
diff --git a/kernel/bpf/diagnostics.h b/kernel/bpf/diagnostics.h
index ab082d2d6e37..d1b79945008a 100644
--- a/kernel/bpf/diagnostics.h
+++ b/kernel/bpf/diagnostics.h
@@ -92,6 +92,8 @@ void bpf_diag_ctx_underflow(struct bpf_verifier_env *env, u32 insn_idx,
 void bpf_diag_program_structure(struct bpf_verifier_env *env, u32 insn_idx,
 				const char *problem, const char *suggestion,
 				const char *reason_fmt, ...) __printf(5, 6);
+void bpf_diag_policy(struct bpf_verifier_env *env, u32 insn_idx, const char *operation,
+		     const char *reason, const char *suggestion);
 void bpf_diag_record_branch(struct bpf_verifier_env *env, u32 insn_idx, bool cond_true);
 void bpf_diag_mod_begin(struct bpf_verifier_env *env, const struct bpf_reg_state *reg,
 			const struct bpf_reg_state *origin, enum bpf_diag_mod_reason reason);
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 6a886650cc40..0bb7ee95c8bd 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2924,6 +2924,10 @@ static int add_subprogs(struct bpf_verifier_env *env)
 
 		if (!env->bpf_capable) {
 			verbose(env, "loading/calling other bpf or kernel functions are allowed for CAP_BPF and CAP_SYS_ADMIN\n");
+			bpf_diag_policy(
+				env, i, "BPF-to-BPF function call",
+				"loading or calling other BPF functions requires CAP_BPF or CAP_SYS_ADMIN",
+				"Load this program with the required capability, or avoid BPF-to-BPF function calls in unprivileged programs.");
 			return -EPERM;
 		}
 
@@ -2976,6 +2980,10 @@ static int add_kfuncs(struct bpf_verifier_env *env)
 
 		if (!env->bpf_capable) {
 			verbose(env, "loading/calling other bpf or kernel functions are allowed for CAP_BPF and CAP_SYS_ADMIN\n");
+			bpf_diag_policy(
+				env, i, "kernel function call",
+				"calling kernel functions requires CAP_BPF or CAP_SYS_ADMIN",
+				"Load this program with the required capability, or avoid kernel function calls in unprivileged programs.");
 			return -EPERM;
 		}
 
@@ -10748,17 +10756,31 @@ static int check_helper_call(struct bpf_verifier_env *env, struct bpf_insn *insn
 	if (err) {
 		verbose(env, "program of this type cannot use helper %s#%d\n",
 			func_id_name(func_id), func_id);
+		operation = bpf_diag_fmt(env, "helper %s#%d", func_id_name(func_id), func_id);
+		bpf_diag_policy(
+			env, insn_idx, operation, "this program type does not allow the helper",
+			"Use a helper allowed for this program type, or move the logic to a compatible program type.");
 		return err;
 	}
 
 	/* eBPF programs must be GPL compatible to use GPL-ed functions */
 	if (!env->prog->gpl_compatible && fn->gpl_only) {
 		verbose(env, "cannot call GPL-restricted function from non-GPL compatible program\n");
+		operation = bpf_diag_fmt(env, "helper %s#%d", func_id_name(func_id), func_id);
+		bpf_diag_policy(
+			env, insn_idx, operation,
+			"this helper is restricted to GPL-compatible programs",
+			"Use a GPL-compatible license, or replace the helper with one that is available to non-GPL programs.");
 		return -EINVAL;
 	}
 
 	if (fn->allowed && !fn->allowed(env->prog)) {
 		verbose(env, "helper call is not allowed in probe\n");
+		operation = bpf_diag_fmt(env, "helper %s#%d", func_id_name(func_id), func_id);
+		bpf_diag_policy(
+			env, insn_idx, operation,
+			"the helper-specific policy callback rejected this program",
+			"Use the helper only from an allowed attach point or program configuration.");
 		return -EINVAL;
 	}
 
@@ -13643,8 +13665,13 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 		return 0;
 
 	err = bpf_fetch_kfunc_arg_meta(env, insn->imm, insn->off, &meta);
-	if (err == -EACCES && meta.func_name)
+	if (err == -EACCES && meta.func_name) {
 		verbose(env, "calling kernel function %s is not allowed\n", meta.func_name);
+		operation = bpf_diag_fmt(env, "kfunc %s", meta.func_name);
+		bpf_diag_policy(
+			env, insn_idx, operation, "this program cannot call the kfunc",
+			"Use a kfunc allowed for this program type and attach point, or change the program context.");
+	}
 	if (err)
 		return err;
 	desc_btf = meta.btf;
@@ -13691,6 +13718,10 @@ static int check_kfunc_call(struct bpf_verifier_env *env, struct bpf_insn *insn,
 
 	if (is_kfunc_destructive(&meta) && !capable(CAP_SYS_BOOT)) {
 		verbose(env, "destructive kfunc calls require CAP_SYS_BOOT capability\n");
+		operation = bpf_diag_fmt(env, "destructive kfunc %s", meta.func_name);
+		bpf_diag_policy(
+			env, insn_idx, operation, "destructive kfuncs require CAP_SYS_BOOT",
+			"Load the program with CAP_SYS_BOOT, or avoid destructive kfuncs.");
 		return -EACCES;
 	}