From 2e418779a00e0f95bcfe3177c71ea196e0134765 Mon Sep 17 00:00:00 2001 From: Amery Hung Date: Fri, 11 Sep 2026 15:04:06 -0700 Subject: [PATCH] bpf: Consolidate runtime argument type resolution A function argument type can require call-site refinement before register admission. Helpers refine map-value arguments according to the recorded map type, while kfuncs reinterpret a pointer to a scalar-only BTF struct as fixed-size memory when the register does not carry a BTF ID. Add resolve_func_arg_type() as the common entry point. It delegates helper map-value refinement to the existing resolve_map_arg_type(), then handles the kfunc BTF-to-memory fallback. It updates the effective argument type and size consumed by the subsequent checks. Preserve PTR_MAYBE_NULL when changing the base type so later nullability validation observes the BTF contract. Keep OBJ_RELEASE arguments in their original pointer class. The latter is not a bug fix: existing kfunc checking already validates ownership before this resolver. It preserves release metadata for the later shared checking order, where ownership validation follows register admission. Moving the kfunc fallback before admission lets the resulting fixed-size memory argument enter the compatibility check directly. This is another step toward routing both call types through check_func_arg(). Signed-off-by: Amery Hung Link: https://lore.kernel.org/r/20260911220415.1396439-15-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov --- kernel/bpf/verifier.c | 192 ++++++++++++++++++++++++------------------ 1 file changed, 108 insertions(+), 84 deletions(-) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 615a5667e569..4e7230cb5791 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -8196,8 +8196,8 @@ static bool is_kfunc_call(const struct bpf_call_arg_meta *meta, u32 btf_id) } static int resolve_map_arg_type(struct bpf_verifier_env *env, - const struct bpf_call_arg_meta *meta, - enum bpf_arg_type *arg_type) + const struct bpf_call_arg_meta *meta, + enum bpf_arg_type *arg_type) { if (!meta->map.ptr) { /* kernel subsystem misconfigured verifier */ @@ -8225,6 +8225,11 @@ static int resolve_map_arg_type(struct bpf_verifier_env *env, return 0; } +static int resolve_func_arg_type(struct bpf_verifier_env *env, + struct bpf_reg_state *reg, u32 arg, + struct bpf_call_arg_meta *meta, int insn_idx, + enum bpf_arg_type *arg_type, u32 *arg_size); + struct bpf_reg_types { const enum bpf_reg_type types[10]; u32 *btf_id; @@ -8840,6 +8845,7 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, int regno = reg_from_argno(argno); enum bpf_reg_type type = reg->type; const u32 *arg_btf_id = NULL; + u32 arg_size = arg_type & MEM_FIXED_SIZE ? fn->arg_size[arg] : 0; u32 key_size; int err = 0; @@ -8872,11 +8878,9 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, return -EACCES; } - if (base_type(arg_type) == ARG_PTR_TO_MAP_VALUE) { - err = resolve_map_arg_type(env, meta, &arg_type); - if (err) - return err; - } + err = resolve_func_arg_type(env, reg, arg, meta, insn_idx, &arg_type, &arg_size); + if (err) + return err; if (bpf_register_is_null(reg) && type_may_be_null(arg_type)) { /* A NULL register has a SCALAR_VALUE type, so skip @@ -9017,12 +9021,12 @@ static int check_func_arg(struct bpf_verifier_env *env, u32 arg, * next is_mem_size argument below. */ if (arg_type & MEM_FIXED_SIZE) { - err = check_mem_reg(env, reg, argno, fn->arg_size[arg], + err = check_mem_reg(env, reg, argno, arg_size, arg_type & MEM_WRITE ? BPF_WRITE : BPF_READ, meta, NULL); if (err) return err; if (arg_type & MEM_ALIGNED) - err = check_ptr_alignment(env, reg, 0, fn->arg_size[arg], true); + err = check_ptr_alignment(env, reg, 0, arg_size, true); } break; case ARG_MEM_SIZE: @@ -11911,6 +11915,65 @@ static bool btf_type_is_scalar_struct(struct bpf_verifier_env *env, return btf_struct_is_composed_of(env, btf, t, BTF_MEMBER_SCALAR); } +static int resolve_func_arg_type(struct bpf_verifier_env *env, + struct bpf_reg_state *reg, u32 arg, + struct bpf_call_arg_meta *meta, int insn_idx, + enum bpf_arg_type *arg_type, u32 *arg_size) +{ + argno_t argno = argno_from_arg(arg + 1); + const struct btf_param *args; + const struct btf_type *ref_t, *resolve_ret; + const struct btf *btf; + const char *ref_tname; + u32 ref_id; + + if (base_type(*arg_type) == ARG_PTR_TO_MAP_VALUE) + return resolve_map_arg_type(env, meta, arg_type); + + if (base_type(*arg_type) != ARG_PTR_TO_BTF_ID) + return 0; + + if (!meta->btf || arg_type_is_release(*arg_type) || + base_type(reg->type) == PTR_TO_BTF_ID || + reg2btf_ids[base_type(reg->type)]) + return 0; + args = btf_params(meta->func_proto); + ref_id = *meta->fn->arg_btf_id[arg]; + btf = is_kfunc_arg_map(meta->btf, &args[arg]) ? btf_vmlinux : meta->btf; + ref_t = btf_type_skip_modifiers(btf, ref_id, &ref_id); + ref_tname = btf_name_by_offset(btf, ref_t->name_off); + + if (!btf_type_is_scalar_struct(env, btf, ref_t)) { + 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), + btf_type_str(ref_t), ref_tname); + 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, meta->func_name, + "Pass a verifier-tracked pointer to the expected kernel object type, not a pointer to stack storage or another memory buffer.", + "the function 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; + } + + resolve_ret = btf_resolve_size(btf, ref_t, arg_size); + if (IS_ERR(resolve_ret)) { + verbose(env, "%s reference type('%s %s') size cannot be determined: %ld\n", + reg_arg_name(env, argno), btf_type_str(ref_t), ref_tname, + PTR_ERR(resolve_ret)); + return -EINVAL; + } + *arg_type = ARG_PTR_TO_MEM | MEM_FIXED_SIZE | (*arg_type & PTR_MAYBE_NULL); + + return 0; +} + static void btf_member_path_str(const struct btf *btf, const struct btf_member_path *path, char *buf, size_t buf_sz) { @@ -12990,7 +13053,7 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me for (i = 0; i < nargs; i++) { struct bpf_reg_state *reg = get_func_arg_reg(caller, regs, i); enum bpf_arg_type arg_type = meta->fn->arg_type[i]; - const struct btf_type *t, *ref_t, *resolve_ret; + const struct btf_type *t, *ref_t; argno_t argno = argno_from_arg(i + 1); int regno = reg_from_argno(argno); u32 ref_id = args[i].type; @@ -13053,11 +13116,9 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me if (base_type(arg_type) == ARG_PTR_TO_BTF_ID) ref_id = *meta->fn->arg_btf_id[i]; - if (is_kfunc_arg_map(btf, &args[i])) { - ref_t = btf_type_by_id(btf_vmlinux, ref_id); - ref_tname = btf_name_by_offset(btf, ref_t->name_off); - } - + ret = resolve_func_arg_type(env, reg, i, meta, insn_idx, &arg_type, &arg_size); + if (ret < 0) + return ret; ret = check_func_arg_reg_off(env, reg, argno, arg_type); if (ret < 0) return ret; @@ -13306,80 +13367,43 @@ static int check_kfunc_args(struct bpf_verifier_env *env, struct bpf_call_arg_me return ret; break; case ARG_PTR_TO_BTF_ID: - /* Only base_type is checked, further checks are done here */ - if (base_type(reg->type) == PTR_TO_BTF_ID || - reg2btf_ids[base_type(reg->type)]) { - if (!is_trusted_reg(env, reg) || - bpf_type_has_unsafe_modifiers(reg->type)) { - if (!(arg_type & MEM_RCU)) { - const char *expected_type; + if (!is_trusted_reg(env, reg) || + bpf_type_has_unsafe_modifiers(reg->type)) { + if (!(arg_type & MEM_RCU)) { + const char *actual_type, *arg_name, *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; - } + 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)); + arg_name = reg_arg_name(env, argno); + actual_type = bpf_diag_reg_type_plain(env, reg->type); + 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, arg_name, actual_type); + return -EINVAL; } + if (!is_rcu_reg(reg)) { + const char *actual_type, *arg_name, *expected_type; - ret = process_kf_arg_ptr_to_btf_id(env, reg, ref_t, ref_tname, ref_id, meta, i, argno); - if (ret < 0) - return ret; - break; + 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)); + arg_name = reg_arg_name(env, argno); + actual_type = bpf_diag_reg_type_plain(env, reg->type); + 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, arg_name, actual_type); + return -EINVAL; + } } - if (!btf_type_is_scalar_struct(env, meta->btf, ref_t)) { - 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), - btf_type_str(ref_t), ref_tname); - 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; - } - - /* - * If the register does not contain btf id but the argument type is a pointer to - * scalar-only struct, allow verifying it as a fixed size memory. - */ - resolve_ret = btf_resolve_size(btf, ref_t, &arg_size); - if (IS_ERR(resolve_ret)) { - verbose(env, - "%s reference type('%s %s') size cannot be determined: %ld\n", - reg_arg_name(env, argno), btf_type_str(ref_t), - ref_tname, PTR_ERR(resolve_ret)); - return -EINVAL; - } - arg_type = ARG_PTR_TO_MEM | MEM_FIXED_SIZE; - fallthrough; + ret = process_kf_arg_ptr_to_btf_id(env, reg, ref_t, ref_tname, + ref_id, meta, i, argno); + if (ret < 0) + return ret; + break; case ARG_PTR_TO_MEM: if (arg_type & MEM_FIXED_SIZE) { bool known_memory;