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selftests/bpf: Test for unaligned flow_dissector ctx access

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This patch adds tests for two context fields where unaligned accesses
were not properly rejected.

Note the new macro is similar to the existing narrow_load macro, but we
need a different description and access offset. Combining the two
macros into one is probably doable but I don't think it would help
readability.

vmlinux.h is included in place of bpf.h so we have the definition of
struct bpf_nf_ctx.

Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Tested-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
Link: https://lore.kernel.org/r/bf014046ddcf41677fb8b98d150c14027e9fddba.1754039605.git.paul.chaignon@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Paul Chaignon 2025-08-01 11:49:44 +02:00 committed by Alexei Starovoitov
parent f914876eec
commit d8d2d9d12f
1 changed files with 22 additions and 1 deletions
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23
tools/testing/selftests/bpf/progs/verifier_ctx.c
View File

@ -1,10 +1,12 @@
// SPDX-License-Identifier: GPL-2.0
/* Converted from tools/testing/selftests/bpf/verifier/ctx.c */
#include <linux/bpf.h>
#include "vmlinux.h"
#include <bpf/bpf_helpers.h>
#include "bpf_misc.h"
#define sizeof_field(TYPE, MEMBER) sizeof((((TYPE *)0)->MEMBER))
SEC("tc")
__description("context stores via BPF_ATOMIC")
__failure __msg("BPF_ATOMIC stores into R1 ctx is not allowed")
@ -243,4 +245,23 @@ narrow_load("sockops", bpf_sock_ops, skb_data);
narrow_load("sockops", bpf_sock_ops, skb_data_end);
narrow_load("sockops", bpf_sock_ops, skb_hwtstamp);
#define unaligned_access(type, ctx, field) \
SEC(type) \
__description("unaligned access on field " #field " of " #ctx) \
__failure __msg("invalid bpf_context access") \
__naked void unaligned_ctx_access_##ctx##field(void) \
{ \
asm volatile (" \
r1 = *(u%[size] *)(r1 + %[off]); \
r0 = 0; \
exit;" \
: \
: __imm_const(size, sizeof_field(struct ctx, field) * 8), \
__imm_const(off, offsetof(struct ctx, field) + 1) \
: __clobber_all); \
}
unaligned_access("flow_dissector", __sk_buff, data);
unaligned_access("netfilter", bpf_nf_ctx, skb);
char _license[] SEC("license") = "GPL";