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selftests/bpf: Test invalid narrower ctx load

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This patch adds selftests to cover invalid narrower loads on the
context. These used to cause kernel warnings before the previous patch.
To trigger the warning, the load had to be aligned, to read an affected
context field (ex., skb->sk), and not starting at the beginning of the
field.

The nine new cases all fail without the previous patch.

Suggested-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Paul Chaignon <paul.chaignon@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://patch.msgid.link/44cd83ea9c6868079943f0a436c6efa850528cc1.1753194596.git.paul.chaignon@gmail.com
This commit is contained in:
Paul Chaignon 2025-07-22 16:33:37 +02:00 committed by Martin KaFai Lau
parent e09299225d
commit ba578b87fe
1 changed files with 25 additions and 0 deletions
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25
tools/testing/selftests/bpf/progs/verifier_ctx.c
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@ -218,4 +218,29 @@ __naked void null_check_8_null_bind(void)
: __clobber_all);
}
#define narrow_load(type, ctx, field) \
SEC(type) \
__description("narrow load on field " #field " of " #ctx) \
__failure __msg("invalid bpf_context access") \
__naked void invalid_narrow_load##ctx##field(void) \
{ \
asm volatile (" \
r1 = *(u32 *)(r1 + %[off]); \
r0 = 0; \
exit;" \
: \
: __imm_const(off, offsetof(struct ctx, field) + 4) \
: __clobber_all); \
}
narrow_load("cgroup/getsockopt", bpf_sockopt, sk);
narrow_load("cgroup/getsockopt", bpf_sockopt, optval);
narrow_load("cgroup/getsockopt", bpf_sockopt, optval_end);
narrow_load("tc", __sk_buff, sk);
narrow_load("cgroup/bind4", bpf_sock_addr, sk);
narrow_load("sockops", bpf_sock_ops, sk);
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);
char _license[] SEC("license") = "GPL";