[PATCH bpf-next 1/1] selftests/bpf: Test changing packet data from kfunc

[PATCH bpf-next 1/1] selftests/bpf: Test changing packet data from kfunc

[Amery Hung]

bpf_xdp_pull_data() is the first kfunc that changes packet data. Make
sure the verifier clear all packet pointers after calling packet data
changing kfunc.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
---
 tools/testing/selftests/bpf/progs/verifier_sock.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/tools/testing/selftests/bpf/progs/verifier_sock.c b/tools/testing/selftests/bpf/progs/verifier_sock.c
index b4d31f10a976..2b4610b53382 100644
--- a/tools/testing/selftests/bpf/progs/verifier_sock.c
+++ b/tools/testing/selftests/bpf/progs/verifier_sock.c
@@ -1096,6 +1096,20 @@ int invalidate_xdp_pkt_pointers_from_global_func(struct xdp_md *x)
 	return XDP_PASS;
 }
 
+/* XDP packet changing kfunc calls invalidate packet pointers */
+SEC("xdp")
+__failure __msg("invalid mem access")
+int invalidate_xdp_pkt_pointers(struct xdp_md *x)
+{
+	int *p = (void *)(long)x->data;
+
+	if ((void *)(p + 1) > (void *)(long)x->data_end)
+		return XDP_DROP;
+	bpf_xdp_pull_data(x, 0);
+	*p = 42; /* this is unsafe */
+	return XDP_PASS;
+}
+
 __noinline
 int tail_call(struct __sk_buff *sk)
 {
-- 
2.47.3

Re: [PATCH bpf-next 1/1] selftests/bpf: Test changing packet data from kfunc

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Martin KaFai Lau <martin.lau@kernel.org>:

On Fri, 26 Sep 2025 09:41:42 -0700 you wrote:
> bpf_xdp_pull_data() is the first kfunc that changes packet data. Make
> sure the verifier clear all packet pointers after calling packet data
> changing kfunc.
> 
> Signed-off-by: Amery Hung <ameryhung@gmail.com>
> ---
>  tools/testing/selftests/bpf/progs/verifier_sock.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)

Here is the summary with links:
  - [bpf-next,1/1] selftests/bpf: Test changing packet data from kfunc
    https://git.kernel.org/bpf/bpf-next/c/991e555efffd

You are awesome, thank you!
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