* [PATCH] selftests/bpf: Fix null pointer check in skb_pkt_end.c
@ 2025-04-22 18:23 Prabhav Kumar Vaish
2025-04-22 22:15 ` Martin KaFai Lau
0 siblings, 1 reply; 3+ messages in thread
From: Prabhav Kumar Vaish @ 2025-04-22 18:23 UTC (permalink / raw)
To: ast, daniel, andrii, martin.lau, eddyz87, song, yonghong.song,
john.fastabend, kpsingh, sdf, haoluo, jolsa, mykolal, shuah
Cc: Prabhav Kumar Vaish, bpf, linux-kselftest, linux-kernel
Ensure that 'tcp' is checked for NULL before dereferencing. This resolves
a potential null pointer dereference warning reported by static analysis.
Signed-off-by: Prabhav Kumar Vaish <pvkumar5749404@gmail.com>
---
tools/testing/selftests/bpf/progs/skb_pkt_end.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/tools/testing/selftests/bpf/progs/skb_pkt_end.c b/tools/testing/selftests/bpf/progs/skb_pkt_end.c
index 3bb4451524a1..db33ff2839f7 100644
--- a/tools/testing/selftests/bpf/progs/skb_pkt_end.c
+++ b/tools/testing/selftests/bpf/progs/skb_pkt_end.c
@@ -45,10 +45,10 @@ int main_prog(struct __sk_buff *skb)
goto out;
tcp = (void*)(ip + 1);
- if (tcp->dest != 0)
- goto out;
if (!tcp)
goto out;
+ if (tcp->dest != 0)
+ goto out;
urg_ptr = tcp->urg_ptr;
--
2.34.1
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] selftests/bpf: Fix null pointer check in skb_pkt_end.c
2025-04-22 18:23 [PATCH] selftests/bpf: Fix null pointer check in skb_pkt_end.c Prabhav Kumar Vaish
@ 2025-04-22 22:15 ` Martin KaFai Lau
2025-04-23 17:58 ` [PATCH] selftests/bpf: Fix potential null pointer dereference " Prabhav Kumar Vaish
0 siblings, 1 reply; 3+ messages in thread
From: Martin KaFai Lau @ 2025-04-22 22:15 UTC (permalink / raw)
To: Prabhav Kumar Vaish
Cc: ast, daniel, andrii, eddyz87, song, yonghong.song, john.fastabend,
kpsingh, sdf, haoluo, jolsa, mykolal, shuah, bpf, linux-kselftest,
linux-kernel
On 4/22/25 11:23 AM, Prabhav Kumar Vaish wrote:
> Ensure that 'tcp' is checked for NULL before dereferencing. This resolves
> a potential null pointer dereference warning reported by static analysis.
>
> Signed-off-by: Prabhav Kumar Vaish <pvkumar5749404@gmail.com>
> ---
> tools/testing/selftests/bpf/progs/skb_pkt_end.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/tools/testing/selftests/bpf/progs/skb_pkt_end.c b/tools/testing/selftests/bpf/progs/skb_pkt_end.c
> index 3bb4451524a1..db33ff2839f7 100644
> --- a/tools/testing/selftests/bpf/progs/skb_pkt_end.c
> +++ b/tools/testing/selftests/bpf/progs/skb_pkt_end.c
> @@ -45,10 +45,10 @@ int main_prog(struct __sk_buff *skb)
> goto out;
>
> tcp = (void*)(ip + 1);
> - if (tcp->dest != 0)
> - goto out;
> if (!tcp)
This case will never be hit, so this change is not doing anything other than
silencing the static checker. Take a look at commit 9cc873e85800
("selftests/bpf: Add skb_pkt_end test"). The test was written to have a specific
llvm generated code. You will need to check the generated code is still testing
what it is supposed to test.
pw-bot: cr
> goto out;
> + if (tcp->dest != 0)
> + goto out;
>
> urg_ptr = tcp->urg_ptr;
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] selftests/bpf: Fix potential null pointer dereference in skb_pkt_end.c
2025-04-22 22:15 ` Martin KaFai Lau
@ 2025-04-23 17:58 ` Prabhav Kumar Vaish
0 siblings, 0 replies; 3+ messages in thread
From: Prabhav Kumar Vaish @ 2025-04-23 17:58 UTC (permalink / raw)
To: martin.lau
Cc: andrii, ast, bpf, daniel, eddyz87, haoluo, john.fastabend, jolsa,
kpsingh, linux-kernel, linux-kselftest, mykolal, pvkumar5749404,
sdf, shuah, song, yonghong.song
From: Prabhav Kumar <pvkumar5749404@gmail.com>
Hi Martin,
Thank you for the feedback.
You're right — I reviewed commit 9cc873e85800 and now understand that the test is designed to validate specific LLVM code generation, not just runtime behavior. I see how my change, although addressing the warning, could unintentionally alter the generated instructions and defeat the purpose of the test.
I'll drop this patch to preserve the original test intent. Thanks again for the context!
Best Regards,
Prabhav
^ permalink raw reply [flat|nested] 3+ messages in thread
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2025-04-22 18:23 [PATCH] selftests/bpf: Fix null pointer check in skb_pkt_end.c Prabhav Kumar Vaish
2025-04-22 22:15 ` Martin KaFai Lau
2025-04-23 17:58 ` [PATCH] selftests/bpf: Fix potential null pointer dereference " Prabhav Kumar Vaish
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