From: Yonghong Song <yonghong.song@linux.dev>
To: Puranjay Mohan <puranjay@kernel.org>, bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
Andrii Nakryiko <andrii@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Martin KaFai Lau <martin.lau@kernel.org>,
Eduard Zingerman <eddyz87@gmail.com>,
kkd@meta.com, kernel-team@meta.com
Subject: Re: [PATCH bpf-next] selftests/bpf: fix list_del() in arena list
Date: Fri, 17 Oct 2025 09:31:30 -0700 [thread overview]
Message-ID: <9552754b-b7e0-4f39-9d2f-11aaa8993b66@linux.dev> (raw)
In-Reply-To: <20251017141727.51355-1-puranjay@kernel.org>
On 10/17/25 7:17 AM, Puranjay Mohan wrote:
> The __list_del fuction doesn't set the previous node's next pointer to
> the next node of the node to be deleted. It just updates the local variable
> and not the actual pointer in the previous node.
>
> The test was passing up till now because the bpf code is doing bpf_free()
> after list_del and therfore reading head->first from the userspace will
> read all zeroes. But after arena_list_del() is finished, head->first should
> point to NULL;
>
> If you remove the bpf_free() call in arena_list_del(), the test will start
> crashing because now the userpsace will read 0x100 (LIST_POISON1) in
> head->first and segfault.
>
> Signed-off-by: Puranjay Mohan <puranjay@kernel.org>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
next prev parent reply other threads:[~2025-10-17 16:31 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-10-17 14:17 [PATCH bpf-next] selftests/bpf: fix list_del() in arena list Puranjay Mohan
2025-10-17 16:31 ` Yonghong Song [this message]
2025-10-17 18:35 ` Eduard Zingerman
2025-10-17 19:09 ` Puranjay Mohan
2025-10-17 19:30 ` Yonghong Song
2025-10-17 19:55 ` Eduard Zingerman
2025-10-17 18:41 ` Alexei Starovoitov
2025-10-17 19:18 ` Puranjay Mohan
2025-10-17 21:11 ` Alexei Starovoitov
2025-10-19 2:30 ` patchwork-bot+netdevbpf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=9552754b-b7e0-4f39-9d2f-11aaa8993b66@linux.dev \
--to=yonghong.song@linux.dev \
--cc=andrii@kernel.org \
--cc=ast@kernel.org \
--cc=bpf@vger.kernel.org \
--cc=daniel@iogearbox.net \
--cc=eddyz87@gmail.com \
--cc=kernel-team@meta.com \
--cc=kkd@meta.com \
--cc=martin.lau@kernel.org \
--cc=puranjay@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox