linux-kernel - Re: [PATCH] bpf: Fix NULL deref in __list_del_clearprev for flush

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <CAADnVQJxso-6vnGDQQitqCjQQRjc4R09ofdFKroZLFtENJq4dw@mail.gmail.com>
Date: Mon, 15 Dec 2025 20:06:14 -0800
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: donglaipang@....com
Cc: syzbot+2b3391f44313b3983e91@...kaller.appspotmail.com, 
	Andrii Nakryiko <andrii@...nel.org>, Alexei Starovoitov <ast@...nel.org>, bpf <bpf@...r.kernel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, "David S. Miller" <davem@...emloft.net>, Eduard <eddyz87@...il.com>, 
	Hao Luo <haoluo@...gle.com>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, Jiri Olsa <jolsa@...nel.org>, 
	KP Singh <kpsingh@...nel.org>, Jakub Kicinski <kuba@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Network Development <netdev@...r.kernel.org>, Stanislav Fomichev <sdf@...ichev.me>, Song Liu <song@...nel.org>, 
	syzkaller-bugs <syzkaller-bugs@...glegroups.com>, Yonghong Song <yonghong.song@...ux.dev>
Subject: Re: [PATCH] bpf: Fix NULL deref in __list_del_clearprev for flush_node

On Mon, Dec 15, 2025 at 7:14 PM <donglaipang@....com> wrote:
>
> From: DLpang <donglaipang@....com>
>
> #syz test
>
> Hi,
>
> This patch fixes a NULL pointer dereference in the BPF subsystem that occurs
> when __list_del_clearprev() is called on an already-cleared flush_node list_head.
>
> The fix includes two parts:
> 1. Properly initialize the flush_node list_head during per-CPU bulk queue allocation
>    using INIT_LIST_HEAD(&bq->flush_node)
> 2. Add defensive checks before calling __list_del_clearprev() to ensure the node
>    is actually in the list by checking if (bq->flush_node.prev)
>
> According to the __list_del_clearprev documentation in include/linux/list.h,
> 'The code that uses this needs to check the node 'prev' pointer instead of calling list_empty()'.
>
> This patch fixes the following syzbot-reported issue:
> https://syzkaller.appspot.com/bug?extid=2b3391f44313b3983e91
>
> Reported-by: syzbot+2b3391f44313b3983e91@...kaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=2b3391f44313b3983e91
> Signed-off-by: DLpang <donglaipang@....com>

If you're going to throw AI slop at us, please do your homework
and root cause the issue.
Nothing in this AI generated commit log explains the bug.

pw-bot: cr