From: Dominique Martinet <asmadeus@codewreck.org>
To: Deepanshu Kartikey <kartikey406@gmail.com>
Cc: ericvh@kernel.org, lucho@ionkov.net, linux_oss@crudebyte.com,
v9fs@lists.linux.dev, linux-kernel@vger.kernel.org,
syzbot+344c09c64fcd8d3d2782@syzkaller.appspotmail.com
Subject: Re: [PATCH] 9p: don't WARN_ONCE on racy symlink fid lookup failure
Date: Sun, 13 Sep 2026 22:33:56 +0900 [thread overview]
Message-ID: <aqamRApMunI1mef9@codewreck.org> (raw)
In-Reply-To: <20260725014448.18711-1-kartikey406@gmail.com>
Deepanshu Kartikey wrote on Sat, Jul 25, 2026 at 07:14:48AM +0530:
> v9fs_init_request() WARN_ONCE()s when v9fs_fid_lookup() fails for a
> symlink read via the page cache. This is a benign TOCTOU race: a
> concurrent unlink()/rename() can remove the target between the walk
> finding the dentry and p9_client_walk() completing, so the lookup
> legitimately fails with -ENOENT (observed: dentry=/file0, err=-2).
>
> With panic_on_warn=1, this WARN escalates to a full kernel panic --
> an unprivileged local DoS reachable by racing mount() against a
> concurrent unlink/rename.
>
> Return the error directly instead of WARN_ONCE().
>
> Reported-by: syzbot+344c09c64fcd8d3d2782@syzkaller.appspotmail.com
> Closes: https://syzkaller.appspot.com/bug?extid=344c09c64fcd8d3d2782
> Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Fair enough, picked up for 7.4
--
Dominique Martinet | Asmadeus
prev parent reply other threads:[~2026-09-13 13:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-25 1:44 [PATCH] 9p: don't WARN_ONCE on racy symlink fid lookup failure Deepanshu Kartikey
2026-08-06 8:25 ` Deepanshu Kartikey
2026-08-21 1:49 ` Deepanshu Kartikey
2026-09-13 13:33 ` Dominique Martinet [this message]
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