From: "Jérémy Jean" <jeremy.jean@oss.cyber.gouv.fr>
To: Jan Kara <jack@suse.cz>
Cc: tytso@mit.edu, Andreas Dilger <adilger.kernel@dilger.ca>,
Baokun Li <libaokun@linux.alibaba.com>,
Ojaswin Mujoo <ojaswin@linux.ibm.com>,
Ritesh Harjani <ritesh.list@gmail.com>,
Zhang Yi <yi.zhang@huawei.com>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH] ext4: fix OOB write in fast-commit replay
Date: Mon, 09 Nov 2026 21:47:51 +0100 [thread overview]
Message-ID: <038be9b9541cbcc43ed35cf7950b9361@oss.cyber.gouv.fr> (raw)
In-Reply-To: <idqh5j5m3rhjsdu77h7dchk5vxj47fcsls7tcdhu4wdf75cthu@sxwipa7u2hyl>
On 2026-11-09 14:19, Jan Kara wrote:
> On Sun 08-11-26 20:43:46, Jérémy Jean wrote:
>> Fast-commit recovery checks record bounds and lengths during scan.
>> Replay reads the records again without these checks. A corrupt
>> filesystem
>> can make an earlier replay operation overwrite a later record. Its new
>
> This fact looks like the real problem. I think we should validate the
> replay does not corrupt the journal. How does this happen? Otherwise we
> have to fully redo the validation of each record done in
> ext4_fc_replay_scan().
The replay can corrupt the journal because a corrupted image can make
metadata blocks used during replay overlap with fast-commit blocks. I
agree that making sure that replay does not corrupt the journal would
be a stronger fix, but I'm not sure I see a simple way to fix this
properly. Rechecking bounds as I proposed fixes a memory issue but it
indeed does not address the root cause.
Regards,
Jérémy
prev parent reply other threads:[~2026-11-09 20:47 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-08 20:43 Jérémy Jean
2026-11-09 13:19 ` Jan Kara
2026-11-09 20:47 ` Jérémy Jean [this message]
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