linux-ext4 - Re: [PATCH v2] ext4: fix i_data_sem unlock order in ext4_ind

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Date: Thu, 9 May 2024 10:51:24 -0400
From: "Theodore Ts'o" <tytso@....edu>
To: Mikhail Ukhin <mish.uxin2012@...dex.ru>
Cc: stable@...r.kernel.org, Andreas Dilger <adilger.kernel@...ger.ca>,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michail Ivanov <iwanov-23@...ru>,
        Pavel Koshutin <koshutin.pavel@...dex.ru>,
        lvc-project@...uxtesting.org, Ritesh Harjani <ritesh.list@...il.com>,
        Artem Sadovnikov <ancowi69@...il.com>
Subject: Re: [PATCH v2] ext4: fix i_data_sem unlock order in
 ext4_ind_migrate()

On Sat, Apr 06, 2024 at 12:08:03AM +0300, Mikhail Ukhin wrote:
> Fuzzing reports a possible deadlock in jbd2_log_wait_commit.
> 
> The problem occurs in ext4_ind_migrate due to an incorrect order of
> unlocking of the journal and write semaphores - the order of unlocking
> must be the reverse of the order of locking.
> 
> Found by Linux Verification Center (linuxtesting.org) with syzkaller.
> 
> Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> Signed-off-by: Artem Sadovnikov <ancowi69@...il.com>
> Signed-off-by: Mikhail Ukhin <mish.uxin2012@...dex.ru>

Thanks.  This has been addressed by commit 00d873c17e29 ("ext4: avoid
deadlock in fs reclaim with page writeback"), with the same code
change.

						- Ted