From: "Theodore Ts'o" <tytso@mit.edu>
To: Mikhail Ukhin <mish.uxin2012@yandex.ru>
Cc: stable@vger.kernel.org, Andreas Dilger <adilger.kernel@dilger.ca>,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
Michail Ivanov <iwanov-23@bk.ru>,
Pavel Koshutin <koshutin.pavel@yandex.ru>,
Artem Sadovnikov <ancowi69@gmail.com>
Subject: Re: [PATCH] ext4: fix i_data_sem unlock order in ext4_ind_migrate()
Date: Thu, 4 Apr 2024 22:26:51 -0400 [thread overview]
Message-ID: <20240405022651.GB13376@mit.edu> (raw)
In-Reply-To: <20240404095000.5872-1-mish.uxin2012@yandex.ru>
On Thu, Apr 04, 2024 at 12:50:00PM +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.
This doesn't make any sense. Lock order matters; the order in which
you unlock shouldn't (and doesn't) make a difference. This is also
something which lockdep doesn't complain about --- because it's not a
problem.
So how was this "found by syzkaller"?
- Ted
next prev parent reply other threads:[~2024-04-05 2:27 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-04 9:50 [PATCH] ext4: fix i_data_sem unlock order in ext4_ind_migrate() Mikhail Ukhin
2024-04-04 9:58 ` kernel test robot
2024-04-04 10:00 ` Greg KH
2024-04-05 2:26 ` Theodore Ts'o [this message]
2024-04-05 18:40 ` Artem Sadovnikov
-- strict thread matches above, loose matches on Subject: below --
2024-04-04 16:02 [PATCH] ext4: fix semaphore unlocking order Ritesh Harjani
2024-04-05 20:22 ` [PATCH] ext4: fix i_data_sem unlock order in ext4_ind_migrate() Mikhail Ukhin
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