linux-ext4 - Re: [PATCH] ext4: Fix timer use-after-free on failed mount

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Message-ID: <YFbLUUL8f5RMHY96@mit.edu>
Date:   Sun, 21 Mar 2021 00:28:01 -0400
From:   "Theodore Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org,
        syzbot+628472a2aac693ab0fcd@...kaller.appspotmail.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] ext4: Fix timer use-after-free on failed mount

On Mon, Mar 15, 2021 at 05:59:06PM +0100, Jan Kara wrote:
> When filesystem mount fails because of corrupted filesystem we first
> cancel the s_err_report timer reminding fs errors every day and only
> then we flush s_error_work. However s_error_work may report another fs
> error and re-arm timer thus resulting in timer use-after-free. Fix the
> problem by first flushing the work and only after that canceling the
> s_err_report timer.
> 
> Reported-by: syzbot+628472a2aac693ab0fcd@...kaller.appspotmail.com
> Fixes: 2d01ddc86606 ("ext4: save error info to sb through journal if available")
> CC: stable@...r.kernel.org
> Signed-off-by: Jan Kara <jack@...e.cz>

Thanks, applied.

					- Ted