linux-ext4 - Re: [syzbot] possible deadlock in fscrypt

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Date:   Thu, 21 Apr 2022 01:42:18 +0000
From:   Eric Biggers <ebiggers@...nel.org>
To:     syzbot <syzbot+1a748d0007eeac3ab079@...kaller.appspotmail.com>
Cc:     jaegeuk@...nel.org, linux-fscrypt@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        tytso@....edu, linux-ext4@...r.kernel.org
Subject: Re: [syzbot] possible deadlock in fscrypt_initialize

On Wed, Apr 20, 2022 at 06:05:24PM -0700, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    90ea17a9e27b Merge tag 'scsi-fixes' of git://git.kernel.or..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=16bf09d0f00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ac042ae170e2c50f
> dashboard link: https://syzkaller.appspot.com/bug?extid=1a748d0007eeac3ab079
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
> 
> Unfortunately, I don't have any reproducer for this issue yet.
> 
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+1a748d0007eeac3ab079@...kaller.appspotmail.com
> 
> ======================================================
> WARNING: possible circular locking dependency detected
> 5.18.0-rc2-syzkaller-00291-g90ea17a9e27b #0 Not tainted
> ------------------------------------------------------
> syz-executor.0/3694 is trying to acquire lock:
> ffffffff8bf36428 (fscrypt_init_mutex){+.+.}-{3:3}, at: fscrypt_initialize+0x3c/0xa0 fs/crypto/crypto.c:324
> 
> but task is already holding lock:
> ffff8880430c8990 (jbd2_handle){++++}-{0:0}, at: start_this_handle+0xfb4/0x14a0 fs/jbd2/transaction.c:461

This is a regression from a while back from the ext4 fast_commit changes,
specifically commit a80f7fcf1867 ("ext4: fixup ext4_fc_track_* functions'
signature") which extended the scope of the transaction in ext4_unlink() too
far.  It's been on my TODO list to fix, along with the reports of fast_commit
and encryption not working together.  I'll try to get to it soon.

- Eric