linux-kernel - Re: [syzbot] possible deadlock in bd_register_pending

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Message-ID: <d4d71dc8-0373-b7a9-2a95-ba2d3c87f968@I-love.SAKURA.ne.jp>
Date:   Sat, 11 Sep 2021 01:57:53 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     syzbot <syzbot+f5608de5d89cc0d998c7@...kaller.appspotmail.com>,
        axboe@...nel.dk, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] possible deadlock in bd_register_pending_holders

Since commit dfbb3409b27fa42b in axboe/linux-block.git#block-5.15 breaks
"sb_writers#$N => &p->lock => major_names_lock" dependency chain,
I think that this dependency chain should be no longer possible.

#syz fix: block: genhd: don't call blkdev_show() with major_names_lock held

On 2021/09/10 23:42, syzbot wrote:
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    27151f177827 Merge tag 'perf-tools-for-v5.15-2021-09-04' o..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=104612b3300000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=ac2f9cc43f6b17e4
> dashboard link: https://syzkaller.appspot.com/bug?extid=f5608de5d89cc0d998c7
> compiler:       gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.1
> 
> 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+f5608de5d89cc0d998c7@...kaller.appspotmail.com