linux-kernel - Re: possible deadlock in blk_trace

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Message-ID: <20171204004427.GA13374@zzz.localdomain>
Date:   Sun, 3 Dec 2017 16:44:27 -0800
From:   Eric Biggers <ebiggers3@...il.com>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     syzbot 
        <bot+583353673e394aa41e5fb68ddc8b8d9d5c8d576f@...kaller.appspotmail.com>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, rostedt@...dmis.org,
        syzkaller-bugs@...glegroups.com
Subject: Re: possible deadlock in blk_trace_remove

On Sun, Dec 03, 2017 at 05:24:32PM -0700, Jens Axboe wrote:
> On 12/03/2017 01:24 PM, Eric Biggers wrote:
> > On Sun, Nov 19, 2017 at 02:36:01AM -0800, syzbot wrote:
> >> Hello,
> >>
> >> syzkaller hit the following crash on
> >> d9e0e63d9a6f88440eb201e1491fcf730272c706
> >> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master
> >> compiler: gcc (GCC) 7.1.1 20170620
> >> .config is attached
> >> Raw console output is attached.
> >>
> >> Unfortunately, I don't have any reproducer for this bug yet.
> >>
> >>
> >> Use struct sctp_sack_info instead
> >>
> >> ============================================
> >> WARNING: possible recursive locking detected
> >> 4.14.0-rc8-next-20171110+ #40 Not tainted
> >> --------------------------------------------
> >> syz-executor6/21462 is trying to acquire lock:
> >>  (&q->blk_trace_mutex){+.+.}, at: [<ffffffff81760261>]
> >> blk_trace_remove+0x21/0x40 kernel/trace/blktrace.c:373
> >>
> >> but task is already holding lock:
> >>  (&q->blk_trace_mutex){+.+.}, at: [<ffffffff81763b38>]
> >> blk_trace_setup+0x38/0x70 kernel/trace/blktrace.c:606
> >>
> >> other info that might help us debug this:
> >>  Possible unsafe locking scenario:
> > 
> > #syz fix: blktrace: fix trace mutex deadlock
> 
> This is fixed in current -git.
> 

I know, but syzbot needed to be told what commit fixes the bug.
See https://github.com/google/syzkaller/blob/master/docs/syzbot.md