linux-kernel - Re: possible deadlock in blk_trace

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Date:   Sun, 3 Dec 2017 17:24:32 -0700
From:   Jens Axboe <axboe@...nel.dk>
To:     Eric Biggers <ebiggers3@...il.com>,
        syzbot 
        <bot+583353673e394aa41e5fb68ddc8b8d9d5c8d576f@...kaller.appspotmail.com>
Cc:     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 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.

-- 
Jens Axboe