linux-kernel - Re: BUG: unable to handle kernel paging request in io_wq_cancel

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Message-ID: <5e420723-8cc0-42ac-2ca4-d708af70fe3d@kernel.dk>
Date:   Fri, 1 Nov 2019 12:07:21 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzbot <syzbot+221cc24572a2fed23b6b@...kaller.appspotmail.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        David Howells <dhowells@...hat.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        linux-block <linux-block@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>, mchehab+samsung@...nel.org,
        Ingo Molnar <mingo@...hat.com>, patrick.bellasi@....com,
        Richard Guy Briggs <rgb@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>
Subject: Re: BUG: unable to handle kernel paging request in io_wq_cancel_all

On 11/1/19 12:03 PM, Dmitry Vyukov wrote:
> On Fri, Nov 1, 2019 at 6:56 PM Jens Axboe <axboe@...nel.dk> wrote:
>>
>> On 11/1/19 11:50 AM, Dmitry Vyukov wrote:
>>> On Wed, Oct 30, 2019 at 3:41 PM Jens Axboe <axboe@...nel.dk> wrote:
>>>>
>>>> On 10/30/19 1:44 AM, syzbot wrote:
>>>>> syzbot has bisected this bug to:
>>>>>
>>>>> commit ef0524d3654628ead811f328af0a4a2953a8310f
>>>>> Author: Jens Axboe <axboe@...nel.dk>
>>>>> Date:   Thu Oct 24 13:25:42 2019 +0000
>>>>>
>>>>>         io_uring: replace workqueue usage with io-wq
>>>>>
>>>>> bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=16acf5d0e00000
>>>>> start commit:   c57cf383 Add linux-next specific files for 20191029
>>>>> git tree:       linux-next
>>>>> final crash:    https://syzkaller.appspot.com/x/report.txt?x=15acf5d0e00000
>>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=11acf5d0e00000
>>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=cb86688f30db053d
>>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=221cc24572a2fed23b6b
>>>>> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=168671d4e00000
>>>>> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=140f4898e00000
>>>>>
>>>>> Reported-by: syzbot+221cc24572a2fed23b6b@...kaller.appspotmail.com
>>>>> Fixes: ef0524d36546 ("io_uring: replace workqueue usage with io-wq")
>>>>
>>>> Good catch, it's a case of NULL vs ERR_PTR() confusion. I'll fold in
>>>> the below fix.
>>>
>>> Hi Jens,
>>>
>>> Please either add the syzbot tag to commit, or close manually with
>>> "#syz fix" (though requires waiting until the fixed commit is in
>>> linux-next).
>>> See https://goo.gl/tpsmEJ#rebuilt-treesamended-patches for details.
>>> Otherwise, the bug will be considered open and will waste time of
>>> humans looking at open bugs and prevent syzbot from reporting new bugs
>>> in io_uring.
>>
>> It's queued up since two days ago:
>>
>> http://git.kernel.dk/cgit/linux-block/commit/?h=for-5.5/io_uring&id=975c99a570967dd48e917dd7853867fee3febabd
>>
>> and should have the right attributions, so hopefully it'll catch up
>> eventually.
>>
>> --
>> Jens Axboe
>>
> 
> Cool! Thanks!
> I've seen "fold in" and historically lots of developers did not add
> the tag during amending, so wanted to double check.

I'm often guilty of that, I think, but for this one I just kept it
separate since I didn't want to rebase things at this point. So I do
appreciate the reminder, I'm sure it'll be pertinent in many other
cases...

-- 
Jens Axboe