linux-kernel - Re: WARNING: bad unlock balance in xfs

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Date:   Tue, 8 May 2018 22:32:01 -0500
From:   Eric Sandeen <sandeen@...deen.net>
To:     Eric Biggers <ebiggers3@...il.com>,
        Dave Chinner <david@...morbit.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        syzbot <syzbot+84a67953651a971809ba@...kaller.appspotmail.com>,
        "Darrick J. Wong" <darrick.wong@...cle.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-xfs@...r.kernel.org,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>
Subject: Re: WARNING: bad unlock balance in xfs_iunlock



On 5/8/18 9:37 PM, Eric Biggers wrote:
> On Wed, May 09, 2018 at 10:50:11AM +1000, Dave Chinner wrote:
>> On Tue, May 08, 2018 at 09:56:01AM +0200, Dmitry Vyukov wrote:
>>> On Wed, May 2, 2018 at 12:51 AM, Dave Chinner <david@...morbit.com> wrote:
>>>>>>>> Hello,
>>>>>>>>
>>>>>>>> syzbot hit the following crash on upstream commit
>>>>>>>> 86bbbebac1933e6e95e8234c4f7d220c5ddd38bc (Mon Apr 2 18:47:07 2018 +0000)
>>>>>>>> Merge branch 'ras-core-for-linus' of
>>>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
>>>>>>>> syzbot dashboard link:
>>>>>>>> https://syzkaller.appspot.com/bug?extid=84a67953651a971809ba
>>>>>>>>
>>>>>>>> C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5719304272084992
>>>>>>>> syzkaller reproducer:
>>>>>>>> https://syzkaller.appspot.com/x/repro.syz?id=5767783983874048
>>>>>>>
>>>>>>> What a mess. A hand built, hopelessly broken filesystem image made
>>>>>>> up of hex dumps, written into a mmap()d region of memory, then
>>>>>>> copied into a tmpfs file and mounted with the loop device.
>>>>>>>
>>>>>>> Engineers that can debug broken filesystems don't grow on trees.  If
>>>>>>> we are to have any hope of understanding what the hell this test is
>>>>>>> doing, the bot needs to supply us with a copy of the built
>>>>>>> filesystem image the test uses. We need to be able to point forensic
>>>>>>> tools at the image to decode all the structures into human readable
>>>>>>> format - if we are forced to do that by hand or jump through hoops
>>>>>>> to create our own filesystem image than I'm certainly not going to
>>>>>>> waste time looking at these reports...
>>>>>>
>>>>>> Hi Dave,
>>>>>>
>>>>>> Here is the image:
>>>>>> https://drive.google.com/file/d/1jzhGGe5SBJcqfsjxCLHoh4Kazke1oTfC/view
>>>>>
>>>>> Have anybody looked at the bug and the image yet?
>>>>
>>>> Yes, I did that a couple of weeks ago. Couldn't reproduce on a TOT
>>>> kernel here.
>>>
>>> Do you think it is fixed now? What fixed it? The bug was there.
>>
>> We merge fixes for fuzzing issues all the time. IIRC a big batch of
>> them from the xfstests fuzzing infrastructure went into 4.17-rc1.
>>
>> If you want a commit, then do a bisect....
>>
> 
> The fix was commit 8241f7f983b9728:
> 
> #syz fix: xfs: don't iunlock the quota ip when quota block

Ah, thanks.  Interestingly that one was sent to the xfs list on 2/22, a couple
months before this bug report.  Took some time to get reviewed and merged
upstream, and it actually landed upstream in Linus' kernel not long after
this report...

-Eric