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

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Date:   Tue, 8 May 2018 19:37:21 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     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 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

- Eric