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

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Message-ID: <20180509135528.GE28388@thunk.org>
Date:   Wed, 9 May 2018 09:55:28 -0400
From:   "Theodore Y. Ts'o" <tytso@....edu>
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

>>> 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

A suggestion --- insteading of forcing human beings --- either
overworked file system developers, or understaffed fuzzing tool teams,
to have to manually pull out the file system image out from the C
repro, if it's too hard to add a link where the file system iamge can
be downloaded from the Syzkaller web application --- how about adding
an option to the C repro template which causes it to dump the image to
a file and then immediately exit?

					- Ted