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

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Date:   Tue, 8 May 2018 09:54:30 +0200
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Eric Sandeen <sandeen@...deen.net>
Cc:     "Darrick J. Wong" <darrick.wong@...cle.com>,
        Dave Chinner <david@...morbit.com>,
        syzbot <syzbot+84a67953651a971809ba@...kaller.appspotmail.com>,
        LKML <linux-kernel@...r.kernel.org>, linux-xfs@...r.kernel.org,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        "Theodore Ts'o" <tytso@....edu>,
        syzkaller <syzkaller@...glegroups.com>
Subject: Re: WARNING: bad unlock balance in xfs_iunlock

On Mon, Apr 30, 2018 at 5:14 PM, Eric Sandeen <sandeen@...deen.net> wrote:
> On 4/30/18 9:02 AM, Dmitry Vyukov wrote:
>> On Mon, Apr 30, 2018 at 3:49 PM, Eric Sandeen <sandeen@...deen.net> wrote:
>
> ...
>
>>>> It just extracted kernel source file name that looked relevant
>>>> to this crash and run get_maintainers.pl on it.
>>>> Also the image can contain dynamically generated data, which makes it
>>>> impossible to have as a file at all.
>>>
>>> I guess I'm not sure what this means, can you explain?
>>
>> Say, a value that we generally pass to close system call is not static
>> and can't be dumped to a static file. It's whatever a previous open
>> system call has returned. Inside of the program we memorize the return
>> value of open in a variable and then pass it to close. This generally
>> stands for all system calls. Say, an image can contain an uid, and
>> that uid can be obtained from a system call too.
>
> Ok, but that's the syscall side.  You are operating on a static xfs image,
> correct?  We're only asking for the actual filesystem you're operating
> against.
>
> (When I say "image" I am talking only about the filesystem itself, not any
> other syzkaller state)
>
> ...
>
>>> That was not at all clear to me.  I thought when syzkaller was telling us
>>> "on upstream commit XYZ," it meant that it had identified commit XYZ as bad.
>>> I'm not sure if anyone else made that mistake, but  perhaps you could also clarify
>>> the bug report text in this regard?
>>
>> Suggestions are welcome. Currently it says "syzbot hit the following
>> crash on upstream commit SHA1", which was supposed to mean just the
>> state of the source tree when the crash happened. But I am not a
>> native speaker, so perhaps I am saying not what I intend to say.
>>
>> There are also suggestions on report format improvement from +Ted
>> currently in works:
>> https://github.com/google/syzkaller/issues/565#issuecomment-380792942
>> Not sure if they make this distinction 100% clear, though.
>
> Maybe I was the only one who misunderstood, but something like
>
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
> HEAD:           f5c754d63d06 mm/swap_state.c: make bool enable_vma_readahead and swap_vma_readahead()
>
> to make it clear that it has not identified that commit as the culprit, it's
> just the head of the tree you were testing?  (I think I have the correct git
> nomenclature ...)


This is done now, you can see example of new format here:

https://lkml.org/lkml/2018/5/8/36

It says "HEAD commit" and also "syzbot engineers can be reached at <email>".