linux-kernel - Re: [uml-devel] Issues with a rather unusual configured NFS server

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Message-ID: <CAFLxGvyK5+nB9TgW1uPho9KGwQrWQHx=wEpj+o-mZcN92bWAOg@mail.gmail.com>
Date:	Thu, 29 Aug 2013 11:57:45 +0200
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Toralf Förster <toralf.foerster@....de>
Cc:	"J. Bruce Fields" <bfields@...ldses.org>,
	Linux NFS mailing list <linux-nfs@...r.kernel.org>,
	"J. Bruce Fields" <bfields@...hat.com>,
	"user-mode-linux-devel@...ts.sourceforge.net" 
	<user-mode-linux-devel@...ts.sourceforge.net>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Jan Kara <jack@...e.cz>, linux-ext4@...r.kernel.org
Subject: Re: [uml-devel] Issues with a rather unusual configured NFS server

On Wed, Aug 28, 2013 at 7:21 PM, Toralf Förster <toralf.foerster@....de> wrote:
> On 08/27/2013 08:06 PM, J. Bruce Fields wrote:
>> On Tue, Aug 13, 2013 at 05:53:14PM -0400, bfields wrote:
>>> On Mon, Aug 12, 2013 at 04:36:40PM +0200, Jan Kara wrote:
>>>> On Sun 11-08-13 11:48:49, Toralf Förster wrote:
>>>>> so that the server either crashes (if it is a user mode linux image) or at least its reboot functionality got broken
>>>>> - if the NFS server is hammered with scary NFS calls using a fuzzy tool running at a remote NFS client under a non-privileged user id.
>>>>>
>>>>> It can re reproduced, if
>>>>>    - the NFS share is an EXT3 or EXT4 directory
>>>>>    - and it is created at file located at tempfs and mounted via loop device
>>>>>    - and the NFS server is forced to umount the NFS share
>>>>>    - and the server forced to restart the NSF service afterwards
>>>>>    - and trinity is used
>>>>>
>>>>> I could find a scenario for an automated bisect. 2 times it brought this commit
>>>>> commit 68a3396178e6688ad7367202cdf0af8ed03c8727
>>>>> Author: J. Bruce Fields <bfields@...hat.com>
>>>>> Date:   Thu Mar 21 11:21:50 2013 -0400
>>>>>
>>>>>     nfsd4: shut down more of delegation earlier
>>>
>>> Thanks for the report.  I think I see the problem--after this commit
>>> nfs4_set_delegation() failures result in nfs4_put_delegation being
>>> called, but nfs4_put_delegation doesn't free the nfs4_file that has
>>> already been set by alloc_init_deleg().
>>>
>>> Let me think about how to fix that....
>>
>> Sorry for the slow response--can you check whether this fixes the
>> problem?
>>
> Yes.
>
> With the attached patch the problem can't be reproduced any longer with
> the prepared test case and current git kernels.

BTW: Is nobody else fuzz testing NFS?
Or are these bugs just more likely to hit on UML?
This is not the first NFS issue found by Toralf using UML and Trinity.

-- 
Thanks,
//richard
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