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

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Date:	Fri, 30 Aug 2013 16:36:23 +0200
From:	Richard Weinberger <richard@....at>
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

Am 30.08.2013 16:10, schrieb Toralf Förster:
> On 08/29/2013 03:30 PM, J. Bruce Fields wrote:
>> On Thu, Aug 29, 2013 at 11:57:45AM +0200, richard -rw- weinberger wrote:
>>> 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?
>>
>> I don't know.  Toralf's reports are the only ones I recall off the top
>> of my head, but I may have forgotten others.
>>
> 
> well, 7255e71 and 3c50ba8 I'd say.
> 
>>> Or are these bugs just more likely to hit on UML?
> 
> This definitely not. I observed at a real system EXT4 corruptions/
> issues but reported them to the EXT4 mailing list.
> It just took me a longer time to figure out a reliable configuration
> with 2 UML machiens to automatic bisect it.
> 
> 
>> That's also possible.
>>
>>> This is not the first NFS issue found by Toralf using UML and Trinity.
>>
>> Yep.  The testing is definitely appreciated.
> 
> Thx - in the mean while although my UML bisect scripts are working fine
> and trinity is stable enough even in UML environments to be trust worth.

That's good to know.
Thanks you and trinity we got rid of some nasty UML bugs.

Thanks,
//richard

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