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

["Toralf Förster" <toralf.foerster@gmx.de>]

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@gmx.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@redhat.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.

> 
> --b.
> 


-- 
MfG/Sincerely
Toralf Förster
pgp finger print: 7B1A 07F4 EC82 0F90 D4C2 8936 872A E508 7DB6 9DA3