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

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

On 08/30/2013 04:36 PM, Richard Weinberger wrote:
> 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@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.
> 
> That's good to know.
> Thanks you and trinity we got rid of some nasty UML bugs.

yeah, but there's (among others) one of them still in the wild:
If I start an UML and resize the terminal (KDE Konsole) during the boot
phase then it just crashes sometimes.


> Thanks,
> //richard
> 
> 


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

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