Re: Xen 4.0.0x allows for data corruption in Dom0

[Joanna Rutkowska <joanna@invisiblethingslab.com>]

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On 03/09/2010 12:22 AM, Daniel Stodden wrote:
> On Sun, 2010-03-07 at 11:12 -0500, Pasi Kärkkäinen wrote:
>> On Sun, Mar 07, 2010 at 02:39:09PM +0000, Keir Fraser wrote:
>>> On 07/03/2010 14:36, "Pasi Kärkkäinen" <pasik@iki.fi> wrote:
>>>
>>>>> Tried a few times and no luck reproducing so far. I hope some other people
>>>>> on the list also will give it a go, since it's so easy to try it out.
>>>>>
>>>>
>>>> I'm able to reproduce this with xen/master 2.6.31.6 dom0 kernel (from
>>>> 2010-02-20),
>>>> but I'm not able to reproduce it with the current xen/stable 2.6.32.9.
>>>>
>>>> I'll try with the most recent 2.6.31.6 dom0 kernel aswell..
>>>
>>> Thanks Pasi!
>>>
>>
>> It seems to happen with the latest xen/master 2.6.31.6 aswell!
> 
> Does this look to you like we're corrupting memory or on-disk storage?
> 
> E.g. does a
> $ dd if=/dev/zero bs=1M | hexdump -C 
> have the same issue?
> 

I think there might be a chance that the above executes correctly, even
if we have memory corruption -- this might be e.g. because the actual
"dest" buffer here would be much smaller than the fs cache buffer used
when we copy onto disk. And so our small dest buffer might just not be
so likely to be hit with this presumably random corruption.

Perhaps dd'ing onto /dev/shm would be a better way to check this?

joanna.


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