Re: [Xen-devel] [PATCH linux-2.6.18] xen: mark pvscsi frontend request consumed only after last read

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 30.01.15 at 15:22, <JBeulich@xxxxxxxx> wrote:
>>>> On 30.01.15 at 14:51, <"jgross@xxxxxxxx".non-mime.internet> wrote:
>> A request in the ring buffer mustn't be read after it has been marked
>> as consumed. Otherwise it might already have been reused by the
>> frontend without violating the ring protocol.
>> 
>> To avoid inconsistencies in the backend only work on a private copy
>> of the request. This will ensure a malicious guest not being able to
>> bypass consistency checks of the backend by modifying an active
>> request.
> 
> I'm not convinced we need this in this version of the driver: c/s
> 590:c4134d1a3e3f took care of reading each ring_req field just
> once.

I should have clarified that I didn't mean we don't need to change
anything here: We should still move down the point where the
ring slot gets accounted as consumed.

Jan


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