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

On 01/30/2015 03:32 PM, Jan Beulich wrote:
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

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

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.

My solution is more robust, I think. You don't have to be careful not
to introduce another double read somewhere.


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