On 09.07.21 10:55, Roger Pau Monné wrote:
On Thu, Jul 08, 2021 at 02:43:44PM +0200, Juergen Gross wrote:In order to avoid a malicious backend being able to influence the local copy of a request build the request locally first and then copy it to the ring page instead of doing it the other way round as today. Signed-off-by: Juergen Gross <jgross@xxxxxxxx> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxx> Thanks! One unrelated comment below.
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@@ -798,7 +801,9 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri ring_req->u.rw.nr_segments = num_grant; if (unlikely(require_extra_req)) { extra_id = blkif_ring_get_request(rinfo, req, - &extra_ring_req); + &final_extra_ring_req); + extra_ring_req = &rinfo->shadow[extra_id].req;I'm slightly confused about this extra request stuff because I cannot find any check that asserts we have two empty slots on the ring before getting here (I only see a RING_FULL check in blkif_queue_rq). This is AFAIK only used on Arm when guest page size > 4KB.
I agree that this is a bug and should be fixed. Juergen
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