On 13.05.2021 12:02, 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>
with one remark/question:
> @@ -703,6 +704,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
> {
> struct blkfront_info *info = rinfo->dev_info;
> struct blkif_request *ring_req, *extra_ring_req = NULL;
> + struct blkif_request *final_ring_req, *final_extra_ring_req;
Without setting final_extra_ring_req to NULL just like is done for
extra_ring_req, ...
> @@ -840,10 +845,10 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
> if (setup.segments)
> kunmap_atomic(setup.segments);
>
> - /* Keep a private copy so we can reissue requests when recovering. */
> - rinfo->shadow[id].req = *ring_req;
> + /* Copy request(s) to the ring page. */
> + *final_ring_req = *ring_req;
> if (unlikely(require_extra_req))
> - rinfo->shadow[extra_id].req = *extra_ring_req;
> + *final_extra_ring_req = *extra_ring_req;
... are you sure all supported compilers will recognize the
conditional use and not warn about use of a possibly uninitialized
variable?
Jan
