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Commit 80baa775 authored by Juergen Gross's avatar Juergen Gross Committed by Greg Kroah-Hartman
Browse files

xen/blkfront: don't take local copy of a request from the ring page 



commit 8f5a695d99000fc3aa73934d7ced33cfc64dcdab upstream.

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: default avatarJuergen Gross <jgross@suse.com>
Reviewed-by: default avatarJan Beulich <jbeulich@suse.com>
Acked-by: default avatarRoger Pau Monné <roger.pau@citrix.com>
Link: https://lore.kernel.org/r/20210730103854.12681-3-jgross@suse.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent b647c449

drivers/block/xen-blkfront.c

+15 −10
Original line number Diff line number Diff line
@@ -536,7 +536,7 @@ static unsigned long blkif_ring_get_request(struct blkfront_ring_info *rinfo, 
	rinfo->shadow[id].status = REQ_WAITING;

	rinfo->shadow[id].associated_id = NO_ASSOCIATED_ID;



	(*ring_req)->u.rw.id = id;

	rinfo->shadow[id].req.u.rw.id = id;



	return id;

}
@@ -544,11 +544,12 @@ static unsigned long blkif_ring_get_request(struct blkfront_ring_info *rinfo, 
static int blkif_queue_discard_req(struct request *req, struct blkfront_ring_info *rinfo)

{

	struct blkfront_info *info = rinfo->dev_info;

	struct blkif_request *ring_req;

	struct blkif_request *ring_req, *final_ring_req;

	unsigned long id;



	/* Fill out a communications ring structure. */

	id = blkif_ring_get_request(rinfo, req, &ring_req);

	id = blkif_ring_get_request(rinfo, req, &final_ring_req);

	ring_req = &rinfo->shadow[id].req;



	ring_req->operation = BLKIF_OP_DISCARD;

	ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
@@ -559,8 +560,8 @@ static int blkif_queue_discard_req(struct request *req, struct blkfront_ring_inf 
	else

		ring_req->u.discard.flag = 0;



	/* Keep a private copy so we can reissue requests when recovering. */

	rinfo->shadow[id].req = *ring_req;

	/* Copy the request to the ring page. */

	*final_ring_req = *ring_req;



	return 0;

}
@@ -693,6 +694,7 @@ 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 = NULL;

	unsigned long id, extra_id = NO_ASSOCIATED_ID;

	bool require_extra_req = false;

	int i;
@@ -737,7 +739,8 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri 
	}



	/* Fill out a communications ring structure. */

	id = blkif_ring_get_request(rinfo, req, &ring_req);

	id = blkif_ring_get_request(rinfo, req, &final_ring_req);

	ring_req = &rinfo->shadow[id].req;



	num_sg = blk_rq_map_sg(req->q, req, rinfo->shadow[id].sg);

	num_grant = 0;
@@ -788,7 +791,9 @@ 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;



			/*

			 * Only the first request contains the scatter-gather

			 * list.
@@ -830,10 +835,10 @@ 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;



	if (new_persistent_gnts)

		gnttab_free_grant_references(setup.gref_head);