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Commit 5e8cdf4c 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 7225148b

drivers/block/xen-blkfront.c

+26 −12
Original line number Diff line number Diff line
@@ -456,16 +456,31 @@ static int blkif_ioctl(struct block_device *bdev, fmode_t mode, 
	return 0;

}



static unsigned long blkif_ring_get_request(struct blkfront_info *info,

					    struct request *req,

					    struct blkif_request **ring_req)

{

	unsigned long id;



	*ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);

	info->ring.req_prod_pvt++;



	id = get_id_from_freelist(info);

	info->shadow[id].request = req;

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



	return id;

}



static int blkif_queue_discard_req(struct request *req)

{

	struct blkfront_info *info = req->rq_disk->private_data;

	struct blkif_request *ring_req;

	struct blkif_request *ring_req, *final_ring_req;

	unsigned long id;



	/* Fill out a communications ring structure. */

	ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);

	id = get_id_from_freelist(info);

	info->shadow[id].request = req;

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

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



	ring_req->operation = BLKIF_OP_DISCARD;

	ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
@@ -478,8 +493,8 @@ static int blkif_queue_discard_req(struct request *req) 


	info->ring.req_prod_pvt++;



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

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

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

	*final_ring_req = *ring_req;



	return 0;

}
@@ -569,7 +584,7 @@ static void blkif_setup_rw_req_grant(unsigned long gfn, unsigned int offset, 
static int blkif_queue_rw_req(struct request *req)

{

	struct blkfront_info *info = req->rq_disk->private_data;

	struct blkif_request *ring_req;

	struct blkif_request *ring_req, *final_ring_req;

	unsigned long id;

	int i;

	struct setup_rw_req setup = {
@@ -613,9 +628,8 @@ static int blkif_queue_rw_req(struct request *req) 
		new_persistent_gnts = 0;



	/* Fill out a communications ring structure. */

	ring_req = RING_GET_REQUEST(&info->ring, info->ring.req_prod_pvt);

	id = get_id_from_freelist(info);

	info->shadow[id].request = req;

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

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



	BUG_ON(info->max_indirect_segments == 0 &&

	       GREFS(req->nr_phys_segments) > BLKIF_MAX_SEGMENTS_PER_REQUEST);
@@ -696,8 +710,8 @@ static int blkif_queue_rw_req(struct request *req) 


	info->ring.req_prod_pvt++;



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

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

	/* Copy request(s) to the ring page. */

	*final_ring_req = *ring_req;



	if (new_persistent_gnts)

		gnttab_free_grant_references(setup.gref_head);