| From foo@baz Mon Nov 29 07:12:46 PM CET 2021 |
| From: Juergen Gross <jgross@suse.com> |
| Date: Mon, 29 Nov 2021 14:00:21 +0100 |
| Subject: xen/blkfront: don't take local copy of a request from the ring page |
| |
| From: Juergen Gross <jgross@suse.com> |
| |
| 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: Juergen Gross <jgross@suse.com> |
| Reviewed-by: Jan Beulich <jbeulich@suse.com> |
| Acked-by: Roger Pau Monné <roger.pau@citrix.com> |
| Link: https://lore.kernel.org/r/20210730103854.12681-3-jgross@suse.com |
| Signed-off-by: Juergen Gross <jgross@suse.com> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| drivers/block/xen-blkfront.c | 38 ++++++++++++++++++++++++++------------ |
| 1 file changed, 26 insertions(+), 12 deletions(-) |
| |
| --- a/drivers/block/xen-blkfront.c |
| +++ b/drivers/block/xen-blkfront.c |
| @@ -456,16 +456,31 @@ static int blkif_ioctl(struct block_devi |
| 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(struc |
| |
| 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(uns |
| 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 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 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); |