This is a note to let you know that I've just added the patch titled
xen/blkfront: don't take local copy of a request from the ring page
to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-blkfront-don-t-take-local-copy-of-a-request-from-the-ring-page.patch
and it can be found in the queue-4.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Mon Nov 29 07:12:46 PM CET 2021
From: Juergen Gross <jgross@xxxxxxxx>
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@xxxxxxxx>
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@xxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210730103854.12681-3-jgross@xxxxxxxx
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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);
Patches currently in stable-queue which might be from jgross@xxxxxxxx are
queue-4.4/xen-blkfront-read-response-from-backend-only-once.patch
queue-4.4/tty-hvc-replace-bug_on-with-negative-return-value.patch
queue-4.4/xen-blkfront-don-t-trust-the-backend-response-data-blindly.patch
queue-4.4/xen-sync-include-xen-interface-io-ring.h-with-xen-s-newest-version.patch
queue-4.4/xen-blkfront-don-t-take-local-copy-of-a-request-from-the-ring-page.patch
queue-4.4/xen-detect-uninitialized-xenbus-in-xenbus_init.patch
queue-4.4/xen-netfront-don-t-read-data-from-request-on-the-ring-page.patch
queue-4.4/xen-netfront-disentangle-tx_skb_freelist.patch
queue-4.4/xen-netfront-read-response-from-backend-only-once.patch
queue-4.4/xen-netfront-don-t-trust-the-backend-response-data-blindly.patch
