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

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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>
This commit is contained in:
Juergen Gross 2021-07-30 12:38:53 +02:00
parent 71b66243f9
commit 8f5a695d99
1 changed files with 15 additions and 10 deletions
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25
drivers/block/xen-blkfront.c
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@ -533,7 +533,7 @@ 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;
}
@ -541,11 +541,12 @@ 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);
@ -556,8 +557,8 @@ 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;
}
@ -690,6 +691,7 @@ 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;
@ -734,7 +736,8 @@ 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;
@ -785,7 +788,9 @@ 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.
@ -827,10 +832,10 @@ 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);