lkml.org 
[lkml]   [2021]   [Dec]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 4.9 30/62] xen/blkfront: dont take local copy of a request from the ring page
    Date
    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 | 25 +++++++++++++++----------
    1 file changed, 15 insertions(+), 10 deletions(-)

    --- a/drivers/block/xen-blkfront.c
    +++ b/drivers/block/xen-blkfront.c
    @@ -532,7 +532,7 @@ static unsigned long blkif_ring_get_requ
    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;
    }
    @@ -540,11 +540,12 @@ static unsigned long blkif_ring_get_requ
    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);
    @@ -555,8 +556,8 @@ static int blkif_queue_discard_req(struc
    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;
    }
    @@ -689,6 +690,7 @@ static int blkif_queue_rw_req(struct req
    {
    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;
    @@ -730,7 +732,8 @@ static int blkif_queue_rw_req(struct req
    }

    /* 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;
    @@ -781,7 +784,9 @@ static int blkif_queue_rw_req(struct req
    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.
    @@ -823,10 +828,10 @@ static int blkif_queue_rw_req(struct req
    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 (max_grefs > 0)
    gnttab_free_grant_references(setup.gref_head);

    \
     
     \ /
      Last update: 2021-12-06 16:04    [W:2.906 / U:0.000 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site