[Xen-changelog] [qemu-xen master] xen/disk: don't leak stack data via response ring

[patchbot@xxxxxxx]

commit f3bee573a9d69e1add0bb1c5da1db2b0b49abdee
Author:     Stefano Stabellini <sstabellini@xxxxxxxxxx>
AuthorDate: Tue Jun 27 14:45:34 2017 -0700
Commit:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
CommitDate: Wed Aug 2 16:07:24 2017 +0100

    xen/disk: don't leak stack data via response ring
    
    Rather than constructing a local structure instance on the stack, fill
    the fields directly on the shared ring, just like other (Linux)
    backends do. Build on the fact that all response structure flavors are
    actually identical (aside from alignment and padding at the end).
    
    This is XSA-216.
    
    Reported by: Anthony Perard <anthony.perard@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Signed-off-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
    Acked-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
    (cherry picked from commit b0ac694fdb9113b973048ebe5619927e74965f61)
---
 hw/block/xen_disk.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 456a2d5..590f46f 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -769,31 +769,30 @@ static int blk_send_response_one(struct ioreq *ioreq)
     struct XenBlkDev  *blkdev = ioreq->blkdev;
     int               send_notify   = 0;
     int               have_requests = 0;
-    blkif_response_t  resp;
-    void              *dst;
-
-    resp.id        = ioreq->req.id;
-    resp.operation = ioreq->req.operation;
-    resp.status    = ioreq->status;
+    blkif_response_t  *resp;
 
     /* Place on the response ring for the relevant domain. */
     switch (blkdev->protocol) {
     case BLKIF_PROTOCOL_NATIVE:
-        dst = RING_GET_RESPONSE(&blkdev->rings.native, 
blkdev->rings.native.rsp_prod_pvt);
+        resp = (blkif_response_t *) RING_GET_RESPONSE(&blkdev->rings.native,
+                                 blkdev->rings.native.rsp_prod_pvt);
         break;
     case BLKIF_PROTOCOL_X86_32:
-        dst = RING_GET_RESPONSE(&blkdev->rings.x86_32_part,
-                                blkdev->rings.x86_32_part.rsp_prod_pvt);
+        resp = (blkif_response_t *) 
RING_GET_RESPONSE(&blkdev->rings.x86_32_part,
+                                 blkdev->rings.x86_32_part.rsp_prod_pvt);
         break;
     case BLKIF_PROTOCOL_X86_64:
-        dst = RING_GET_RESPONSE(&blkdev->rings.x86_64_part,
-                                blkdev->rings.x86_64_part.rsp_prod_pvt);
+        resp = (blkif_response_t *) 
RING_GET_RESPONSE(&blkdev->rings.x86_64_part,
+                                 blkdev->rings.x86_64_part.rsp_prod_pvt);
         break;
     default:
-        dst = NULL;
         return 0;
     }
-    memcpy(dst, &resp, sizeof(resp));
+
+    resp->id        = ioreq->req.id;
+    resp->operation = ioreq->req.operation;
+    resp->status    = ioreq->status;
+
     blkdev->rings.common.rsp_prod_pvt++;
 
     RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blkdev->rings.common, send_notify);
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master

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