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

[patchbot@xxxxxxx]

commit 414d069b38ab114b89085e44989bf57604ea86d7
Author:     Jan Beulich <jbeulich@xxxxxxxx>
AuthorDate: Wed Jun 21 16:27:06 2017 +0100
Commit:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
CommitDate: Wed Jun 21 16:27:06 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 (the old code did make this assumption too).
    
    This is XSA-216.
    
    Reported-by: Anthony Perard <anthony.perard@xxxxxxxxxx>
    Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
    Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
    Acked-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
---
 hw/block/xen_blkif.h | 21 +++------------------
 hw/block/xen_disk.c  | 25 ++++++++++++-------------
 2 files changed, 15 insertions(+), 31 deletions(-)

diff --git a/hw/block/xen_blkif.h b/hw/block/xen_blkif.h
index 3300b6f..0554b94 100644
--- a/hw/block/xen_blkif.h
+++ b/hw/block/xen_blkif.h
@@ -14,9 +14,6 @@
 struct blkif_common_request {
     char dummy;
 };
-struct blkif_common_response {
-    char dummy;
-};
 
 /* i386 protocol version */
 #pragma pack(push, 4)
@@ -36,13 +33,7 @@ struct blkif_x86_32_request_discard {
     blkif_sector_t sector_number;    /* start sector idx on disk (r/w only)  */
     uint64_t       nr_sectors;       /* # of contiguous sectors to discard   */
 };
-struct blkif_x86_32_response {
-    uint64_t        id;              /* copied from request */
-    uint8_t         operation;       /* copied from request */
-    int16_t         status;          /* BLKIF_RSP_???       */
-};
 typedef struct blkif_x86_32_request blkif_x86_32_request_t;
-typedef struct blkif_x86_32_response blkif_x86_32_response_t;
 #pragma pack(pop)
 
 /* x86_64 protocol version */
@@ -62,20 +53,14 @@ struct blkif_x86_64_request_discard {
     blkif_sector_t sector_number;    /* start sector idx on disk (r/w only)  */
     uint64_t       nr_sectors;       /* # of contiguous sectors to discard   */
 };
-struct blkif_x86_64_response {
-    uint64_t       __attribute__((__aligned__(8))) id;
-    uint8_t         operation;       /* copied from request */
-    int16_t         status;          /* BLKIF_RSP_???       */
-};
 typedef struct blkif_x86_64_request blkif_x86_64_request_t;
-typedef struct blkif_x86_64_response blkif_x86_64_response_t;
 
 DEFINE_RING_TYPES(blkif_common, struct blkif_common_request,
-                  struct blkif_common_response);
+                  struct blkif_response);
 DEFINE_RING_TYPES(blkif_x86_32, struct blkif_x86_32_request,
-                  struct blkif_x86_32_response);
+                  struct blkif_response QEMU_PACKED);
 DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request,
-                  struct blkif_x86_64_response);
+                  struct blkif_response);
 
 union blkif_back_rings {
     blkif_back_ring_t        native;
diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 456a2d5..33a51cc 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 = 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 = 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 = 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

_______________________________________________
Xen-changelog mailing list
Xen-changelog@xxxxxxxxxxxxx
https://lists.xenproject.org/xen-changelog