blkback/blktap: 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 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@citrix.com>
Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Orabug: 26315576
Signed-off-by: Chuck Anderson <chuck.anderson@oracle.com>
Conflicts:
	drivers/block/xen-blkback/blkback.c (code base)

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index 6a41383b3f072d29a9525db5fcf1c6e70b8819e9..83ab268701962f6dc53462b6cf3750d4c8b8b2f7 100644 (file)
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -1431,34 +1431,35 @@ static int dispatch_rw_block_io(struct xen_blkif_ring *ring,
 static void make_response(struct xen_blkif_ring *ring, u64 id,
                          unsigned short op, int st)
 {
-       struct blkif_response  resp;
+       struct blkif_response *resp;
        unsigned long     flags;
        union blkif_back_rings *blk_rings;
        int notify;
 
-       resp.id        = id;
-       resp.operation = op;
-       resp.status    = st;
-
        spin_lock_irqsave(&ring->blk_ring_lock, flags);
        blk_rings = &ring->blk_rings;
        /* Place on the response ring for the relevant domain. */
        switch (ring->blkif->blk_protocol) {
        case BLKIF_PROTOCOL_NATIVE:
-               memcpy(RING_GET_RESPONSE(&blk_rings->native, blk_rings->native.rsp_prod_pvt),
-                      &resp, sizeof(resp));
+               resp = RING_GET_RESPONSE(&blk_rings->native,
+                                        blk_rings->native.rsp_prod_pvt);
                break;
        case BLKIF_PROTOCOL_X86_32:
-               memcpy(RING_GET_RESPONSE(&blk_rings->x86_32, blk_rings->x86_32.rsp_prod_pvt),
-                      &resp, sizeof(resp));
+               resp = RING_GET_RESPONSE(&blk_rings->x86_32,
+                                        blk_rings->x86_32.rsp_prod_pvt);
                break;
        case BLKIF_PROTOCOL_X86_64:
-               memcpy(RING_GET_RESPONSE(&blk_rings->x86_64, blk_rings->x86_64.rsp_prod_pvt),
-                      &resp, sizeof(resp));
+               resp = RING_GET_RESPONSE(&blk_rings->x86_64,
+                                        blk_rings->x86_64.rsp_prod_pvt);
                break;
        default:
                BUG();
        }
+
+       resp->id        = id;
+       resp->operation = op;
+       resp->status    = st;
+
        blk_rings->common.rsp_prod_pvt++;
        RING_PUSH_RESPONSES_AND_CHECK_NOTIFY(&blk_rings->common, notify);
        spin_unlock_irqrestore(&ring->blk_ring_lock, flags);

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index dea61f6ab8cbdbaffedceb4c64bda239b51a63a4..aca9397277e95c268de0ecaee4a791a6644bd5fa 100644 (file)
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -75,9 +75,8 @@ extern unsigned int xenblk_max_queues;
 struct blkif_common_request {
        char dummy;
 };
-struct blkif_common_response {
-       char dummy;
-};
+
+/* i386 protocol version */
 
 struct blkif_x86_32_request_rw {
        uint8_t        nr_segments;  /* number of segments                   */
@@ -129,14 +128,6 @@ struct blkif_x86_32_request {
        } u;
 } __attribute__((__packed__));
 
-/* i386 protocol version */
-#pragma pack(push, 4)
-struct blkif_x86_32_response {
-       uint64_t        id;              /* copied from request */
-       uint8_t         operation;       /* copied from request */
-       int16_t         status;          /* BLKIF_RSP_???       */
-};
-#pragma pack(pop)
 /* x86_64 protocol version */
 
 struct blkif_x86_64_request_rw {
@@ -193,18 +184,12 @@ struct blkif_x86_64_request {
        } u;
 } __attribute__((__packed__));
 
-struct blkif_x86_64_response {
-       uint64_t       __attribute__((__aligned__(8))) id;
-       uint8_t         operation;       /* copied from request */
-       int16_t         status;          /* BLKIF_RSP_???       */
-};
-
 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 __packed);
 DEFINE_RING_TYPES(blkif_x86_64, struct blkif_x86_64_request,
-                 struct blkif_x86_64_response);
+                 struct blkif_response);
 
 union blkif_back_rings {
        struct blkif_back_ring        native;