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[PULL,1/2] hw/virtio/virtio: Don't allow guests to add/remove queues

Message ID 1376305261-29561-2-git-send-email-peter.maydell@linaro.org
State New
Headers show

Commit Message

Peter Maydell Aug. 12, 2013, 11:01 a.m. UTC 
A queue size of 0 is used to indicate a nonexistent queue, so
don't allow the guest to flip a queue between zero-size and
non-zero-size. Don't permit setting of negative queue sizes
either.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1374853288-9912-2-git-send-email-peter.maydell@linaro.org
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/virtio/virtio.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)
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Patch

diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 09f62c6..60653f7 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -673,10 +673,16 @@  hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)
 
 void virtio_queue_set_num(VirtIODevice *vdev, int n, int num)
 {
-    if (num <= VIRTQUEUE_MAX_SIZE) {
-        vdev->vq[n].vring.num = num;
-        virtqueue_init(&vdev->vq[n]);
+    /* Don't allow guest to flip queue between existent and
+     * nonexistent states, or to set it to an invalid size.
+     */
+    if (!!num != !!vdev->vq[n].vring.num ||
+        num > VIRTQUEUE_MAX_SIZE ||
+        num < 0) {
+        return;
     }
+    vdev->vq[n].vring.num = num;
+    virtqueue_init(&vdev->vq[n]);
 }
 
 int virtio_queue_get_num(VirtIODevice *vdev, int n)