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-rw-r--r--hw/virtio/virtio.c12
1 files changed, 9 insertions, 3 deletions
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 09f62c6c70..60653f764e 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)