virtio-ccw: fix range check for SET_VQ

VIRTIO_PCI_QUEUE_MAX is already too big; a malicious guest would be
able to trigger a write beyond the VirtQueue structure.

Cc: qemu-stable@nongnu.org
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>

hw/s390x/virtio-ccw.c

@@ -266,7 +266,7 @@ static int virtio_ccw_set_vqs(SubchDev *sch, uint64_t addr, uint32_t align,
 {
     VirtIODevice *vdev = virtio_ccw_get_vdev(sch);
 
-    if (index > VIRTIO_PCI_QUEUE_MAX) {
+    if (index >= VIRTIO_PCI_QUEUE_MAX) {
         return -EINVAL;
     }