virtio-ccw: range check in READ_VQ_CONF

Processing for READ_VQ_CONF needs to check whether the requested queue
value is actually in the supported range and post a channel program
check if not.

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

hw/s390x/virtio-ccw.c

@@ -549,6 +549,10 @@ static int virtio_ccw_cb(SubchDev *sch, CCW1 ccw)
             ret = -EFAULT;
         } else {
             vq_config.index = lduw_be_phys(&address_space_memory, ccw.cda);
+            if (vq_config.index >= VIRTIO_PCI_QUEUE_MAX) {
+                ret = -EINVAL;
+                break;
+            }
             vq_config.num_max = virtio_queue_get_num(vdev,
                                                      vq_config.index);
             stw_be_phys(&address_space_memory,