Commit 34c6bf22 authored Mar 01, 2017 by Cornelia Huck Committed by Michael S. Tsirkin Mar 02, 2017

virtio: guard vring access when setting notification



Switching to vring caches exposed an existing bug in
virtio_queue_set_notification(): We can't access vring structures
if they have not been set up yet. This may happen, for example,
for virtio-blk devices with multiple queues: The code will try to
switch notifiers for every queue, but the guest may have only set up
a subset of them.

Fix this by guarding access to the vring memory by checking for
vring.desc. The first aio poll will iron out any remaining
inconsistencies for later-configured queues (buggy legacy drivers).

Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

parent dd3dd4ba

hw/virtio/virtio.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -288,6 +288,10 @@ void virtio_queue_set_notification(VirtQueue *vq, int enable)
		{
		vq->notification = enable;

		if (!vq->vring.desc) {
		return;
		}

		rcu_read_lock();
		if (virtio_vdev_has_feature(vq->vdev, VIRTIO_RING_F_EVENT_IDX)) {
		vring_set_avail_event(vq, vring_avail_idx(vq));