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virtio: guard vring access when setting notification

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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>
This commit is contained in:
Cornelia Huck 2017-03-01 18:58:52 +01:00 committed by Michael S. Tsirkin
parent dd3dd4ba7b
commit 34c6bf22a8
1 changed files with 4 additions and 0 deletions
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4
hw/virtio/virtio.c
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@ -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));