From 34c6bf22a8d9b60c513df151aa0a791ef53bf81d Mon Sep 17 00:00:00 2001
From: Cornelia Huck <cornelia.huck@de.ibm.com>
Date: Wed, 1 Mar 2017 18:58:52 +0100
Subject: [PATCH] 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>
---
hw/virtio/virtio.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index e487e36cda..bf8a644677 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -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));
--
2.30.2