From 34c6bf22a8d9b60c513df151aa0a791ef53bf81d Mon Sep 17 00:00:00 2001 From: Cornelia Huck 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 Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- 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)); -- GitLab