From fb1131b674e492a5f91abd77b9fcc9a9e2b88eb7 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 21 Sep 2016 16:52:26 +0100 Subject: [PATCH] virtio: handle virtqueue_get_head() errors Stop processing the vring if virtqueue_get_head() fetches an out-of-bounds head index. Signed-off-by: Stefan Hajnoczi Reviewed-by: Cornelia Huck Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin Reviewed-by: Cornelia Huck --- hw/virtio/virtio.c | 27 +++++++++++++++++---------- 1 file changed, 17 insertions(+), 10 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index b7ac356..18ce333 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -360,21 +360,20 @@ static int virtqueue_num_heads(VirtQueue *vq, unsigned int idx) return num_heads; } -static unsigned int virtqueue_get_head(VirtQueue *vq, unsigned int idx) +static bool virtqueue_get_head(VirtQueue *vq, unsigned int idx, + unsigned int *head) { - unsigned int head; - /* Grab the next descriptor number they're advertising, and increment * the index we've seen. */ - head = vring_avail_ring(vq, idx % vq->vring.num); + *head = vring_avail_ring(vq, idx % vq->vring.num); /* If their number is silly, that's a fatal mistake. */ - if (head >= vq->vring.num) { - error_report("Guest says index %u is available", head); - exit(1); + if (*head >= vq->vring.num) { + virtio_error(vq->vdev, "Guest says index %u is available", *head); + return false; } - return head; + return true; } enum { @@ -426,7 +425,11 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, max = vq->vring.num; num_bufs = total_bufs; - i = virtqueue_get_head(vq, idx++); + + if (!virtqueue_get_head(vq, idx++, &i)) { + goto err; + } + desc_pa = vq->vring.desc; vring_desc_read(vdev, &desc, desc_pa, i); @@ -660,11 +663,15 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) return NULL; } - i = head = virtqueue_get_head(vq, vq->last_avail_idx++); + if (!virtqueue_get_head(vq, vq->last_avail_idx++, &head)) { + return NULL; + } + if (virtio_vdev_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX)) { vring_set_avail_event(vq, vq->last_avail_idx); } + i = head; vring_desc_read(vdev, &desc, desc_pa, i); if (desc.flags & VRING_DESC_F_INDIRECT) { if (desc.len % sizeof(VRingDesc)) { -- 2.7.4