From 22f4cb04e3660b6be75ee9b6a4a8f8cfe8f8070f Mon Sep 17 00:00:00 2001 From: P J P Date: Mon, 25 Jul 2016 17:37:18 +0530 Subject: [PATCH] virtio: error out if guest exceeds virtqueue size A broken or malicious guest can submit more requests than the virtqueue size permits. The guest can submit requests without bothering to wait for completion and is therefore not bound by virtqueue size. This requires reusing vring descriptors in more than one request, which is incorrect but possible. Processing a request allocates a VirtQueueElement and therefore causes unbounded memory allocation controlled by the guest. Exit with an error if the guest provides more requests than the virtqueue size permits. This bounds memory allocation and makes the buggy guest visible to the user. upstream-commit-id: afd9096eb1882f23929f5b5c177898ed231bac66 Reported-by: Zhenhao Hong Signed-off-by: Stefan Hajnoczi Signed-off-by: Stefano Stabellini --- hw/virtio.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/hw/virtio.c b/hw/virtio.c index f7f12114b..f583e06b3 100644 --- a/hw/virtio.c +++ b/hw/virtio.c @@ -449,6 +449,11 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem) max = vq->vring.num; + if (vq->inuse >= max) { + error_report("Virtqueue size exceeded"); + exit(1); + } + i = head = virtqueue_get_head(vq, vq->last_avail_idx++); if (vq->vdev->guest_features & (1 << VIRTIO_RING_F_EVENT_IDX)) { vring_avail_event(vq, vring_avail_idx(vq)); -- 2.39.5