From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34948) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akwGj-0002TL-Sl for qemu-devel@nongnu.org; Tue, 29 Mar 2016 12:13:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1akwGh-00028Y-HX for qemu-devel@nongnu.org; Tue, 29 Mar 2016 12:13:25 -0400 Received: from mx1.redhat.com ([209.132.183.28]:40092) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1akwGh-00028T-AO for qemu-devel@nongnu.org; Tue, 29 Mar 2016 12:13:23 -0400 From: Stefan Hajnoczi Date: Tue, 29 Mar 2016 17:13:01 +0100 Message-Id: <1459267981-23408-10-git-send-email-stefanha@redhat.com> In-Reply-To: <1459267981-23408-1-git-send-email-stefanha@redhat.com> References: <1459267981-23408-1-git-send-email-stefanha@redhat.com> Subject: [Qemu-devel] [RFC v2 9/9] virtio: handle virtqueue_get_head() errors List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Cornelia Huck , Fam Zheng , Stefan Hajnoczi , "Michael S. Tsirkin" Stop processing the vring if virtqueue_get_head() fetches an out-of-bounds head index. Signed-off-by: Stefan Hajnoczi --- hw/virtio/virtio.c | 26 ++++++++++++++++---------- 1 file changed, 16 insertions(+), 10 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 8ffcddc..0dd48d4 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -333,21 +333,20 @@ 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 { @@ -399,7 +398,11 @@ 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); @@ -618,11 +621,14 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) max = vq->vring.num; - 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)) { -- 2.5.5