From 412e0e81b17488e228b4f8451df6a4af26064bb4 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Wed, 21 Sep 2016 16:52:24 +0100 Subject: [PATCH] virtio: handle virtqueue_read_next_desc() errors Stop processing the vring if an avail ring index is invalid. 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 | 45 ++++++++++++++++++++++++++++++++------------- 1 file changed, 32 insertions(+), 13 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 973d0c2228..82142c6703 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -377,28 +377,33 @@ static unsigned int virtqueue_get_head(VirtQueue *vq, unsigned int idx) return head; } -static unsigned virtqueue_read_next_desc(VirtIODevice *vdev, VRingDesc *desc, - hwaddr desc_pa, unsigned int max) -{ - unsigned int next; +enum { + VIRTQUEUE_READ_DESC_ERROR = -1, + VIRTQUEUE_READ_DESC_DONE = 0, /* end of chain */ + VIRTQUEUE_READ_DESC_MORE = 1, /* more buffers in chain */ +}; +static int virtqueue_read_next_desc(VirtIODevice *vdev, VRingDesc *desc, + hwaddr desc_pa, unsigned int max, + unsigned int *next) +{ /* If this descriptor says it doesn't chain, we're done. */ if (!(desc->flags & VRING_DESC_F_NEXT)) { - return max; + return VIRTQUEUE_READ_DESC_DONE; } /* Check they're not leading us off end of descriptors. */ - next = desc->next; + *next = desc->next; /* Make sure compiler knows to grab that: we don't want it changing! */ smp_wmb(); - if (next >= max) { - error_report("Desc next is %u", next); - exit(1); + if (*next >= max) { + virtio_error(vdev, "Desc next is %u", *next); + return VIRTQUEUE_READ_DESC_ERROR; } - vring_desc_read(vdev, desc, desc_pa, next); - return next; + vring_desc_read(vdev, desc, desc_pa, *next); + return VIRTQUEUE_READ_DESC_MORE; } void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, @@ -407,6 +412,7 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, { unsigned int idx; unsigned int total_bufs, in_total, out_total; + int rc; idx = vq->last_avail_idx; @@ -459,7 +465,13 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, if (in_total >= max_in_bytes && out_total >= max_out_bytes) { goto done; } - } while ((i = virtqueue_read_next_desc(vdev, &desc, desc_pa, max)) != max); + + rc = virtqueue_read_next_desc(vdev, &desc, desc_pa, max, &i); + } while (rc == VIRTQUEUE_READ_DESC_MORE); + + if (rc == VIRTQUEUE_READ_DESC_ERROR) { + goto err; + } if (!indirect) total_bufs = num_bufs; @@ -621,6 +633,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) hwaddr addr[VIRTQUEUE_MAX_SIZE]; struct iovec iov[VIRTQUEUE_MAX_SIZE]; VRingDesc desc; + int rc; if (unlikely(vdev->broken)) { return NULL; @@ -688,7 +701,13 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz) virtio_error(vdev, "Looped descriptor"); goto err_undo_map; } - } while ((i = virtqueue_read_next_desc(vdev, &desc, desc_pa, max)) != max); + + rc = virtqueue_read_next_desc(vdev, &desc, desc_pa, max, &i); + } while (rc == VIRTQUEUE_READ_DESC_MORE); + + if (rc == VIRTQUEUE_READ_DESC_ERROR) { + goto err_undo_map; + } /* Now copy what we have collected and mapped */ elem = virtqueue_alloc_element(sz, out_num, in_num); -- 2.11.0