[dpdk-dev] [PATCH v2 7/7] vhost: do sanity check for desc->next

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

A malicious guest may easily forge some illegal vring desc buf.
To make our vhost robust, we need make sure desc->next will not
go beyond the vq->desc[] array.

Suggested-by: Rich Lane <rich.lane@bigswitch.com>
Signed-off-by: Yuanhan Liu <yuanhan.liu@linux.intel.com>
---
 lib/librte_vhost/vhost_rxtx.c | 15 +++++++++++----
 1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index c2adcd9..b0c0c94 100644
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -148,6 +148,8 @@ copy_mbuf_to_desc(struct virtio_net *dev, struct vhost_virtqueue *vq,
 				/* Room in vring buffer is not enough */
 				return -1;
 			}
+			if (unlikely(desc->next >= vq->size))
+				return -1;
 
 			desc = &vq->desc[desc->next];
 			desc_addr   = gpa_to_vva(dev, desc->addr);
@@ -302,7 +304,7 @@ fill_vec_buf(struct vhost_virtqueue *vq, uint32_t avail_idx,
 	uint32_t len    = *allocated;
 
 	while (1) {
-		if (vec_id >= BUF_VECTOR_MAX)
+		if (unlikely(vec_id >= BUF_VECTOR_MAX || idx >= vq->size))
 			return -1;
 
 		len += vq->desc[idx].len;
@@ -671,6 +673,8 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	while (desc_avail || (desc->flags & VRING_DESC_F_NEXT) != 0) {
 		/* This desc reachs to its end, get the next one */
 		if (desc_avail == 0) {
+			if (unlikely(desc->next >= vq->size))
+				goto fail;
 			desc = &vq->desc[desc->next];
 
 			desc_addr = gpa_to_vva(dev, desc->addr);
@@ -691,9 +695,7 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 			if (unlikely(!cur)) {
 				RTE_LOG(ERR, VHOST_DATA, "Failed to "
 					"allocate memory for mbuf.\n");
-				if (head)
-					rte_pktmbuf_free(head);
-				return NULL;
+				goto fail;
 			}
 			if (!head) {
 				head = cur;
@@ -729,6 +731,11 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	}
 
 	return head;
+
+fail:
+	if (head)
+		rte_pktmbuf_free(head);
+	return NULL;
 }
 
 uint16_t
-- 
1.9.0