vhost: check for ring descriptors overflow

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>

diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
index c1760ff..b0d0dff 100644 (file)
--- a/lib/librte_vhost/vhost_rxtx.c
+++ b/lib/librte_vhost/vhost_rxtx.c
@@ -183,6 +183,8 @@ 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);
@@ -345,7 +347,7 @@ 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;
@@ -761,6 +763,8 @@ copy_desc_to_mbuf(struct virtio_net *dev, struct vhost_virtqueue *vq,
        while (desc_avail != 0 || (desc->flags & VRING_DESC_F_NEXT) != 0) {
                /* This desc reaches to its end, get the next one */
                if (desc_avail == 0) {
+                       if (unlikely(desc->next >= vq->size))
+                               return -1;
                        desc = &vq->desc[desc->next];
 
                        desc_addr = gpa_to_vva(dev, desc->addr);