vhost: fix access for indirect descriptors

Fix a possible out of bound access which may happen when handling
indirect descs in split ring.

Fixes: 1be4ebb1c464 ("vhost: support indirect descriptor in mergeable Rx")
Cc: stable@dpdk.org
Reported-by: Haiyue Wang <haiyue.wang@intel.com>
Signed-off-by: Tiwei Bie <tiwei.bie@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 0893a1d..37a4c00 100644 (file)
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -310,6 +310,7 @@ fill_vec_buf_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
        uint32_t len    = 0;
        uint64_t dlen;
        uint32_t nr_descs = vq->size;
+       uint32_t cnt    = 0;
        struct vring_desc *descs = vq->desc;
        struct vring_desc *idesc = NULL;
 
@@ -348,12 +349,7 @@ fill_vec_buf_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
        }
 
        while (1) {
-               if (unlikely(idx >= vq->size)) {
-                       free_ind_table(idesc);
-                       return -1;
-               }
-
-               if (unlikely(nr_descs-- == 0)) {
+               if (unlikely(idx >= nr_descs || cnt++ >= nr_descs)) {
                        free_ind_table(idesc);
                        return -1;
                }