[dpdk-stable] [PATCH 17.11] vhost: fix access for indirect descriptors

[Tiwei Bie <tiwei.bie@intel.com>]

[ backported from upstream commit 48006390003b81f6d5c7b78e3f02ed49d1049945 ]

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")

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>
---
 lib/librte_vhost/virtio_net.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/librte_vhost/virtio_net.c b/lib/librte_vhost/virtio_net.c
index 3e2935992..07d4609ee 100644
--- a/lib/librte_vhost/virtio_net.c
+++ b/lib/librte_vhost/virtio_net.c
@@ -565,6 +565,7 @@ fill_vec_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	uint16_t idx = vq->avail->ring[avail_idx & (vq->size - 1)];
 	uint32_t vec_id = *vec_idx;
 	uint32_t len    = 0;
+	uint32_t nr_descs = vq->size;
 	uint64_t dlen;
 	struct vring_desc *descs = vq->desc;
 	struct vring_desc *idesc = NULL;
@@ -576,6 +577,7 @@ fill_vec_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 
 	if (vq->desc[idx].flags & VRING_DESC_F_INDIRECT) {
 		dlen = vq->desc[idx].len;
+		nr_descs = dlen / sizeof(struct vring_desc);
 		descs = (struct vring_desc *)(uintptr_t)
 			vhost_iova_to_vva(dev, vq, vq->desc[idx].addr,
 						&dlen,
@@ -599,7 +601,7 @@ fill_vec_buf(struct virtio_net *dev, struct vhost_virtqueue *vq,
 	}
 
 	while (1) {
-		if (unlikely(vec_id >= BUF_VECTOR_MAX || idx >= vq->size)) {
+		if (unlikely(vec_id >= BUF_VECTOR_MAX || idx >= nr_descs)) {
 			free_ind_table(idesc);
 			return -1;
 		}
-- 
2.17.1