vhost: fix missing vring call check on virtqueue access

[ upstream commit af7f683615244675fc4f472a2aa42880896476ad ]

Acquiring the access lock is not enough to ensure
virtqueue's metadata such as vring pointers are valid.

The access status must also be checked.

Fixes: 6c299bb ("vhost: introduce vring call API")
Fixes: c573699 ("vhost: fix missing virtqueue lock protection")
Fixes: 830f7e7 ("vhost: add non-blocking API for posting interrupt")

Reported-by: Li Feng <fengli@smartx.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: David Marchand <david.marchand@redhat.com>

lib/librte_vhost/vhost.c

@@ -1253,6 +1253,7 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
 {
 	struct virtio_net *dev;
 	struct vhost_virtqueue *vq;
+	int ret = 0;
 
 	dev = get_device(vid);
 	if (!dev)
@@ -1267,21 +1268,28 @@ rte_vhost_vring_call(int vid, uint16_t vring_idx)
 
 	rte_spinlock_lock(&vq->access_lock);
 
+	if (unlikely(!vq->access_ok)) {
+		ret = -1;
+		goto out_unlock;
+	}
+
 	if (vq_is_packed(dev))
 		vhost_vring_call_packed(dev, vq);
 	else
 		vhost_vring_call_split(dev, vq);
 
+out_unlock:
 	rte_spinlock_unlock(&vq->access_lock);
 
-	return 0;
+	return ret;
 }
 
 int
 rte_vhost_vring_call_nonblock(int vid, uint16_t vring_idx)
 {
 	struct virtio_net *dev;
 	struct vhost_virtqueue *vq;
+	int ret = 0;
 
 	dev = get_device(vid);
 	if (!dev)
@@ -1297,14 +1305,20 @@ rte_vhost_vring_call_nonblock(int vid, uint16_t vring_idx)
 	if (!rte_spinlock_trylock(&vq->access_lock))
 		return -EAGAIN;
 
+	if (unlikely(!vq->access_ok)) {
+		ret = -1;
+		goto out_unlock;
+	}
+
 	if (vq_is_packed(dev))
 		vhost_vring_call_packed(dev, vq);
 	else
 		vhost_vring_call_split(dev, vq);
 
+out_unlock:
 	rte_spinlock_unlock(&vq->access_lock);
 
-	return 0;
+	return ret;
 }
 
 uint16_t