vhost: fix check on virtqueue access in in-flight getter

[ upstream commit 288cd1f8ca3ebaf20aeed92966da9020a5793852 ]

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: 0c0935c ("vhost: allow to check in-flight packets for async vhost")

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

lib/vhost/vhost.c

@@ -1929,9 +1929,15 @@ rte_vhost_async_get_inflight(int vid, uint16_t queue_id)
 		return ret;
 	}
 
+	if (unlikely(!vq->access_ok)) {
+		ret = -1;
+		goto out_unlock;
+	}
+
 	if (vq->async)
 		ret = vq->async->pkts_inflight_n;
 
+out_unlock:
 	rte_spinlock_unlock(&vq->access_lock);
 
 	return ret;