virtio_ring: Fix potential mem leak in virtqueue_add_indirect_packed

'desc' should be freed before leaving from err handing path.

Fixes: 1ce9e6055f ("virtio_ring: introduce packed ring support")
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
stable@vger.kernel.org

drivers/virtio/virtio_ring.c

@@ -1004,6 +1004,7 @@ static int virtqueue_add_indirect_packed(struct vring_virtqueue *vq,
 
 	if (unlikely(vq->vq.num_free < 1)) {
 		pr_debug("Can't add buf len 1 - avail = 0\n");
+		kfree(desc);
 		END_USE(vq);
 		return -ENOSPC;
 	}