vsock/virtio: initialize vdev->priv before using VQs

When we fill VQs with empty buffers and kick the host, it may send
an interrupt. `vdev->priv` must be initialized before this since it
is used in the virtqueue callbacks.

Fixes: 0deab08 ("vsock/virtio: use RCU to avoid use-after-free on the_virtio_vsock")
Suggested-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: stefano-garzarella

net/vmw_vsock/virtio_transport.c

@@ -622,6 +622,8 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 	INIT_WORK(&vsock->event_work, virtio_transport_event_work);
 	INIT_WORK(&vsock->send_pkt_work, virtio_transport_send_pkt_work);
 
+	vdev->priv = vsock;
+
 	mutex_lock(&vsock->tx_lock);
 	vsock->tx_run = true;
 	mutex_unlock(&vsock->tx_lock);
@@ -639,7 +641,6 @@ static int virtio_vsock_probe(struct virtio_device *vdev)
 	if (virtio_has_feature(vdev, VIRTIO_VSOCK_F_SEQPACKET))
 		vsock->seqpacket_allow = true;
 
-	vdev->priv = vsock;
 	rcu_assign_pointer(the_virtio_vsock, vsock);
 
 	mutex_unlock(&the_virtio_vsock_mutex);