vsock/virtio: fix sock refcnt holding during the shutdown

The "42f5cda5" commit rightly set SOCK_DONE on peer shutdown,
but there is an issue if we receive the SHUTDOWN(RDWR) while the
virtio_transport_close_timeout() is scheduled.
In this case, when the timeout fires, the SOCK_DONE is already
set and the virtio_transport_close_timeout() will not call
virtio_transport_reset() and virtio_transport_do_close().
This causes that both sockets remain open and will never be released,
preventing the unloading of [virtio|vhost]_transport modules.

This patch fixes this issue, calling virtio_transport_reset() and
virtio_transport_do_close() when we receive the SHUTDOWN(RDWR)
and there is nothing left to read.

Fixes: 42f5cda5 ("vsock/virtio: set SOCK_DONE on peer shutdown")
Cc: Stephen Barber <smbarber@chromium.org>
Signed-off-by: NStefano Garzarella <sgarzare@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/vmw_vsock/virtio_transport_common.c

@@ -947,9 +947,11 @@ virtio_transport_recv_connected(struct sock *sk,
 		if (le32_to_cpu(pkt->hdr.flags) & VIRTIO_VSOCK_SHUTDOWN_SEND)
 			vsk->peer_shutdown |= SEND_SHUTDOWN;
 		if (vsk->peer_shutdown == SHUTDOWN_MASK &&
-		    vsock_stream_has_data(vsk) <= 0) {
-			sock_set_flag(sk, SOCK_DONE);
-			sk->sk_state = TCP_CLOSING;
+		    vsock_stream_has_data(vsk) <= 0 &&
+		    !sock_flag(sk, SOCK_DONE)) {
+			(void)virtio_transport_reset(vsk, NULL);
+
+			virtio_transport_do_close(vsk, true);
 		}
 		if (le32_to_cpu(pkt->hdr.flags))
 			sk->sk_state_change(sk);