tipc: orphan sock in tipc_release()

Before we unlock the sock in tipc_release(), we have to
detach sk->sk_socket from sk, otherwise a parallel
tipc_sk_fill_sock_diag() could stil read it after we
free this socket.

Fixes: c30b70deb5f4 ("tipc: implement socket diagnostics for AF_TIPC")
Reported-and-tested-by: syzbot+48804b87c16588ad491d@syzkaller.appspotmail.com
Cc: Jon Maloy <jon.maloy@ericsson.com>
Cc: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/tipc/socket.c

@@ -576,6 +576,7 @@ static int tipc_release(struct socket *sock)
 	sk_stop_timer(sk, &sk->sk_timer);
 	tipc_sk_remove(tsk);
 
+	sock_orphan(sk);
 	/* Reject any messages that accumulated in backlog queue */
 	release_sock(sk);
 	tipc_dest_list_purge(&tsk->cong_links);