void tcp_done(struct sock *sk)
{
	struct request_sock *req = tcp_sk(sk)->fastopen_rsk;

	if (sk->sk_state == TCP_SYN_SENT || sk->sk_state == TCP_SYN_RECV)
		TCP_INC_STATS(sock_net(sk), TCP_MIB_ATTEMPTFAILS);

	tcp_set_state(sk, TCP_CLOSE);
	tcp_clear_xmit_timers(sk);
	if (req)
		reqsk_fastopen_remove(sk, req, false);

	sk->sk_shutdown = SHUTDOWN_MASK;

	if (!sock_flag(sk, SOCK_DEAD))
		sk->sk_state_change(sk);
	else
		inet_csk_destroy_sock(sk);
}

The product divides a value by zero.