void rose_start_heartbeat(struct sock *sk)
{
	del_timer(&sk->sk_timer);

	sk->sk_timer.function = rose_heartbeat_expiry;
	sk->sk_timer.expires  = jiffies + 5 * HZ;

	add_timer(&sk->sk_timer);
}
Referencing memory after it has been freed can cause a program to crash, use unexpected values, or execute code.