static struct pid *good_sigevent(sigevent_t * event)
{
	struct task_struct *rtn = current->group_leader;

	switch (event->sigev_notify) {
	case SIGEV_SIGNAL | SIGEV_THREAD_ID:
		rtn = find_task_by_vpid(event->sigev_notify_thread_id);
		if (!rtn || !same_thread_group(rtn, current))
			return NULL;
		/* FALLTHRU */
	case SIGEV_SIGNAL:
	case SIGEV_THREAD:
		if (event->sigev_signo <= 0 || event->sigev_signo > SIGRTMAX)
			return NULL;
		/* FALLTHRU */
	case SIGEV_NONE:
		return task_pid(rtn);
	default:
		return NULL;
	}
}
The software reads data past the end, or before the beginning, of the intended buffer.