static int check_and_subscribe_port(struct snd_seq_client *client,
				    struct snd_seq_client_port *port,
				    struct snd_seq_subscribers *subs,
				    bool is_src, bool exclusive, bool ack)
{
	struct snd_seq_port_subs_info *grp;
	struct list_head *p;
	struct snd_seq_subscribers *s;
	int err;

	grp = is_src ? &port->c_src : &port->c_dest;
	err = -EBUSY;
	down_write(&grp->list_mutex);
	if (exclusive) {
		if (!list_empty(&grp->list_head))
			goto __error;
	} else {
		if (grp->exclusive)
			goto __error;
		/* check whether already exists */
		list_for_each(p, &grp->list_head) {
			s = get_subscriber(p, is_src);
			if (match_subs_info(&subs->info, &s->info))
				goto __error;
		}
	}

	err = subscribe_port(client, port, grp, &subs->info, ack);
	if (err < 0) {
		grp->exclusive = 0;
		goto __error;
	}

	/* add to list */
	write_lock_irq(&grp->list_lock);
	if (is_src)
		list_add_tail(&subs->src_list, &grp->list_head);
	else
		list_add_tail(&subs->dest_list, &grp->list_head);
	grp->exclusive = exclusive;
	atomic_inc(&subs->ref_count);
	write_unlock_irq(&grp->list_lock);
	err = 0;

 __error:
	up_write(&grp->list_mutex);
	return err;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.