int snd_seq_delete_all_ports(struct snd_seq_client *client)
{
	unsigned long flags;
	struct list_head deleted_list;
	struct snd_seq_client_port *port, *tmp;
	
	/* move the port list to deleted_list, and
	 * clear the port list in the client data.
	 */
	mutex_lock(&client->ports_mutex);
	write_lock_irqsave(&client->ports_lock, flags);
	if (! list_empty(&client->ports_list_head)) {
		list_add(&deleted_list, &client->ports_list_head);
		list_del_init(&client->ports_list_head);
	} else {
		INIT_LIST_HEAD(&deleted_list);
	}
	client->num_ports = 0;
	write_unlock_irqrestore(&client->ports_lock, flags);

	/* remove each port in deleted_list */
	list_for_each_entry_safe(port, tmp, &deleted_list, list) {
		list_del(&port->list);
		snd_seq_system_client_ev_port_exit(port->addr.client, port->addr.port);
		port_delete(client, port);
	}
	mutex_unlock(&client->ports_mutex);
	return 0;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.