static void clear_subscriber_list(struct snd_seq_client *client,
				  struct snd_seq_client_port *port,
				  struct snd_seq_port_subs_info *grp,
				  int is_src)
{
	struct list_head *p, *n;

	list_for_each_safe(p, n, &grp->list_head) {
		struct snd_seq_subscribers *subs;
		struct snd_seq_client *c;
		struct snd_seq_client_port *aport;

		subs = get_subscriber(p, is_src);
		if (is_src)
			aport = get_client_port(&subs->info.dest, &c);
		else
			aport = get_client_port(&subs->info.sender, &c);
		delete_and_unsubscribe_port(client, port, subs, is_src, false);

		if (!aport) {
			/* looks like the connected port is being deleted.
			 * we decrease the counter, and when both ports are deleted
			 * remove the subscriber info
			 */
			if (atomic_dec_and_test(&subs->ref_count))
				kfree(subs);
			continue;
		}

		/* ok we got the connected port */
		delete_and_unsubscribe_port(c, aport, subs, !is_src, true);
		kfree(subs);
		snd_seq_port_unlock(aport);
		snd_seq_client_unlock(c);
	}
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.