static int snd_seq_ioctl_get_subscription(struct snd_seq_client *client,
					  void *arg)
{
	struct snd_seq_port_subscribe *subs = arg;
	int result;
	struct snd_seq_client *sender = NULL;
	struct snd_seq_client_port *sport = NULL;
	struct snd_seq_subscribers *p;

	result = -EINVAL;
	if ((sender = snd_seq_client_use_ptr(subs->sender.client)) == NULL)
		goto __end;
	if ((sport = snd_seq_port_use_ptr(sender, subs->sender.port)) == NULL)
		goto __end;
	p = snd_seq_port_get_subscription(&sport->c_src, &subs->dest);
	if (p) {
		result = 0;
		*subs = p->info;
	} else
		result = -ENOENT;

      __end:
      	if (sport)
		snd_seq_port_unlock(sport);
	if (sender)
		snd_seq_client_unlock(sender);

	return result;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.