static long snd_seq_ioctl(struct file *file, unsigned int cmd,
			  unsigned long arg)
{
	struct snd_seq_client *client = file->private_data;
	/* To use kernel stack for ioctl data. */
	union {
		int pversion;
		int client_id;
		struct snd_seq_system_info	system_info;
		struct snd_seq_running_info	running_info;
		struct snd_seq_client_info	client_info;
		struct snd_seq_port_info	port_info;
		struct snd_seq_port_subscribe	port_subscribe;
		struct snd_seq_queue_info	queue_info;
		struct snd_seq_queue_status	queue_status;
		struct snd_seq_queue_tempo	tempo;
		struct snd_seq_queue_timer	queue_timer;
		struct snd_seq_queue_client	queue_client;
		struct snd_seq_client_pool	client_pool;
		struct snd_seq_remove_events	remove_events;
		struct snd_seq_query_subs	query_subs;
	} buf;
	const struct ioctl_handler *handler;
	unsigned long size;
	int err;

	if (snd_BUG_ON(!client))
		return -ENXIO;

	for (handler = ioctl_handlers; handler->cmd > 0; ++handler) {
		if (handler->cmd == cmd)
			break;
	}
	if (handler->cmd == 0)
		return -ENOTTY;

	memset(&buf, 0, sizeof(buf));

	/*
	 * All of ioctl commands for ALSA sequencer get an argument of size
	 * within 13 bits. We can safely pick up the size from the command.
	 */
	size = _IOC_SIZE(handler->cmd);
	if (handler->cmd & IOC_IN) {
		if (copy_from_user(&buf, (const void __user *)arg, size))
			return -EFAULT;
	}

	err = handler->func(client, &buf);
	if (err >= 0) {
		/* Some commands includes a bug in 'dir' field. */
		if (handler->cmd == SNDRV_SEQ_IOCTL_SET_QUEUE_CLIENT ||
		    handler->cmd == SNDRV_SEQ_IOCTL_SET_CLIENT_POOL ||
		    (handler->cmd & IOC_OUT))
			if (copy_to_user((void __user *)arg, &buf, size))
				return -EFAULT;
	}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.