int snd_seq_event_port_attach(int client,
			      struct snd_seq_port_callback *pcbp,
			      int cap, int type, int midi_channels,
			      int midi_voices, char *portname)
{
	struct snd_seq_port_info portinfo;
	int  ret;

	/* Set up the port */
	memset(&portinfo, 0, sizeof(portinfo));
	portinfo.addr.client = client;
	strlcpy(portinfo.name, portname ? portname : "Unamed port",
		sizeof(portinfo.name));

	portinfo.capability = cap;
	portinfo.type = type;
	portinfo.kernel = pcbp;
	portinfo.midi_channels = midi_channels;
	portinfo.midi_voices = midi_voices;

	/* Create it */
	ret = snd_seq_kernel_client_ctl(client,
					SNDRV_SEQ_IOCTL_CREATE_PORT,
					&portinfo);

	if (ret >= 0)
		ret = portinfo.addr.port;

	return ret;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.