static int usb_console_setup(struct console *co, char *options)
{
	struct usbcons_info *info = &usbcons_info;
	int baud = 9600;
	int bits = 8;
	int parity = 'n';
	int doflow = 0;
	int cflag = CREAD | HUPCL | CLOCAL;
	char *s;
	struct usb_serial *serial;
	struct usb_serial_port *port;
	int retval;
	struct tty_struct *tty = NULL;
	struct ktermios dummy;

	if (options) {
		baud = simple_strtoul(options, NULL, 10);
		s = options;
		while (*s >= '0' && *s <= '9')
			s++;
		if (*s)
			parity = *s++;
		if (*s)
			bits   = *s++ - '0';
		if (*s)
			doflow = (*s++ == 'r');
	}
	
	/* Sane default */
	if (baud == 0)
		baud = 9600;

	switch (bits) {
	case 7:
		cflag |= CS7;
		break;
	default:
	case 8:
		cflag |= CS8;
		break;
	}
	switch (parity) {
	case 'o': case 'O':
		cflag |= PARODD;
		break;
	case 'e': case 'E':
		cflag |= PARENB;
		break;
	}
	co->cflag = cflag;

	/*
	 * no need to check the index here: if the index is wrong, console
	 * code won't call us
	 */
	port = usb_serial_port_get_by_minor(co->index);
	if (port == NULL) {
		/* no device is connected yet, sorry :( */
		pr_err("No USB device connected to ttyUSB%i\n", co->index);
		return -ENODEV;
	}
	serial = port->serial;

	retval = usb_autopm_get_interface(serial->interface);
	if (retval)
		goto error_get_interface;

	tty_port_tty_set(&port->port, NULL);

	info->port = port;

	++port->port.count;
	if (!tty_port_initialized(&port->port)) {
		if (serial->type->set_termios) {
			/*
			 * allocate a fake tty so the driver can initialize
			 * the termios structure, then later call set_termios to
			 * configure according to command line arguments
			 */
			tty = kzalloc(sizeof(*tty), GFP_KERNEL);
			if (!tty) {
				retval = -ENOMEM;
				goto reset_open_count;
			}
			kref_init(&tty->kref);
			tty->driver = usb_serial_tty_driver;
			tty->index = co->index;
			init_ldsem(&tty->ldisc_sem);
			spin_lock_init(&tty->files_lock);
			INIT_LIST_HEAD(&tty->tty_files);
			kref_get(&tty->driver->kref);
			__module_get(tty->driver->owner);
			tty->ops = &usb_console_fake_tty_ops;
			tty_init_termios(tty);
			tty_port_tty_set(&port->port, tty);
		}

		/* only call the device specific open if this
		 * is the first time the port is opened */
		retval = serial->type->open(NULL, port);
		if (retval) {
			dev_err(&port->dev, "could not open USB console port\n");
			goto fail;
		}

		if (serial->type->set_termios) {
			tty->termios.c_cflag = cflag;
			tty_termios_encode_baud_rate(&tty->termios, baud, baud);
			memset(&dummy, 0, sizeof(struct ktermios));
			serial->type->set_termios(tty, port, &dummy);

			tty_port_tty_set(&port->port, NULL);
			tty_kref_put(tty);
		}
		tty_port_set_initialized(&port->port, 1);
	}
	/* Now that any required fake tty operations are completed restore
	 * the tty port count */
	--port->port.count;
	/* The console is special in terms of closing the device so
	 * indicate this port is now acting as a system console. */
	port->port.console = 1;

	mutex_unlock(&serial->disc_mutex);
	return retval;

 fail:
	tty_port_tty_set(&port->port, NULL);
 	tty_kref_put(tty);
  reset_open_count:
 	port->port.count = 0;
	info->port = NULL;
 	usb_autopm_put_interface(serial->interface);
  error_get_interface:
 	usb_serial_put(serial);
	mutex_unlock(&serial->disc_mutex);
	return retval;
}

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.