void hci_uart_set_flow_control(struct hci_uart *hu, bool enable)
{
	struct tty_struct *tty = hu->tty;
	struct ktermios ktermios;
	int status;
	unsigned int set = 0;
	unsigned int clear = 0;

	if (hu->serdev) {
		serdev_device_set_flow_control(hu->serdev, !enable);
		serdev_device_set_rts(hu->serdev, !enable);
		return;
	}

	if (enable) {
		/* Disable hardware flow control */
		ktermios = tty->termios;
		ktermios.c_cflag &= ~CRTSCTS;
		status = tty_set_termios(tty, &ktermios);
		BT_DBG("Disabling hardware flow control: %s",
		       status ? "failed" : "success");

		/* Clear RTS to prevent the device from sending */
		/* Most UARTs need OUT2 to enable interrupts */
		status = tty->driver->ops->tiocmget(tty);
		BT_DBG("Current tiocm 0x%x", status);

		set &= ~(TIOCM_OUT2 | TIOCM_RTS);
		clear = ~set;
		set &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
		       TIOCM_OUT2 | TIOCM_LOOP;
		clear &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
			 TIOCM_OUT2 | TIOCM_LOOP;
		status = tty->driver->ops->tiocmset(tty, set, clear);
		BT_DBG("Clearing RTS: %s", status ? "failed" : "success");
	} else {
		/* Set RTS to allow the device to send again */
		status = tty->driver->ops->tiocmget(tty);
		BT_DBG("Current tiocm 0x%x", status);

		set |= (TIOCM_OUT2 | TIOCM_RTS);
		clear = ~set;
		set &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
		       TIOCM_OUT2 | TIOCM_LOOP;
		clear &= TIOCM_DTR | TIOCM_RTS | TIOCM_OUT1 |
			 TIOCM_OUT2 | TIOCM_LOOP;
		status = tty->driver->ops->tiocmset(tty, set, clear);
		BT_DBG("Setting RTS: %s", status ? "failed" : "success");

		/* Re-enable hardware flow control */
		ktermios = tty->termios;
		ktermios.c_cflag |= CRTSCTS;
		status = tty_set_termios(tty, &ktermios);
		BT_DBG("Enabling hardware flow control: %s",
		       status ? "failed" : "success");
	}
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.