int hci_uart_tx_wakeup(struct hci_uart *hu)
{
	/* This may be called in an IRQ context, so we can't sleep. Therefore
	 * we try to acquire the lock only, and if that fails we assume the
	 * tty is being closed because that is the only time the write lock is
	 * acquired. If, however, at some point in the future the write lock
	 * is also acquired in other situations, then this must be revisited.
	 */
	if (!percpu_down_read_trylock(&hu->proto_lock))
		return 0;

	if (!test_bit(HCI_UART_PROTO_READY, &hu->flags))
		goto no_schedule;

	if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
		set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
		goto no_schedule;
	}

	BT_DBG("");

	schedule_work(&hu->write_work);

no_schedule:
	percpu_up_read(&hu->proto_lock);

	return 0;
}

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 Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.