Bluetooth: hci_serdev: Fix use-after-free in hci_uart_unregister_device()

hci_uart_unregister_device() frees the HCI device (hci_free_dev)
before cancelling write_work via cancel_work_sync(). If write_work
is executing concurrently on another CPU, it can access hu->hdev
and write to hdev->stat after the memory has been freed.

Additionally, HCI_UART_PROTO_READY is not cleared until after
cancel_work_sync, so the write_wakeup serdev callback can still
schedule write_work via hci_uart_tx_wakeup() even after
hci_free_dev has freed the device.

Fix this by mirroring the same ordering used in the tty/ldisc path
(hci_uart_tty_close, hci_ldisc.c:565-593):
1. Save the PROTO_READY state and clear it under the write lock so
   a concurrent hci_uart_tx_wakeup() cannot re-schedule write_work
2. Cancel write_work (no new work can be scheduled and no work is
   in flight)
3. Unregister the HCI device
4. Close the protocol (may access hu->hdev and the serdev device)
5. Close the serdev port (safe now that write_work is quiesced and
   protocol is done)
6. Free the HCI device

Also free any partially transmitted frame (hu->tx_skb) left over by
write_work once the transmit path is quiesced, since hci_uart_close()
would skip hci_uart_flush() because HCI_UART_PROTO_READY is cleared.

Signed-off-by: ZhaoJinming <zhaojinming@uniontech.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>

0 files changed, 0 insertions, 0 deletions