[PATCH] Bluetooth: hci_uart: clear HCI_UART_SENDING when write_work is canceled

[Pauli Virtanen]

HCI_UART_SENDING bit in tx_state means write_work is pending and blocks
queueing it again.  Currently this bit is not cleared when canceling the
work in hci_uart_close(), which blocks future writes when device is
reopened later if write_work was pending.

Fix by clearing HCI_UART_SENDING when canceling the work.

Also make clearing of tx_skb safe by using disable_work_sync +
enable_work instead of just cancel_work_sync.  hci_uart_flush() purges
the proto tx queue so we can cancel the pending write_work there,
instead of doing it just in hci_uart_close().

Fixes: c1bb9336ae6b ("Bluetooth: hci_uart: fix UAFs and race conditions in close and init paths")
Link: https://lore.kernel.org/linux-bluetooth/07e0a28650773abec711ee492fdb1bf5d21a6c98.camel@xxxxxx/
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Pauli Virtanen <pav@xxxxxx>
---
 drivers/bluetooth/hci_ldisc.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 47f4902b40b4..b0708ec9751c 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -239,10 +239,17 @@ static int hci_uart_flush(struct hci_dev *hdev)
 
 	BT_DBG("hdev %p tty %p", hdev, tty);
 
+	disable_work_sync(&hu->write_work);
+
 	if (hu->tx_skb) {
 		kfree_skb(hu->tx_skb); hu->tx_skb = NULL;
 	}
 
+	if (test_and_clear_bit(HCI_UART_SENDING, &hu->tx_state))
+		wake_up_bit(&hu->tx_state, HCI_UART_SENDING);
+
+	enable_work(&hu->write_work);
+
 	/* Flush any pending characters in the driver and discipline. */
 	tty_ldisc_flush(tty);
 	tty_driver_flush_buffer(tty);
@@ -271,12 +278,8 @@ static int hci_uart_open(struct hci_dev *hdev)
 /* Close device */
 static int hci_uart_close(struct hci_dev *hdev)
 {
-	struct hci_uart *hu = hci_get_drvdata(hdev);
-
 	BT_DBG("hdev %p", hdev);
 
-	cancel_work_sync(&hu->write_work);
-
 	hci_uart_flush(hdev);
 	hdev->flush = NULL;
 	return 0;
-- 
2.54.0