Patch "Bluetooth: hci_ldisc: Fix another race when closing the tty." has been added to the 4.14-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    Bluetooth: hci_ldisc: Fix another race when closing the tty.

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     bluetooth-hci_ldisc-fix-another-race-when-closing-the-tty.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Mon Dec 18 13:28:59 CET 2017
From: Ronald Tschal�r <ronald@innovation.ch>
Date: Wed, 25 Oct 2017 22:15:19 -0700
Subject: Bluetooth: hci_ldisc: Fix another race when closing the tty.

From: Ronald Tschal�r <ronald@innovation.ch>


[ Upstream commit 0338b1b393ec7910898e8f7b25b3bf31a7282e16 ]

The following race condition still existed:

         P1                                P2
  cancel_work_sync()
                                     hci_uart_tx_wakeup()
                                     hci_uart_write_work()
                                     hci_uart_dequeue()
  clear_bit(HCI_UART_PROTO_READY)
  hci_unregister_dev(hdev)
  hci_free_dev(hdev)
  hu->proto->close(hu)
  kfree(hu)
                                     access to hdev and hu

Cancelling the work after clearing the HCI_UART_PROTO_READY bit avoids
this as any hci_uart_tx_wakeup() issued after the flag is cleared will
detect that and not schedule further work.

Signed-off-by: Ronald Tschalär <ronald@innovation.ch>
Reviewed-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/bluetooth/hci_ldisc.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -510,13 +510,13 @@ static void hci_uart_tty_close(struct tt
 	if (hdev)
 		hci_uart_close(hdev);
 
-	cancel_work_sync(&hu->write_work);
-
 	if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) {
 		write_lock_irqsave(&hu->proto_lock, flags);
 		clear_bit(HCI_UART_PROTO_READY, &hu->flags);
 		write_unlock_irqrestore(&hu->proto_lock, flags);
 
+		cancel_work_sync(&hu->write_work);
+
 		if (hdev) {
 			if (test_bit(HCI_UART_REGISTERED, &hu->flags))
 				hci_unregister_dev(hdev);


Patches currently in stable-queue which might be from ronald@innovation.ch are

queue-4.14/bluetooth-hci_ldisc-fix-another-race-when-closing-the-tty.patch