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Subject[PATCH] Bluetooth: hci_ldisc: Fix another race when closing the tty.
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>
Cc: Dean Jenkins <Dean_Jenkins@mentor.com>
Cc: Lukas Wunner <lukas@wunner.de>
Cc: Marcel Holtmann <marcel@holtmann.org>
Cc: Gustavo Padovan <gustavo@padovan.org>
Cc: Johan Hedberg <johan.hedberg@gmail.com>
---
drivers/bluetooth/hci_ldisc.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index 31def781a562..c823914b3a80 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -523,13 +523,13 @@ static void hci_uart_tty_close(struct tty_struct *tty)
if (hdev)
hci_uart_close(hdev);

- cancel_work_sync(&hu->write_work);
-
if (test_bit(HCI_UART_PROTO_READY, &hu->flags)) {
percpu_down_write(&hu->proto_lock);
clear_bit(HCI_UART_PROTO_READY, &hu->flags);
percpu_up_write(&hu->proto_lock);

+ cancel_work_sync(&hu->write_work);
+
if (hdev) {
if (test_bit(HCI_UART_REGISTERED, &hu->flags))
hci_unregister_dev(hdev);
--
2.13.6
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