From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:42230 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932483AbeCWKJk (ORCPT ); Fri, 23 Mar 2018 06:09:40 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Dean Jenkins , Marcel Holtmann , Sasha Levin Subject: [PATCH 4.9 107/177] Bluetooth: hci_ldisc: Add protocol check to hci_uart_tx_wakeup() Date: Fri, 23 Mar 2018 10:53:55 +0100 Message-Id: <20180323094209.999581866@linuxfoundation.org> In-Reply-To: <20180323094205.090519271@linuxfoundation.org> References: <20180323094205.090519271@linuxfoundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: stable-owner@vger.kernel.org List-ID: 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Dean Jenkins [ Upstream commit 2d6f1da168e1d62c47f7d50135ac4cbd8411dcb1 ] Before attempting to schedule a work-item onto hu->write_work in hci_uart_tx_wakeup(), check that the Data Link protocol layer is still bound to the HCI UART driver. Failure to perform this protocol check causes a race condition between the work queue hu->write_work running hci_uart_write_work() and the Data Link protocol layer being unbound (closed) in hci_uart_tty_close(). Note hci_uart_tty_close() does have a "cancel_work_sync(&hu->write_work)" but it is ineffective because it cannot prevent work-items being added to hu->write_work after cancel_work_sync() has run. Therefore, add a check for HCI_UART_PROTO_READY into hci_uart_tx_wakeup() which prevents scheduling of the work queue when HCI_UART_PROTO_READY is in the clear state. However, note a small race condition remains because the hci_uart_tx_wakeup() thread can run in parallel with the hci_uart_tty_close() thread so it is possible that a schedule of hu->write_work can occur when HCI_UART_PROTO_READY is cleared. A complete solution needs locking of the threads which is implemented in a future commit. Signed-off-by: Dean Jenkins Signed-off-by: Marcel Holtmann Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/bluetooth/hci_ldisc.c | 3 +++ 1 file changed, 3 insertions(+) --- a/drivers/bluetooth/hci_ldisc.c +++ b/drivers/bluetooth/hci_ldisc.c @@ -125,6 +125,9 @@ static inline struct sk_buff *hci_uart_d int hci_uart_tx_wakeup(struct hci_uart *hu) { + if (!test_bit(HCI_UART_PROTO_READY, &hu->flags)) + return 0; + if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) { set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state); return 0;