[3.11.y.z extended stable] Patch "bluetooth: hci_ldisc: fix deadlock condition" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    bluetooth: hci_ldisc: fix deadlock condition

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 790e89a63bf4ec56fc75d19f7d4dbedc55618bb8 Mon Sep 17 00:00:00 2001
From: Felipe Balbi <balbi at ti.com>
Date: Wed, 23 Apr 2014 09:58:26 -0500
Subject: bluetooth: hci_ldisc: fix deadlock condition
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

commit da64c27d3c93ee9f89956b9de86c4127eb244494 upstream.

LDISCs shouldn't call tty->ops->write() from within
->write_wakeup().

->write_wakeup() is called with port lock taken and
IRQs disabled, tty->ops->write() will try to acquire
the same port lock and we will deadlock.

Acked-by: Marcel Holtmann <marcel at holtmann.org>
Reviewed-by: Peter Hurley <peter at hurleysoftware.com>
Reported-by: Huang Shijie <b32955 at freescale.com>
Signed-off-by: Felipe Balbi <balbi at ti.com>
Tested-by: Andreas Bießmann <andreas at biessmann.de>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/bluetooth/hci_ldisc.c | 24 +++++++++++++++++++-----
 drivers/bluetooth/hci_uart.h  |  1 +
 2 files changed, 20 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index bc68a440d432..c4d2f0e48685 100644
--- a/drivers/bluetooth/hci_ldisc.c
+++ b/drivers/bluetooth/hci_ldisc.c
@@ -118,10 +118,6 @@ static inline struct sk_buff *hci_uart_dequeue(struct hci_uart *hu)

 int hci_uart_tx_wakeup(struct hci_uart *hu)
 {
-	struct tty_struct *tty = hu->tty;
-	struct hci_dev *hdev = hu->hdev;
-	struct sk_buff *skb;
-
 	if (test_and_set_bit(HCI_UART_SENDING, &hu->tx_state)) {
 		set_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);
 		return 0;
@@ -129,6 +125,22 @@ int hci_uart_tx_wakeup(struct hci_uart *hu)

 	BT_DBG("");

+	schedule_work(&hu->write_work);
+
+	return 0;
+}
+
+static void hci_uart_write_work(struct work_struct *work)
+{
+	struct hci_uart *hu = container_of(work, struct hci_uart, write_work);
+	struct tty_struct *tty = hu->tty;
+	struct hci_dev *hdev = hu->hdev;
+	struct sk_buff *skb;
+
+	/* REVISIT: should we cope with bad skbs or ->write() returning
+	 * and error value ?
+	 */
+
 restart:
 	clear_bit(HCI_UART_TX_WAKEUP, &hu->tx_state);

@@ -153,7 +165,6 @@ restart:
 		goto restart;

 	clear_bit(HCI_UART_SENDING, &hu->tx_state);
-	return 0;
 }

 static void hci_uart_init_work(struct work_struct *work)
@@ -289,6 +300,7 @@ static int hci_uart_tty_open(struct tty_struct *tty)
 	tty->receive_room = 65536;

 	INIT_WORK(&hu->init_ready, hci_uart_init_work);
+	INIT_WORK(&hu->write_work, hci_uart_write_work);

 	spin_lock_init(&hu->rx_lock);

@@ -326,6 +338,8 @@ static void hci_uart_tty_close(struct tty_struct *tty)
 	if (hdev)
 		hci_uart_close(hdev);

+	cancel_work_sync(&hu->write_work);
+
 	if (test_and_clear_bit(HCI_UART_PROTO_SET, &hu->flags)) {
 		if (hdev) {
 			if (test_bit(HCI_UART_REGISTERED, &hu->flags))
diff --git a/drivers/bluetooth/hci_uart.h b/drivers/bluetooth/hci_uart.h
index fffa61ff5cb1..12df101ca942 100644
--- a/drivers/bluetooth/hci_uart.h
+++ b/drivers/bluetooth/hci_uart.h
@@ -68,6 +68,7 @@ struct hci_uart {
 	unsigned long		hdev_flags;

 	struct work_struct	init_ready;
+	struct work_struct	write_work;

 	struct hci_uart_proto	*proto;
 	void			*priv;
--
1.9.1