bluetooth: hci_ldisc: fix deadlock condition

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@holtmann.org>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Reported-by: Huang Shijie <b32955@freescale.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>
Tested-by: Andreas Bießmann <andreas@biessmann.de>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 20 insertions, 5 deletions

diff --git a/drivers/bluetooth/hci_ldisc.c b/drivers/bluetooth/hci_ldisc.c
index f1fbf4f1e5be..e00f8f5b5c8e 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)
@@ -282,6 +293,7 @@ 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);
 
@@ -319,6 +331,8 @@ 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;