[ 061/124] USB: quatech2: fix use-after-free in TIOCMIWAIT

[Greg Kroah-Hartman]

3.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <jhovold@xxxxxxxxx>

commit 69f87f40d2b98e8b4ab82a121fd2bd584690b887 upstream.

Use the port wait queue and make sure to check the serial disconnected
flag before accessing private port data after waking up.

This is is needed as the private port data (including the wait queue
itself) can be gone when waking up after a disconnect.

Signed-off-by: Johan Hovold <jhovold@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/serial/quatech2.c |   12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

--- a/drivers/usb/serial/quatech2.c
+++ b/drivers/usb/serial/quatech2.c
@@ -128,7 +128,6 @@ struct qt2_port_private {
 	u8          shadowLSR;
 	u8          shadowMSR;
 
-	wait_queue_head_t   delta_msr_wait; /* Used for TIOCMIWAIT */
 	struct async_icount icount;
 
 	struct usb_serial_port *port;
@@ -506,8 +505,9 @@ static int wait_modem_info(struct usb_se
 	spin_unlock_irqrestore(&priv->lock, flags);
 
 	while (1) {
-		wait_event_interruptible(priv->delta_msr_wait,
-					 ((priv->icount.rng != prev.rng) ||
+		wait_event_interruptible(port->delta_msr_wait,
+					 (port->serial->disconnected ||
+					  (priv->icount.rng != prev.rng) ||
 					  (priv->icount.dsr != prev.dsr) ||
 					  (priv->icount.dcd != prev.dcd) ||
 					  (priv->icount.cts != prev.cts)));
@@ -515,6 +515,9 @@ static int wait_modem_info(struct usb_se
 		if (signal_pending(current))
 			return -ERESTARTSYS;
 
+		if (port->serial->disconnected)
+			return -EIO;
+
 		spin_lock_irqsave(&priv->lock, flags);
 		cur = priv->icount;
 		spin_unlock_irqrestore(&priv->lock, flags);
@@ -841,7 +844,6 @@ static int qt2_port_probe(struct usb_ser
 
 	spin_lock_init(&port_priv->lock);
 	spin_lock_init(&port_priv->urb_lock);
-	init_waitqueue_head(&port_priv->delta_msr_wait);
 	port_priv->port = port;
 
 	port_priv->write_urb = usb_alloc_urb(0, GFP_KERNEL);
@@ -984,7 +986,7 @@ static void qt2_update_msr(struct usb_se
 		if (newMSR & UART_MSR_TERI)
 			port_priv->icount.rng++;
 
-		wake_up_interruptible(&port_priv->delta_msr_wait);
+		wake_up_interruptible(&port->delta_msr_wait);
 	}
 }
 


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