USB: oti6858: fix use-after-free in TIOCMIWAIT

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.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/oti6858.c

@@ -188,7 +188,6 @@ struct oti6858_private {
 	u8 setup_done;
 	struct delayed_work delayed_setup_work;
 
-	wait_queue_head_t intr_wait;
 	struct usb_serial_port *port;   /* USB port with which associated */
 };
 
@@ -339,7 +338,6 @@ static int oti6858_port_probe(struct usb_serial_port *port)
 		return -ENOMEM;
 
 	spin_lock_init(&priv->lock);
-	init_waitqueue_head(&priv->intr_wait);
 	priv->port = port;
 	INIT_DELAYED_WORK(&priv->delayed_setup_work, setup_line);
 	INIT_DELAYED_WORK(&priv->delayed_write_work, send_data);
@@ -664,11 +662,15 @@ static int wait_modem_info(struct usb_serial_port *port, unsigned int arg)
 	spin_unlock_irqrestore(&priv->lock, flags);
 
 	while (1) {
-		wait_event_interruptible(priv->intr_wait,
+		wait_event_interruptible(port->delta_msr_wait,
+					port->serial->disconnected ||
 					priv->status.pin_state != prev);
 		if (signal_pending(current))
 			return -ERESTARTSYS;
 
+		if (port->serial->disconnected)
+			return -EIO;
+
 		spin_lock_irqsave(&priv->lock, flags);
 		status = priv->status.pin_state & PIN_MASK;
 		spin_unlock_irqrestore(&priv->lock, flags);
@@ -763,7 +765,7 @@ static void oti6858_read_int_callback(struct urb *urb)
 
 		if (!priv->transient) {
 			if (xs->pin_state != priv->status.pin_state)
-				wake_up_interruptible(&priv->intr_wait);
+				wake_up_interruptible(&port->delta_msr_wait);
 			memcpy(&priv->status, xs, OTI6858_CTRL_PKT_SIZE);
 		}