USB: spcp8x5: 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/spcp8x5.c

@@ -149,7 +149,6 @@ enum spcp8x5_type {
 struct spcp8x5_private {
 	spinlock_t 	lock;
 	enum spcp8x5_type	type;
-	wait_queue_head_t	delta_msr_wait;
 	u8 			line_control;
 	u8 			line_status;
 };
@@ -179,7 +178,6 @@ static int spcp8x5_port_probe(struct usb_serial_port *port)
 		return -ENOMEM;
 
 	spin_lock_init(&priv->lock);
-	init_waitqueue_head(&priv->delta_msr_wait);
 	priv->type = type;
 
 	usb_set_serial_port_data(port , priv);
@@ -475,7 +473,7 @@ static void spcp8x5_process_read_urb(struct urb *urb)
 	priv->line_status &= ~UART_STATE_TRANSIENT_MASK;
 	spin_unlock_irqrestore(&priv->lock, flags);
 	/* wake up the wait for termios */
-	wake_up_interruptible(&priv->delta_msr_wait);
+	wake_up_interruptible(&port->delta_msr_wait);
 
 	if (!urb->actual_length)
 		return;
@@ -526,12 +524,15 @@ static int spcp8x5_wait_modem_info(struct usb_serial_port *port,
 
 	while (1) {
 		/* wake up in bulk read */
-		interruptible_sleep_on(&priv->delta_msr_wait);
+		interruptible_sleep_on(&port->delta_msr_wait);
 
 		/* see if a signal did it */
 		if (signal_pending(current))
 			return -ERESTARTSYS;
 
+		if (port->serial->disconnected)
+			return -EIO;
+
 		spin_lock_irqsave(&priv->lock, flags);
 		status = priv->line_status;
 		spin_unlock_irqrestore(&priv->lock, flags);