USB: spcp8x5: fix use-after-free in TIOCMIWAIT

commit d1baabc8 upstream.

commit dbcea761 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@gmail.com>
[bwh: Backported to 3.2: adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/spcp8x5.c

@@ -162,7 +162,6 @@ static struct usb_driver spcp8x5_driver = {
 struct spcp8x5_private {
 	spinlock_t 	lock;
 	enum spcp8x5_type	type;
-	wait_queue_head_t	delta_msr_wait;
 	u8 			line_control;
 	u8 			line_status;
 };
@@ -196,7 +195,6 @@ static int spcp8x5_startup(struct usb_serial *serial)
 			goto cleanup;
 
 		spin_lock_init(&priv->lock);
-		init_waitqueue_head(&priv->delta_msr_wait);
 		priv->type = type;
 		usb_set_serial_port_data(serial->port[i] , priv);
 	}
@@ -499,7 +497,7 @@ 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;
@@ -549,12 +547,15 @@ 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);