USB: io_ti: 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/io_ti.c

@@ -87,9 +87,6 @@ struct edgeport_port {
 	int close_pending;
 	int lsr_event;
 	struct async_icount	icount;
-	wait_queue_head_t	delta_msr_wait;	/* for handling sleeping while
-						   waiting for msr change to
-						   happen */
 	struct edgeport_serial	*edge_serial;
 	struct usb_serial_port	*port;
 	__u8 bUartMode;		/* Port type, 0: RS232, etc. */
@@ -1459,7 +1456,7 @@ static void handle_new_msr(struct edgeport_port *edge_port, __u8 msr)
 			icount->dcd++;
 		if (msr & EDGEPORT_MSR_DELTA_RI)
 			icount->rng++;
-		wake_up_interruptible(&edge_port->delta_msr_wait);
+		wake_up_interruptible(&edge_port->port->delta_msr_wait);
 	}
 
 	/* Save the new modem status */
@@ -1754,7 +1751,6 @@ static int edge_open(struct tty_struct *tty, struct usb_serial_port *port)
 	dev = port->serial->dev;
 
 	memset(&(edge_port->icount), 0x00, sizeof(edge_port->icount));
-	init_waitqueue_head(&edge_port->delta_msr_wait);
 
 	/* turn off loopback */
 	status = ti_do_config(edge_port, UMPC_SET_CLR_LOOPBACK, 0);
@@ -2434,10 +2430,14 @@ static int edge_ioctl(struct tty_struct *tty,
 		dev_dbg(&port->dev, "%s - TIOCMIWAIT\n", __func__);
 		cprev = edge_port->icount;
 		while (1) {
-			interruptible_sleep_on(&edge_port->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;
+
 			cnow = edge_port->icount;
 			if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr &&
 			    cnow.dcd == cprev.dcd && cnow.cts == cprev.cts)