USB: ti_usb_3410_5052: fix use-after-free in TIOCMIWAIT

commit fc98ab87 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/serial/ti_usb_3410_5052.c

@@ -75,7 +75,6 @@ struct ti_port {
 	int			tp_flags;
 	int			tp_closing_wait;/* in .01 secs */
 	struct async_icount	tp_icount;
-	wait_queue_head_t	tp_msr_wait;	/* wait for msr change */
 	wait_queue_head_t	tp_write_wait;
 	struct ti_device	*tp_tdev;
 	struct usb_serial_port	*tp_port;
@@ -447,7 +446,6 @@ static int ti_startup(struct usb_serial *serial)
 		tport->tp_uart_base_addr = (i == 0 ?
 				TI_UART1_BASE_ADDR : TI_UART2_BASE_ADDR);
 		tport->tp_closing_wait = closing_wait;
-		init_waitqueue_head(&tport->tp_msr_wait);
 		init_waitqueue_head(&tport->tp_write_wait);
 		if (kfifo_alloc(&tport->write_fifo, TI_WRITE_BUF_SIZE,
 								GFP_KERNEL)) {
@@ -848,9 +846,13 @@ static int ti_ioctl(struct tty_struct *tty,
 		dbg("%s - (%d) TIOCMIWAIT", __func__, port->number);
 		cprev = tport->tp_icount;
 		while (1) {
-			interruptible_sleep_on(&tport->tp_msr_wait);
+			interruptible_sleep_on(&port->delta_msr_wait);
 			if (signal_pending(current))
 				return -ERESTARTSYS;
+
+			if (port->serial->disconnected)
+				return -EIO;
+
 			cnow = tport->tp_icount;
 			if (cnow.rng == cprev.rng && cnow.dsr == cprev.dsr &&
 			    cnow.dcd == cprev.dcd && cnow.cts == cprev.cts)
@@ -1481,7 +1483,7 @@ static void ti_handle_new_msr(struct ti_port *tport, __u8 msr)
 			icount->dcd++;
 		if (msr & TI_MSR_DELTA_RI)
 			icount->rng++;
-		wake_up_interruptible(&tport->tp_msr_wait);
+		wake_up_interruptible(&tport->tp_port->delta_msr_wait);
 		spin_unlock_irqrestore(&tport->tp_lock, flags);
 	}