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

commit 33357625 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: Ben Hutchings <ben@decadent.org.uk>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/serial/io_edgeport.c

@@ -114,7 +114,6 @@ struct edgeport_port {
 	wait_queue_head_t	wait_chase;		/* for handling sleeping while waiting for chase to finish */
 	wait_queue_head_t	wait_open;		/* for handling sleeping while waiting for open to finish */
 	wait_queue_head_t	wait_command;		/* for handling sleeping while waiting for command to finish */
-	wait_queue_head_t	delta_msr_wait;		/* for handling sleeping while waiting for msr change to happen */
 
 	struct async_icount	icount;
 	struct usb_serial_port	*port;			/* loop back to the owner of this object */
@@ -884,7 +883,6 @@ static int edge_open(struct tty_struct *tty, struct usb_serial_port *port)
 	/* initialize our wait queues */
 	init_waitqueue_head(&edge_port->wait_open);
 	init_waitqueue_head(&edge_port->wait_chase);
-	init_waitqueue_head(&edge_port->delta_msr_wait);
 	init_waitqueue_head(&edge_port->wait_command);
 
 	/* initialize our icount structure */
@@ -1701,13 +1699,17 @@ static int edge_ioctl(struct tty_struct *tty,
 		dbg("%s (%d) TIOCMIWAIT", __func__,  port->number);
 		cprev = edge_port->icount;
 		while (1) {
-			prepare_to_wait(&edge_port->delta_msr_wait,
+			prepare_to_wait(&port->delta_msr_wait,
 						&wait, TASK_INTERRUPTIBLE);
 			schedule();
-			finish_wait(&edge_port->delta_msr_wait, &wait);
+			finish_wait(&port->delta_msr_wait, &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)
@@ -2088,7 +2090,7 @@ static void handle_new_msr(struct edgeport_port *edge_port, __u8 newMsr)
 			icount->dcd++;
 		if (newMsr & 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 */