USB: serial: console: fix use-after-free on disconnect

A clean-up patch removing two redundant NULL-checks from the console
disconnect handler inadvertently also removed a third check. This could
lead to the struct usb_serial being prematurely freed by the console
code when a driver accepts but does not register any ports for an
interface which also lacks endpoint descriptors.

Fixes: 0e517c9 ("USB: serial: console: clean up sanity checks")
Cc: stable <[email protected]>     # 4.11
Reported-by: Andrey Konovalov <[email protected]>
Acked-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Johan Hovold <[email protected]>

Author: jhovold

drivers/usb/serial/console.c

@@ -265,7 +265,7 @@ static struct console usbcons = {
 
 void usb_serial_console_disconnect(struct usb_serial *serial)
 {
-	if (serial->port[0] == usbcons_info.port) {
+	if (serial->port[0] && serial->port[0] == usbcons_info.port) {
 		usb_serial_console_exit();
 		usb_serial_put(serial);
 	}