[PATCH] usbserial: Fixes use-after-free in serial_open().

If the device is disconnected while serial_open() is executing and
either try_module_get() or the device specific open function fails, the
kref_put() call in the 'bailout_kref_put' label will free the memory
pointed out by 'port'.

The subsequent dereferences in the 'bailout_kref_put' label will be
invalid.

The fix is just to assure kref_put() is called after any 'port' usage.
Signed-off-by: NLuiz Fernando N. Capitulino <lcapitulino@mandriva.com.br>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/serial/usb-serial.c

@@ -225,9 +225,9 @@ static int serial_open (struct tty_struct *tty, struct file * filp)
 bailout_module_put:
 	module_put(serial->type->driver.owner);
 bailout_kref_put:
-	kref_put(&serial->kref, destroy_serial);
 	port->open_count = 0;
 	mutex_unlock(&port->mutex);
+	kref_put(&serial->kref, destroy_serial);
 	return retval;
 }