staging: comedi: 8255: fix I/O region leak on failure

The Comedi "8255" driver does not clean up properly on failure.  It can
leave requested I/O port regions unreleased.  Specifically, the Comedi
"attach" handler (`dev_8255_attach()`) requests a specified I/O port
region before calling `subdev_8255_init()` to set up the subdevice.  If
that fails, the "attach" handler returns an error and the Comedi core
will call the "detach" handler (`dev_8255_detach()`) to clean up.  The
"detach" handler is responsible for releasing the I/O port regions
successfully requested by the "attach" handler.  Unfortunately, it is
unable to obtain the base address of the region if the call to
`subdev_8255_init()` failed.

Fix the I/O region leak by releasing the region in the "attach" handler
directly if the call to `subdev_8255_init()` fails.
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Reviewed-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/drivers/8255.c

@@ -306,8 +306,15 @@ static int dev_8255_attach(struct comedi_device *dev,
 			s->type = COMEDI_SUBD_UNUSED;
 		} else {
 			ret = subdev_8255_init(dev, s, NULL, iobase);
-			if (ret)
+			if (ret) {
+				/*
+				 * Release the I/O port region here, as the
+				 * "detach" handler cannot find it.
+				 */
+				release_region(iobase, I8255_SIZE);
+				s->type = COMEDI_SUBD_UNUSED;
 				return ret;
+			}
 		}
 	}