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>

diff --git a/drivers/staging/comedi/drivers/8255.c b/drivers/staging/comedi/drivers/8255.c
index ba89321df65d8ef97afad5bf471149e1934fd5ae..0fdf8342c995d11549712b9e2d63a19e5480d303 100644 (file)
--- a/drivers/staging/comedi/drivers/8255.c
+++ b/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;
+                       }
                }
        }