linux-kernel - [PATCH 02/46] comedi: 8255: Add some I/O base address sanity checks

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Message-ID: <20260130170416.49994-3-abbotti@mev.co.uk>
Date: Fri, 30 Jan 2026 16:47:27 +0000
From: Ian Abbott <abbotti@....co.uk>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Ian Abbott <abbotti@....co.uk>,
	H Hartley Sweeten <hsweeten@...ionengravers.com>
Subject: [PATCH 02/46] comedi: 8255: Add some I/O base address sanity checks

The "8255" driver allows a COMEDI device to be constructed from one or
more 8255 chips, each at an I/O port base address specified by the
admin-supplied configuration options (`it->options[]`).  Currently, the
driver allows any I/O base addresses to be specified as long as the I/O
regions can be reserved, and it converts the specified `int` option
values holding the base address to `unsigned long`.

It doesn't make sense to allow base addresses that are not aligned to
4-byte boundaries because the hardware register addresses would not be
decoded properly, so add a check for valid alignment.

Convert the option values that specify the base addresses from `int` to
`unsigned int` instead of `unsigned long` so they end up the same on
32-bit and 64-bit systems.

Signed-off-by: Ian Abbott <abbotti@....co.uk>
---
 drivers/comedi/drivers/8255.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/comedi/drivers/8255.c b/drivers/comedi/drivers/8255.c
index 5f70938b4477..ff45248ebb29 100644
--- a/drivers/comedi/drivers/8255.c
+++ b/drivers/comedi/drivers/8255.c
@@ -47,7 +47,7 @@ static int dev_8255_attach(struct comedi_device *dev,
 			   struct comedi_devconfig *it)
 {
 	struct comedi_subdevice *s;
-	unsigned long iobase;
+	unsigned int iobase;
 	int ret;
 	int i;

@@ -70,13 +70,15 @@ static int dev_8255_attach(struct comedi_device *dev,
 		iobase = it->options[i];

 		/*
-		 * __comedi_request_region() does not set dev->iobase.
+		 * __comedi_check_request_region() does not set dev->iobase.
 		 *
 		 * For 8255 devices that are manually attached using
 		 * comedi_config, the 'iobase' is the actual I/O port
-		 * base address of the chip.
+		 * base address of the chip.  It should be aligned on
+		 * a 4-byte boundary.
 		 */
-		ret = __comedi_request_region(dev, iobase, I8255_SIZE);
+		ret = __comedi_check_request_region(dev, iobase, I8255_SIZE,
+						    0, UINT_MAX, 4);
 		if (ret)
 			return ret;
 		ret = subdev_8255_io_init(dev, s, iobase);
-- 
2.51.0