[ 3.5.y.z extended stable ] Patch "staging: comedi: disallow COMEDI_DEVCONFIG on non-board" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    staging: comedi: disallow COMEDI_DEVCONFIG on non-board

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 2640fbffe08f6368f69b0977052eb50b660d13b5 Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti at mev.co.uk>
Date: Mon, 28 Jan 2013 16:14:31 +0000
Subject: [PATCH] staging: comedi: disallow COMEDI_DEVCONFIG on non-board
 minors

commit 754ab5c0e55dd118273ca2c217c4d95e9fbc8259 upstream.

Comedi has two sorts of minor devices:
(a) normal board minor devices in the range 0 to
COMEDI_NUM_BOARD_MINORS-1 inclusive; and
(b) special subdevice minor devices in the range COMEDI_NUM_BOARD_MINORS
upwards that are used to open the same underlying comedi device as the
normal board minor devices, but with non-default read and write
subdevices for asynchronous commands.

The special subdevice minor devices get created when a board supporting
asynchronous commands is attached to a normal board minor device, and
destroyed when the board is detached from the normal board minor device.
One way to attach or detach a board is by using the COMEDI_DEVCONFIG
ioctl.  This should only be used on normal board minors as the special
subdevice minors are too ephemeral.  In particular, the change
introduced in commit 7d3135af399e92cf4c9bbc5f86b6c140aab3b88c ("staging:
comedi: prevent auto-unconfig of manually configured devices") breaks
horribly for special subdevice minor devices.

Since there's no legitimate use for the COMEDI_DEVCONFIG ioctl on a
special subdevice minor device node, disallow it and return -ENOTTY.

Signed-off-by: Ian Abbott <abbotti at mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/staging/comedi/comedi_fops.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index d231193..2831080 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -425,6 +425,11 @@ static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
 	/* Device config is special, because it must work on
 	 * an unconfigured device. */
 	if (cmd == COMEDI_DEVCONFIG) {
+		if (minor >= COMEDI_NUM_BOARD_MINORS) {
+			/* Device config not appropriate on non-board minors. */
+			rc = -ENOTTY;
+			goto done;
+		}
 		rc = do_devconfig_ioctl(dev,
 					(struct comedi_devconfig __user *)arg);
 		if (rc == 0)
--
1.8.1.2