[ 3.5.y.z extended stable ] Patch "staging: comedi: prevent auto-unconfig of manually" has been added to staging queue

[Herton Ronaldo Krzesinski]

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

    staging: comedi: prevent auto-unconfig of manually

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.
-Herton

------

>From faeaaaa013aa861c6055f652960a7278a9d2e0fe Mon Sep 17 00:00:00 2001
From: Ian Abbott <abbotti at mev.co.uk>
Date: Tue, 4 Dec 2012 15:59:55 +0000
Subject: [PATCH] staging: comedi: prevent auto-unconfig of manually
 configured devices

commit 7d3135af399e92cf4c9bbc5f86b6c140aab3b88c upstream.

When a low-level comedi driver auto-configures a device, a `struct
comedi_dev_file_info` is allocated (as well as a `struct
comedi_device`) by `comedi_alloc_board_minor()`.  A pointer to the
hardware `struct device` is stored as a cookie in the `struct
comedi_dev_file_info`.  When the low-level comedi driver
auto-unconfigures the device, `comedi_auto_unconfig()` uses the cookie
to find the `struct comedi_dev_file_info` so it can detach the comedi
device from the driver, clean it up and free it.

A problem arises if the user manually unconfigures and reconfigures the
comedi device using the `COMEDI_DEVCONFIG` ioctl so that is no longer
associated with the original hardware device.  The problem is that the
cookie is not cleared, so that a call to `comedi_auto_unconfig()` from
the low-level driver will still find it, detach it, clean it up and free
it.

Stop this problem occurring by always clearing the `hardware_device`
cookie in the `struct comedi_dev_file_info` whenever the
`COMEDI_DEVCONFIG` ioctl call is successful.

Signed-off-by: Ian Abbott <abbotti at mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski at canonical.com>
---
 drivers/staging/comedi/comedi_fops.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
index d77219a..d231193 100644
--- a/drivers/staging/comedi/comedi_fops.c
+++ b/drivers/staging/comedi/comedi_fops.c
@@ -427,6 +427,9 @@ static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
 	if (cmd == COMEDI_DEVCONFIG) {
 		rc = do_devconfig_ioctl(dev,
 					(struct comedi_devconfig __user *)arg);
+		if (rc == 0)
+			/* Evade comedi_auto_unconfig(). */
+			dev_file_info->hardware_device = NULL;
 		goto done;
 	}

--
1.7.9.5