staging: comedi: prevent auto-unconfig of manually configured devices
authorIan Abbott <abbotti@mev.co.uk>
Tue, 4 Dec 2012 15:59:55 +0000 (15:59 +0000)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Thu, 17 Jan 2013 16:50:55 +0000 (08:50 -0800)
commite7b67acb37508a8a173038a928816d9e826b6363
treec89bf4c44c89b0f39404475ed7240cf70907dc03
parent1d757c9abbfb218c89d6b0586ff89b4032a3601d
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@mev.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/staging/comedi/comedi_fops.c