Commit 7d3135af authored Dec 04, 2012 by Ian Abbott Committed by Greg Kroah-Hartman Jan 07, 2013

staging: comedi: prevent auto-unconfig of manually configured devices



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>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent 34b55d8c

drivers/staging/comedi/comedi_fops.c

+3 −0

Original line number	Original line	Diff line number	Diff line
	@@ -1549,6 +1549,9 @@ static long comedi_unlocked_ioctl(struct file *file, unsigned int cmd,
	if (cmd == COMEDI_DEVCONFIG) {		if (cmd == COMEDI_DEVCONFIG) {
	rc = do_devconfig_ioctl(dev,		rc = do_devconfig_ioctl(dev,
	(struct comedi_devconfig __user *)arg);		(struct comedi_devconfig __user *)arg);
			if (rc == 0)
			/* Evade comedi_auto_unconfig(). */
			dev_file_info->hardware_device = NULL;
	goto done;		goto done;
	}		}