[RESEND PATCH] staging: comedi: prevent auto-unconfig of manually configured devices

Greg Kroah-Hartman gregkh at linuxfoundation.org
Mon Jan 7 23:23:20 UTC 2013


On Wed, Jan 02, 2013 at 04:21:23PM +0000, Ian Abbott wrote:
> 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>
> Cc: stable at vger.kernel.org
> ---
> @Greg: This was originally sent on 4th December.  It clashes with
> Hartley's "[PATCH 04/26] staging: comedi: use comedi_dev_from_minor()"
> of 19th December.  It would be nice if my patch takes precedence so that
> it can be used as-is in the stable kernels, though unfortunately that
> would require a slight re-work of Hartley's patch.

I've applied this, and Hartley's patches, and merged the branches
together.  I've fixed up the obvious build error, can both of you verify
that I didn't do anything wrong?  It should be in the staging-next
branch now.

thanks,

greg k-h



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