Re: [PATCH] staging: comedi: remove __user annotation inside of struct's

Ian Abbott
2012-05-09T10:20:15Z

On 2012-05-09 00:55, H Hartley Sweeten wrote:
> On Tuesday, May 08, 2012 4:41 PM, H Hartley Sweeten wrote:
>>
>> The structs' comedi_insn, coomedi_insnlist, comedi_cmd,
>> comedi_chaninfo, and comedi_rangeinfo are all passed to
>> the kernel from user space using ioctl commands. They
>> are then copied to kernel space using copy_from_user()
>> before the data is passed to the drivers.
>>
>> The __user annotation should not be used with variables
>> inside the struct. This produces a lot of sparse warnings
>> like:
>>
>> warning: dereference of noderef expression
>>
>> Signed-off-by: H Hartley Sweeten<hsweeten@visionengravers.com>
>> Cc: Ian Abbott<abbotti@mev.co.uk>
>> Cc: Mori Hess<fmhess@users.sourceforge.net>
>> Cc: Greg Kroah-Hartman<gregkh@linuxfoundation.org>
>>
>> ---
>>
>> Note: This patch exposes some new warnings about different
>> address space. These will be addressed.
>
> Please ignore this patch.
>
> It appears the annotations in the struct definitions are correct.

Personally, I think you were on the mark with the patch. It's better to
avoid using __user in comedi.h so it can be used as-is in user-space.
All of the structures in comedi.h are used in user-space (although
Comedilib uses its own version of comedi.h without all the typedef
eliminations that have been done in "staging") and some of them are also
deep-copied into kernel-space objects of the same type, where the
pointers in the structs would no longer be user-space pointers.

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