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    SubjectRe: [PATCH] staging: comedi: remove __user annotation inside of struct's
    On Wed, May 09, 2012 at 11:20:07AM +0100, Ian Abbott wrote:
    > 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.

    When the kernel exports .h files, stuff like this should work
    "automatically", so there is no need to not put __user markings.

    So please, yes, continue to work to get this correct, it is very
    essencial to ensure we don't mess stuff up.

    thanks,

    greg k-h


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