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

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Message-ID: <20120509103111.GR22134@mwanda>
Date:	Wed, 9 May 2012 13:31:11 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Ian Abbott <abbotti@....co.uk>
Cc:	H Hartley Sweeten <hartleys@...ionengravers.com>,
	"devel@...verdev.osuosl.org" <devel@...verdev.osuosl.org>,
	"fmhess@...rs.sourceforge.net" <fmhess@...rs.sourceforge.net>,
	Ian Abbott <ian.abbott@....co.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>
Subject: Re: [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@...ionengravers.com>
> >>Cc: Ian Abbott<abbotti@....co.uk>
> >>Cc: Mori Hess<fmhess@...rs.sourceforge.net>
> >>Cc: Greg Kroah-Hartman<gregkh@...uxfoundation.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.

Sparse is useful so we shouldn't break it.  I always run sparse over
my patches before submission and look at the warnings.  Except if
they scroll off the page.  In that case, I just figure that the
author deserves the bugs.

We could just do some ifdeferry to fix it for userspace.

regards,
dan carpenter

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