linux-kernel - Re: [PATCH] bitmap: bitmap_parse takes a kernel buffer instead of a user buffer

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Date:	Wed, 4 Oct 2006 10:14:05 -0400
From:	Joe Korty <joe.korty@...r.com>
To:	Andrew Morton <akpm@...l.org>
Cc:	Reinette Chatre <reinette.chatre@...ux.intel.com>,
	linux-kernel@...r.kernel.org,
	Inaky Perez-Gonzalez <inaky@...ux.intel.com>,
	Paul Jackson <pj@....com>
Subject: Re: [PATCH] bitmap: bitmap_parse takes a kernel buffer instead of a user buffer

On Tue, Oct 03, 2006 at 04:39:36PM -0700, Andrew Morton wrote:
> On Tue, 3 Oct 2006 08:16:27 -0700
> Reinette Chatre <reinette.chatre@...ux.intel.com> wrote:
> 
> > lib/bitmap.c:bitmap_parse() is a library function that received as
> > input a  user buffer. This seemed to have originated from the way the
> > write_proc function of the /proc filesystem operates.
> > 
> > This function will be useful for other uses as well;
> > for example, taking input  for /sysfs instead of /proc,
> > so it was changed to accept kernel buffers. We have this
> > use for the Linux UWB project, as part as the upcoming
> > bandwidth allocator code.
> > 
> > Only a few routines used this function and they were changed too.
> 
> Fair enough.  But this: [ ... ] is sending us a message ;)
> 
> How about adding a new bitmap_parse_user() (and cpumask_parse_user())
> which does the above?


I am slightly concerned about using a kmalloc where 'count' is specified
by userspace.  There might be a DoS attack in here somewhere.....

Perhaps we can reverse Andrew's idea: rename the existing bitmap_parse
to bitmap_parse_user, then make the kernel-buffer version, bitmap_parse,
be a wrapper around that.

Joe
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