linux-kernel - Re: [patch 4/4] c/r: prctl: Extend PR_SET_MM to set up more mm

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Date:	Fri, 3 Feb 2012 09:26:55 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Cyrill Gorcunov <gorcunov@...nvz.org>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Emelyanov <xemul@...nvz.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	Tejun Heo <tj@...nel.org>, Andrew Vagin <avagin@...nvz.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Pavel Emelyanov <xemul@...allels.com>,
	Vasiliy Kulikov <segoon@...nwall.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [patch 4/4] c/r: prctl: Extend PR_SET_MM to set up more mm_struct entries

On Fri, Feb 3, 2012 at 9:10 AM, Cyrill Gorcunov <gorcunov@...nvz.org> wrote:
> On Fri, Feb 03, 2012 at 08:56:20AM -0800, Kees Cook wrote:
>> On Fri, Feb 3, 2012 at 7:19 AM, Cyrill Gorcunov <gorcunov@...nvz.org> wrote:
>> > +       case PR_SET_MM_AUXV: {
>> > +               unsigned long user_auxv[AT_VECTOR_SIZE];
>> > +
>> > +               if (arg4 > sizeof(mm->saved_auxv))
>> > +                       goto out;
>>
>> While these are both AT_VECTOR_SIZE, I think it might be better to use
>> sizeof(mm->saved_auxv) instead of AT_VECTOR_SIZE, just so that they
>> can never get out sync and there's a single reference for the size.
>>
>
> I suppose you meant ARRAY_SIZE rather since plain sizeof will give you
> the summary size in bytes, but I think I have better idea -- lets put
> BUILD_BUG_ON here, like below.

Ah, cool. Works for me. :)

Acked-by: Kees Cook <keescook@...omium.org>

-Kees

-- 
Kees Cook
ChromeOS Security
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