linux-kernel - Re: [PATCH] x86: Enable full randomization on i386 and X86

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Message-ID: <CAGXu5jKyxQ+7rJAhs_O3sGHxXP7Te81mEJ4HJ+f8zBbu1PpZSw@mail.gmail.com>
Date:	Fri, 11 Mar 2016 08:19:49 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Hector Marco-Gisbert <hecmargi@....es>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	"x86@...nel.org" <x86@...nel.org>,
	Ismael Ripoll Ripoll <iripoll@....es>,
	Harvey Harrison <harvey.harrison@...il.com>
Subject: Re: [PATCH] x86: Enable full randomization on i386 and X86_32.

On Fri, Mar 11, 2016 at 12:53 AM, Ingo Molnar <mingo@...nel.org> wrote:
>
> * Kees Cook <keescook@...omium.org> wrote:
>
>> On Thu, Mar 10, 2016 at 12:53 PM, Arjan van de Ven
>> <arjan@...ux.intel.com> wrote:
>> >> Arjan, or other folks, can you remember why x86_32 disabled mmap
>> >> randomization here? There doesn't seem to be a good reason for it that
>> >> I see.
>> >
>> >
>> > for unlimited stack it got really messy with threaded apps.
>>
>> Seems like it'd only cause problems for really really giant processes?
>> (I think it's telling that the other 32-bit archs don't disable ASLR
>> in this case...)
>
> IIRC there was some sort of specific breakage with unlimited stack apps - I don't
> remember the exact details.
>
>> > anyway, I don't mind seeing if this will indeed work, with time running out
>> > where 32 bit is going extinct... in a few years we just won't have enough
>> > testing on this kind of change anymore.
>>
>> Sounds good. Ingo, can you pull this in and we can try it for -next?
>
> Ok, we can certainly try. If there's breakage with old distros then we might need
> to put this behind a legacy Kconfig switch.

Okay, sounds good. Thanks!

-Kees

-- 
Kees Cook
Chrome OS & Brillo Security