linux-kernel - Re: [PATCH] [RESEND] PIE executable randomization

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Date:	Wed, 15 Aug 2007 13:39:51 -0400
From:	Chuck Ebbert <cebbert@...hat.com>
To:	Jiri Kosina <jkosina@...e.cz>
CC:	Jakub Jelinek <jakub@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Roland McGrath <roland@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Ulrich Kunitz <kune@...ne-taler.de>,
	Bret Towe <magnade@...il.com>, linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>
Subject: Re: [PATCH] [RESEND] PIE executable randomization

On 08/14/2007 04:41 PM, Jiri Kosina wrote:
> (added Arjan to CC, as he has been working on the kernel part of the 
> randomization previously)
> 
> On Tue, 14 Aug 2007, Jakub Jelinek wrote:
> 
>> If I'm reading the above hunk correctly, this means we will randomize 
>> all PIEs and even all dynamic linkers invoked as executables on i?86 and 
>> x86_64, and on the rest of arches we won't randomize at all, instead 
>> load ET_DYN objects at ELF_ET_DYN_BASE address. But I don't see anything 
>> i?86/x86_64 specific on this.
> 
> Hi Jakub,
> 
> actually, it is currently arch-specific, and that's because of different 
> memory layouts on different archs.
> 
> It turned out recently that PIE-compiled binaries on x86_64, that perform 
> larger amount of brk-allocations (for example bash) will not work (but 
> they will work on ?86). This is because currently on ?86 the memory layout 
> is as follows:

But your patch is enabling randomization for x86_64, because CONFIG_X86
includes both 32 and 64 bit archs.

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