linux-kernel - Re: [PATCH] ASLRv3: randomize_va_space=3 preventing offset2lib attack

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Message-ID: <alpine.LNX.2.00.1412222047090.1680@pobox.suse.cz>
Date:	Mon, 22 Dec 2014 20:49:54 +0100 (CET)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Andy Lutomirski <luto@...capital.net>
cc:	Hector Marco Gisbert <hecmargi@....es>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Ingo Molnar <mingo@...hat.com>,
	Anton Blanchard <anton@...ba.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	"H. Peter Anvin" <hpa@...or.com>,
	David Daney <ddaney.cavm@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arun Chandran <achandran@...sta.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ismael Ripoll <iripoll@...ca.upv.es>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Hanno Böck <hanno@...eck.de>,
	Will Deacon <will.deacon@....com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Kees Cook <keescook@...omium.org>,
	Reno Robert <renorobert@...il.com>
Subject: Re: [PATCH] ASLRv3: randomize_va_space=3 preventing offset2lib
 attack

On Mon, 22 Dec 2014, Andy Lutomirski wrote:

> a. With PIE executables, the offset from the executable to the
> libraries is constant.  This is unfortunate when your threat model
> allows you to learn the executable base address and all your gadgets
> are in shared libraries.

When I was originally pushing PIE executable randomization, I have been 
thinking about ways to solve this.

In theory, we could start playing games with load_addr in 
load_elf_interp() and randomizing it completely independently from mmap() 
base randomization, but the question is whether it's really worth the 
hassle and binfmt_elf code complication. I am not convinced.

-- 
Jiri Kosina
SUSE Labs
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