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

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Date:	Mon, 22 Dec 2014 21:03:26 +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:

> It could be worth having a mode that goes all out: randomize every
> single allocation independently in, say, a 45 or 46-byte range.  That
> would be about as strong ASLR as we could possibly have, it would
> result in guard intervals around mmap data allocations (which has real
> value), and it would still leave plenty of space for big address space
> hogs like the Chromium sandbox.
> 
> The main downside would be lots of memory used for page tables.

Plus get_random_int() during every mmap() call. Plus the resulting VA 
space fragmentation.

-- 
Jiri Kosina
SUSE Labs
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