linux-kernel - Re: [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking

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Message-ID: <Pine.LNX.4.64.0802071143090.11914@vixen.sonytel.be>
Date:	Thu, 7 Feb 2008 11:43:43 +0100 (CET)
From:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Jiri Kosina <jkosina@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Hugh Dickins <hugh@...itas.com>, Pavel Machek <pavel@....cz>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ASLR: add possibility for more fine-grained tweaking

On Thu, 7 Feb 2008, Ingo Molnar wrote:
> * Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com> wrote:
> > On Wed, 6 Feb 2008, Ingo Molnar wrote:
> > > @@ -541,6 +541,18 @@ config ELF_CORE
> > >  	help
> > >  	  Enable support for generating core dumps. Disabling saves about 4k.
> > >  
> > > +config COMPAT_BRK
> > > +	bool "Disable heap randomization"
> > > +	default y
> > > +	help
> > > +	  Randomizing heap placement makes heap exploits harder, but it
> > > +	  also breaks ancient binaries (including anything libc5 based).
> > > +	  This option changes the bootup default to heap randomization
> > > +	  disabled, and can be overriden runtime by setting
> > > +	  /proc/sys/kernel/randomize_va_space to 2.
> > > +
> > > +	  On non-ancient distros (post-2000 ones) Y is usually a safe choice.
> > 
> > Somehow my belly feeling tells me something is wrong with this description...
> > 
> > Ah, a negative option (Y -> disable).  So Y is always safe.
> > 
> > `non-ancient distros' really means `recent distros', and if you have 
> > one, then _N_ should be a safe choice, too?
> 
> yeah, you are right :-) I'll fix this.
> 
> btw., "non-ancient distros" does not just mean "recent distros", it 
> really means "just about any distro you picked up in the past 10 years". 
> You'd have to go out on a limb to find something historic (or keep 
> copying /lib/libc5 binaries to new distros like Pavel did) to still have 
> this particular libc5 assumption/breakage. [ Or at least so i hope =B-)]

Bummer, I guess my good old m68k recovery ramdisk is affected ;-)

With kind regards,

Geert Uytterhoeven
Software Architect

Sony Network and Software Technology Center Europe
The Corporate Village · Da Vincilaan 7-D1 · B-1935 Zaventem · Belgium

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E-mail:   Geert.Uytterhoeven@...ycom.com
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