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

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Message-ID: <20080207103231.GD16735@elte.hu>
Date:	Thu, 7 Feb 2008 11:32:32 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Geert Uytterhoeven <Geert.Uytterhoeven@...ycom.com>
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


* 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-)]

	Ingo
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