linux-kernel - Re: [PATCH] get_random_long() and AT

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Message-ID: <20070625051210.GF11115@waste.org>
Date:	Mon, 25 Jun 2007 00:12:10 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Arjan van de Ven <arjan@...radead.org>
Cc:	Alexander Gabert <pappy@...too.org>, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, libc-alpha@...rceware.org,
	hardened@...too.org
Subject: Re: [PATCH] get_random_long() and AT_ENTROPY for auxv, kernel 2.6.21.5

On Sun, Jun 24, 2007 at 09:43:03PM -0700, Arjan van de Ven wrote:
> On Sun, 2007-06-24 at 22:45 -0500, Matt Mackall wrote:
> > On Sun, Jun 24, 2007 at 07:45:04PM +0200, Alexander Gabert wrote:
> > > Hi Linus,
> > > hi LKML,
> > > 
> > > i would like to thank LKML and especially Eric (thanks for the per_cpu 
> > > macro tips and design guidelines!) and the other contributors to this idea.
> > > 
> > > This time the patch is rather big because it also removes 
> > > get_random_int() and introduces get_random_long() throughout the kernel.
> > 
> > Stop right there. You still haven't answered my original question.
> > What is the point of this exercise in the first place, please?
> > 
> > Am I right in thinking you have three unrelated patches here?
> > 
> > - something to do with aux vector headers
> 
> the primary goal is to pass a random value to userspace at process
> start; this to save glibc from having to open /dev/urandom on ever
> program start (which it does now for all apps compiled with
> -fstack-protector, which in various distros is "everything").

Interesting.

What are our requirements here? Defending against local attackers who
can build exploits on the fly probably means something stronger than get_random_int.
 
> > - sweeping change of get_random_int to get_random_long for no obvious reason
> 
> and this is because Alexander wants 2 and not 1 random int to be passed
> for his own glibc proposed change (combined with get_random_int() being
> designed for only 4 bytes per process ;-)

Sure. Still, separate patches.

-- 
Mathematics is the supreme nostalgia of our time.
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