linux-kernel - Re: [PATCH for 2.6.18-rc2] [2/8] i386/x86-64: Don't randomize stack top when no randomization personality is set

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Message-ID: <20060716211126.GA2880@elte.hu>
Date:	Sun, 16 Jul 2006 23:11:27 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Andi Kleen <ak@...e.de>
Cc:	torvalds@...l.org, akpm@...l.org, discuss@...-64.org,
	linux-kernel@...r.kernel.org,
	Chuck Ebbert <76306.1226@...puserve.com>
Subject: Re: [PATCH for 2.6.18-rc2] [2/8] i386/x86-64: Don't randomize stack top when no randomization personality is set


* Andi Kleen <ak@...e.de> wrote:

> On Sunday 16 July 2006 22:47, Ingo Molnar wrote:
> > * Andi Kleen <ak@...e.de> wrote:
> > >  unsigned long arch_align_stack(unsigned long sp)
> > >  {
> > > -	if (randomize_va_space)
> > > +	if (!(current->personality & ADDR_NO_RANDOMIZE) && randomize_va_space)
> > >  		sp -= get_random_int() % 8192;
> > >  	return sp & ~0xf;
> >
> > i'm not opposing this patch at all, but didnt the performance problems
> > go away when the 0xf was changed to 0x7f?
> 
> Yes, but i sent the patch before that other patch was available.

excuses, excuses ;)

> I guess it's a separate issue anyways - this patch is just concerned 
> about disabling randomization consistently. Performance optimization 
> can be done in another one.

yeah. There's one security issue: the 'dont randomize' flag must be 
cleared when we cross a protection domain. When for example suid-ing in 
exec().

	Ingo
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