linux-kernel - Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue

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Date:	Sun, 24 Jul 2011 20:12:10 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Borislav Petkov <bp@...64.org>, "H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	"Przywara, Andre" <Andre.Przywara@....com>,
	"Pohlack, Martin" <Martin.Pohlack@....com>
Subject: Re: [PATCH] x86, AMD: Correct F15h IC aliasing issue


* Linus Torvalds <torvalds@...ux-foundation.org> wrote:

> On Sun, Jul 24, 2011 at 10:22 AM, Borislav Petkov <bp@...64.org> wrote:
> >
> >> So at a MINIMUM, I would say that this is acceptable only when the
> >> process doing the allocation hasn't got ASLR disabled.
> >
> > I guess I could look at randomize_va_space before enabling it.
> 
> That's not what I meant - I meant the per-process PF_RANDOMIZE and 
> ADDR_NO_RANDOMIZE personality flags (although the global 
> "randomize_va_space" thing obviously is one input to that too)
> 
> In fact, if 99% of your problem is ASLR-induced, might I suggest 
> just making the whole thing a tweak to ASLR instead, and not use 
> ASLR for bits 14:12? That should be fundamentally much safer: it 
> doesn't change any semantics at all, it just makes for slightly 
> less random bits to be used.

Indeed - that would be much nicer and smaller as well. It could also 
go away easily if this bug is fixed in a future CPU.

Thanks,

	Ingo
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