linux-kernel - Re: [PATCH v3 0/6] kernel ASLR

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Date:	Fri, 26 Apr 2013 11:53:28 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	Jarkko Sakkinen <jarkko.sakkinen@...el.com>,
	Matthew Garrett <mjg@...hat.com>,
	Matt Fleming <matt.fleming@...el.com>,
	Eric Northup <digitaleric@...gle.com>,
	Dan Rosenberg <drosenberg@...curity.com>,
	Julien Tinnes <jln@...gle.com>, Will Drewry <wad@...omium.org>
Subject: Re: [PATCH v3 0/6] kernel ASLR

On Thu, Apr 25, 2013 at 3:01 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 04/25/2013 02:54 PM, Kees Cook wrote:
>> This continues to build on the tip/kaslr patches for KASLR. This series
>> converts the logic to C, and moves both relocation and address selection
>> into the decompress_kernel path. Several areas were refactored to allow
>> for some code reuse (e.g. CPU flags, kernel command line).
>>
>> This does not yet attempt to rework the page tables to handle an arbitrary
>> physical memory location on x86_64. I would love some suggestions on
>> how to do this. :)
>>
>
> We *should* already support arbitrary physical memory locations at least
> in the kernel proper (the decompressor might need some work.)
>
> We may want to do in the decompressor what we already do in the kernel,
> and set up a #PF handler which creates page tables on demand.  That way
> you can simply treat the entire memory space as a single linear space.

I'll need to compare the logic used for that against what's in
head_64.S for setting up the initial tables. And mapping the kernel
chunk as not 1-to-1, etc.

In the meantime, I'll send a v4 series with the other identified
changes since everything else (up to the 64-bit phy/virt detachment)
seems to be working.

-Kees

--
Kees Cook
Chrome OS Security
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