kernel-hardening - Re: [PATCH 3/3] x86: kernel base offset ASLR

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Message-ID: <CAE9FiQVCC2-yF0+bt2MryHDs2vK8bcsU1aE-is_ejDDF0dTbMQ@mail.gmail.com>
Date: Fri, 5 Apr 2013 13:01:04 -0700
From: Yinghai Lu <yinghai@...nel.org>
To: "H. Peter Anvin" <hpa@...or.com>
Cc: Kees Cook <keescook@...omium.org>, 
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, kernel-hardening@...ts.openwall.com, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, 
	"the arch/x86 maintainers" <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 3/3] x86: kernel base offset ASLR

On Thu, Apr 4, 2013 at 1:21 PM, H. Peter Anvin <hpa@...or.com> wrote:
> I have to admit to being somewhat skeptical toward KASLR with only 8
> bits of randomness.  There are at least two potential ways of
> dramatically increasing the available randomness:
>
> 1. actually compose the kernel of multiple independently relocatable
>    pieces (maybe chunk it on 2M boundaries or something.)
>
> 2. compile the kernel as one of the memory models which can be executed
>    anywhere in the 64-bit address space.  The cost of this would have
>    to be quantified, of course.

Why just let bootloader to load kernel on random address instead?

For our 64bit bzImage, boot loader could load kernel to anywhere above 4G.

Thanks

Yinghai

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