Openwall GNU/*/Linux - a small security-enhanced Linux distro for servers
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Date: Fri, 5 Apr 2013 13:19:39 -0700
From: Julien Tinnes <jln@...gle.com>
To: Borislav Petkov <bp@...en8.de>, Kees Cook <keescook@...omium.org>, 
	LKML <linux-kernel@...r.kernel.org>, 
	"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "H. Peter Anvin" <hpa@...or.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 3/3] x86: kernel base offset ASLR

On Fri, Apr 5, 2013 at 7:49 AM, Borislav Petkov <bp@...en8.de> wrote:
> On Thu, Apr 04, 2013 at 01:07:35PM -0700, Kees Cook wrote:
>> This creates CONFIG_RANDOMIZE_BASE, so that the base offset of the kernel
>> can be randomized at boot.
>
> Right,
>
> if I'm reading this whole deal correctly, I have an issue with this
> in the sense that if this thing is enabled by default and people are
> running stripped kernels, an oops which is being reported is worth sh*t
> since all the addresses there are random and one simply can't map them
> back to which functions the callstack frames are pointing to. Which will
> majorly hinder debuggability, IMHO...

I think it'd be perfectly ok for OOPS to print out the kernel base.

Restricting access to these oopses becomes a different problem
(privilege separation). Some existing sandboxes (Chromium, vsftpd,
openssh..) are already defending against it.

Julien

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