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Date: Fri, 5 Apr 2013 13:19:39 -0700
Message-ID: <CAKyRK=iEXpq9KnG_VJMYW-tpBxU_2TGaO_hZRkNY=J+7SNoQkA@mail.gmail.com>
Subject: Re: [PATCH 3/3] x86: kernel base offset ASLR
From: Julien Tinnes <jln@google.com>
To: Borislav Petkov <bp@alien8.de>, Kees Cook <keescook@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "kernel-hardening@lists.openwall.com" 
	<kernel-hardening@lists.openwall.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, "x86@kernel.org" <x86@kernel.org>,
        Jarkko Sakkinen <jarkko.sakkinen@intel.com>,
        Matthew Garrett <mjg@redhat.com>,
        Matt Fleming <matt.fleming@intel.com>,
        Eric Northup <digitaleric@google.com>,
        Dan Rosenberg <drosenberg@vsecurity.com>,
        Julien Tinnes <jln@google.com>, Will Drewry <wad@chromium.org>
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On Fri, Apr 5, 2013 at 7:49 AM, Borislav Petkov <bp@alien8.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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