linux-kernel - Re: [PATCH] x86: Lock down MSR writing in secure boot

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Message-ID: <20130208230655.GB28990@pd.tnic>
Date:	Sat, 9 Feb 2013 00:06:55 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Kees Cook <keescook@...omium.org>,
	Matthew Garrett <matthew.garrett@...ula.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
	linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH] x86: Lock down MSR writing in secure boot

On Fri, Feb 08, 2013 at 02:30:52PM -0800, H. Peter Anvin wrote:
> Also, keep in mind that there is a very simple way to deny MSR access
> completely, which is to not include the driver in your kernel (and not
> allow module loading, but if you can load modules you can just load a
> module to muck with whatever MSR you want.)

I was contemplating that too. What is the use case of having
msr.ko in a secure boot environment? Isn't that an all-no-tools,
you-can't-do-sh*t-except-what-you're-explicitly-allowed-to environment which
simply doesn't need to write MSRs in the first place?

-- 
Regards/Gruss,
    Boris.

Sent from a fat crate under my desk. Formatting is fine.
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