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

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Date:	Tue, 12 Feb 2013 16:48:12 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Matthew Garrett <matthew.garrett@...ula.com>
CC:	Borislav Petkov <bp@...en8.de>, Kees Cook <keescook@...omium.org>,
	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 02/09/2013 07:11 AM, Matthew Garrett wrote:
> On Sat, 2013-02-09 at 10:29 +0100, Borislav Petkov wrote:
>> On Fri, Feb 08, 2013 at 10:45:35PM -0800, Kees Cook wrote:
>>> Also, _reading_ MSRs from userspace arguably has utility that doesn't
>>> compromise ring-0.
>>
>> And to come back to the original question: what is that utility, who
>> would need it on a secure boot system and why?
> 
> Things like Turbostat are useful, although perhaps that information
> should be exposed in a better way.
> 

OK... what none of this gets into:

Why should CAP_RAWIO be allowed on a secure boot system, when there are
2^n known ways of compromise a system with CAP_RAWIO?

	-hpa

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