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

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Message-ID: <511BCB6E.8080102@zytor.com>
Date:	Wed, 13 Feb 2013 09:20:46 -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 02/12/2013 10:41 PM, Matthew Garrett wrote:
> On Tue, 2013-02-12 at 22:33 -0800, H. Peter Anvin wrote:
>
>> That is just batshit crazy.  If you have CAP_SYS_RAWIO you can do iopl()
>> which means you can reprogram your northbridge, at which point you most
>> definitely *can* modify the running kernel.
>
> Well right, that's the point of this patchset - it adds some extra
> permission checks to some of the existing CAP_SYS_RAWIO checks.
> CAP_SYS_RAWIO hasn't meant "I can perform arbitrary pio and mmio" for
> years - it means "I can do things that might maybe break something
> somehow". So sure, removing CAP_SYS_RAWIO would give us basically all
> the security we want in a secure boot environment, but it would also
> block things that we *want* to work.
>

So, let 's see...

Problem:

Someone adds SYS_CAP_RAWIO to some places it definitely does not
belong.

Solution:

Break all the *appropriate* (as defined)uses of SYS_CAP_RAWIO?

What the heck?

	-hpa



-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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