linux-kernel - Re: [PATCH 12/27] x86/msr: Restrict MSR access when the kernel is locked down

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Message-ID: <20171020190939.569cedd2@alans-desktop>
Date:   Fri, 20 Oct 2017 19:09:39 +0100
From:   Alan Cox <gnomes@...rguk.ukuu.org.uk>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-security-module@...r.kernel.org, linux-efi@...r.kernel.org,
        matthew.garrett@...ula.com, gregkh@...uxfoundation.org,
        linux-kernel@...r.kernel.org, jforbes@...hat.com
Subject: Re: [PATCH 12/27] x86/msr: Restrict MSR access when the kernel is
 locked down

On Thu, 19 Oct 2017 15:52:04 +0100
David Howells <dhowells@...hat.com> wrote:

> From: Matthew Garrett <matthew.garrett@...ula.com>
> 
> Writing to MSRs should not be allowed if the kernel is locked down, since
> it could lead to execution of arbitrary code in kernel mode.  Based on a
> patch by Kees Cook.

There are a load of standard tools that use this so I think you are going
to need a whitelist. Can you at least log *which* MSR in the failing case
so a whitelist can be built over time ?

Alan