linux-kernel - Re: RFC: Tainting the kernel on raw I/O access

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Message-ID: <20140904174709.5bcb9b28@alan.etchedpixels.co.uk>
Date:	Thu, 4 Sep 2014 17:47:09 +0100
From:	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Matthew Garrett <mjg59@...f.ucam.org>
Subject: Re: RFC: Tainting the kernel on raw I/O access

On Thu, 4 Sep 2014 07:07:39 +0200
Ingo Molnar <mingo@...nel.org> wrote:

> 
> * H. Peter Anvin <h.peter.anvin@...el.com> wrote:
> 
> > In a meeting earlier today, we discussed MSR access and that it could be
> > used to do bad things.  The same applies to other forms of raw I/O
> > (/dev/mem, /dev/port, ioperm, iopl, etc.)
> > 
> > This is basically the same problem with which the secure boot people
> > have been struggling.
> > 
> > Peter Z. suggested we should taint the kernel on raw I/O access, and I
> > tend to concur.
> 
> Lets start with the 'only for developers and the crazy' 
> interfaces, like /dev/msr access, and extend it step by step?

/dev/msr is used by standard distribution tools like powertop, and by
chromeos power management layers like dptf.

msr writes might fit the crazy book but I think you'd need to take a
close look at the standard tools first

This is the need a whitelist problem.

Alan
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