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

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Message-ID: <18499.1508532496@warthog.procyon.org.uk>
Date:   Fri, 20 Oct 2017 21:48:16 +0100
From:   David Howells <dhowells@...hat.com>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>
Cc:     dhowells@...hat.com, 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

Alan Cox <gnomes@...rguk.ukuu.org.uk> wrote:

> 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 ?

Probably.  Is it just the file position for msr_write()?  Should the register
number increment with the copy loop?

What about for the X86_IOC_WRMSR_REGS ioctl?  What's the reg number there?

And do you know where wrmsr_safe_regs() might be found?  I can see things
using it and exporting it, but no implementation, so I'm guessing it's
macroised somewhere.

David