linux-kernel - Re: [PATCH 0/5] security, efi: Set lockdown if in secure boot mode

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Date:   Tue, 06 Jun 2017 10:34:51 +0100
From:   David Howells <dhowells@...hat.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:     dhowells@...hat.com, Matthew Garrett <matthew.garrett@...ula.com>,
        linux-security-module <linux-security-module@...r.kernel.org>,
        "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 0/5] security, efi: Set lockdown if in secure boot mode

Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:

> and print a subsequent line for every lockdown feature that is enabled, e.g.,
> 
> lockdown: disabling MSRs
> lockdown: disabling hibernate support

There's another problem with this idea: the lockdown facility is passive - it
doesn't go looking for things to lock down; rather, things that can be locked
down inquire as to whether lockdown is in effect at the point someone tries to
use them.

Now, I could reserve a variable for each thing we lock down to make sure that
we don't emit the message more than once, but I'm loathe to waste memory this
way.

I can't so easily switch the facility to being active either, since a lot of
the lockdownables are in modules.

David