linux-kernel - Re: [GIT PULL] Kernel lockdown for secure boot

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Message-ID: <CACdnJuvFqXGLsAv1Km3MmdssHBfuH5-C_vG3A4eq4Yuj0HhFBA@mail.gmail.com>
Date:   Wed, 04 Apr 2018 00:10:47 +0000
From:   Matthew Garrett <mjg59@...gle.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     luto@...nel.org, David Howells <dhowells@...hat.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>, jmorris@...ei.org,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        jforbes@...hat.com, linux-man@...r.kernel.org, jlee@...e.com,
        LSM List <linux-security-module@...r.kernel.org>,
        linux-api@...r.kernel.org, Kees Cook <keescook@...omium.org>,
        linux-efi <linux-efi@...r.kernel.org>
Subject: Re: [GIT PULL] Kernel lockdown for secure boot

On Tue, Apr 3, 2018 at 5:06 PM Linus Torvalds
<torvalds@...ux-foundation.org>
wrote:

> On Tue, Apr 3, 2018 at 4:59 PM, Matthew Garrett <mjg59@...gle.com> wrote:
> >
> > Ok. So we can build distribution kernels that *always* have this on,
and to
> > turn it off you have to disable Secure Boot and install a different
kernel.

> Bingo.

> Exactly like EVERY OTHER KERNEL CONFIG OPTION.

So your argument is that we should make the user experience worse? Without
some sort of verified boot mechanism, lockdown is just security theater.
There's no good reason to enable it unless you have some mechanism for
verifying that you booted something you trust.