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

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Message-ID: <CA+55aFxKzxdRZthzaokaGPAsWCp3a-p3aVfJSutF+9Fp9sbaVA@mail.gmail.com>
Date:   Tue, 3 Apr 2018 15:46:11 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Andy Lutomirski <luto@...nel.org>
Cc:     David Howells <dhowells@...hat.com>,
        Matthew Garrett <mjg59@...gle.com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        James Morris <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>,
        Justin Forbes <jforbes@...hat.com>,
        linux-man <linux-man@...r.kernel.org>, joeyli <jlee@...e.com>,
        LSM List <linux-security-module@...r.kernel.org>,
        Linux API <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 3:39 PM, Andy Lutomirski <luto@...nel.org> wrote:
>
> Sure.  I have no problem with having an upstream kernel have a
> lockdown feature, although I think that feature should distinguish
> between reads and writes.  But I don't think the upstream kernel
> should apply a patch that ties any of this to Secure Boot without a
> genuine technical reason why it makes sense.

So this is where I violently agree with Andy.

For example, I love signed kernel modules. The fact that I love them
has absolutely zero to do with secure boot, though. There is
absolutely no linkage between the two issues: I use (self-)signed
kernel modules simply because I think it's a good thing in general.

The same thing is true of some lockdown patch. Maybe it's a good thing
in general. But whether it's a good thing is _entirely_ independent of
any secure boot issue. I can see using secure boot without it, but I
can very much also see using lockdown without secure boot.

The two things are simply entirely orthogonal. They have _zero_
overlap. I'm not seeing why they'd be linked at all in any way.

               Linus