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

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Message-ID: <CACdnJuuXOP5T-BRAwMvc7XF8S49wyvp4ZYgcU=EZkaGNgPAQig@mail.gmail.com>
Date:   Tue, 03 Apr 2018 20:54:55 +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 1:53 PM Linus Torvalds
<torvalds@...ux-foundation.org>
wrote:

> On Tue, Apr 3, 2018 at 9:29 AM, Matthew Garrett <mjg59@...gle.com> wrote:
> > On Tue, Apr 3, 2018 at 8:11 AM Andy Lutomirski <luto@...nel.org> wrote:
> >> Can you explain that much more clearly?  I'm asking why booting via
> >> UEFI Secure Boot should enable lockdown, and I don't see what this has
> >> to do with kexec.  And "someone blacklist[ing] your key in the
> >> bootloader" sounds like a political issue, not a technical issue.
> >
> > A kernel that allows users arbitrary access to ring 0 is just an
> > overfeatured bootloader. Why would you want secure boot in that case?

> .. maybe you don't *want* secure boot, but it's been pushed in your
> face by people with an agenda?

Then turn it off, or build a self-signed kernel that doesn't do this?