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From:   Matthew Garrett <mjg59@google.com>
Date:   Tue, 03 Apr 2018 20:54:55 +0000
Message-ID: <CACdnJuuXOP5T-BRAwMvc7XF8S49wyvp4ZYgcU=EZkaGNgPAQig@mail.gmail.com>
Subject: Re: [GIT PULL] Kernel lockdown for secure boot
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     luto@kernel.org, David Howells <dhowells@redhat.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>, jmorris@namei.org,
        Alan Cox <gnomes@lxorguk.ukuu.org.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        jforbes@redhat.com, linux-man@vger.kernel.org, jlee@suse.com,
        LSM List <linux-security-module@vger.kernel.org>,
        linux-api@vger.kernel.org, Kees Cook <keescook@chromium.org>,
        linux-efi <linux-efi@vger.kernel.org>
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On Tue, Apr 3, 2018 at 1:53 PM Linus Torvalds
<torvalds@linux-foundation.org>
wrote:

> On Tue, Apr 3, 2018 at 9:29 AM, Matthew Garrett <mjg59@google.com> wrote:
> > On Tue, Apr 3, 2018 at 8:11 AM Andy Lutomirski <luto@kernel.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?