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From:   Andy Lutomirski <luto@kernel.org>
Date:   Tue, 3 Apr 2018 17:18:09 -0700
Message-ID: <CALCETrVF2vSvoz0sBCrfMKcbJ4hmi=1QJZbUxdvurkimVXr0nA@mail.gmail.com>
Subject: Re: [GIT PULL] Kernel lockdown for secure boot
To:     Matthew Garrett <mjg59@google.com>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Lutomirski <luto@kernel.org>,
        David Howells <dhowells@redhat.com>,
        Ard Biesheuvel <ard.biesheuvel@linaro.org>,
        James Morris <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>,
        Justin Forbes <jforbes@redhat.com>,
        linux-man <linux-man@vger.kernel.org>, joeyli <jlee@suse.com>,
        LSM List <linux-security-module@vger.kernel.org>,
        Linux API <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 5:16 PM, Matthew Garrett <mjg59@google.com> wrote:
> On Tue, Apr 3, 2018 at 5:15 PM Linus Torvalds
> <torvalds@linux-foundation.org>
> wrote:
>> On Tue, Apr 3, 2018 at 5:10 PM, Matthew Garrett <mjg59@google.com> wrote:
>> >
>> >> 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.
>
>> Wow. Way to snip the rest of the email where I told you what the
>> solution was. Let me repeat it here, since you so conveniently missed
>> it and deleted it:
>
> I ignored it because it's not a viable option. Part of the patchset
> disables various kernel command line options. If there's a kernel command
> line option that disables the patchset then it's pointless.

if your secure boot-enabled bootloader can't prevent a bad guy from
using malicious kernel command line parameters, then fix it.