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From:   Matthew Garrett <mjg59@google.com>
Date:   Tue, 03 Apr 2018 23:47:53 +0000
Message-ID: <CACdnJutkO9dgz=HZpPRR9PZC=+cHh97dRUiGB+D3gruZr6U9Kg@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 4:39 PM Linus Torvalds
<torvalds@linux-foundation.org>
wrote:

> On Tue, Apr 3, 2018 at 4:26 PM, Linus Torvalds
> <torvalds@linux-foundation.org> wrote:
> >
> > Magically changing kernel behavior depending on some subtle and often
> > unintentional bootup behavior detail is completely idiotic.

> Another way of looking at this: if lockdown is a good idea to enable
> when you booted using secure boot, then why isn't it a good idea when
> you *didn't* boot using secure boot?

Because it's then trivial to circumvent and the restrictions aren't worth
the benefit.