linux-kernel - Re: [RFC PATCH v2] x86/boot: add .sbat section to the bzImage

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Message-ID: <CAMw=ZnSa-NqfbEd9vchEwHwdUujNAXo=gb3dfd=HDw4W37RNjQ@mail.gmail.com>
Date:   Wed, 12 Jul 2023 20:56:36 +0100
From:   Luca Boccassi <bluca@...ian.org>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Daniel P. Berrangé <berrange@...hat.com>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>, lennart@...ttering.net,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexander Potapenko <glider@...gle.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] x86/boot: add .sbat section to the bzImage

On Wed, 12 Jul 2023 at 20:42, Borislav Petkov <bp@...en8.de> wrote:
>
> On Wed, Jul 12, 2023 at 08:35:14PM +0100, Luca Boccassi wrote:
> > No, all will not be fine, because stable branches exist, so it would
> > not be _one_ kernel version but N, with monotonically increasing
> > values of N. That doesn't work, and the reason for that are explained
> > in the protocol documentation that was linked in the initial mail.
>
> Lemme give Peter's example from earlier today:
>
> Bugfix A -> number 2
> Bugfix B -> number 3
>
> Tree backports only Bugfix B. Which number do you use?
>
> And so on and so on.

Everything < 3 is revoked _and_ the generation id in the stable branch
is _not_ bumped, because it's still vulnerable and so that branch is
effectively dead and unbootable on any system with secure boot
enabled. This is a revocation mechanism, not a bug tracking mechanism.
There's no mix-and-matching.

> Patch your own trees - this doesn't belong upstream.

Nah, it belongs in both places. Please read the documentation and
spend at least some time trying to understand the actual problem being
solved before commenting - or don't comment at all, that's fine too.