linux-kernel - Re: [PATCH v1 2/2] kexec: Introduce kexec_reboot

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Message-ID: <CANiDSCs6jyNBiO+wO-MHB3qv5am0mmGbv7y4eHv1PSLQh5EPTA@mail.gmail.com>
Date:   Mon, 12 Dec 2022 22:43:59 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Philipp Rudo <prudo@...hat.com>,
        Eric Biederman <ebiederm@...ssion.com>,
        Jonathan Corbet <corbet@....net>,
        Sergey Senozhatsky <senozhatsky@...omium.org>,
        linux-kernel@...r.kernel.org, kexec@...ts.infradead.org,
        Ross Zwisler <zwisler@...nel.org>, linux-doc@...r.kernel.org,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>
Subject: Re: [PATCH v1 2/2] kexec: Introduce kexec_reboot_disabled

Hi Philipp

On Tue, 29 Nov 2022 at 15:32, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> On Tue, 29 Nov 2022 14:44:50 +0100
> Philipp Rudo <prudo@...hat.com> wrote:
>
> > An alternative approach and sort of compromise I see is to convert
> > kexec_load_disabled from a simple on/off switch to a counter on how
> > often a kexec load can be made (in practice a tristate on/off/one-shot
> > should be sufficient). Ideally the reboot and panic path will
> > have separate counters. With that you could for example use
> > kexec_load_limit.reboot=0 and kexec_load_limit.panic=1 to disable the
> > load of images for reboot while still allow to load a crash kernel
> > once. With this you have the flexibility you need while also preventing
> > a race where an attacker overwrites your crash kernel before you can
> > toggle the switch. What do you think?
>
> I actually like this idea :-)

In case you missed it.  I sent an initial implementation of this at
https://lore.kernel.org/lkml/20221114-disable-kexec-reset-v2-0-c498313c1bb5@chromium.org/

Regards!

>
> -- Steve



-- 
Ricardo Ribalda