From: Philipp Rudo <prudo@redhat.com>
To: "Jan Hendrik Farr" <kernel@jfarr.cc>
Cc: "Lennart Poettering" <mzxreary@0pointer.de>,
linux-kernel@vger.kernel.org, kexec@lists.infradead.org,
x86@kernel.org, tglx@linutronix.de, dhowells@redhat.com,
vgoyal@redhat.com, keyrings@vger.kernel.org,
akpm@linux-foundation.org, "Baoquan He" <bhe@redhat.com>,
bhelgaas@google.com, "Luca Boccassi" <bluca@debian.org>
Subject: Re: [PATCH v2 0/2] x86/kexec: UKI Support
Date: Mon, 18 Sep 2023 17:36:07 +0200 [thread overview]
Message-ID: <20230918173607.421d2616@rotkaeppchen> (raw)
In-Reply-To: <0e1984af-88ca-4908-a5ca-3191d96aa63f@app.fastmail.com>
Hi Jan,
On Thu, 14 Sep 2023 23:04:32 +0200
"Jan Hendrik Farr" <kernel@jfarr.cc> wrote:
> On Thu, Sep 14, 2023, at 8:51 PM, Philipp Rudo wrote:
> > [...]
> >
> > In this context I hope it is also clear to you that when more and more
> > people rely on the spec you need a more formal process when including
> > changes. Especially when the change might break the implementation of
> > others. So no more making the .cmdline optional and allowing it to be
> > overwritten all on the same day.
> >
> > Having that said, what does "local override" exactly mean? Does that
> > mean a distro can allow a user to freely choose the cmdline without
> > checking any signatures?
>
> The behavior of systemd-stub is to allow the bootloader (or whatever
> called sd-stub) supplied cmdline when there is no .cmdline section in
> the UKI. That's how I understand "local override" here. For WIP v3 of
> this patch the behavior is to use the cmdline supplied by userspace to
> the kexec_file_load syscall if no .cmdline section is in the UKI.
>
> empty .cmdline section -> empty cmdline always passed to kernel
> .cmdline section -> use bootloader/user supplied cmdline (which would
> be empty by default)
>
> This setup does not make sense for a locked down / secure system though.
>
> Maybe the word "override" is not ideal. There is nothing actually being
> overridden as there is no cmdline in the UKI in the first place.
>
> sd-stub also allows the bootloader supplied cmdline if not using secure
> boot. So maybe the kernel could allow user supplied cmdline if not in
> lockdown mode for kexec maybe? If not in lockdown mode somebody can just
> kexec an unsigned kernel + unsigned cmdline using the kexec_load syscall
> anyways. For this case the word "override" makes sense.
>
> The logic for all of this in sd-stub is in [1].
>
> > I.e. does that mean we can get rid of this
> > https://github.com/systemd/systemd/issues/24539
>
> This is a different usecase IMO.
Yeah, I expected that. The whole question was meant to be rhetorical.
The point I wanted to make was that when a spec uses terms like "local
override" it needs to explain what it means.
Thanks
Philipp
> >> Hence, seeing the spec as set in stone and as inherently low quality
> >> is the wrong way to see it I am sure. Instead, the goal here is to
> >> adjust the spec to make it work really nicely for *both* systemd and
> >> the kernel.
> >
> > Sorry, I never wanted to intend that the spec inherently low quality.
> > Just that it doesn't meat my expectations, yet. But that is fine. The
> > spec isn't even a year old and there's only a single implementation,
> > yet. So it's more documentation rather than a spec.
>
> Let's make it happen.
>
>
> [1] https://github.com/systemd/systemd/blob/5898cef22a35ceefa068d5f46929eced2baab0ed/src/boot/efi/stub.c#L140
>
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prev parent reply other threads:[~2023-09-18 15:36 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-11 5:25 [PATCH v2 0/2] x86/kexec: UKI Support Jan Hendrik Farr
2023-09-11 5:25 ` [PATCH v2 1/2] move pefile_parse_binary to its own file Jan Hendrik Farr
2023-09-11 5:25 ` [PATCH v2 2/2] x86/kexec: UKI support Jan Hendrik Farr
2023-09-12 1:03 ` [PATCH v2 0/2] x86/kexec: UKI Support Baoquan He
2023-09-12 19:25 ` Jan Hendrik Farr
2023-09-13 14:00 ` Philipp Rudo
2023-09-13 14:42 ` Jan Hendrik Farr
2023-09-14 19:09 ` Philipp Rudo
2023-09-20 7:43 ` Dave Young
2023-09-20 8:40 ` Dave Young
2023-09-20 10:50 ` Ard Biesheuvel
2023-09-20 12:07 ` Dave Young
2023-09-20 12:18 ` Dave Young
2023-09-21 3:14 ` Dave Young
2023-09-20 22:02 ` Jan Hendrik Farr
2023-09-25 14:36 ` Philipp Rudo
2023-09-14 9:32 ` Lennart Poettering
2023-09-14 12:26 ` Jarkko Sakkinen
2023-09-14 15:33 ` Jarkko Sakkinen
2023-09-14 16:11 ` Jan Hendrik Farr
2023-09-14 21:14 ` Jarkko Sakkinen
2023-09-14 18:51 ` Philipp Rudo
2023-09-14 21:04 ` Jan Hendrik Farr
2023-09-18 15:36 ` Philipp Rudo [this message]
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