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From: Ard Biesheuvel <ardb@kernel.org>
Date: Thu, 25 Jan 2024 09:12:33 +0100
Message-ID: <CAMj1kXG1Fkpy2UDFAuGr9czTCft6N-tUQ0CTOvysqW5mX_xMTQ@mail.gmail.com>
Subject: Re: [PATCH] efivarfs: Iterate variables with increasing name buffer sizes
To: Peter Jones <pjones@redhat.com>
Cc: Tim Schumacher <timschumi@gmx.de>, Matthew Garrett <mjg59@srcf.ucam.org>, linux-efi@vger.kernel.org, 
	Jeremy Kerr <jk@ozlabs.org>, linux-kernel@vger.kernel.org
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On Wed, 24 Jan 2024 at 22:25, Peter Jones <pjones@redhat.com> wrote:
>
> On Tue, Jan 23, 2024 at 12:33=E2=80=AFPM Tim Schumacher <timschumi@gmx.de=
> wrote:
> >
> > On 23.01.24 15:09, Ard Biesheuvel wrote:
> > > On Tue, 23 Jan 2024 at 14:55, Tim Schumacher <timschumi@gmx.de> wrote=
:
> > >>
> > >> I'd rather avoid introducing deviations from the specifications on t=
he
> > >> kernel side as well.
> > >
> > > Which specification would this deviate from?
> >
> > The preexisting comment claims "Per EFI spec", and it appears that I go=
t
> > mislead by that. Neither the UEFI specification, nor the newest revisio=
n
> > of the EFI specification (which I guess is what would have been current
> > back in 2004, when this comment was introduced) seem to make any mentio=
n
> > of a maximum length for the variable name.
>
> Curiously, I can't find it in the 1.02 spec (the oldest I can find)
> either.  When I inherited efibootmgr around 2013, this was a
> limitation there, but I don't see anything in that tree that claims
> it's a spec limitation either.  My suspicion is this is a former
> Itanium firmware limit that got promoted to "the spec says" by word of
> mouth, or was in some very early ia64 implementation spec.
>

Also, the comment (and similar ones I've seen in the past) seem to
refer to the entire variable (name + payload) rather than just the
name.

So I am still leaning towards simply reducing this to 512 bytes.