Re: [PATCH 8/8] efi: pstore: Add module parameter for setting the record size

From: Kees Cook
Date: Thu Oct 06 2022 - 19:16:43 EST

On Thu, Oct 06, 2022 at 07:42:12PM -0300, Guilherme G. Piccoli wrote:
> By default, the efi-pstore backend hardcode the UEFI variable size
> as 1024 bytes. That's not a big deal, but at the same time having
> no way to change that in the kernel is a bit bummer for specialized
> users - there is not such a limit in the UEFI specification.

It seems to have been added in commit
e0d59733f6b1 ("efivars, efi-pstore: Hold off deletion of sysfs entry until the scan is completed")

But I see no mention of why it was introduced or how it was chosen.

I remember hearing some horror stories from Matthew Garrett about older
EFI implementations bricking themselves when they stored large
variables, or something like that, but I don't know if that's meaningful
here at all.

I think it'd be great to make it configurable! Ard, do you have any
sense of what the max/min, etc, should be here?

Kees Cook