Re: [PATCH] efi: libstub: Disable struct randomization

[Kees Cook <keescook@chromium.org>]

On Mon, Aug 22, 2022 at 07:29:53PM +0200, Ard Biesheuvel wrote:
> The EFI stub is a wrapper around the core kernel that makes it look like
> a EFI compatible PE/COFF application to the EFI firmware. EFI
> applications run on top of the EFI runtime, which is heavily based on
> so-called protocols, which are struct types consisting [mostly] of
> function pointer members that are instantiated and recorded in a
> protocol database.
> 
> These structs look like the ideal randomization candidates to the
> randstruct plugin (as they only carry function pointers), but of course,
> these protocols are contracts between the firmware that exposes them,
> and the EFI applications (including our stubbed kernel) that invoke
> them. This means that struct randomization for EFI protocols is not a
> great idea, and given that the stub shares very little data with the
> core kernel that is represented as a randomizable struct, we're better
> off just disabling it completely here.
> 
> Reported-by: Daniel Marth <daniel.marth@inso.tuwien.ac.at>
> Tested-by: Daniel Marth <daniel.marth@inso.tuwien.ac.at>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

Acked-by: Kees Cook <keescook@chromium.org>

-Kees

-- 
Kees Cook