Re: [PATCH v4 07/10] x86/ibt: Add paranoid FineIBT mode

Kees Cook
2025-02-24T19:00:35Z

On Mon, Feb 24, 2025 at 01:37:10PM +0100, Peter Zijlstra wrote:
> Due to concerns about circumvention attacks against FineIBT on 'naked'
> ENDBR, add an additional caller side hash check to FineIBT. This
> should make it impossible to pivot over such a 'naked' ENDBR
> instruction at the cost of an additional load.
>
> The specific pivot reported was against the SYSCALL entry site and
> FRED will have all those holes fixed up.
>
> https://lore.kernel.org/linux-hardening/Z60NwR4w%2F28Z7XUa@ubun/
>
> This specific fineibt_paranoid_start[] sequence was concocted by
> Scott.
>
> Reported-by: Jennifer Miller <jmill@asu.edu>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

Great! I'm happy to see the pre-call checking. :)

Reviewed-by: Kees Cook <kees@kernel.org>

--
Kees Cook