Re: [PATCH] slab: Decouple slab_debug and no_hash_pointers

David Rientjes
2025-04-13T23:00:44Z

On Thu, 10 Apr 2025, Kees Cook wrote:

> Some system owners use slab_debug=FPZ (or similar) as a hardening option,
> but do not want to be forced into having kernel addresses exposed due
> to the implicit "no_hash_pointers" boot param setting.[1]
>
> Introduce the "hash_pointers" boot param, which defaults to "auto"
> (the current behavior), but also includes "always" (forcing on hashing
> even when "slab_debug=..." is defined), and "never". The existing
> "no_hash_pointers" boot param becomes an alias for "hash_pointers=never".
>
> This makes it possible to boot with "slab_debug=FPZ hash_pointers=always".
>
> Link: https://github.com/KSPP/linux/issues/368 [1]
> Fixes: 792702911f58 ("slub: force on no_hash_pointers when slub_debug is enabled")
> Co-developed-by: Sergio Perez Gonzalez <sperezglz@gmail.com>
> Signed-off-by: Sergio Perez Gonzalez <sperezglz@gmail.com>
> Signed-off-by: Kees Cook <kees@kernel.org>

Acked-by: David Rientjes <rientjes@google.com>