Re: [PATCH v2] slab: Decouple slab_debug and no_hash_pointers

Kees Cook
2025-06-05T20:15:33Z

On Wed, Apr 16, 2025 at 02:06:21PM +0200, Petr Mladek wrote:
> On Tue 2025-04-15 10:02:33, 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>
> > Acked-by: Vlastimil Babka <vbabka@suse.cz>
> > Acked-by: David Rientjes <rientjes@google.com>
> > Reviewed-by: Bagas Sanjaya <bagasdotme@gmail.com>
> > Signed-off-by: Kees Cook <kees@kernel.org>
>
> Tested-by: Petr Mladek <pmladek@suse.com>
> Reviewed-by: Petr Mladek <pmladek@suse.com>
>
> I am going to wait few more days for a potential feedback.
> I'll queue it for 6.16 unless anyone complains.

Hi,

Is this still planned for 6.16? I just noticed it wasn't in -next, and
we're almost to the end of the merge window...

-Kees

--
Kees Cook