Re: [PATCH] kasan, slub: fix HW_TAGS zeroing with slub_debug

[Andrey Konovalov]

On Wed, Jul 5, 2023 at 2:51 PM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> On Wed, 5 Jul 2023 at 14:44, <andrey.konovalov@xxxxxxxxx> wrote:
> >
> > From: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> >
> > Commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated
> > kmalloc space than requested") added precise kmalloc redzone poisoning
> > to the slub_debug functionality.
> >
> > However, this commit didn't account for HW_TAGS KASAN fully initializing
> > the object via its built-in memory initialization feature. Even though
> > HW_TAGS KASAN memory initialization contains special memory initialization
> > handling for when slub_debug is enabled, it does not account for in-object
> > slub_debug redzones. As a result, HW_TAGS KASAN can overwrite these
> > redzones and cause false-positive slub_debug reports.
> >
> > To fix the issue, avoid HW_TAGS KASAN memory initialization when slub_debug
> > is enabled altogether. Implement this by moving the __slub_debug_enabled
> > check to slab_post_alloc_hook. Common slab code seems like a more
> > appropriate place for a slub_debug check anyway.
> >
> > Fixes: 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated kmalloc space than requested")
> > Cc: <stable@xxxxxxxxxxxxxxx>
> > Reported-by: Mark Rutland <mark.rutland@xxxxxxx>
>
> Is it fixing this issue:
>
>   https://lore.kernel.org/all/20230628154714.GB22090@willie-the-truck/

Yes, my bad, messed up the Reported-by tag. The correct one should be:

Reported-by: Will Deacon <will@xxxxxxxxxx>

> Other than the question above, it looks sane:
>
> Acked-by: Marco Elver <elver@xxxxxxxxxx>

Thank you, Marco!