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

[Vlastimil Babka]

On 7/5/23 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>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>

Acked-by: Vlastimil Babka <vbabka@xxxxxxx>

Thanks!