Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based mode

[Vincenzo Frascino]

Hi Andrey,

On 06/12/2018 12:24, Andrey Konovalov wrote:
> This commit adds tag-based KASAN specific hooks implementation and
> adjusts common generic and tag-based KASAN ones.
> 
> 1. When a new slab cache is created, tag-based KASAN rounds up the size of
>    the objects in this cache to KASAN_SHADOW_SCALE_SIZE (== 16).
> 
> 2. On each kmalloc tag-based KASAN generates a random tag, sets the shadow
>    memory, that corresponds to this object to this tag, and embeds this
>    tag value into the top byte of the returned pointer.
> 
> 3. On each kfree tag-based KASAN poisons the shadow memory with a random
>    tag to allow detection of use-after-free bugs.
> 
> The rest of the logic of the hook implementation is very much similar to
> the one provided by generic KASAN. Tag-based KASAN saves allocation and
> free stack metadata to the slab object the same way generic KASAN does.
> 
> Reviewed-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> Signed-off-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> ---
>  mm/kasan/common.c | 116 ++++++++++++++++++++++++++++++++++++++--------
>  mm/kasan/kasan.h  |   8 ++++
>  mm/kasan/tags.c   |  48 +++++++++++++++++++
>  3 files changed, 153 insertions(+), 19 deletions(-)
>


[...]

> @@ -265,6 +290,8 @@ void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
>  		return;
>  	}
>  
> +	cache->align = round_up(cache->align, KASAN_SHADOW_SCALE_SIZE);
> +

Did you consider to set ARCH_SLAB_MINALIGN instead of this round up?

-- 
Regards,
Vincenzo