Re: [PATCH v2 15/20] kasan: don't round_up too much

[Marco Elver <elver@google.com>]

On Tue, Nov 10, 2020 at 11:20PM +0100, Andrey Konovalov wrote:
> For hardware tag-based mode kasan_poison_memory() already rounds up the
> size. Do the same for software modes and remove round_up() from the common
> code.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
> Link: https://linux-review.googlesource.com/id/Ib397128fac6eba874008662b4964d65352db4aa4
> ---
>  mm/kasan/common.c | 8 ++------
>  mm/kasan/shadow.c | 1 +
>  2 files changed, 3 insertions(+), 6 deletions(-)

Reviewed-by: Marco Elver <elver@google.com>

> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 60793f8695a8..69ab880abacc 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -218,9 +218,7 @@ void __kasan_unpoison_object_data(struct kmem_cache *cache, void *object)
>  
>  void __kasan_poison_object_data(struct kmem_cache *cache, void *object)
>  {
> -	kasan_poison_memory(object,
> -			round_up(cache->object_size, KASAN_GRANULE_SIZE),
> -			KASAN_KMALLOC_REDZONE);
> +	kasan_poison_memory(object, cache->object_size, KASAN_KMALLOC_REDZONE);
>  }
>  
>  /*
> @@ -293,7 +291,6 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
>  {
>  	u8 tag;
>  	void *tagged_object;
> -	unsigned long rounded_up_size;
>  
>  	tag = get_tag(object);
>  	tagged_object = object;
> @@ -314,8 +311,7 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
>  		return true;
>  	}
>  
> -	rounded_up_size = round_up(cache->object_size, KASAN_GRANULE_SIZE);
> -	kasan_poison_memory(object, rounded_up_size, KASAN_KMALLOC_FREE);
> +	kasan_poison_memory(object, cache->object_size, KASAN_KMALLOC_FREE);
>  
>  	if (!kasan_stack_collection_enabled())
>  		return false;
> diff --git a/mm/kasan/shadow.c b/mm/kasan/shadow.c
> index 8e4fa9157a0b..3f64c9ecbcc0 100644
> --- a/mm/kasan/shadow.c
> +++ b/mm/kasan/shadow.c
> @@ -82,6 +82,7 @@ void kasan_poison_memory(const void *address, size_t size, u8 value)
>  	 * addresses to this function.
>  	 */
>  	address = kasan_reset_tag(address);
> +	size = round_up(size, KASAN_GRANULE_SIZE);
>  
>  	shadow_start = kasan_mem_to_shadow(address);
>  	shadow_end = kasan_mem_to_shadow(address + size);
> -- 
> 2.29.2.222.g5d2a92d10f8-goog
>