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

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Date:   Tue, 11 Dec 2018 16:22:43 +0000
From:   Vincenzo Frascino <vincenzo.frascino@....com>
To:     Andrey Konovalov <andreyknvl@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Christoph Lameter <cl@...ux.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Mark Rutland <mark.rutland@....com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Marc Zyngier <marc.zyngier@....com>,
        Dave Martin <dave.martin@....com>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Ingo Molnar <mingo@...nel.org>,
        Paul Lawrence <paullawrence@...gle.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        kasan-dev@...glegroups.com, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sparse@...r.kernel.org, linux-mm@...ck.org,
        linux-kbuild@...r.kernel.org
Cc:     Vishwath Mohan <vishwath@...gle.com>,
        Chintan Pandya <cpandya@...eaurora.org>,
        Jacob Bramley <Jacob.Bramley@....com>,
        Jann Horn <jannh@...gle.com>,
        Ruben Ayrapetyan <Ruben.Ayrapetyan@....com>,
        Lee Smith <Lee.Smith@....com>,
        Kostya Serebryany <kcc@...gle.com>,
        Mark Brand <markbrand@...gle.com>,
        Ramana Radhakrishnan <Ramana.Radhakrishnan@....com>,
        Evgeniy Stepanov <eugenis@...gle.com>
Subject: Re: [PATCH v13 19/25] kasan: add hooks implementation for tag-based
 mode

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@...tuozzo.com>
> Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> ---
>  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