linux-kernel - Re: [PATCH 04/12] kasan: clean up setting free info in kasan_slab

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Date:   Tue, 2 Feb 2021 18:03:46 +0100
From:   Marco Elver <elver@...gle.com>
To:     Andrey Konovalov <andreyknvl@...gle.com>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Will Deacon <will.deacon@....com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Peter Collingbourne <pcc@...gle.com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        kasan-dev@...glegroups.com, linux-arm-kernel@...ts.infradead.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 04/12] kasan: clean up setting free info in
 kasan_slab_free

On Mon, Feb 01, 2021 at 08:43PM +0100, Andrey Konovalov wrote:
> Put kasan_stack_collection_enabled() check and kasan_set_free_info()
> calls next to each other.
> 
> The way this was previously implemented was a minor optimization that
> relied of the the fact that kasan_stack_collection_enabled() is always
> true for generic KASAN. The confusion that this brings outweights saving
> a few instructions.
> 
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>

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

> ---
>  mm/kasan/common.c | 6 ++----
>  1 file changed, 2 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index a7eb553c8e91..086bb77292b6 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -350,13 +350,11 @@ static bool ____kasan_slab_free(struct kmem_cache *cache, void *object,
>  
>  	kasan_poison(object, cache->object_size, KASAN_KMALLOC_FREE);
>  
> -	if (!kasan_stack_collection_enabled())
> -		return false;
> -
>  	if ((IS_ENABLED(CONFIG_KASAN_GENERIC) && !quarantine))
>  		return false;
>  
> -	kasan_set_free_info(cache, object, tag);
> +	if (kasan_stack_collection_enabled())
> +		kasan_set_free_info(cache, object, tag);
>  
>  	return kasan_quarantine_put(cache, object);
>  }
> -- 
> 2.30.0.365.g02bc693789-goog
>