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Date: Mon, 1 Feb 2016 21:34:27 -0800
From: Andrew Morton <akpm@linux-foundation.org>
To: Alexander Potapenko <glider@google.com>
Cc: adech.fo@gmail.com, cl@linux.com, dvyukov@google.com,
        ryabinin.a.a@gmail.com, rostedt@goodmis.org,
        kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH v1 1/8] kasan: Change the behavior of
 kmalloc_large_oob_right test
Message-Id: <20160201213427.f428b08d.akpm@linux-foundation.org>
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On Wed, 27 Jan 2016 19:25:06 +0100 Alexander Potapenko <glider@google.com> wrote:

> depending on which allocator (SLAB or SLUB) is being used
> 
> ...
>
> --- a/lib/test_kasan.c
> +++ b/lib/test_kasan.c
> @@ -68,7 +68,22 @@ static noinline void __init kmalloc_node_oob_right(void)
>  static noinline void __init kmalloc_large_oob_right(void)
>  {
>  	char *ptr;
> -	size_t size = KMALLOC_MAX_CACHE_SIZE + 10;
> +	size_t size;
> +
> +	if (KMALLOC_MAX_CACHE_SIZE == KMALLOC_MAX_SIZE) {
> +		/*
> +		 * We're using the SLAB allocator. Allocate a chunk that fits
> +		 * into a slab.
> +		 */
> +		size = KMALLOC_MAX_CACHE_SIZE - 256;
> +	} else {
> +		/*
> +		 * KMALLOC_MAX_SIZE > KMALLOC_MAX_CACHE_SIZE.
> +		 * We're using the SLUB allocator. Allocate a chunk that does
> +		 * not fit into a slab to trigger the page allocator.
> +		 */
> +		size = KMALLOC_MAX_CACHE_SIZE + 10;
> +	}

This seems a weird way of working out whether we're using SLAB or SLUB.

Can't we use, umm, #ifdef CONFIG_SLAB?  If not that then let's cook up
something standardized rather than a weird just-happens-to-work like
this.