linux-hardening - Re: [PATCH 1/6] slab: Clean up SLOB vs kmalloc() definition

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Date:   Thu, 3 Nov 2022 22:32:38 +0900
From:   Hyeonggon Yoo <42.hyeyoo@...il.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>, linux-mm@...ck.org,
        David Gow <davidgow@...gle.com>,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Guenter Roeck <linux@...ck-us.net>,
        Andy Shevchenko <andriy.shevchenko@...el.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org, llvm@...ts.linux.dev
Subject: Re: [PATCH 1/6] slab: Clean up SLOB vs kmalloc() definition

On Tue, Nov 01, 2022 at 03:33:09PM -0700, Kees Cook wrote:
> As already done for kmalloc_node(), clean up the #ifdef usage in the
> definition of kmalloc() so that the SLOB-only version is an entirely
> separate and much more readable function.
> 
> Cc: Vlastimil Babka <vbabka@...e.cz>
> Cc: Christoph Lameter <cl@...ux.com>
> Cc: Pekka Enberg <penberg@...nel.org>
> Cc: David Rientjes <rientjes@...gle.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@....com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Roman Gushchin <roman.gushchin@...ux.dev>
> Cc: Hyeonggon Yoo <42.hyeyoo@...il.com>
> Cc: linux-mm@...ck.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
>  include/linux/slab.h | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 90877fcde70b..e08fe7978b5c 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -559,15 +559,15 @@ void *kmalloc_large_node(size_t size, gfp_t flags, int node) __assume_page_align
>   *	Try really hard to succeed the allocation but fail
>   *	eventually.
>   */
> +#ifndef CONFIG_SLOB
>  static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
>  {
>  	if (__builtin_constant_p(size)) {
> -#ifndef CONFIG_SLOB
>  		unsigned int index;
> -#endif
> +
>  		if (size > KMALLOC_MAX_CACHE_SIZE)
>  			return kmalloc_large(size, flags);
> -#ifndef CONFIG_SLOB
> +
>  		index = kmalloc_index(size);
>  
>  		if (!index)
> @@ -576,10 +576,18 @@ static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
>  		return kmalloc_trace(
>  				kmalloc_caches[kmalloc_type(flags)][index],
>  				flags, size);
> -#endif
>  	}
>  	return __kmalloc(size, flags);
>  }
> +#else
> +static __always_inline __alloc_size(1) void *kmalloc(size_t size, gfp_t flags)
> +{
> +	if (__builtin_constant_p(size) && size > KMALLOC_MAX_CACHE_SIZE)
> +		return kmalloc_large(size, flags);
> +
> +	return __kmalloc(size, flags);
> +}
> +#endif
>  
>  #ifndef CONFIG_SLOB
>  static __always_inline __alloc_size(1) void *kmalloc_node(size_t size, gfp_t flags, int node)
> -- 
> 2.34.1

Looks good to me.

Reviewed-by: Hyeonggon Yoo <42.hyeyoo@...il.com>

-- 
Thanks,
Hyeonggon