linux-hardening - Re: [PATCH] slab: Introduce kmalloc

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Message-ID: <cd446dfc-d6b6-781f-3a07-5af1edbf2230@google.com>
Date: Fri, 19 Jul 2024 20:50:41 -0700 (PDT)
From: David Rientjes <rientjes@...gle.com>
To: Kees Cook <kees@...nel.org>
cc: Vlastimil Babka <vbabka@...e.cz>, Christoph Lameter <cl@...ux.com>, 
    Pekka Enberg <penberg@...nel.org>, Joonsoo Kim <iamjoonsoo.kim@....com>, 
    Andrew Morton <akpm@...ux-foundation.org>, 
    Roman Gushchin <roman.gushchin@...ux.dev>, 
    Hyeonggon Yoo <42.hyeyoo@...il.com>, 
    "Gustavo A . R . Silva" <gustavoars@...nel.org>, 
    Bill Wendling <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>, 
    Jann Horn <jannh@...gle.com>, 
    Przemek Kitszel <przemyslaw.kitszel@...el.com>, 
    Marco Elver <elver@...gle.com>, linux-mm@...ck.org, 
    Nathan Chancellor <nathan@...nel.org>, 
    Nick Desaulniers <ndesaulniers@...gle.com>, linux-kernel@...r.kernel.org, 
    llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH] slab: Introduce kmalloc_obj() and family

On Fri, 19 Jul 2024, Kees Cook wrote:

> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 7247e217e21b..3817554f2d51 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -665,6 +665,44 @@ static __always_inline __alloc_size(1) void *kmalloc_noprof(size_t size, gfp_t f
>  }
>  #define kmalloc(...)				alloc_hooks(kmalloc_noprof(__VA_ARGS__))
>  
> +#define __alloc_obj3(ALLOC, P, COUNT, FLAGS)			\
> +({								\
> +	size_t __obj_size = size_mul(sizeof(*P), COUNT);	\
> +	void *__obj_ptr;					\
> +	(P) = __obj_ptr = ALLOC(__obj_size, FLAGS);		\
> +	if (!__obj_ptr)						\
> +		__obj_size = 0;					\
> +	__obj_size;						\
> +})
> +
> +#define __alloc_obj2(ALLOC, P, FLAGS)	__alloc_obj3(ALLOC, P, 1, FLAGS)
> +
> +#define __alloc_obj4(ALLOC, P, FAM, COUNT, FLAGS)		\
> +({								\
> +	size_t __obj_size = struct_size(P, FAM, COUNT);		\
> +	void *__obj_ptr;					\
> +	(P) = __obj_ptr = ALLOC(__obj_size, FLAGS);		\
> +	if (!__obj_ptr)						\
> +		__obj_size = 0;					\
> +	__obj_size;						\
> +})
> +
> +#define kmalloc_obj(...)					\
> +	CONCATENATE(__alloc_obj,				\
> +		    COUNT_ARGS(__VA_ARGS__))(kmalloc, __VA_ARGS__)
> +
> +#define kzalloc_obj(...)					\
> +	CONCATENATE(__alloc_obj,				\
> +		    COUNT_ARGS(__VA_ARGS__))(kzalloc, __VA_ARGS__)
> +
> +#define kvmalloc_obj(...)					\
> +	CONCATENATE(__alloc_obj,				\
> +		    COUNT_ARGS(__VA_ARGS__))(kvmalloc, __VA_ARGS__)
> +
> +#define kvzalloc_obj(...)					\
> +	CONCATENATE(__alloc_obj,				\
> +		    COUNT_ARGS(__VA_ARGS__))(kvzalloc, __VA_ARGS__)
> +
>  static __always_inline __alloc_size(1) void *kmalloc_node_noprof(size_t size, gfp_t flags, int node)
>  {
>  	if (__builtin_constant_p(size) && size) {

I'm supportive of this especially because it will pave a pathway toward 
future hardening work.  Request: could we get an addition to 
Documentation/ that explains how common idioms today can be converted to 
these new macros for future users?  The above makes sense only when 
accompanied by your commit description :)