Re: [PATCH] slab: Introduce kmalloc_obj() and family

David Rientjes
2024-07-20T03:50:47Z

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 :)