Re: [PATCH v2 4/7] slab: Add __alloc_size attributes for better bounds checking

[Nick Desaulniers <ndesaulniers@google.com>]

On Wed, Aug 18, 2021 at 2:40 PM Kees Cook <keescook@chromium.org> wrote:
>
> As already done in GrapheneOS, add the __alloc_size attribute for
> regular kmalloc interfaces, to provide additional hinting for better
> bounds checking, assisting CONFIG_FORTIFY_SOURCE and other compiler
> optimizations.
>
> Co-developed-by: Daniel Micay <danielmicay@gmail.com>
> Signed-off-by: Daniel Micay <danielmicay@gmail.com>
> Cc: Christoph Lameter <cl@linux.com>
> Cc: Pekka Enberg <penberg@kernel.org>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Vlastimil Babka <vbabka@suse.cz>
> Cc: linux-mm@kvack.org
> Signed-off-by: Kees Cook <keescook@chromium.org>

This is a good start, so
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

Do we also want to attribute:
* __kmalloc_index
* kmem_cache_free_bulk
* kmem_cache_alloc_bulk
* kmem_cache_alloc_trace
* kmalloc_order
* kmalloc_order_trace
* kmalloc_large
* kmalloc_node
* __kmalloc_track_caller
* kmalloc_array_node
* __kmalloc_node_track_caller

> ---
>  include/linux/slab.h | 20 ++++++++++++++++++--
>  1 file changed, 18 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/slab.h b/include/linux/slab.h
> index 10fd0a8c816a..6ce826d8194d 100644
> --- a/include/linux/slab.h
> +++ b/include/linux/slab.h
> @@ -181,7 +181,7 @@ int kmem_cache_shrink(struct kmem_cache *s);
>  /*
>   * Common kmalloc functions provided by all allocators
>   */
> -__must_check
> +__must_check __alloc_size(2)
>  void *krealloc(const void *objp, size_t new_size, gfp_t flags);
>  void kfree(const void *objp);
>  void kfree_sensitive(const void *objp);
> @@ -426,6 +426,7 @@ static __always_inline unsigned int __kmalloc_index(size_t size,
>  #define kmalloc_index(s) __kmalloc_index(s, true)
>  #endif /* !CONFIG_SLOB */
>
> +__alloc_size(1)
>  void *__kmalloc(size_t size, gfp_t flags) __assume_kmalloc_alignment __malloc;
>  void *kmem_cache_alloc(struct kmem_cache *s, gfp_t flags) __assume_kmalloc_alignment __malloc;
>  void kmem_cache_free(struct kmem_cache *s, void *objp);
> @@ -450,6 +451,7 @@ static __always_inline void kfree_bulk(size_t size, void **p)
>  }
>
>  #ifdef CONFIG_NUMA
> +__alloc_size(1)
>  void *__kmalloc_node(size_t size, gfp_t flags, int node) __assume_slab_alignment __malloc;
>  void *kmem_cache_alloc_node(struct kmem_cache *s, gfp_t flags, int node)
>                             __assume_slab_alignment __malloc;
> @@ -574,6 +576,7 @@ static __always_inline void *kmalloc_large(size_t size, gfp_t flags)
>   *     Try really hard to succeed the allocation but fail
>   *     eventually.
>   */
> +__alloc_size(1)
>  static __always_inline void *kmalloc(size_t size, gfp_t flags)
>  {
>         if (__builtin_constant_p(size)) {
> @@ -596,6 +599,7 @@ static __always_inline void *kmalloc(size_t size, gfp_t flags)
>         return __kmalloc(size, flags);
>  }
>
> +__alloc_size(1)
>  static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
>  {
>  #ifndef CONFIG_SLOB
> @@ -620,6 +624,7 @@ static __always_inline void *kmalloc_node(size_t size, gfp_t flags, int node)
>   * @size: element size.
>   * @flags: the type of memory to allocate (see kmalloc).
>   */
> +__alloc_size(1, 2)
>  static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
>  {
>         size_t bytes;
> @@ -638,7 +643,7 @@ static inline void *kmalloc_array(size_t n, size_t size, gfp_t flags)
>   * @new_size: new size of a single member of the array
>   * @flags: the type of memory to allocate (see kmalloc)
>   */
> -__must_check
> +__must_check __alloc_size(2, 3)
>  static inline void *krealloc_array(void *p, size_t new_n, size_t new_size,
>                                    gfp_t flags)
>  {
> @@ -656,6 +661,7 @@ static inline void *krealloc_array(void *p, size_t new_n, size_t new_size,
>   * @size: element size.
>   * @flags: the type of memory to allocate (see kmalloc).
>   */
> +__alloc_size(1, 2)
>  static inline void *kcalloc(size_t n, size_t size, gfp_t flags)
>  {
>         return kmalloc_array(n, size, flags | __GFP_ZERO);
> @@ -685,6 +691,7 @@ static inline void *kmalloc_array_node(size_t n, size_t size, gfp_t flags,
>         return __kmalloc_node(bytes, flags, node);
>  }
>
> +__alloc_size(1, 2)
>  static inline void *kcalloc_node(size_t n, size_t size, gfp_t flags, int node)
>  {
>         return kmalloc_array_node(n, size, flags | __GFP_ZERO, node);
> @@ -718,6 +725,7 @@ static inline void *kmem_cache_zalloc(struct kmem_cache *k, gfp_t flags)
>   * @size: how many bytes of memory are required.
>   * @flags: the type of memory to allocate (see kmalloc).
>   */
> +__alloc_size(1)
>  static inline void *kzalloc(size_t size, gfp_t flags)
>  {
>         return kmalloc(size, flags | __GFP_ZERO);
> @@ -729,25 +737,31 @@ static inline void *kzalloc(size_t size, gfp_t flags)
>   * @flags: the type of memory to allocate (see kmalloc).
>   * @node: memory node from which to allocate
>   */
> +__alloc_size(1)
>  static inline void *kzalloc_node(size_t size, gfp_t flags, int node)
>  {
>         return kmalloc_node(size, flags | __GFP_ZERO, node);
>  }
>
> +__alloc_size(1)
>  extern void *kvmalloc_node(size_t size, gfp_t flags, int node);
> +__alloc_size(1)
>  static inline void *kvmalloc(size_t size, gfp_t flags)
>  {
>         return kvmalloc_node(size, flags, NUMA_NO_NODE);
>  }
> +__alloc_size(1)
>  static inline void *kvzalloc_node(size_t size, gfp_t flags, int node)
>  {
>         return kvmalloc_node(size, flags | __GFP_ZERO, node);
>  }
> +__alloc_size(1)
>  static inline void *kvzalloc(size_t size, gfp_t flags)
>  {
>         return kvmalloc(size, flags | __GFP_ZERO);
>  }
>
> +__alloc_size(1, 2)
>  static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags)
>  {
>         size_t bytes;
> @@ -758,11 +772,13 @@ static inline void *kvmalloc_array(size_t n, size_t size, gfp_t flags)
>         return kvmalloc(bytes, flags);
>  }
>
> +__alloc_size(1, 2)
>  static inline void *kvcalloc(size_t n, size_t size, gfp_t flags)
>  {
>         return kvmalloc_array(n, size, flags | __GFP_ZERO);
>  }
>
> +__alloc_size(3)
>  extern void *kvrealloc(const void *p, size_t oldsize, size_t newsize,
>                 gfp_t flags);
>  extern void kvfree(const void *addr);
> --

-- 
Thanks,
~Nick Desaulniers