Re: [PATCH v2 -next 2/2] mm/kasan: simplify and refine kasan_cache code

[Andrey Konovalov]

On Wed, Nov 23, 2022 at 1:35 PM Feng Tang <feng.tang@xxxxxxxxx> wrote:
>
> struct 'kasan_cache' has a member 'is_kmalloc' indicating whether
> its host kmem_cache is a kmalloc cache. With newly introduced
> is_kmalloc_cache() helper, 'is_kmalloc' and its related function can
> be replaced and removed.
>
> Also 'kasan_cache' is only needed by KASAN generic mode, and not by
> SW/HW tag modes, so refine its protection macro accordingly, suggested
> by Andrey Konoval.
>
> Signed-off-by: Feng Tang <feng.tang@xxxxxxxxx>
> ---
> Changlog:
>
>   Since v1
>   * Use CONFIG_KASAN_GENERIC instead of CONFIG_KASAN for 'kasan_cache',
>     as suggested by Andrey Konovalov
>
>  include/linux/kasan.h    | 22 +++++-----------------
>  include/linux/slab_def.h |  2 +-
>  include/linux/slub_def.h |  2 +-
>  mm/kasan/common.c        |  9 ++-------
>  mm/slab_common.c         |  1 -
>  5 files changed, 9 insertions(+), 27 deletions(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index dff604912687..0ff382f79f80 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -96,15 +96,6 @@ static inline bool kasan_has_integrated_init(void)
>  }
>
>  #ifdef CONFIG_KASAN
> -
> -struct kasan_cache {
> -#ifdef CONFIG_KASAN_GENERIC
> -       int alloc_meta_offset;
> -       int free_meta_offset;
> -#endif
> -       bool is_kmalloc;
> -};
> -
>  void __kasan_unpoison_range(const void *addr, size_t size);
>  static __always_inline void kasan_unpoison_range(const void *addr, size_t size)
>  {
> @@ -129,13 +120,6 @@ static __always_inline bool kasan_unpoison_pages(struct page *page,
>         return false;
>  }
>
> -void __kasan_cache_create_kmalloc(struct kmem_cache *cache);
> -static __always_inline void kasan_cache_create_kmalloc(struct kmem_cache *cache)
> -{
> -       if (kasan_enabled())
> -               __kasan_cache_create_kmalloc(cache);
> -}
> -
>  void __kasan_poison_slab(struct slab *slab);
>  static __always_inline void kasan_poison_slab(struct slab *slab)
>  {
> @@ -252,7 +236,6 @@ static inline void kasan_poison_pages(struct page *page, unsigned int order,
>                                       bool init) {}
>  static inline bool kasan_unpoison_pages(struct page *page, unsigned int order,
>                                         bool init) { return false; }
> -static inline void kasan_cache_create_kmalloc(struct kmem_cache *cache) {}
>  static inline void kasan_poison_slab(struct slab *slab) {}
>  static inline void kasan_unpoison_object_data(struct kmem_cache *cache,
>                                         void *object) {}
> @@ -303,6 +286,11 @@ static inline void kasan_unpoison_task_stack(struct task_struct *task) {}
>
>  #ifdef CONFIG_KASAN_GENERIC
>
> +struct kasan_cache {
> +       int alloc_meta_offset;
> +       int free_meta_offset;
> +};
> +
>  size_t kasan_metadata_size(struct kmem_cache *cache, bool in_object);
>  slab_flags_t kasan_never_merge(void);
>  void kasan_cache_create(struct kmem_cache *cache, unsigned int *size,
> diff --git a/include/linux/slab_def.h b/include/linux/slab_def.h
> index f0ffad6a3365..39f7f1f95de2 100644
> --- a/include/linux/slab_def.h
> +++ b/include/linux/slab_def.h
> @@ -72,7 +72,7 @@ struct kmem_cache {
>         int obj_offset;
>  #endif /* CONFIG_DEBUG_SLAB */
>
> -#ifdef CONFIG_KASAN
> +#ifdef CONFIG_KASAN_GENERIC
>         struct kasan_cache kasan_info;
>  #endif
>
> diff --git a/include/linux/slub_def.h b/include/linux/slub_def.h
> index f9c68a9dac04..4e7cdada4bbb 100644
> --- a/include/linux/slub_def.h
> +++ b/include/linux/slub_def.h
> @@ -132,7 +132,7 @@ struct kmem_cache {
>         unsigned int *random_seq;
>  #endif
>
> -#ifdef CONFIG_KASAN
> +#ifdef CONFIG_KASAN_GENERIC
>         struct kasan_cache kasan_info;
>  #endif
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 1f30080a7a4c..6e265beefc27 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -122,11 +122,6 @@ void __kasan_poison_pages(struct page *page, unsigned int order, bool init)
>                              KASAN_PAGE_FREE, init);
>  }
>
> -void __kasan_cache_create_kmalloc(struct kmem_cache *cache)
> -{
> -       cache->kasan_info.is_kmalloc = true;
> -}
> -
>  void __kasan_poison_slab(struct slab *slab)
>  {
>         struct page *page = slab_page(slab);
> @@ -326,7 +321,7 @@ void * __must_check __kasan_slab_alloc(struct kmem_cache *cache,
>         kasan_unpoison(tagged_object, cache->object_size, init);
>
>         /* Save alloc info (if possible) for non-kmalloc() allocations. */
> -       if (kasan_stack_collection_enabled() && !cache->kasan_info.is_kmalloc)
> +       if (kasan_stack_collection_enabled() && !is_kmalloc_cache(cache))
>                 kasan_save_alloc_info(cache, tagged_object, flags);
>
>         return tagged_object;
> @@ -372,7 +367,7 @@ static inline void *____kasan_kmalloc(struct kmem_cache *cache,
>          * Save alloc info (if possible) for kmalloc() allocations.
>          * This also rewrites the alloc info when called from kasan_krealloc().
>          */
> -       if (kasan_stack_collection_enabled() && cache->kasan_info.is_kmalloc)
> +       if (kasan_stack_collection_enabled() && is_kmalloc_cache(cache))
>                 kasan_save_alloc_info(cache, (void *)object, flags);
>
>         /* Keep the tag that was set by kasan_slab_alloc(). */
> diff --git a/mm/slab_common.c b/mm/slab_common.c
> index 8276022f0da4..a5480d67f391 100644
> --- a/mm/slab_common.c
> +++ b/mm/slab_common.c
> @@ -663,7 +663,6 @@ struct kmem_cache *__init create_kmalloc_cache(const char *name,
>
>         create_boot_cache(s, name, size, flags | SLAB_KMALLOC, useroffset,
>                                                                 usersize);
> -       kasan_cache_create_kmalloc(s);
>         list_add(&s->list, &slab_caches);
>         s->refcount = 1;
>         return s;
> --
> 2.34.1
>

Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxx>

Thanks!