linux-kernel - Re: [PATCH -next 2/2] mm/kasan: simplify is

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Message-ID: <CA+fCnZenKqb9_a2e5b25-DQ3uAKPgm=+tTDOP+D9c6wbDSjMNA@mail.gmail.com>
Date:   Mon, 21 Nov 2022 16:15:32 +0100
From:   Andrey Konovalov <andreyknvl@...il.com>
To:     Feng Tang <feng.tang@...el.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        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>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        linux-mm@...ck.org, kasan-dev@...glegroups.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH -next 2/2] mm/kasan: simplify is_kmalloc check

On Mon, Nov 21, 2022 at 2:53 PM Feng Tang <feng.tang@...el.com> wrote:
>
> Use new is_kmalloc_cache() to simplify the code of checking whether
> a kmem_cache is a kmalloc cache.
>
> Signed-off-by: Feng Tang <feng.tang@...el.com>

Hi Feng,

Nice simplification!

> ---
>  include/linux/kasan.h | 9 ---------
>  mm/kasan/common.c     | 9 ++-------
>  mm/slab_common.c      | 1 -
>  3 files changed, 2 insertions(+), 17 deletions(-)
>
> diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> index dff604912687..fc46f5d6f404 100644
> --- a/include/linux/kasan.h
> +++ b/include/linux/kasan.h
> @@ -102,7 +102,6 @@ struct kasan_cache {
>         int alloc_meta_offset;
>         int free_meta_offset;
>  #endif
> -       bool is_kmalloc;
>  };

We can go even further here, and only define the kasan_cache struct
and add the kasan_info field to kmem_cache when CONFIG_KASAN_GENERIC
is enabled.

>
>  void __kasan_unpoison_range(const void *addr, size_t size);
> @@ -129,13 +128,6 @@ 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 +244,6 @@ 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) {}
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 1f30080a7a4c..f7e0e5067e7a 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
>