Date:   Thu, 12 Nov 2020 02:05:24 +0100
From:   Andrey Konovalov <andreyknvl@...gle.com>
To:     Marco Elver <elver@...gle.com>
Cc:     Dmitry Vyukov <dvyukov@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Vincenzo Frascino <vincenzo.frascino@....com>,
        Evgenii Stepanov <eugenis@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>,
        Branislav Rankov <Branislav.Rankov@....com>,
        Kevin Brodsky <kevin.brodsky@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 14/20] kasan, mm: rename kasan_poison_kfree

On Wed, Nov 11, 2020 at 7:53 PM Marco Elver <elver@...gle.com> wrote:
>
> On Tue, Nov 10, 2020 at 11:20PM +0100, Andrey Konovalov wrote:
> > Rename kasan_poison_kfree() to kasan_slab_free_mempool() as it better
> > reflects what this annotation does.
>
> This function is again so simple, and now it seems it's mempool
> specific, can't we just remove it and open-code it in mempool.c?

The simplification introduced in the previous patch is based on a
false assumption and will be reverted. Thus will keep this as a
separate function.

>
> > No functional changes.
> >
> > Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
> > Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com>
> > Link: https://linux-review.googlesource.com/id/I5026f87364e556b506ef1baee725144bb04b8810
> > ---
> >  include/linux/kasan.h | 16 ++++++++--------
> >  mm/kasan/common.c     | 16 ++++++++--------
> >  mm/mempool.c          |  2 +-
> >  3 files changed, 17 insertions(+), 17 deletions(-)
> >
> > diff --git a/include/linux/kasan.h b/include/linux/kasan.h
> > index 779f8e703982..534ab3e2935a 100644
> > --- a/include/linux/kasan.h
> > +++ b/include/linux/kasan.h
> > @@ -177,6 +177,13 @@ static inline bool kasan_slab_free(struct kmem_cache *s, void *object, unsigned
> >       return false;
> >  }
> >
> > +void __kasan_slab_free_mempool(void *ptr, unsigned long ip);
> > +static inline void kasan_slab_free_mempool(void *ptr, unsigned long ip)
> > +{
> > +     if (kasan_enabled())
> > +             __kasan_slab_free_mempool(ptr, ip);
> > +}
> > +
> >  void * __must_check __kasan_slab_alloc(struct kmem_cache *s,
> >                                      void *object, gfp_t flags);
> >  static inline void * __must_check kasan_slab_alloc(struct kmem_cache *s,
> > @@ -217,13 +224,6 @@ static inline void * __must_check kasan_krealloc(const void *object,
> >       return (void *)object;
> >  }
> >
> > -void __kasan_poison_kfree(void *ptr, unsigned long ip);
> > -static inline void kasan_poison_kfree(void *ptr, unsigned long ip)
> > -{
> > -     if (kasan_enabled())
> > -             __kasan_poison_kfree(ptr, ip);
> > -}
> > -
> >  void __kasan_kfree_large(void *ptr, unsigned long ip);
> >  static inline void kasan_kfree_large(void *ptr, unsigned long ip)
> >  {
> > @@ -263,6 +263,7 @@ static inline bool kasan_slab_free(struct kmem_cache *s, void *object,
> >  {
> >       return false;
> >  }
> > +static inline void kasan_slab_free_mempool(void *ptr, unsigned long ip) {}
> >  static inline void *kasan_slab_alloc(struct kmem_cache *s, void *object,
> >                                  gfp_t flags)
> >  {
> > @@ -282,7 +283,6 @@ static inline void *kasan_krealloc(const void *object, size_t new_size,
> >  {
> >       return (void *)object;
> >  }
> > -static inline void kasan_poison_kfree(void *ptr, unsigned long ip) {}
> >  static inline void kasan_kfree_large(void *ptr, unsigned long ip) {}
> >
> >  #endif /* CONFIG_KASAN */
> > diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> > index 819403548f2e..60793f8695a8 100644
> > --- a/mm/kasan/common.c
> > +++ b/mm/kasan/common.c
> > @@ -336,6 +336,14 @@ bool __kasan_slab_free(struct kmem_cache *cache, void *object, unsigned long ip)
> >       return ____kasan_slab_free(cache, object, ip, true);
> >  }
> >
> > +void __kasan_slab_free_mempool(void *ptr, unsigned long ip)
> > +{
> > +     struct page *page;
> > +
> > +     page = virt_to_head_page(ptr);
> > +     ____kasan_slab_free(page->slab_cache, ptr, ip, false);
> > +}
> > +
> >  static void set_alloc_info(struct kmem_cache *cache, void *object, gfp_t flags)
> >  {
> >       kasan_set_track(&kasan_get_alloc_meta(cache, object)->alloc_track, flags);
> > @@ -427,14 +435,6 @@ void * __must_check __kasan_krealloc(const void *object, size_t size, gfp_t flag
> >                                               flags, true);
> >  }
> >
> > -void __kasan_poison_kfree(void *ptr, unsigned long ip)
> > -{
> > -     struct page *page;
> > -
> > -     page = virt_to_head_page(ptr);
> > -     ____kasan_slab_free(page->slab_cache, ptr, ip, false);
> > -}
> > -
> >  void __kasan_kfree_large(void *ptr, unsigned long ip)
> >  {
> >       if (ptr != page_address(virt_to_head_page(ptr)))
> > diff --git a/mm/mempool.c b/mm/mempool.c
> > index f473cdddaff0..b1f39fa75ade 100644
> > --- a/mm/mempool.c
> > +++ b/mm/mempool.c
> > @@ -104,7 +104,7 @@ static inline void poison_element(mempool_t *pool, void *element)
> >  static __always_inline void kasan_poison_element(mempool_t *pool, void *element)
> >  {
> >       if (pool->alloc == mempool_alloc_slab || pool->alloc == mempool_kmalloc)
> > -             kasan_poison_kfree(element, _RET_IP_);
> > +             kasan_slab_free_mempool(element, _RET_IP_);
>
> This is already a kasan-prefixed function, so if
> kasan_slab_free_mempool() is only ever called in this function, we
> should just call kasan_slab_free() here directly with the 2 extra args
> it requires open-coded.
>
> >       else if (pool->alloc == mempool_alloc_pages)
> >               kasan_free_pages(element, (unsigned long)pool->pool_data);
> >  }
>
> Thanks,
> -- Marco

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