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From:   Dmitry Vyukov <dvyukov@google.com>
Date:   Wed, 28 Oct 2020 17:57:33 +0100
Message-ID: <CACT4Y+bk9n6+v5dkcm8ngxQ=HbK9jS2N1nCm3F1vQLSxBiiTSA@mail.gmail.com>
Subject: Re: [PATCH RFC v2 17/21] kasan: simplify kasan_poison_kfree
To:     Andrey Konovalov <andreyknvl@google.com>
Cc:     Catalin Marinas <catalin.marinas@arm.com>,
        Will Deacon <will.deacon@arm.com>,
        Vincenzo Frascino <vincenzo.frascino@arm.com>,
        Alexander Potapenko <glider@google.com>,
        Marco Elver <elver@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Kostya Serebryany <kcc@google.com>,
        Peter Collingbourne <pcc@google.com>,
        Serban Constantinescu <serbanc@google.com>,
        Andrey Ryabinin <aryabinin@virtuozzo.com>,
        Elena Petrova <lenaptr@google.com>,
        Branislav Rankov <Branislav.Rankov@arm.com>,
        Kevin Brodsky <kevin.brodsky@arm.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        kasan-dev <kasan-dev@googlegroups.com>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
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On Thu, Oct 22, 2020 at 3:20 PM Andrey Konovalov <andreyknvl@google.com> wrote:
>
> kasan_poison_kfree() is currently only called for mempool allocations
> that are backed by either kmem_cache_alloc() or kmalloc(). Therefore, the
> page passed to kasan_poison_kfree() is always PageSlab() and there's no
> need to do the check.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
> Link: https://linux-review.googlesource.com/id/If31f88726745da8744c6bea96fb32584e6c2778c

Reviewed-by: Dmitry Vyukov <dvyukov@google.com>

> ---
>  mm/kasan/common.c | 11 +----------
>  1 file changed, 1 insertion(+), 10 deletions(-)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index a581937c2a44..b82dbae0c5d6 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -441,16 +441,7 @@ void __kasan_poison_kfree(void *ptr, unsigned long ip)
>         struct page *page;
>
>         page = virt_to_head_page(ptr);
> -
> -       if (unlikely(!PageSlab(page))) {
> -               if (ptr != page_address(page)) {
> -                       kasan_report_invalid_free(ptr, ip);
> -                       return;
> -               }
> -               kasan_poison_memory(ptr, page_size(page), KASAN_FREE_PAGE);
> -       } else {
> -               ____kasan_slab_free(page->slab_cache, ptr, ip, false);
> -       }
> +       ____kasan_slab_free(page->slab_cache, ptr, ip, false);
>  }
>
>  void __kasan_kfree_large(void *ptr, unsigned long ip)
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>