Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
MIME-Version: 1.0
References: <cover.1655150842.git.andreyknvl@google.com> <91406e5f2a1c0a1fddfc4e7f17df22fda852591c.1655150842.git.andreyknvl@google.com>
In-Reply-To: <91406e5f2a1c0a1fddfc4e7f17df22fda852591c.1655150842.git.andreyknvl@google.com>
From:   Marco Elver <elver@google.com>
Date:   Mon, 20 Jun 2022 15:39:25 +0200
Message-ID: <CANpmjNMB6gJjqXuXBOnDtnEncNoKHcZKxsUU_Mc_y8=KFg=W2g@mail.gmail.com>
Subject: Re: [PATCH 01/32] kasan: check KASAN_NO_FREE_META in __kasan_metadata_size
To:     andrey.konovalov@linux.dev
Cc:     Alexander Potapenko <glider@google.com>,
        Andrey Konovalov <andreyknvl@gmail.com>,
        Dmitry Vyukov <dvyukov@google.com>,
        Andrey Ryabinin <ryabinin.a.a@gmail.com>,
        kasan-dev@googlegroups.com, Peter Collingbourne <pcc@google.com>,
        Evgenii Stepanov <eugenis@google.com>,
        Florian Mayer <fmayer@google.com>,
        Andrew Morton <akpm@linux-foundation.org>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org,
        Andrey Konovalov <andreyknvl@google.com>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Mon, 13 Jun 2022 at 22:15, <andrey.konovalov@linux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@google.com>
>
> __kasan_metadata_size() calculates the size of the redzone for objects
> in a slab cache.
>
> When accounting for presence of kasan_free_meta in the redzone, this
> function only compares free_meta_offset with 0. But free_meta_offset could
> also be equal to KASAN_NO_FREE_META, which indicates that kasan_free_meta
> is not present at all.
>
> Add a comparison with KASAN_NO_FREE_META into __kasan_metadata_size().
>
> Signed-off-by: Andrey Konovalov <andreyknvl@google.com>

Reviewed-by: Marco Elver <elver@google.com>


> ---
>
> This is a minor fix that only affects slub_debug runs, so it is probably
> not worth backporting.
> ---
>  mm/kasan/common.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index c40c0e7b3b5f..968d2365d8c1 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -223,8 +223,9 @@ size_t __kasan_metadata_size(struct kmem_cache *cache)
>                 return 0;
>         return (cache->kasan_info.alloc_meta_offset ?
>                 sizeof(struct kasan_alloc_meta) : 0) +
> -               (cache->kasan_info.free_meta_offset ?
> -               sizeof(struct kasan_free_meta) : 0);
> +               ((cache->kasan_info.free_meta_offset &&
> +                 cache->kasan_info.free_meta_offset != KASAN_NO_FREE_META) ?
> +                sizeof(struct kasan_free_meta) : 0);
>  }
>
>  struct kasan_alloc_meta *kasan_get_alloc_meta(struct kmem_cache *cache,
> --
> 2.25.1
>
> --
> You received this message because you are subscribed to the Google Groups "kasan-dev" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to kasan-dev+unsubscribe@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/kasan-dev/91406e5f2a1c0a1fddfc4e7f17df22fda852591c.1655150842.git.andreyknvl%40google.com.