Re: [PATCH v2 2/2] kasan, slub: reset tag when printing address

From: Marco Elver <elver@google.com>
To: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
Cc: Nicholas Tang <nicholas.tang@mediatek.com>,
	Andrew Yang <andrew.tang@mediatek.com>,
	 Andrey Konovalov <andreyknvl@gmail.com>,
	Andrey Ryabinin <ryabinin.a.a@gmail.com>,
	 Alexander Potapenko <glider@google.com>,
	Catalin Marinas <catalin.marinas@arm.com>,
	 Chinwen Chang <chinwen.chang@mediatek.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	 kasan-dev@googlegroups.com, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org,
	linux-mediatek@lists.infradead.org
Subject: Re: [PATCH v2 2/2] kasan, slub: reset tag when printing address
Date: Wed, 4 Aug 2021 10:41:25 +0200	[thread overview]
Message-ID: <CANpmjNMAw=rcp_V+G_vjRjArj+09AkOxtC+wUNs-e1RRvfQm6w@mail.gmail.com> (raw)
In-Reply-To: <20210804082230.10837-3-Kuan-Ying.Lee@mediatek.com>

On Wed, 4 Aug 2021 at 10:23, Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com> wrote:
>
> The address still includes the tags when it is printed.
> With hardware tag-based kasan enabled, we will get a
> false positive KASAN issue when we access metadata.
>
> Reset the tag before we access the metadata.
>
> Fixes: aa1ef4d7b3f6 ("kasan, mm: reset tags when accessing metadata")
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@mediatek.com>
> Suggested-by: Marco Elver <elver@google.com>

Note, in this case Suggested-by is inappropriate, because I did not
suggest the change in any way (you already had it in v1). I just
commented on the fact that it's missing a Fixes so stable can pick it
up and some clarification.

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

> ---
>  mm/slub.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index b6c5205252eb..f77d8cd79ef7 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -576,8 +576,8 @@ static void print_section(char *level, char *text, u8 *addr,
>                           unsigned int length)
>  {
>         metadata_access_enable();
> -       print_hex_dump(level, kasan_reset_tag(text), DUMP_PREFIX_ADDRESS,
> -                       16, 1, addr, length, 1);
> +       print_hex_dump(level, text, DUMP_PREFIX_ADDRESS,
> +                       16, 1, kasan_reset_tag((void *)addr), length, 1);
>         metadata_access_disable();
>  }
>
> --
> 2.18.0

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