linux-kernel - Re: [PATCH 2/2] kasan, mm: reset tag for hex dump address

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Message-ID: <CANpmjNNOkCspsf4=gPLLw=29vtv4qEDaErB1i1sz-p+bzLxNKg@mail.gmail.com>
Date:   Tue, 27 Jul 2021 09:20:59 +0200
From:   Marco Elver <elver@...gle.com>
To:     Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>
Cc:     Nicholas Tang <nicholas.tang@...iatek.com>,
        Andrew Yang <andrew.yang@...iatek.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Andrey Ryabinin <ryabinin.a.a@...il.com>,
        Alexander Potapenko <glider@...gle.com>,
        Chinwen Chang <chinwen.chang@...iatek.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 2/2] kasan, mm: reset tag for hex dump address

On Tue, 27 Jul 2021 at 06:00, Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com> wrote:
>
> Text is a string. We need to move this kasan_reset_tag()
> to address but text.
>
> Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@...iatek.com>

This patch also makes sense (I think), thanks for sending. But it's
unclear what the problem is. The fact that when the address is printed
it still includes the tag? Or a false positive?
It'd be good to clarify in the commit message.

Here I'd also use a more descriptive patch title, something like
"kasan, slub: reset tag when printing address".

Also, I think this patch requires a:

  Fixes: aa1ef4d7b3f6 ("kasan, mm: reset tags when accessing metadata")

So that stable kernels can pick this up if appropriate.

> ---
>  mm/slub.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/mm/slub.c b/mm/slub.c
> index 6dad2b6fda6f..d20674f839ba 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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