linux-kernel - Re: [PATCH v3 1/3] kasan: Archs don't check memmove if not support it.

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Message-ID: <mhng-5f3ce9b5-2b64-48d7-a661-7bedf58c50a5@palmer-si-x1e>
Date:   Wed, 16 Oct 2019 12:23:02 -0700 (PDT)
From:   Palmer Dabbelt <palmer@...ive.com>
To:     nickhu@...estech.com
CC:     alankao@...estech.com, Paul Walmsley <paul.walmsley@...ive.com>,
        aou@...s.berkeley.edu, aryabinin@...tuozzo.com, glider@...gle.com,
        dvyukov@...gle.com, corbet@....net, alexios.zavras@...el.com,
        allison@...utok.net, Anup Patel <Anup.Patel@....com>,
        tglx@...utronix.de, Greg KH <gregkh@...uxfoundation.org>,
        Atish Patra <Atish.Patra@....com>,
        kstewart@...uxfoundation.org, linux-doc@...r.kernel.org,
        linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        kasan-dev@...glegroups.com, linux-mm@...ck.org,
        nickhu@...estech.com
Subject:     Re: [PATCH v3 1/3] kasan: Archs don't check memmove if not support it.

On Mon, 07 Oct 2019 23:11:51 PDT (-0700), nickhu@...estech.com wrote:
> Skip the memmove checking for those archs who don't support it.
>
> Signed-off-by: Nick Hu <nickhu@...estech.com>
> ---
>  mm/kasan/common.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/mm/kasan/common.c b/mm/kasan/common.c
> index 6814d6d6a023..897f9520bab3 100644
> --- a/mm/kasan/common.c
> +++ b/mm/kasan/common.c
> @@ -107,6 +107,7 @@ void *memset(void *addr, int c, size_t len)
>  	return __memset(addr, c, len);
>  }
>
> +#ifdef __HAVE_ARCH_MEMMOVE
>  #undef memmove
>  void *memmove(void *dest, const void *src, size_t len)
>  {
> @@ -115,6 +116,7 @@ void *memmove(void *dest, const void *src, size_t len)
>
>  	return __memmove(dest, src, len);
>  }
> +#endif
>
>  #undef memcpy
>  void *memcpy(void *dest, const void *src, size_t len)

I think this is backwards: we shouldn't be defining an arch-specific memmove 
symbol when KASAN is enabled.  If we do it this way then we're defeating the 
memmove checks, which doesn't seem like the right way to go.