linux-kernel - Re: [PATCH] tomoyo: fix clang pointer arithmetic warning

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Date:   Wed, 11 Nov 2020 12:00:37 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Kentaro Takeda <takedakn@...data.co.jp>,
        Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Toshiharu Harada <haradats@...data.co.jp>,
        Arnd Bergmann <arnd@...db.de>,
        linux-security-module@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH] tomoyo: fix clang pointer arithmetic warning

On Mon, Oct 26, 2020 at 2:52 PM Arnd Bergmann <arnd@...nel.org> wrote:
>
> From: Arnd Bergmann <arnd@...db.de>
>
> clang warns about additions on NULL pointers being undefined in C:
>
> security/tomoyo/securityfs_if.c:226:59: warning: arithmetic on a null pointer treated as a cast from integer to pointer is a GNU extension [-Wnull-pointer-arithmetic]
>         securityfs_create_file(name, mode, parent, ((u8 *) NULL) + key,
>
> Change the code to instead use a cast through uintptr_t to avoid
> the warning.
>
> Fixes: 9590837b89aa ("Common functions for TOMOYO Linux.")
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks for the patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@...gle.com>

> ---
>  security/tomoyo/securityfs_if.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/security/tomoyo/securityfs_if.c b/security/tomoyo/securityfs_if.c
> index 546281c5b233..0a5f00073ef1 100644
> --- a/security/tomoyo/securityfs_if.c
> +++ b/security/tomoyo/securityfs_if.c
> @@ -223,7 +223,7 @@ static const struct file_operations tomoyo_operations = {
>  static void __init tomoyo_create_entry(const char *name, const umode_t mode,
>                                        struct dentry *parent, const u8 key)
>  {
> -       securityfs_create_file(name, mode, parent, ((u8 *) NULL) + key,
> +       securityfs_create_file(name, mode, parent, (u8 *)(uintptr_t)key,
>                                &tomoyo_operations);
>  }
>
> --
> 2.27.0
>


-- 
Thanks,
~Nick Desaulniers