linux-kernel - Re: [PATCH v2 2/2] auxdisplay: panel: avoid gcc 8's Wstringop-truncation warning

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Date:   Wed, 1 Aug 2018 11:47:47 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>, Willy Tarreau <w@....eu>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Martin Sebor <msebor@...il.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will.deacon@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        David Rientjes <rientjes@...gle.com>,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v2 2/2] auxdisplay: panel: avoid gcc 8's
 Wstringop-truncation warning

On Wed, Aug 1, 2018 at 10:58 AM, Miguel Ojeda
<miguel.ojeda.sandonis@...il.com> wrote:
> Let gcc know it is not meant to be NUL-terminated by annotating with
> the new __nonstring variable attribute; and remove the comment since it
> conveys the same information.
>
> Cc: Willy Tarreau <w@....eu>
> Cc: Geert Uytterhoeven <geert@...ux-m68k.org>
> Cc: Martin Sebor <msebor@...il.com>
> Signed-off-by: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
> ---
>  drivers/auxdisplay/panel.c | 7 +++----
>  1 file changed, 3 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/auxdisplay/panel.c b/drivers/auxdisplay/panel.c
> index 3b25a643058c..21b9b2f2470a 100644
> --- a/drivers/auxdisplay/panel.c
> +++ b/drivers/auxdisplay/panel.c
> @@ -155,10 +155,9 @@ struct logical_input {
>                         int release_data;
>                 } std;
>                 struct {        /* valid when type == INPUT_TYPE_KBD */
> -                       /* strings can be non null-terminated */
> -                       char press_str[sizeof(void *) + sizeof(int)];
> -                       char repeat_str[sizeof(void *) + sizeof(int)];
> -                       char release_str[sizeof(void *) + sizeof(int)];
> +                       char press_str[sizeof(void *) + sizeof(int)] __nonstring;
> +                       char repeat_str[sizeof(void *) + sizeof(int)] __nonstring;
> +                       char release_str[sizeof(void *) + sizeof(int)] __nonstring;
>                 } kbd;
>         } u;
>  };

If it's not a string, why not use "u8" instead of "char"? Does the
warning persist?

-Kees

-- 
Kees Cook
Pixel Security