linux-hardening - Re: [PATCH] md/bcache: Mark _

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Message-ID: <CAMj1kXHfearSZG6TFTxxX87qmRkUmAefQm-TfPNS8j09kWxujQ@mail.gmail.com>
Date: Thu, 17 Apr 2025 08:16:45 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Kees Cook <kees@...nel.org>
Cc: Coly Li <colyli@...nel.org>, Kent Overstreet <kent.overstreet@...ux.dev>, 
	linux-bcache@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] md/bcache: Mark __nonstring look-up table

On Thu, 17 Apr 2025 at 00:01, Kees Cook <kees@...nel.org> wrote:
>
> GCC 15's new -Wunterminated-string-initialization notices that the 16
> character lookup table "zero_uuid" (which is not used as a C-String)
> needs to be marked as "nonstring":
>
> drivers/md/bcache/super.c: In function 'uuid_find_empty':
> drivers/md/bcache/super.c:549:43: warning: initializer-string for array of 'char' truncates NUL terminator but destination lacks 'nonstring' attribute (17 chars into 16 available) [-Wunterminated-string-initialization]
>   549 |         static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>       |                                           ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Add the annotation to silence the GCC warning.
>
> Signed-off-by: Kees Cook <kees@...nel.org>
> ---
> Cc: Coly Li <colyli@...nel.org>
> Cc: Kent Overstreet <kent.overstreet@...ux.dev>
> Cc: linux-bcache@...r.kernel.org
> ---
>  drivers/md/bcache/super.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index e42f1400cea9..577d048170fe 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -546,7 +546,7 @@ static struct uuid_entry *uuid_find(struct cache_set *c, const char *uuid)
>
>  static struct uuid_entry *uuid_find_empty(struct cache_set *c)
>  {
> -       static const char zero_uuid[16] = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
> +       static const char zero_uuid[] __nonstring = "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0";
>

Just

static const char zero_uuid[16] = {};

should work fine here too. No need for the initializer.


>         return uuid_find(c, zero_uuid);
>  }
> --
> 2.34.1
>
>