linux-kernel - Re: [PATCH] wifi: mwifiex: Add __nonstring annotations for unterminated strings

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Message-ID: <Z-Mw1gvbkBQ1fZ7y@google.com>
Date: Tue, 25 Mar 2025 15:40:22 -0700
From: Brian Norris <briannorris@...omium.org>
To: Kees Cook <kees@...nel.org>
Cc: Francesco Dolcini <francesco@...cini.it>,
	Johannes Berg <johannes@...solutions.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Allison Randal <allison@...utok.net>,
	linux-wireless@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH] wifi: mwifiex: Add __nonstring annotations for
 unterminated strings

On Mon, Mar 10, 2025 at 03:23:32PM -0700, Kees Cook wrote:
> When a character array without a terminating NUL character has a static
> initializer, GCC 15's -Wunterminated-string-initialization will only
> warn if the array lacks the "nonstring" attribute[1]. Mark the arrays
> with __nonstring to and correctly identify the char array as "not a C
> string" and thereby eliminate the warning.
> 
> Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117178 [1]
> Cc: Brian Norris <briannorris@...omium.org>
> Cc: Francesco Dolcini <francesco@...cini.it>
> Cc: Johannes Berg <johannes@...solutions.net>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Allison Randal <allison@...utok.net>
> Cc: linux-wireless@...r.kernel.org
> Signed-off-by: Kees Cook <kees@...nel.org>

This code is kinda weird, because only 2 bytes actually end up used, and
yet we explicitly initialize it with 3 non-NUL bytes.

This solutions seems fine though, as it is indeed not a C string and
does not desire nor rely on a NUL byte:

Acked-by: Brian Norris <briannorris@...omium.org>

Looks like Johannes already applied it anyway.