linux-hardening - Re: [PATCH v2] kbuild: Re-enable -Wunterminated-string-initialization

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Message-ID: <202508071458.A97B471@keescook>
Date: Thu, 7 Aug 2025 15:00:24 -0700
From: Kees Cook <kees@...nel.org>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: Nathan Chancellor <nathan@...nel.org>,
	Masahiro Yamada <masahiroy@...nel.org>,
	Nicolas Schier <nicolas.schier@...ux.dev>,
	linux-kbuild@...r.kernel.org,
	Nick Desaulniers <nick.desaulniers+lkml@...il.com>,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>, linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] kbuild: Re-enable -Wunterminated-string-initialization

On Thu, Aug 07, 2025 at 03:31:05PM +0200, Alexander Lobakin wrote:
> Sure, lots of drivers uses normal string copy functions etc.
> But Ethtool strings *must* be NUL-terminated, so this fixed-size +
> memcpy() only hurts.

This is the misunderstanding: they're only NUL padded, but not strictly
NUL terminated. You can see ethtool itself has to be careful with the
strings, limiting the fprintf to their sizeof():

https://git.kernel.org/pub/scm/network/ethtool/ethtool.git/tree/ethtool.c#n1013

or using strncmp everywhere.

-- 
Kees Cook