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

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Message-ID: <3fd91204-629f-4024-8d49-c76c7b344735@intel.com>
Date: Mon, 11 Aug 2025 16:25:26 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Kees Cook <kees@...nel.org>
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

From: Kees Cook <kees@...nel.org>
Date: Thu, 7 Aug 2025 15:00:24 -0700

> 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.

Maybe we should add a check to the Ethtool core that every 32-th array
symbol == \0 to detect misbehaving drivers like this one :D

Thanks,
Olek