linux-kernel - Re: [PATCH v3] net: macb: Add __nonstring annotations for unterminated strings

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Message-ID: <202503131042.F6C9F4CA06@keescook>
Date: Thu, 13 Mar 2025 10:44:09 -0700
From: Kees Cook <kees@...nel.org>
To: Andrew Lunn <andrew@...n.ch>
Cc: Nicolas Ferre <nicolas.ferre@...rochip.com>,
	Claudiu Beznea <claudiu.beznea@...on.dev>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v3] net: macb: Add __nonstring annotations for
 unterminated strings

On Thu, Mar 13, 2025 at 02:25:09PM +0100, Andrew Lunn wrote:
> >  struct gem_statistic {
> > -	char stat_string[ETH_GSTRING_LEN];
> > +	char stat_string[ETH_GSTRING_LEN] __nonstring;
> 
> This general pattern of a char foo[ETH_GSTRING_LEN]' will appear
> throughout drivers/net/ethernet. Maybe Coccinelle can find them all
> and add the __nonstring ?

I had that same thought but then rediscovered ethtool_puts() and
ethtool_sprintf(), which operate on C Strings and write out C Strings...
so _some_ ethtool stats are being constructed in a way that we can't
just universally apply __nonstring to all ETH_GSTRING_LEN strings. :(

-- 
Kees Cook