linux-hardening - Re: [PATCH] net: dsa: realtek: replace deprecated strncpy with ethtool

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Message-ID: <CACRpkdbkhQZn5zF1Qx9JyoW8p6KMuMx9PkOrYEzKVs2xAOzH0w@mail.gmail.com>
Date: Tue, 10 Oct 2023 11:08:46 +0200
From: Linus Walleij <linus.walleij@...aro.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Alvin Šipraga <alsi@...g-olufsen.dk>, 
	Andrew Lunn <andrew@...n.ch>, Florian Fainelli <f.fainelli@...il.com>, 
	Vladimir Oltean <olteanv@...il.com>, "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] net: dsa: realtek: replace deprecated strncpy with ethtool_sprintf

On Tue, Oct 10, 2023 at 12:47 AM Justin Stitt <justinstitt@...gle.com> wrote:


> `strncpy` is deprecated for use on NUL-terminated destination strings
> [1] and as such we should prefer more robust and less ambiguous string
> interfaces.
>
> ethtool_sprintf() is designed specifically for get_strings() usage.
> Let's replace strncpy in favor of this more robust and easier to
> understand interface.
>
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://manpages.debian.org/testing/linux-manual-4.8/strscpy.9.en.html [2]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
(...)
> -               mib = &priv->mib_counters[i];
> -               strncpy(data + i * ETH_GSTRING_LEN,
> -                       mib->name, ETH_GSTRING_LEN);
> +               ethtool_sprintf(&data, "%s", priv->mib_counters[i].name);

Not only does it harden the kernel, it also makes it way easier to read!

Way to go.
Reviewed-by: Linus Walleij <linus.walleij@...aro.org>

Yours,
Linus Walleij