linux-hardening - Re: [PATCH] net: dsa: realtek: rtl8365mb: replace deprecated strncpy with ethtool

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Date: Tue, 10 Oct 2023 14:07:17 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Alvin Šipraga <alsi@...g-olufsen.dk>,
	Andrew Lunn <andrew@...n.ch>,
	Florian Fainelli <f.fainelli@...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: rtl8365mb: replace deprecated strncpy
 with ethtool_sprintf

Hello Justin,

On Mon, Oct 09, 2023 at 10:43:59PM +0000, Justin Stitt 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>
> ---
> Note: build-tested only.
> ---
>  drivers/net/dsa/realtek/rtl8365mb.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/realtek/rtl8365mb.c b/drivers/net/dsa/realtek/rtl8365mb.c
> index 41ea3b5a42b1..d171c18dd354 100644
> --- a/drivers/net/dsa/realtek/rtl8365mb.c
> +++ b/drivers/net/dsa/realtek/rtl8365mb.c
> @@ -1303,8 +1303,7 @@ static void rtl8365mb_get_strings(struct dsa_switch *ds, int port, u32 stringset
>  
>  	for (i = 0; i < RTL8365MB_MIB_END; i++) {
>  		struct rtl8365mb_mib_counter *mib = &rtl8365mb_mib_counters[i];
> -
> -		strncpy(data + i * ETH_GSTRING_LEN, mib->name, ETH_GSTRING_LEN);
> +		ethtool_sprintf(&data, "%s", mib->name);

Is there any particular reason why you opted for the "%s" printf format
specifier when you could have simply given mib->name as the single
argument? This comment applies to all the ethtool_sprintf() patches
you've submitted.