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

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Date: Wed, 11 Oct 2023 01:10:31 +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: replace deprecated strncpy with
 ethtool_sprintf

On Mon, Oct 09, 2023 at 10:47:37PM +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/rtl8366-core.c | 5 +----
>  1 file changed, 1 insertion(+), 4 deletions(-)
> 
> diff --git a/drivers/net/dsa/realtek/rtl8366-core.c b/drivers/net/dsa/realtek/rtl8366-core.c
> index dc5f75be3017..b13766a3acbb 100644
> --- a/drivers/net/dsa/realtek/rtl8366-core.c
> +++ b/drivers/net/dsa/realtek/rtl8366-core.c
> @@ -395,16 +395,13 @@ void rtl8366_get_strings(struct dsa_switch *ds, int port, u32 stringset,
>  			 uint8_t *data)
>  {
>  	struct realtek_priv *priv = ds->priv;
> -	struct rtl8366_mib_counter *mib;
>  	int i;
>  
>  	if (port >= priv->num_ports)
>  		return;
>  
>  	for (i = 0; i < priv->num_mib_counters; i++) {
> -		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);
>  	}

Nitpick, you don't need to resend for this. But if there's just a single
line remaining in the "for" loop, you could have dropped the braces too.

>  }
>  EXPORT_SYMBOL_GPL(rtl8366_get_strings);
> 
> ---
> base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
> change-id: 20231009-strncpy-drivers-net-dsa-realtek-rtl8366-core-c-60a0f0ddc5cc
> 
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
> 

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>