linux-hardening - Re: [PATCH v3] net: dsa: lan9303: use ethtool_puts() for lan9303_get

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Date: Tue, 9 Apr 2024 10:58:41 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Justin Stitt <justinstitt@...gle.com>
CC: 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>, Kees Cook
	<keescook@...omium.org>
Subject: Re: [PATCH v3] net: dsa: lan9303: use ethtool_puts() for
 lan9303_get_strings()

From: Justin Stitt <justinstitt@...gle.com>
Date: Mon, 08 Apr 2024 21:01:57 +0000

> This pattern of strncpy with some pointer arithmetic setting fixed-sized
> intervals with string literal data is a bit weird so let's use
> ethtool_puts() as this has more obvious behavior and is less-error
> prone.
> 
> Nicely, we also get to drop a usage of the now deprecated strncpy() [1].
> 
> Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strncpy-on-nul-terminated-strings [1]
> Link: https://github.com/KSPP/linux/issues/90
> Cc: linux-hardening@...r.kernel.org
> Cc: Kees Cook <keescook@...omium.org>
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> Suggested-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> ---
> Changes in v3:
> - use ethtool_puts over ethtool_sprintf
> - Link to v2: https://lore.kernel.org/r/20231005-strncpy-drivers-net-dsa-lan9303-core-c-v2-1-feb452a532db@google.com
> 
> Changes in v2:
> - use ethtool_sprintf (thanks Alexander)
> - Link to v1: https://lore.kernel.org/r/20231005-strncpy-drivers-net-dsa-lan9303-core-c-v1-1-5a66c538147e@google.com
> ---
>  drivers/net/dsa/lan9303-core.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/dsa/lan9303-core.c b/drivers/net/dsa/lan9303-core.c
> index fcb20eac332a..04d3af0eb28e 100644
> --- a/drivers/net/dsa/lan9303-core.c
> +++ b/drivers/net/dsa/lan9303-core.c
> @@ -1007,14 +1007,14 @@ static const struct lan9303_mib_desc lan9303_mib[] = {
>  static void lan9303_get_strings(struct dsa_switch *ds, int port,
>  				u32 stringset, uint8_t *data)
>  {
> +	u8 *buf = data;
>  	unsigned int u;
>  
>  	if (stringset != ETH_SS_STATS)
>  		return;
>  
>  	for (u = 0; u < ARRAY_SIZE(lan9303_mib); u++) {
> -		strncpy(data + u * ETH_GSTRING_LEN, lan9303_mib[u].name,
> -			ETH_GSTRING_LEN);
> +		ethtool_puts(&buf, lan9303_mib[u].name);
>  	}

The braces { } around ethtool_puts() aren't needed anymore.

>  }
>  
> 
> ---
> base-commit: c85af715cac0a951eea97393378e84bb49384734
> change-id: 20231005-strncpy-drivers-net-dsa-lan9303-core-c-6386858e5c22
> 
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>

Thanks,
Olek