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

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Message-ID: <20231009-strncpy-drivers-net-dsa-realtek-rtl8366-core-c-v1-1-74e1b5190778@google.com>
Date: Mon, 09 Oct 2023 22:47:37 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: Linus Walleij <linus.walleij@...aro.org>, 
	"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>
Cc: netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org, Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH] net: dsa: realtek: replace deprecated strncpy with ethtool_sprintf

`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);
 	}
 }
 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>