linux-hardening - [PATCH] net: dsa: vsc73xx: replace deprecated strncpy with ethtool

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Message-ID: <20231009-strncpy-drivers-net-dsa-vitesse-vsc73xx-core-c-v1-1-e2427e087fad@google.com>
Date: Mon, 09 Oct 2023 22:54:37 +0000
From: Justin Stitt <justinstitt@...gle.com>
To: 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: vsc73xx: 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/vitesse-vsc73xx-core.c | 20 ++++++--------------
 1 file changed, 6 insertions(+), 14 deletions(-)

diff --git a/drivers/net/dsa/vitesse-vsc73xx-core.c b/drivers/net/dsa/vitesse-vsc73xx-core.c
index 4f09e7438f3b..09955fdea2ff 100644
--- a/drivers/net/dsa/vitesse-vsc73xx-core.c
+++ b/drivers/net/dsa/vitesse-vsc73xx-core.c
@@ -928,7 +928,8 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
 	const struct vsc73xx_counter *cnt;
 	struct vsc73xx *vsc = ds->priv;
 	u8 indices[6];
-	int i, j;
+	u8 *buf = data;
+	int i;
 	u32 val;
 	int ret;
 
@@ -948,10 +949,7 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
 	indices[5] = ((val >> 26) & 0x1f); /* TX counter 2 */
 
 	/* The first counters is the RX octets */
-	j = 0;
-	strncpy(data + j * ETH_GSTRING_LEN,
-		"RxEtherStatsOctets", ETH_GSTRING_LEN);
-	j++;
+	ethtool_sprintf(&buf, "RxEtherStatsOctets");
 
 	/* Each port supports recording 3 RX counters and 3 TX counters,
 	 * figure out what counters we use in this set-up and return the
@@ -962,22 +960,16 @@ static void vsc73xx_get_strings(struct dsa_switch *ds, int port, u32 stringset,
 	for (i = 0; i < 3; i++) {
 		cnt = vsc73xx_find_counter(vsc, indices[i], false);
 		if (cnt)
-			strncpy(data + j * ETH_GSTRING_LEN,
-				cnt->name, ETH_GSTRING_LEN);
-		j++;
+			ethtool_sprintf(&buf, "%s", cnt->name);
 	}
 
 	/* TX stats begins with the number of TX octets */
-	strncpy(data + j * ETH_GSTRING_LEN,
-		"TxEtherStatsOctets", ETH_GSTRING_LEN);
-	j++;
+	ethtool_sprintf(&buf, "TxEtherStatsOctets");
 
 	for (i = 3; i < 6; i++) {
 		cnt = vsc73xx_find_counter(vsc, indices[i], true);
 		if (cnt)
-			strncpy(data + j * ETH_GSTRING_LEN,
-				cnt->name, ETH_GSTRING_LEN);
-		j++;
+			ethtool_sprintf(&buf, "%s", cnt->name);
 	}
 }
 

---
base-commit: cbf3a2cb156a2c911d8f38d8247814b4c07f49a2
change-id: 20231009-strncpy-drivers-net-dsa-vitesse-vsc73xx-core-c-1cfd0ac2d81b

Best regards,
--
Justin Stitt <justinstitt@...gle.com>