net: use scnprintf() to avoid potential buffer overflow

strlcpy() returns the total length of the string they tried to create, so
we should not use its return value without any check. scnprintf() returns
the number of characters written into @buf not including the trailing '\0',
so use it instead here.
Signed-off-by: NChangli Gao <xiaosuo@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ethernet/eth.c

@@ -367,7 +367,7 @@ struct net_device *alloc_etherdev_mq(int sizeof_priv, unsigned int queue_count)
 EXPORT_SYMBOL(alloc_etherdev_mq);
 
 static size_t _format_mac_addr(char *buf, int buflen,
-				const unsigned char *addr, int len)
+			       const unsigned char *addr, int len)
 {
 	int i;
 	char *cp = buf;
@@ -376,7 +376,7 @@ static size_t _format_mac_addr(char *buf, int buflen,
 		cp += scnprintf(cp, buflen - (cp - buf), "%02x", addr[i]);
 		if (i == len - 1)
 			break;
-		cp += strlcpy(cp, ":", buflen - (cp - buf));
+		cp += scnprintf(cp, buflen - (cp - buf), ":");
 	}
 	return cp - buf;
 }
@@ -386,7 +386,7 @@ ssize_t sysfs_format_mac(char *buf, const unsigned char *addr, int len)
 	size_t l;
 
 	l = _format_mac_addr(buf, PAGE_SIZE, addr, len);
-	l += strlcpy(buf + l, "\n", PAGE_SIZE - l);
+	l += scnprintf(buf + l, PAGE_SIZE - l, "\n");
 	return ((ssize_t) l);
 }
 EXPORT_SYMBOL(sysfs_format_mac);