net: reject creation of netdev names with colons

colons are used as a separator in netdev device lookup in dev_ioctl.c

Specific functions are SIOCGIFTXQLEN SIOCETHTOOL SIOCSIFNAME
Signed-off-by: NMatthew Thode <mthode@mthode.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -946,7 +946,7 @@ bool dev_valid_name(const char *name)
 		return false;
 
 	while (*name) {
-		if (*name == '/' || isspace(*name))
+		if (*name == '/' || *name == ':' || isspace(*name))
 			return false;
 		name++;
 	}