tc: filter: validate filter priority in userspace.

Because we use the high 16 bits of tcm_info to pass prio value to
kernel, thus it's range would be [0, 0xffff], without validation
in tc when user pass a lager(>65535) priority, the actual priority
set in kernel would confuse the user.

So, add a validation to ensure prio in the range.

tc/tc_filter.c

@@ -105,7 +105,7 @@ int tc_filter_modify(int cmd, unsigned flags, int argc, char **argv)
 			NEXT_ARG();
 			if (prio)
 				duparg("priority", *argv);
-			if (get_u32(&prio, *argv, 0))
+			if (get_u32(&prio, *argv, 0) || prio > 0xFFFF)
 				invarg(*argv, "invalid priority value");
 		} else if (matches(*argv, "protocol") == 0) {
 			__u16 id;