TT#108350 add kernel module version/size check

Change-Id: I636a234c066922c2db604787057320b62105a0d4

daemon/kernel.c

@@ -76,6 +76,7 @@ static int kernel_open_table(unsigned int id) {
 
 	ZERO(msg);
 	msg.cmd = REMG_NOOP;
+	msg.u.size = sizeof(msg);
 	i = write(fd, &msg, sizeof(msg));
 	if (i <= 0)
 		goto fail;

kernel-module/xt_RTPENGINE.c

@@ -3261,7 +3261,8 @@ static inline ssize_t proc_control_read_write(struct file *file, char __user *ub
 
 	switch (msg->cmd) {
 		case REMG_NOOP:
-			DBG("noop.\n");
+			if (msg->u.size != sizeof(*msg))
+				err = -EMSGSIZE;
 			break;
 
 		case REMG_ADD:

kernel-module/xt_RTPENGINE.h

@@ -144,6 +144,7 @@ struct rtpengine_stats_info {
 
 struct rtpengine_message {
 	enum {
+		/* size: */
 		REMG_NOOP = 1,
 
 		/* target_info: */
@@ -170,6 +171,7 @@ struct rtpengine_message {
 	}				cmd;
 
 	union {
+		size_t				size;
 		struct rtpengine_target_info	target;
 		struct rtpengine_call_info	call;
 		struct rtpengine_stream_info	stream;