Fix #78819: Heap Overflow in msg_send

We need to use the proper type.

Closes GH-7386.

Author: cmb69

NEWS

@@ -15,6 +15,9 @@ PHP                                                                        NEWS
 - Standard:
   . Fixed bug #71542 (disk_total_space does not work with relative paths). (cmb)
 
+- SysVMsg:
+  . Fixed bug #78819 (Heap Overflow in msg_send). (cmb)
+
 - XML:
   . Fixed bug #81351 (xml_parse may fail, but has no error code). (cmb, Nikita)
 

ext/sysvmsg/sysvmsg.c

@@ -414,7 +414,7 @@ PHP_FUNCTION(msg_send)
 	sysvmsg_queue_t * mq = NULL;
 	struct php_msgbuf * messagebuffer = NULL; /* buffer to transmit */
 	int result;
-	int message_len = 0;
+	size_t message_len = 0;
 
 	RETVAL_FALSE;