Check for overflow in connection string construction

When constructing the connectionstring for connecting to the QEs,
ensure we don't overflow the assigned buffer.
Reviewed-by: NGang Xiong <gxiong@pivotal.io>

src/backend/cdb/dispatcher/cdbgang.c

@@ -669,10 +669,11 @@ makeOptions(void)
  * to be passed to a qExec that is being started.  NB: Can be called in a
  * thread, so mustn't use palloc/elog/ereport/etc.
  */
-void
+bool
 build_gpqeid_param(char *buf, int bufsz,
 				   bool is_writer, int gangId, int hostSegs)
 {
+	int		len;
 #ifdef HAVE_INT64_TIMESTAMP
 #define TIMESTAMP_FORMAT INT64_FORMAT
 #else
@@ -683,9 +684,11 @@ build_gpqeid_param(char *buf, int bufsz,
 #endif
 #endif
 
-	snprintf(buf, bufsz, "%d;" TIMESTAMP_FORMAT ";%s;%d;%d",
-			 gp_session_id, PgStartTime,
-			 (is_writer ? "true" : "false"), gangId, hostSegs);
+	len = snprintf(buf, bufsz, "%d;" TIMESTAMP_FORMAT ";%s;%d;%d",
+				   gp_session_id, PgStartTime,
+				   (is_writer ? "true" : "false"), gangId, hostSegs);
+
+	return (len > 0 && len < bufsz);
 }
 
 static bool

src/backend/cdb/dispatcher/cdbgang_async.c

@@ -107,6 +107,7 @@ create_gang_retry:
 	{
 		for (i = 0; i < size; i++)
 		{
+			bool		ret;
 			char		gpqeid[100];
 			char	   *options;
 
@@ -122,10 +123,15 @@ create_gang_retry:
 			 * early enough now some locks are taken before command line
 			 * options are recognized.
 			 */
-			build_gpqeid_param(gpqeid, sizeof(gpqeid),
-							   type == GANGTYPE_PRIMARY_WRITER,
-							   gang_id,
-							   segdbDesc->segment_database_info->hostSegs);
+			ret = build_gpqeid_param(gpqeid, sizeof(gpqeid),
+									 type == GANGTYPE_PRIMARY_WRITER,
+									 gang_id,
+									 segdbDesc->segment_database_info->hostSegs);
+
+			if (!ret)
+				ereport(ERROR,
+						(errcode(ERRCODE_GP_INTERCONNECTION_ERROR),
+						 errmsg("failed to construct connectionstring")));
 
 			options = makeOptions();
 

src/backend/cdb/dispatcher/cdbgang_thread.c

@@ -299,6 +299,7 @@ thread_DoConnect(void *arg)
 	 */
 	for (i = 0; i < db_count; i++)
 	{
+		bool		ret;
 		char		gpqeid[100];
 
 		segdbDesc = segdbDescPtrArray[i];
@@ -314,10 +315,19 @@ thread_DoConnect(void *arg)
 		 * early enough now some locks are taken before command line options
 		 * are recognized.
 		 */
-		build_gpqeid_param(gpqeid, sizeof(gpqeid),
-						   pParms->type == GANGTYPE_PRIMARY_WRITER,
-						   pParms->gangId,
-						   segdbDesc->segment_database_info->hostSegs);
+		ret = build_gpqeid_param(gpqeid, sizeof(gpqeid),
+								 pParms->type == GANGTYPE_PRIMARY_WRITER,
+								 pParms->gangId,
+								 segdbDesc->segment_database_info->hostSegs);
+
+		if (!ret)
+		{
+			segdbDesc->errcode = ERRCODE_INTERNAL_ERROR;
+			appendPQExpBuffer(&segdbDesc->error_message,
+							  "Internal error: unable to construct connection string");
+			write_log("thread_DoConnect: unable to construct connection string for segdb %i", i);
+			continue;
+		}
 
 		/* check the result in createGang */
 		cdbconn_doConnect(segdbDesc, gpqeid, pParms->connectOptions);

src/include/cdb/cdbgang.h

@@ -103,7 +103,7 @@ extern struct SegmentDatabaseDescriptor *getSegmentDescriptorFromGang(const Gang
 bool isPrimaryWriterGangAlive(void);
 
 Gang *buildGangDefinition(GangType type, int gang_id, int size, int content);
-void build_gpqeid_param(char *buf, int bufsz, bool is_writer, int gangId, int hostSegs);
+bool build_gpqeid_param(char *buf, int bufsz, bool is_writer, int gangId, int hostSegs);
 char *makeOptions(void);
 extern bool segment_failure_due_to_recovery(const char *error_message);