Fix a data race between the dns_zone and dns_catz modules

The dns_zone_catz_enable_db() and dns_zone_catz_disable_db()
functions can race with similar operations in the catz module
because there is no synchronization between the threads.

Add catz functions which use the view's catalog zones' lock
when registering/unregistering the database update notify callback,
and use those functions in the dns_zone module, instead of doing it
directly.

lib/dns/catz.c

@@ -2191,6 +2191,26 @@ cleanup:
 	return (result);
 }
 
+void
+dns_catz_dbupdate_unregister(dns_db_t *db, dns_catz_zones_t *catzs) {
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(DNS_CATZ_ZONES_VALID(catzs));
+
+	LOCK(&catzs->lock);
+	dns_db_updatenotify_unregister(db, dns_catz_dbupdate_callback, catzs);
+	UNLOCK(&catzs->lock);
+}
+
+void
+dns_catz_dbupdate_register(dns_db_t *db, dns_catz_zones_t *catzs) {
+	REQUIRE(DNS_DB_VALID(db));
+	REQUIRE(DNS_CATZ_ZONES_VALID(catzs));
+
+	LOCK(&catzs->lock);
+	dns_db_updatenotify_register(db, dns_catz_dbupdate_callback, catzs);
+	UNLOCK(&catzs->lock);
+}
+
 static bool
 catz_rdatatype_is_processable(const dns_rdatatype_t type) {
 	return (!dns_rdatatype_isdnssec(type) && type != dns_rdatatype_cds &&

lib/dns/include/dns/catz.h

@@ -354,6 +354,26 @@ dns_catz_dbupdate_callback(dns_db_t *db, void *fn_arg);
  * \li	'fn_arg' is not NULL (casted to dns_catz_zones_t*).
  */
 
+void
+dns_catz_dbupdate_unregister(dns_db_t *db, dns_catz_zones_t *catzs);
+/*%<
+ * Register the catalog zone database update notify callback.
+ *
+ * Requires:
+ * \li	'db' is a valid database.
+ * \li	'catzs' is valid.
+ */
+
+void
+dns_catz_dbupdate_register(dns_db_t *db, dns_catz_zones_t *catzs);
+/*%<
+ * Unregister the catalog zone database update notify callback.
+ *
+ * Requires:
+ * \li	'db' is a valid database.
+ * \li	'catzs' is valid.
+ */
+
 void
 dns_catz_prereconfig(dns_catz_zones_t *catzs);
 /*%<

lib/dns/zone.c

@@ -1939,8 +1939,7 @@ dns_zone_catz_enable_db(dns_zone_t *zone, dns_db_t *db) {
 	REQUIRE(db != NULL);
 
 	if (zone->catzs != NULL) {
-		dns_db_updatenotify_register(db, dns_catz_dbupdate_callback,
+		dns_catz_dbupdate_register(db, zone->catzs);
-					     zone->catzs);
 	}
 }
 
@@ -1950,8 +1949,7 @@ dns_zone_catz_disable_db(dns_zone_t *zone, dns_db_t *db) {
 	REQUIRE(db != NULL);
 
 	if (zone->catzs != NULL) {
-		dns_db_updatenotify_unregister(db, dns_catz_dbupdate_callback,
+		dns_catz_dbupdate_unregister(db, zone->catzs);
-					       zone->catzs);
 	}
 }