MDL-58857 admin: Terminate the session if a major upgrade is required

admin/index.php

@@ -101,6 +101,12 @@
 // indirectly calls the protected init() method is good here.
 core_component::get_core_subsystems();
 
+if (is_major_upgrade_required() && isloggedin()) {
+    // A major upgrade is required.
+    // Terminate the session and redirect back here before anything DB-related happens.
+    redirect_if_major_upgrade_required();
+}
+
 require_once($CFG->libdir.'/adminlib.php');    // various admin-only functions
 require_once($CFG->libdir.'/upgradelib.php');  // general upgrade/install related functions
 

lib/setuplib.php

@@ -1388,16 +1388,34 @@ function disable_output_buffering() {
 }
 
 /**
- * Check whether a major upgrade is needed. That is defined as an upgrade that
- * changes something really fundamental in the database, so nothing can possibly
- * work until the database has been updated, and that is defined by the hard-coded
- * version number in this function.
+ * Check whether a major upgrade is needed.
+ *
+ * That is defined as an upgrade that changes something really fundamental
+ * in the database, so nothing can possibly work until the database has
+ * been updated, and that is defined by the hard-coded version number in
+ * this function.
+ *
+ * @return bool
  */
-function redirect_if_major_upgrade_required() {
+function is_major_upgrade_required() {
     global $CFG;
     $lastmajordbchanges = 2017040403.00;
-    if (empty($CFG->version) or (float)$CFG->version < $lastmajordbchanges or
-            during_initial_install() or !empty($CFG->adminsetuppending)) {
+
+    $required = empty($CFG->version);
+    $required = $required || (float)$CFG->version < $lastmajordbchanges;
+    $required = $required || during_initial_install();
+    $required = $required || !empty($CFG->adminsetuppending);
+
+    return $required;
+}
+
+/**
+ * Redirect to the Notifications page if a major upgrade is required, and
+ * terminate the current user session.
+ */
+function redirect_if_major_upgrade_required() {
+    global $CFG;
+    if (is_major_upgrade_required()) {
         try {
             @\core\session\manager::terminate_current();
         } catch (Exception $e) {