From 7d8c0082a3f64f77b1853c2e70c7b6bccb1f686a Mon Sep 17 00:00:00 2001
From: Jesse Glick <jglick@cloudbees.com>
Date: Fri, 25 Sep 2020 13:19:59 -0400
Subject: [PATCH] [JENKINS-41037] Prevent ConcurrentModificationException
 serializing LibrariesAction.libraries

---
 .../org/jenkinsci/plugins/workflow/libs/LibrariesAction.java | 3 ++-
 .../org/jenkinsci/plugins/workflow/libs/LibraryStep.java     | 5 ++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/jenkinsci/plugins/workflow/libs/LibrariesAction.java b/src/main/java/org/jenkinsci/plugins/workflow/libs/LibrariesAction.java
index 367e406a..86b029d9 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/libs/LibrariesAction.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/libs/LibrariesAction.java
@@ -31,6 +31,7 @@
 import hudson.model.Run;
 import hudson.model.TaskListener;
 import java.io.IOException;
+import java.util.Collections;
 import java.util.List;
 
 /**
@@ -48,7 +49,7 @@ class LibrariesAction extends InvisibleAction {
      * A list of libraries in use.
      */
     public List<LibraryRecord> getLibraries() {
-        return libraries;
+        return Collections.unmodifiableList(libraries);
     }
 
     @Extension public static class LibraryEnvironment extends EnvironmentContributor {
diff --git a/src/main/java/org/jenkinsci/plugins/workflow/libs/LibraryStep.java b/src/main/java/org/jenkinsci/plugins/workflow/libs/LibraryStep.java
index cad49424..9984d5b5 100644
--- a/src/main/java/org/jenkinsci/plugins/workflow/libs/LibraryStep.java
+++ b/src/main/java/org/jenkinsci/plugins/workflow/libs/LibraryStep.java
@@ -48,6 +48,7 @@
 import java.net.URL;
 import java.nio.file.Paths;
 import java.security.CodeSource;
+import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
 import java.util.List;
@@ -197,7 +198,9 @@ public static class Execution extends AbstractSynchronousNonBlockingStepExecutio
                         return new LoadedClasses(name, trusted, changelog, run);
                     }
                 }
-                libraries.add(record);
+                List<LibraryRecord> newLibraries = new ArrayList<>(libraries);
+                newLibraries.add(record);
+                run.replaceAction(new LibrariesAction(newLibraries));
             }
             listener.getLogger().println("Loading library " + record.name + "@" + record.version);
             CpsFlowExecution exec = (CpsFlowExecution) getContext().get(FlowExecution.class);