From c595918fa72461276f8f33d19ebfff5530f4924d Mon Sep 17 00:00:00 2001
From: Martin Pokorny <martin.pokorny@etm.at>
Date: Mon, 20 Apr 2026 22:45:13 +0200
Subject: [PATCH] Fix ConcurrentModificationException in getDeclaredResources
 and getResourcesFromProject

Add synchronized(syncResources) blocks around iterations in
getDeclaredResources() and getResourcesFromProject() to prevent
ConcurrentModificationException when the resources list is modified
concurrently by another thread.

Also changes both methods to iterate over this.resources directly
(inside the sync block) instead of this.getResources() which returns
an unprotected reference.

Fixes #933
---
 .../LockableResourcesManager.java             | 26 +++++++++++--------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/src/main/java/org/jenkins/plugins/lockableresources/LockableResourcesManager.java b/src/main/java/org/jenkins/plugins/lockableresources/LockableResourcesManager.java
index 2a84303f0..ee1a696f3 100644
--- a/src/main/java/org/jenkins/plugins/lockableresources/LockableResourcesManager.java
+++ b/src/main/java/org/jenkins/plugins/lockableresources/LockableResourcesManager.java
@@ -161,13 +161,15 @@ public List<LockableResource> getReadOnlyResources() {
     /** Get declared resources, means only defined in config file (xml or JCaC yaml). */
     @Restricted(NoExternalUse.class)
     public List<LockableResource> getDeclaredResources() {
-        ArrayList<LockableResource> declaredResources = new ArrayList<>();
-        for (LockableResource r : this.getResources()) {
-            if (!r.isEphemeral() && !r.isNodeResource()) {
-                declaredResources.add(r);
+        synchronized (syncResources) {
+            ArrayList<LockableResource> declaredResources = new ArrayList<>();
+            for (LockableResource r : this.resources) {
+                if (!r.isEphemeral() && !r.isNodeResource()) {
+                    declaredResources.add(r);
+                }
             }
+            return declaredResources;
         }
-        return declaredResources;
     }
 
     // ---------------------------------------------------------------------------
@@ -231,14 +233,16 @@ public void setDeclaredResources(List<LockableResource> declaredResources) {
     /** Get all resources used by project. */
     @Restricted(NoExternalUse.class)
     public List<LockableResource> getResourcesFromProject(String fullName) {
-        List<LockableResource> matching = new ArrayList<>();
-        for (LockableResource r : this.getResources()) {
-            String rName = r.getQueueItemProject();
-            if (rName != null && rName.equals(fullName)) {
-                matching.add(r);
+        synchronized (syncResources) {
+            List<LockableResource> matching = new ArrayList<>();
+            for (LockableResource r : this.resources) {
+                String rName = r.getQueueItemProject();
+                if (rName != null && rName.equals(fullName)) {
+                    matching.add(r);
+                }
             }
+            return matching;
         }
-        return matching;
     }
 
     // ---------------------------------------------------------------------------