Fix potential null pointer dereference.

source/common/upstream/cluster_manager_impl.cc

@@ -464,9 +464,22 @@ bool ClusterManagerImpl::addOrUpdateCluster(const envoy::api::v2::Cluster& clust
 
   if (existing_active_cluster != active_clusters_.end() ||
       existing_warming_cluster != warming_clusters_.end()) {
-    // The following init manager remove call is a NOP in the case we are already initialized. It's
-    // just kept here to avoid additional logic.
-    init_helper_.removeCluster(*existing_active_cluster->second->cluster_);
+    if (existing_active_cluster != active_clusters_.end()) {
+      // The following init manager remove call is a NOP in the case we are already initialized.
+      // It's just kept here to avoid additional logic.
+      init_helper_.removeCluster(*existing_active_cluster->second->cluster_);
+    } else {
+      // Validate that warming clusters are not added to the init_helper_.
+      // NOTE: This loop is compiled out in optimized builds.
+      for (const std::list<Cluster*>& cluster_list :
+           {std::cref(init_helper_.primary_init_clusters_),
+            std::cref(init_helper_.secondary_init_clusters_)}) {
+        ASSERT(!std::any_of(cluster_list.begin(), cluster_list.end(),
+                            [&existing_warming_cluster](Cluster* cluster) {
+                              return existing_warming_cluster->second->cluster_.get() == cluster;
+                            }));
+      }
+    }
     cm_stats_.cluster_modified_.inc();
   } else {
     cm_stats_.cluster_added_.inc();

source/common/upstream/cluster_manager_impl.h

@@ -90,6 +90,9 @@ class ProdClusterManagerFactory : public ClusterManagerFactory {
   Singleton::Manager& singleton_manager_;
 };
 
+// For friend declaration in ClusterManagerInitHelper.
+class ClusterManagerImpl;
+
 /**
  * This is a helper class used during cluster management initialization. Dealing with primary
  * clusters, secondary clusters, and CDS, is quite complicated, so this makes it easier to test.
@@ -128,6 +131,10 @@ class ClusterManagerInitHelper : Logger::Loggable<Logger::Id::upstream> {
   State state() const { return state_; }
 
 private:
+  // To enable invariant assertions on the cluster lists.
+  friend ClusterManagerImpl;
+
+  void initializeSecondaryClusters();
   void maybeFinishInitialize();
   void onClusterInit(Cluster& cluster);
 

test/common/upstream/cluster_manager_impl_test.cc

@@ -1232,6 +1232,78 @@ TEST_F(ClusterManagerImplTest, RemoveWarmingCluster) {
   EXPECT_TRUE(Mock::VerifyAndClearExpectations(cluster1.get()));
 }
 
+TEST_F(ClusterManagerImplTest, ModifyWarmingCluster) {
+  time_system_.setSystemTime(std::chrono::milliseconds(1234567891234));
+  create(defaultConfig());
+
+  InSequence s;
+  ReadyWatcher initialized;
+  EXPECT_CALL(initialized, ready());
+  cluster_manager_->setInitializedCb([&]() -> void { initialized.ready(); });
+
+  // Add a "fake_cluster" in warming state.
+  std::shared_ptr<MockClusterMockPrioritySet> cluster1 =
+      std::make_shared<NiceMock<MockClusterMockPrioritySet>>();
+  EXPECT_CALL(factory_, clusterFromProto_(_, _, _, _))
+      .WillOnce(Return(std::make_pair(cluster1, nullptr)));
+  EXPECT_CALL(*cluster1, initializePhase()).Times(0);
+  EXPECT_CALL(*cluster1, initialize(_));
+  EXPECT_TRUE(
+      cluster_manager_->addOrUpdateCluster(defaultStaticCluster("fake_cluster"), "version1"));
+  checkStats(1 /*added*/, 0 /*modified*/, 0 /*removed*/, 0 /*active*/, 1 /*warming*/);
+  EXPECT_EQ(nullptr, cluster_manager_->get("fake_cluster"));
+  checkConfigDump(R"EOF(
+ dynamic_warming_clusters:
+   - version_info: "version1"
+     cluster:
+       name: "fake_cluster"
+       type: STATIC
+       connect_timeout: 0.25s
+       hosts:
+       - socket_address:
+           address: "127.0.0.1"
+           port_value: 11001
+     last_updated:
+       seconds: 1234567891
+       nanos: 234000000
+ )EOF");
+
+  // Update the warming cluster that was just added.
+  std::shared_ptr<MockClusterMockPrioritySet> cluster2 =
+      std::make_shared<NiceMock<MockClusterMockPrioritySet>>();
+  EXPECT_CALL(factory_, clusterFromProto_(_, _, _, _))
+      .WillOnce(Return(std::make_pair(cluster2, nullptr)));
+  EXPECT_CALL(*cluster2, initializePhase()).Times(0);
+  EXPECT_CALL(*cluster2, initialize(_));
+  EXPECT_TRUE(cluster_manager_->addOrUpdateCluster(
+      parseClusterFromV2Json(fmt::sprintf(kDefaultStaticClusterTmpl, "fake_cluster",
+                                          R"EOF(
+"socket_address": {
+  "address": "127.0.0.1",
+  "port_value": 11002
+})EOF")),
+      "version2"));
+  checkStats(1 /*added*/, 1 /*modified*/, 0 /*removed*/, 0 /*active*/, 1 /*warming*/);
+  checkConfigDump(R"EOF(
+ dynamic_warming_clusters:
+   - version_info: "version2"
+     cluster:
+       name: "fake_cluster"
+       type: STATIC
+       connect_timeout: 0.25s
+       hosts:
+       - socket_address:
+           address: "127.0.0.1"
+           port_value: 11002
+     last_updated:
+       seconds: 1234567891
+       nanos: 234000000
+ )EOF");
+
+  EXPECT_TRUE(Mock::VerifyAndClearExpectations(cluster1.get()));
+  EXPECT_TRUE(Mock::VerifyAndClearExpectations(cluster2.get()));
+}
+
 // Verify that shutting down the cluster manager destroys warming clusters.
 TEST_F(ClusterManagerImplTest, ShutdownWithWarming) {
   create(defaultConfig());

test/common/upstream/utility.h

@@ -15,24 +15,26 @@ namespace Envoy {
 namespace Upstream {
 namespace {
 
-inline std::string defaultStaticClusterJson(const std::string& name) {
-  return fmt::sprintf(R"EOF(
+constexpr static const char* kDefaultStaticClusterTmpl = R"EOF(
   {
     "name": "%s",
     "connect_timeout": "0.250s",
     "type": "static",
     "lb_policy": "round_robin",
     "hosts": [
       {
-        "socket_address": {
-          "address": "127.0.0.1",
-          "port_value": 11001
-        }
+        %s,
       }
     ]
   }
-  )EOF",
-                      name);
+  )EOF";
+
+inline std::string defaultStaticClusterJson(const std::string& name) {
+  return fmt::sprintf(kDefaultStaticClusterTmpl, name, R"EOF(
+"socket_address": {
+  "address": "127.0.0.1",
+  "port_value": 11001
+})EOF");
 }
 
 inline envoy::config::bootstrap::v2::Bootstrap