Fix heap-use-after-free error when shutting down envoy. (#758)

The HotRestart holds a socket event for the domain socket used for admin
purpose, it need to be deleted before the envoy server gets deleted, as
the envoy server own the event_base and which already deleted the
registered events with the event_base_free().

include/envoy/server/hot_restart.h

@@ -64,6 +64,11 @@ class HotRestart {
    */
   virtual void terminateParent() PURE;
 
+  /**
+   * Shutdown the hot restarter.
+   */
+  virtual void shutdown() PURE;
+
   /**
    * Return the hot restart compatability version so that operations code can decide whether to
    * perform a full or hot restart.

source/exe/hot_restart.cc

@@ -407,6 +407,8 @@ void HotRestartImpl::terminateParent() {
   parent_terminated_ = true;
 }
 
+void HotRestartImpl::shutdown() { socket_event_.reset(); }
+
 std::string HotRestartImpl::version() { return SharedMemory::version(); }
 
 } // Server

source/exe/hot_restart.h

@@ -112,6 +112,7 @@ class HotRestartImpl : public HotRestart,
   void initialize(Event::Dispatcher& dispatcher, Server::Instance& server) override;
   void shutdownParentAdmin(ShutdownParentAdminInfo& info) override;
   void terminateParent() override;
+  void shutdown() override;
   std::string version() override;
 
   // RawStatDataAllocator

source/server/server.cc

@@ -85,6 +85,8 @@ InstanceImpl::InstanceImpl(Options& options, TestHooks& hooks, HotRestart& resta
   }
 }
 
+InstanceImpl::~InstanceImpl() { restarter_.shutdown(); }
+
 Upstream::ClusterManager& InstanceImpl::clusterManager() { return config_->clusterManager(); }
 
 Tracing::HttpTracer& InstanceImpl::httpTracer() { return config_->httpTracer(); }

source/server/server.h

@@ -94,6 +94,8 @@ class InstanceImpl : Logger::Loggable<Logger::Id::main>, public Instance {
                Thread::BasicLockable& access_log_lock, ComponentFactory& component_factory,
                const LocalInfo::LocalInfo& local_info);
 
+  ~InstanceImpl() override;
+
   void run();
 
   // Server::Instance

test/integration/server.cc

@@ -21,6 +21,7 @@ class TestHotRestart : public HotRestart {
   void initialize(Event::Dispatcher&, Server::Instance&) override {}
   void shutdownParentAdmin(ShutdownParentAdminInfo&) override {}
   void terminateParent() override {}
+  void shutdown() override {}
   std::string version() override { return "1"; }
 };
 

test/mocks/server/mocks.h

@@ -80,6 +80,7 @@ class MockHotRestart : public HotRestart {
   MOCK_METHOD2(initialize, void(Event::Dispatcher& dispatcher, Server::Instance& server));
   MOCK_METHOD1(shutdownParentAdmin, void(ShutdownParentAdminInfo& info));
   MOCK_METHOD0(terminateParent, void());
+  MOCK_METHOD0(shutdown, void());
   MOCK_METHOD0(version, std::string());
 };