libcamera: camera_manager: Construct CameraManager instances manually

The CameraManager class is not supposed to be instantiated multiple
times, which led to a singleton implementation. This requires a global
instance of the CameraManager, which is destroyed when the global
destructors are executed.

Relying on global instances causes issues with cleanup, as the order in
which the global destructors are run can't be controlled. In particular,
the Android camera HAL implementation ends up destroying the
CameraHalManager after the CameraManager, which leads to use-after-free
problems.

To solve this, remove the CameraManager::instance() method and make the
CameraManager class instantiable directly. Multiple instances are still
not allowed, and this is enforced by storing the instance pointer
internally to be checked when an instance is created.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>

include/libcamera/camera_manager.h

@@ -23,6 +23,11 @@ class PipelineHandler;
 class CameraManager : public Object
 {
 public:
+	CameraManager();
+	CameraManager(const CameraManager &) = delete;
+	CameraManager &operator=(const CameraManager &) = delete;
+	~CameraManager();
+
 	int start();
 	void stop();
 
@@ -32,23 +37,18 @@ public:
 	void addCamera(std::shared_ptr<Camera> camera);
 	void removeCamera(Camera *camera);
 
-	static CameraManager *instance();
 	static const std::string &version() { return version_; }
 
 	void setEventDispatcher(std::unique_ptr<EventDispatcher> dispatcher);
 	EventDispatcher *eventDispatcher();
 
 private:
-	CameraManager();
-	CameraManager(const CameraManager &) = delete;
-	CameraManager &operator=(const CameraManager &) = delete;
-	~CameraManager();
-
 	std::unique_ptr<DeviceEnumerator> enumerator_;
 	std::vector<std::shared_ptr<PipelineHandler>> pipes_;
 	std::vector<std::shared_ptr<Camera>> cameras_;
 
 	static const std::string version_;
+	static CameraManager *self_;
 };
 
 } /* namespace libcamera */

src/android/camera_hal_manager.cpp

@@ -59,7 +59,7 @@ void CameraHalManager::run()
 	 * order to bind them to the camera HAL manager thread that
 	 * executes the event dispatcher.
 	 */
-	cameraManager_ = libcamera::CameraManager::instance();
+	cameraManager_ = new CameraManager();
 
 	int ret = cameraManager_->start();
 	if (ret) {
@@ -93,7 +93,10 @@ void CameraHalManager::run()
 
 	/* Clean up the resources we have allocated. */
 	proxies_.clear();
+
 	cameraManager_->stop();
+	delete cameraManager_;
+	cameraManager_ = nullptr;
 }
 
 CameraProxy *CameraHalManager::open(unsigned int id,

src/cam/main.cpp

@@ -23,6 +23,7 @@ class CamApp
 {
 public:
 	CamApp();
+	~CamApp();
 
 	static CamApp *instance();
 
@@ -54,6 +55,11 @@ CamApp::CamApp()
 	CamApp::app_ = this;
 }
 
+CamApp::~CamApp()
+{
+	delete cm_;
+}
+
 CamApp *CamApp::instance()
 {
 	return CamApp::app_;
@@ -67,7 +73,7 @@ int CamApp::init(int argc, char **argv)
 	if (ret < 0)
 		return ret;
 
-	cm_ = CameraManager::instance();
+	cm_ = new CameraManager();
 
 	ret = cm_->start();
 	if (ret) {

src/libcamera/camera_manager.cpp

@@ -35,11 +35,14 @@ LOG_DEFINE_CATEGORY(Camera)
  * in the system to applications. The manager owns all Camera objects and
  * handles hot-plugging and hot-unplugging to manage the lifetime of cameras.
  *
- * To interact with libcamera, an application retrieves the camera manager
+ * To interact with libcamera, an application starts by creating a camera
- * instance with CameraManager::instance(). The manager is initially stopped,
+ * manager instance. Only a single instance of the camera manager may exist at
- * and shall be configured before being started. In particular a custom event
+ * a time. Attempting to create a second instance without first deleting the
- * dispatcher shall be installed if needed with
+ * existing instance results in undefined behaviour.
- * CameraManager::setEventDispatcher().
+ *
+ * The manager is initially stopped, and shall be configured before being
+ * started. In particular a custom event dispatcher shall be installed if
+ * needed with CameraManager::setEventDispatcher().
  *
  * Once the camera manager is configured, it shall be started with start().
  * This will enumerate all the cameras present in the system, which can then be
@@ -56,13 +59,21 @@ LOG_DEFINE_CATEGORY(Camera)
  * removed due to hot-unplug.
  */
 
+CameraManager *CameraManager::self_ = nullptr;
+
 CameraManager::CameraManager()
 	: enumerator_(nullptr)
 {
+	if (self_)
+		LOG(Camera, Fatal)
+			<< "Multiple CameraManager objects are not allowed";
+
+	self_ = this;
 }
 
 CameraManager::~CameraManager()
 {
+	self_ = nullptr;
 }
 
 /**
@@ -212,21 +223,6 @@ void CameraManager::removeCamera(Camera *camera)
 	}
 }
 
-/**
- * \brief Retrieve the camera manager instance
- *
- * The CameraManager is a singleton and can't be constructed manually. This
- * function shall instead be used to retrieve the single global instance of the
- * manager.
- *
- * \return The camera manager instance
- */
-CameraManager *CameraManager::instance()
-{
-	static CameraManager manager;
-	return &manager;
-}
-
 /**
  * \fn const std::string &CameraManager::version()
  * \brief Retrieve the libcamera version string

src/qcam/main.cpp

@@ -63,7 +63,7 @@ int main(int argc, char **argv)
 	sigaction(SIGINT, &sa, nullptr);
 
 	std::unique_ptr<EventDispatcher> dispatcher(new QtEventDispatcher());
-	CameraManager *cm = CameraManager::instance();
+	CameraManager *cm = new CameraManager();
 	cm->setEventDispatcher(std::move(dispatcher));
 
 	ret = cm->start();
@@ -79,5 +79,7 @@ int main(int argc, char **argv)
 	delete mainWindow;
 
 	cm->stop();
+	delete cm;
+
 	return ret;
 }

test/camera/camera_test.cpp

@@ -14,7 +14,7 @@ using namespace std;
 
 int CameraTest::init()
 {
-	cm_ = CameraManager::instance();
+	cm_ = new CameraManager();
 
 	if (cm_->start()) {
 		cout << "Failed to start camera manager" << endl;
@@ -44,4 +44,5 @@ void CameraTest::cleanup()
 	}
 
 	cm_->stop();
+	delete cm_;
 };

test/controls/control_list.cpp

@@ -21,7 +21,7 @@ class ControlListTest : public Test
 protected:
 	int init()
 	{
-		cm_ = CameraManager::instance();
+		cm_ = new CameraManager();
 
 		if (cm_->start()) {
 			cout << "Failed to start camera manager" << endl;
@@ -203,6 +203,7 @@ protected:
 		}
 
 		cm_->stop();
+		delete cm_;
 	}
 
 private:

test/list-cameras.cpp

@@ -20,8 +20,8 @@ class ListTest : public Test
 protected:
 	int init()
 	{
-		cm = CameraManager::instance();
+		cm_ = new CameraManager();
-		cm->start();
+		cm_->start();
 
 		return 0;
 	}
@@ -30,7 +30,7 @@ protected:
 	{
 		unsigned int count = 0;
 
-		for (const std::shared_ptr<Camera> &camera : cm->cameras()) {
+		for (const std::shared_ptr<Camera> &camera : cm_->cameras()) {
 			cout << "- " << camera->name() << endl;
 			count++;
 		}
@@ -40,11 +40,12 @@ protected:
 
 	void cleanup()
 	{
-		cm->stop();
+		cm_->stop();
+		delete cm_;
 	}
 
 private:
-	CameraManager *cm;
+	CameraManager *cm_;
 };
 
 TEST_REGISTER(ListTest)

test/pipeline/ipu3/ipu3_pipeline_test.cpp

@@ -92,7 +92,7 @@ int IPU3PipelineTest::init()
 
 	enumerator.reset(nullptr);
 
-	cameraManager_ = CameraManager::instance();
+	cameraManager_ = new CameraManager();
 	ret = cameraManager_->start();
 	if (ret) {
 		cerr << "Failed to start the CameraManager" << endl;
@@ -120,6 +120,7 @@ int IPU3PipelineTest::run()
 void IPU3PipelineTest::cleanup()
 {
 	cameraManager_->stop();
+	delete cameraManager_;
 }
 
 TEST_REGISTER(IPU3PipelineTest)