Fix crash due to inconsistent state in QLEController during JobDisconnectDevice

This bug was caused by a problem in the patch for QTBUG-55150.

While the termination of an ongoing BTLE connection is being
processed, the QLEController instance is in Connecting state and
the internal socket is still null. If the user triggers a call
to QLEController::disconnectDevice() while the above state is
pending, it crashes due to a call to the socket's close()
function. The time window for this to happen is very small.
It takes the duration of the bluez dbus call to disconnect
a device.

This patch addresses the above crash bug and adds a
bit more debug output to catch similar cases later on.

Task-number: QTBUG-63619
Change-Id: I893990a9ce8ccf55ddbf619fe177379f79dc9ee3
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

2 files changed, 17 insertions, 3 deletions

diff --git a/src/bluetooth/bluez/remotedevicemanager.cpp b/src/bluetooth/bluez/remotedevicemanager.cpp
index f63b21e6..5d17d571 100644
--- a/src/bluetooth/bluez/remotedevicemanager.cpp
+++ b/src/bluetooth/bluez/remotedevicemanager.cpp
@@ -106,6 +106,7 @@ void RemoteDeviceManager::prepareNextJob()
     jobQueue.pop_front();
     jobInProgress = false;
 
+    qDebug(QT_BT_BLUEZ) << "RemoteDeviceManager job queue status:" << jobQueue.empty();
     if (jobQueue.empty())
         emit finished();
     else
@@ -163,8 +164,10 @@ void RemoteDeviceManager::disconnectDevice(const QBluetoothAddress &remote)
         }
     }
 
-    if (!jobStarted)
+    if (!jobStarted) {
+        qDebug(QT_BT_BLUEZ) << "RemoteDeviceManager JobDisconnectDevice failed";
         QTimer::singleShot(0, this, [this](){ prepareNextJob(); });
+    }
 }
 
 QT_END_NAMESPACE
diff --git a/src/bluetooth/qlowenergycontroller_bluez.cpp b/src/bluetooth/qlowenergycontroller_bluez.cpp
index 0744bcc4..d80389da 100644
--- a/src/bluetooth/qlowenergycontroller_bluez.cpp
+++ b/src/bluetooth/qlowenergycontroller_bluez.cpp
@@ -527,8 +527,10 @@ void QLowEnergyControllerPrivate::connectToDevice()
     }
 
     setState(QLowEnergyController::ConnectingState);
-    if (l2cpSocket)
+    if (l2cpSocket) {
         delete l2cpSocket;
+        l2cpSocket = nullptr;
+    }
 
     createServicesForCentralIfRequired();
 
@@ -581,6 +583,7 @@ void QLowEnergyControllerPrivate::activeConnectionTerminationDone()
         qCWarning(QT_BT_BLUEZ) << "Cannot close pending external BTLE connections. Aborting connect attempt";
         setError(QLowEnergyController::ConnectionError);
         setState(QLowEnergyController::UnconnectedState);
+        l2cpDisconnected();
         return;
     } else {
         establishL2cpClientSocket();
@@ -726,8 +729,16 @@ void QLowEnergyControllerPrivate::l2cpConnected()
 void QLowEnergyControllerPrivate::disconnectFromDevice()
 {
     setState(QLowEnergyController::ClosingState);
-    l2cpSocket->close();
+    if (l2cpSocket)
+        l2cpSocket->close();
     resetController();
+
+    // this may happen when RemoteDeviceManager::JobType::JobDisconnectDevice
+    // is pending.
+    if (!l2cpSocket) {
+        qWarning(QT_BT_BLUEZ) << "Unexpected closure of device. Cleaning up internal states.";
+        l2cpDisconnected();
+    }
 }
 
 void QLowEnergyControllerPrivate::l2cpDisconnected()