Fix concurrent access to QBluetoothSocket::canReadLine() on Android

On Android, the socket's read buffer is managed in the Java thread.
QBluetoothSocket::canReadLine() is public API (most likely) being called
by in the main Qt thread though. The function directly called into the
Java buffer instance without proper locking. This can create race conditions.

Starting with this patch canReadLine() calls another QBluetoothSocketPrivate
indirection to allow a platform specific implementation. This affects
WinRT, BlueZ and the dummy backend too.

This is not an issue on macOS as its implementation of QBluetoothSocket
is separate and does not have to deal with multiple
QBluetoothSocketPrivate implementations.

Task-number: QTBUG-58190
Task-number: QTBUG-60830
Change-Id: Idae19f1aee6f809699d36519b01a3c68ad9c563d
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Oliver Wolff <oliver.wolff@qt.io>

8 files changed, 33 insertions, 1 deletions

diff --git a/src/bluetooth/android/inputstreamthread.cpp b/src/bluetooth/android/inputstreamthread.cpp
index ecd9218e..982c477b 100644
--- a/src/bluetooth/android/inputstreamthread.cpp
+++ b/src/bluetooth/android/inputstreamthread.cpp
@@ -77,6 +77,12 @@ qint64 InputStreamThread::bytesAvailable() const
     return m_socket_p->buffer.size();
 }
 
+bool InputStreamThread::canReadLine() const
+{
+    QMutexLocker locker(&m_mutex);
+    return m_socket_p->buffer.canReadLine();
+}
+
 qint64 InputStreamThread::readData(char *data, qint64 maxSize)
 {
     QMutexLocker locker(&m_mutex);
diff --git a/src/bluetooth/android/inputstreamthread_p.h b/src/bluetooth/android/inputstreamthread_p.h
index 741333ac..a6ee0655 100644
--- a/src/bluetooth/android/inputstreamthread_p.h
+++ b/src/bluetooth/android/inputstreamthread_p.h
@@ -68,6 +68,7 @@ public:
     explicit InputStreamThread(QBluetoothSocketPrivate *socket_p);
 
     qint64 bytesAvailable() const;
+    bool canReadLine() const;
     bool run();
 
     qint64 readData(char *data, qint64 maxSize);
diff --git a/src/bluetooth/qbluetoothsocket.cpp b/src/bluetooth/qbluetoothsocket.cpp
index 3e961142..57dd3aa0 100644
--- a/src/bluetooth/qbluetoothsocket.cpp
+++ b/src/bluetooth/qbluetoothsocket.cpp
@@ -624,7 +624,7 @@ void QBluetoothSocket::setSocketState(QBluetoothSocket::SocketState state)
 bool QBluetoothSocket::canReadLine() const
 {
     Q_D(const QBluetoothSocket);
-    return d->buffer.canReadLine() || QIODevice::canReadLine();
+    return d->canReadLine();
 }
 
 /*!
diff --git a/src/bluetooth/qbluetoothsocket_android.cpp b/src/bluetooth/qbluetoothsocket_android.cpp
index 87c9ffc8..c2fc96f2 100644
--- a/src/bluetooth/qbluetoothsocket_android.cpp
+++ b/src/bluetooth/qbluetoothsocket_android.cpp
@@ -879,6 +879,15 @@ qint64 QBluetoothSocketPrivate::bytesAvailable() const
     return 0;
 }
 
+bool QBluetoothSocketPrivate::canReadLine() const
+{
+    // We cannot access buffer directly as it is part of different thread
+    if (inputThread)
+        return inputThread->canReadLine();
+
+    return false;
+}
+
 QT_END_NAMESPACE
 
 #include <qbluetoothsocket_android.moc>
diff --git a/src/bluetooth/qbluetoothsocket_bluez.cpp b/src/bluetooth/qbluetoothsocket_bluez.cpp
index 42c5503b..dca1bc3b 100644
--- a/src/bluetooth/qbluetoothsocket_bluez.cpp
+++ b/src/bluetooth/qbluetoothsocket_bluez.cpp
@@ -592,4 +592,9 @@ qint64 QBluetoothSocketPrivate::bytesAvailable() const
     return buffer.size();
 }
 
+bool QBluetoothSocketPrivate::canReadLine() const
+{
+    return buffer.canReadLine();
+}
+
 QT_END_NAMESPACE
diff --git a/src/bluetooth/qbluetoothsocket_p.cpp b/src/bluetooth/qbluetoothsocket_p.cpp
index 6007b924..dc14e97b 100644
--- a/src/bluetooth/qbluetoothsocket_p.cpp
+++ b/src/bluetooth/qbluetoothsocket_p.cpp
@@ -158,4 +158,9 @@ qint64 QBluetoothSocketPrivate::bytesAvailable() const
     return 0;
 }
 
+bool QBluetoothSocketPrivate::canReadLine() const
+{
+    return false;
+}
+
 QT_END_NAMESPACE
diff --git a/src/bluetooth/qbluetoothsocket_p.h b/src/bluetooth/qbluetoothsocket_p.h
index 177f154a..cfa342bb 100644
--- a/src/bluetooth/qbluetoothsocket_p.h
+++ b/src/bluetooth/qbluetoothsocket_p.h
@@ -166,6 +166,7 @@ public:
                              QBluetoothSocket::OpenMode openMode = QBluetoothSocket::ReadWrite);
 
     qint64 bytesAvailable() const;
+    bool canReadLine() const;
 
 public:
     QPrivateLinearBuffer buffer;
diff --git a/src/bluetooth/qbluetoothsocket_winrt.cpp b/src/bluetooth/qbluetoothsocket_winrt.cpp
index 1f4e6233..a56e10fa 100644
--- a/src/bluetooth/qbluetoothsocket_winrt.cpp
+++ b/src/bluetooth/qbluetoothsocket_winrt.cpp
@@ -569,6 +569,11 @@ qint64 QBluetoothSocketPrivate::bytesAvailable() const
     return buffer.size();
 }
 
+bool QBluetoothSocketPrivate::canReadLine() const
+{
+    return buffer.canReadLine();
+}
+
 void QBluetoothSocketPrivate::handleNewData(const QVector<QByteArray> &data)
 {
     // Defer putting the data into the list until the next event loop iteration