QEvdevKeyboardHandler: use RAII in create()/ctor

Coverity somewhat rightfully complained that the FD may be leaked in
certain cases, e.g. when the new-expression throws. Yes, the plugin
is compiled with exceptions disabled, but the code is still a bug
waiting to happen, because it's too easy to just add an early return
to the function and leak the FD that way.

Fix by writing a small RAII class for FDs (can't use QSharedPointer,
since it's not a pointer we're dealing with). It's quite generically
named, in anticipation that it might come in handy elsewhere, too.

Coverity-Id: 89046
Change-Id: I83d1ed3f11219065d2248c129ed191a651f617c7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/platformsupport/input/evdevkeyboard/qevdevkeyboardhandler.cpp

@@ -52,8 +52,15 @@ Q_LOGGING_CATEGORY(qLcEvdevKeyMap, "qt.qpa.input.keymap")
 // simple builtin US keymap
 #include "qevdevkeyboard_defaultmap_p.h"
 
-QEvdevKeyboardHandler::QEvdevKeyboardHandler(const QString &device, int fd, bool disableZap, bool enableCompose, const QString &keymapFile)
+void QFdContainer::reset() Q_DECL_NOTHROW
-    : m_device(device), m_fd(fd), m_notify(Q_NULLPTR),
+{
+    if (m_fd >= 0)
+        qt_safe_close(m_fd);
+    m_fd = -1;
+}
+
+QEvdevKeyboardHandler::QEvdevKeyboardHandler(const QString &device, QFdContainer &fd, bool disableZap, bool enableCompose, const QString &keymapFile)
+    : m_device(device), m_fd(fd.release()), m_notify(Q_NULLPTR),
       m_modifiers(0), m_composing(0), m_dead_unicode(0xffff),
       m_no_zap(disableZap), m_do_compose(enableCompose),
       m_keymap(0), m_keymap_size(0), m_keycompose(0), m_keycompose_size(0)
@@ -68,16 +75,13 @@ QEvdevKeyboardHandler::QEvdevKeyboardHandler(const QString &device, int fd, bool
         unloadKeymap();
 
     // socket notifier for events on the keyboard device
-    m_notify = new QSocketNotifier(m_fd, QSocketNotifier::Read, this);
+    m_notify = new QSocketNotifier(m_fd.get(), QSocketNotifier::Read, this);
     connect(m_notify, SIGNAL(activated(int)), this, SLOT(readKeycode()));
 }
 
 QEvdevKeyboardHandler::~QEvdevKeyboardHandler()
 {
     unloadKeymap();
-
-    if (m_fd >= 0)
-        qt_safe_close(m_fd);
 }
 
 QEvdevKeyboardHandler *QEvdevKeyboardHandler::create(const QString &device,
@@ -111,13 +115,12 @@ QEvdevKeyboardHandler *QEvdevKeyboardHandler::create(const QString &device,
 
     qCDebug(qLcEvdevKey) << "Opening keyboard at" << device;
 
-    int fd;
+    QFdContainer fd(qt_safe_open(device.toLocal8Bit().constData(), O_RDONLY | O_NDELAY, 0));
-    fd = qt_safe_open(device.toLocal8Bit().constData(), O_RDONLY | O_NDELAY, 0);
+    if (fd.get() >= 0) {
-    if (fd >= 0) {
+        ::ioctl(fd.get(), EVIOCGRAB, grab);
-        ::ioctl(fd, EVIOCGRAB, grab);
         if (repeatDelay > 0 && repeatRate > 0) {
             int kbdrep[2] = { repeatDelay, repeatRate };
-            ::ioctl(fd, EVIOCSREP, kbdrep);
+            ::ioctl(fd.get(), EVIOCSREP, kbdrep);
         }
 
         return new QEvdevKeyboardHandler(device, fd, disableZap, enableCompose, keymapFile);
@@ -137,7 +140,7 @@ void QEvdevKeyboardHandler::switchLed(int led, bool state)
     led_ie.code = led;
     led_ie.value = state;
 
-    qt_safe_write(m_fd, &led_ie, sizeof(led_ie));
+    qt_safe_write(m_fd.get(), &led_ie, sizeof(led_ie));
 }
 
 void QEvdevKeyboardHandler::readKeycode()
@@ -146,7 +149,7 @@ void QEvdevKeyboardHandler::readKeycode()
     int n = 0;
 
     forever {
-        int result = qt_safe_read(m_fd, reinterpret_cast<char *>(buffer) + n, sizeof(buffer) - n);
+        int result = qt_safe_read(m_fd.get(), reinterpret_cast<char *>(buffer) + n, sizeof(buffer) - n);
 
         if (result == 0) {
             qWarning("evdevkeyboard: Got EOF from the input device");
@@ -159,8 +162,7 @@ void QEvdevKeyboardHandler::readKeycode()
                 if (errno == ENODEV) {
                     delete m_notify;
                     m_notify = Q_NULLPTR;
-                    qt_safe_close(m_fd);
+                    m_fd.reset();
-                    m_fd = -1;
                 }
                 return;
             }
@@ -471,7 +473,7 @@ void QEvdevKeyboardHandler::unloadKeymap()
     //Set locks according to keyboard leds
     quint16 ledbits[1];
     memset(ledbits, 0, sizeof(ledbits));
-    if (::ioctl(m_fd, EVIOCGLED(sizeof(ledbits)), ledbits) < 0) {
+    if (::ioctl(m_fd.get(), EVIOCGLED(sizeof(ledbits)), ledbits) < 0) {
         qWarning("evdevkeyboard: Failed to query led states");
         switchLed(LED_NUML,false);
         switchLed(LED_CAPSL, false);

src/platformsupport/input/evdevkeyboard/qevdevkeyboardhandler_p.h

@@ -123,12 +123,25 @@ inline QDataStream &operator<<(QDataStream &ds, const QEvdevKeyboardMap::Composi
     return ds << c.first << c.second << c.result;
 }
 
+class QFdContainer
+{
+    int m_fd;
+    Q_DISABLE_COPY(QFdContainer);
+public:
+    explicit QFdContainer(int fd = -1) Q_DECL_NOTHROW : m_fd(fd) {}
+    ~QFdContainer() { reset(); }
+
+    int get() const Q_DECL_NOTHROW { return m_fd; }
+
+    int release() Q_DECL_NOTHROW { int result = m_fd; m_fd = -1; return result; }
+    void reset() Q_DECL_NOTHROW;
+};
 
 class QEvdevKeyboardHandler : public QObject
 {
     Q_OBJECT
 public:
-    QEvdevKeyboardHandler(const QString &device, int fd, bool disableZap, bool enableCompose, const QString &keymapFile);
+    QEvdevKeyboardHandler(const QString &device, QFdContainer &fd, bool disableZap, bool enableCompose, const QString &keymapFile);
     ~QEvdevKeyboardHandler();
 
     enum KeycodeAction {
@@ -181,7 +194,7 @@ private:
     void switchLed(int, bool);
 
     QString m_device;
-    int m_fd;
+    QFdContainer m_fd;
     QSocketNotifier *m_notify;
 
     // keymap handling