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QDBusConnectionPrivate: Fix race in sendWithReply()

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The message processing may finish before watcherHelper is
setup. Use locking and an additional check for message
processing completion to avoid the race condition.

Move the code to new function inside QDBusPendingCallPrivate,
close to where the waiting without GUI is done.

Add assertions that check that watcherHelper is not overwritten.

Change-Id: I24e54598135edf293c41b3a80369b0a3b46f775c
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
This commit is contained in:
Ievgenii Meshcheriakov 2023-09-20 17:23:41 +02:00
parent 406f676843
commit 24e504d9df
3 changed files with 26 additions and 14 deletions
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19
src/dbus/qdbusintegrator.cpp
View File

@ -2056,20 +2056,10 @@ QDBusMessage QDBusConnectionPrivate::sendWithReply(const QDBusMessage &message,
QDBusPendingCallPrivate *pcall = sendWithReplyAsync(message, nullptr, nullptr, nullptr, timeout);
Q_ASSERT(pcall);
if (pcall->replyMessage.type() == QDBusMessage::InvalidMessage) {
// need to wait for the reply
if (mode == QDBus::BlockWithGui) {
pcall->watcherHelper = new QDBusPendingCallWatcherHelper;
QEventLoop loop;
loop.connect(pcall->watcherHelper, &QDBusPendingCallWatcherHelper::reply, &loop, &QEventLoop::quit);
loop.connect(pcall->watcherHelper, &QDBusPendingCallWatcherHelper::error, &loop, &QEventLoop::quit);
// enter the event loop and wait for a reply
loop.exec(QEventLoop::ExcludeUserInputEvents | QEventLoop::WaitForMoreEvents);
} else {
pcall->waitForFinished();
}
}
if (mode == QDBus::BlockWithGui)
pcall->waitForFinishedWithGui();
else
pcall->waitForFinished();
QDBusMessage reply = pcall->replyMessage;
lastError = QDBusError(reply); // set or clear error
@ -2130,6 +2120,7 @@ QDBusPendingCallPrivate *QDBusConnectionPrivate::sendWithReplyAsync(const QDBusM
pcall->setReplyCallback(receiver, returnMethod);
if (errorMethod) {
Q_ASSERT(!pcall->watcherHelper);
pcall->watcherHelper = new QDBusPendingCallWatcherHelper;
connect(pcall->watcherHelper, SIGNAL(error(QDBusError,QDBusMessage)), receiver, errorMethod,
Qt::QueuedConnection);

20
src/dbus/qdbuspendingcall.cpp
View File

@ -206,6 +206,26 @@ void QDBusPendingCallPrivate::waitForFinished()
waitForFinishedCondition.wait(&mutex);
}
void QDBusPendingCallPrivate::waitForFinishedWithGui()
{
QEventLoop loop;
{
const auto locker = qt_scoped_lock(mutex);
if (replyMessage.type() != QDBusMessage::InvalidMessage)
return; // already finished
Q_ASSERT(!watcherHelper);
watcherHelper = new QDBusPendingCallWatcherHelper;
loop.connect(watcherHelper, &QDBusPendingCallWatcherHelper::reply, &loop,
&QEventLoop::quit);
loop.connect(watcherHelper, &QDBusPendingCallWatcherHelper::error, &loop,
&QEventLoop::quit);
}
loop.exec(QEventLoop::ExcludeUserInputEvents | QEventLoop::WaitForMoreEvents);
}
/*!
Creates a copy of the \a other pending asynchronous call. Note
that both objects will refer to the same pending call.

1
src/dbus/qdbuspendingcall_p.h
View File

@ -68,6 +68,7 @@ public:
~QDBusPendingCallPrivate();
bool setReplyCallback(QObject *target, const char *member);
void waitForFinished();
void waitForFinishedWithGui();
void setMetaTypes(int count, const QMetaType *types);
void checkReceivedSignature();
};