Merge pull request #6869 from nextcloud/backport/6868/stable-3.13

[stable-3.13] avoid deadlock: cancel hydration requests coming from itself

Author: mgallien

src/libsync/vfs/cfapi/cfapiwrapper.cpp

@@ -157,6 +157,12 @@ void CALLBACK cfApiFetchDataCallback(const CF_CALLBACK_INFO *callbackInfo, const
                               callbackInfo->FileSize.QuadPart);
     };
 
+    if (QCoreApplication::applicationPid() == callbackInfo->ProcessInfo->ProcessId) {
+        qCCritical(lcCfApiWrapper) << "implicit hydration triggered by the client itself. Will lead to a deadlock. Cancel";
+        sendTransferError();
+        return;
+    }
+
     auto vfs = reinterpret_cast<OCC::VfsCfApi *>(callbackInfo->CallbackContext);
     Q_ASSERT(vfs->metaObject()->className() == QByteArrayLiteral("OCC::VfsCfApi"));
     const auto path = QString(QString::fromWCharArray(callbackInfo->VolumeDosName) + QString::fromWCharArray(callbackInfo->NormalizedPath));