Fix crash on serializing default-constructed QTimeZone

The serialization code neglected to check against null.  Sinze zones
are saved either by IANA ID or in our special OffsetFromUtc format,
representing an invalid zone by a string that cannot possibly be a
valid IANA ID will do.

Fixes: QTBUG-86019
Pick-to: 5.15
Pick-to: 5.12
Change-Id: I6882026403d00f8b254aab34c645f1cf8f9fcc2d
Reviewed-by: Taylor Braun-Jones <taylor@braun-jones.org>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

1 files changed, 11 insertions, 3 deletions

diff --git a/src/corelib/time/qtimezone.cpp b/src/corelib/time/qtimezone.cpp
index 24834d1284..684639b68e 100644
--- a/src/corelib/time/qtimezone.cpp
+++ b/src/corelib/time/qtimezone.cpp
@@ -1,6 +1,6 @@
 /****************************************************************************
 **
-** Copyright (C) 2013 John Layt <jlayt@kde.org>
+** Copyright (C) 2020 John Layt <jlayt@kde.org>
 ** Contact: https://www.qt.io/licensing/
 **
 ** This file is part of the QtCore module of the Qt Toolkit.
@@ -966,9 +966,15 @@ QList<QByteArray> QTimeZone::windowsIdToIanaIds(const QByteArray &windowsId,
 }
 
 #ifndef QT_NO_DATASTREAM
+// Invalid, as an IANA ID: too long, starts with - and has other invalid characters in it
+static inline QString invalidId() { return QStringLiteral("-No Time Zone Specified!"); }
+
 QDataStream &operator<<(QDataStream &ds, const QTimeZone &tz)
 {
-    tz.d->serialize(ds);
+    if (tz.isValid())
+        tz.d->serialize(ds);
+    else
+        ds << invalidId();
     return ds;
 }
 
@@ -976,7 +982,9 @@ QDataStream &operator>>(QDataStream &ds, QTimeZone &tz)
 {
     QString ianaId;
     ds >> ianaId;
-    if (ianaId == QLatin1String("OffsetFromUtc")) {
+    if (ianaId == invalidId()) {
+        tz = QTimeZone();
+    } else if (ianaId == QLatin1String("OffsetFromUtc")) {
         int utcOffset;
         QString name;
         QString abbreviation;