Fix data corruption when reading byte arrays from QSettings

On macOS, the code that read the plist is using
QByteArray::fromRawCFData. When we return the data directly
we need to detach the QByteArray so that it does not point
CFData's data that will get deallocated just after the call.

Task-number: QTBUG-58531
Change-Id: If829a304b986c99c8fc2aeeb992f2d539a4eef3a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Tor Arne Vestbø <tor.arne.vestbo@qt.io>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/corelib/io/qsettings_mac.cpp b/src/corelib/io/qsettings_mac.cpp
index b79abfb874..0e3520441e 100644
--- a/src/corelib/io/qsettings_mac.cpp
+++ b/src/corelib/io/qsettings_mac.cpp
@@ -269,8 +269,10 @@ static QVariant qtValue(CFPropertyListRef cfvalue)
 
         // Fast-path for QByteArray, so that we don't have to go
         // though the expensive and lossy conversion via UTF-8.
-        if (!byteArray.startsWith('@'))
+        if (!byteArray.startsWith('@')) {
+            byteArray.detach();
             return byteArray;
+        }
 
         const QString str = QString::fromUtf8(byteArray.constData(), byteArray.size());
         return QSettingsPrivate::stringToVariant(str);