Fix crashes when accessing environment variables concurrently

We've seen crashes with QThreadPrivate::start using qgetenv during the creation
of the event dispatcher, while another thread (for example the gui thread)
called qputenv. This is inherently thread-unsafe and there are many places
where we make the assumption that using the environment is safe. However access
to the environment is inherently unsafe in the C runtime and the best that we
can do is add a mutex around the Qt environment access functions, to at least
protect ourselves and our users.

Change-Id: Ie9a718d9f7ce63c423c645f0be3e3f4933e1cb08
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Jørgen Lind <jorgen.lind@theqtcompany.com>

1 files changed, 3 insertions, 3 deletions

diff --git a/src/corelib/io/qsettings.cpp b/src/corelib/io/qsettings.cpp
index afe68125d4..cb6de29532 100644
--- a/src/corelib/io/qsettings.cpp
+++ b/src/corelib/io/qsettings.cpp
@@ -1048,12 +1048,12 @@ static void initDefaultPaths(QMutexLocker *locker)
         // Non XDG platforms (OS X, iOS, Blackberry, Android...) have used this code path erroneously
         // for some time now. Moving away from that would require migrating existing settings.
         QString userPath;
-        char *env = getenv("XDG_CONFIG_HOME");
-        if (env == 0) {
+        QByteArray env = qgetenv("XDG_CONFIG_HOME");
+        if (env.isEmpty()) {
             userPath = QDir::homePath();
             userPath += QLatin1Char('/');
             userPath += QLatin1String(".config");
-        } else if (*env == '/') {
+        } else if (env.startsWith('/')) {
             userPath = QFile::decodeName(env);
         } else {
             userPath = QDir::homePath();