Lock X display while calling XESetWireToEvent and its callback.

Prevent potential race conditions as suggested by Uli Schlachter.

Change-Id: Ia93eb8be1cbbc3d8ae7913a934c195af6b5ec538
Reviewed-by: Jørgen Lind <jorgen.lind@nokia.com>
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Uli Schlachter <psychon@znc.in>

1 files changed, 7 insertions, 3 deletions

diff --git a/src/plugins/platforms/xcb/qxcbconnection.cpp b/src/plugins/platforms/xcb/qxcbconnection.cpp
index ed995fd8cd..8501af15d3 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.cpp
+++ b/src/plugins/platforms/xcb/qxcbconnection.cpp
@@ -570,13 +570,17 @@ void QXcbConnection::handleXcbEvent(xcb_generic_event_t *event)
     if (!handled) {
         // Check if a custom XEvent constructor was registered in xlib for this event type, and call it discarding the constructed XEvent if any.
         // XESetWireToEvent might be used by libraries to intercept messages from the X server e.g. the OpenGL lib waiting for DRI2 events.
-        Bool (*proc)(Display*, XEvent*, xEvent*) = XESetWireToEvent((Display*)m_xlib_display, response_type, 0);
+
+        Display *xdisplay = (Display *)m_xlib_display;
+        XLockDisplay(xdisplay);
+        Bool (*proc)(Display*, XEvent*, xEvent*) = XESetWireToEvent(xdisplay, response_type, 0);
         if (proc) {
-            XESetWireToEvent((Display*)m_xlib_display, response_type, proc);
+            XESetWireToEvent(xdisplay, response_type, proc);
             XEvent dummy;
             event->sequence = LastKnownRequestProcessed(m_xlib_display);
-            proc((Display*)m_xlib_display, &dummy, (xEvent*)event);
+            proc(xdisplay, &dummy, (xEvent*)event);
         }
+        XUnlockDisplay(xdisplay);
     }
 #endif