4 files changed, 16 insertions, 3 deletions
diff --git a/src/plugins/platforms/xcb/qxcbclipboard.cpp b/src/plugins/platforms/xcb/qxcbclipboard.cpp
index cee011bbdf..a293066b93 100644
--- a/src/plugins/platforms/xcb/qxcbclipboard.cpp
+++ b/src/plugins/platforms/xcb/qxcbclipboard.cpp
@@ -607,7 +607,7 @@ void QXcbClipboard::handleSelectionRequest(xcb_selection_request_event_t *req)
         return;
     }
 
-    xcb_selection_notify_event_t event;
+    Q_DECLARE_XCB_EVENT(event, xcb_selection_notify_event_t);
     event.response_type = XCB_SELECTION_NOTIFY;
     event.requestor = req->requestor;
     event.selection = req->selection;
diff --git a/src/plugins/platforms/xcb/qxcbconnection.h b/src/plugins/platforms/xcb/qxcbconnection.h
index a9208ffe09..01a97a187a 100644
--- a/src/plugins/platforms/xcb/qxcbconnection.h
+++ b/src/plugins/platforms/xcb/qxcbconnection.h
@@ -734,6 +734,19 @@ private:
     QXcbConnection *m_connection;
 };
 
+template <typename T>
+union q_padded_xcb_event {
+  T event;
+  char padding[32];
+};
+
+// The xcb_send_event() requires all events to have 32 bytes. It calls memcpy() on the
+// passed in event. If the passed in event is less than 32 bytes, memcpy() reaches into
+// unrelated memory.
+#define Q_DECLARE_XCB_EVENT(event_var, event_type) \
+    q_padded_xcb_event<event_type> store = {}; \
+    auto &event_var = store.event;
+
 #ifdef Q_XCB_DEBUG
 template <typename cookie_t>
 cookie_t q_xcb_call_template(const cookie_t &cookie, QXcbConnection *connection, const char *file,
diff --git a/src/plugins/platforms/xcb/qxcbdrag.cpp b/src/plugins/platforms/xcb/qxcbdrag.cpp
index 58fb1f3918..60d142157f 100644
--- a/src/plugins/platforms/xcb/qxcbdrag.cpp
+++ b/src/plugins/platforms/xcb/qxcbdrag.cpp
@@ -1163,7 +1163,7 @@ static xcb_window_t findXdndAwareParent(QXcbConnection *c, xcb_window_t window)
 
 void QXcbDrag::handleSelectionRequest(const xcb_selection_request_event_t *event)
 {
-    xcb_selection_notify_event_t notify;
+    Q_DECLARE_XCB_EVENT(notify, xcb_selection_notify_event_t);
     notify.response_type = XCB_SELECTION_NOTIFY;
     notify.requestor = event->requestor;
     notify.selection = event->selection;
diff --git a/src/plugins/platforms/xcb/qxcbwindow.cpp b/src/plugins/platforms/xcb/qxcbwindow.cpp
index ffbe9a2325..78d000c774 100644
--- a/src/plugins/platforms/xcb/qxcbwindow.cpp
+++ b/src/plugins/platforms/xcb/qxcbwindow.cpp
@@ -864,7 +864,7 @@ void QXcbWindow::hide()
     Q_XCB_CALL(xcb_unmap_window(xcb_connection(), m_window));
 
     // send synthetic UnmapNotify event according to icccm 4.1.4
-    xcb_unmap_notify_event_t event;
+    Q_DECLARE_XCB_EVENT(event, xcb_unmap_notify_event_t);
     event.response_type = XCB_UNMAP_NOTIFY;
     event.event = xcbScreen()->root();
     event.window = m_window;