Xi: fix potential use-after-free in DeepCopyPointerClasses

CVE-2023-0494, ZDI-CAN-19596

This vulnerability was discovered by:
Jan-Niklas Sohn working with Trend Micro Zero Day Initiative

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
(cherry picked from commit 0ba6d8c37071131a49790243cdac55392ecf71ec)

1 files changed, 3 insertions, 1 deletions

diff --git a/Xi/exevents.c b/Xi/exevents.c
index 217baa956..dcd4efb3b 100644
--- a/Xi/exevents.c
+++ b/Xi/exevents.c
@@ -619,8 +619,10 @@ DeepCopyPointerClasses(DeviceIntPtr from, DeviceIntPtr to)
             memcpy(to->button->xkb_acts, from->button->xkb_acts,
                    sizeof(XkbAction));
         }
-        else
+        else {
             free(to->button->xkb_acts);
+            to->button->xkb_acts = NULL;
+        }
 
         memcpy(to->button->labels, from->button->labels,
                from->button->numButtons * sizeof(Atom));