[gnome-calendar/mcatanzaro/#434] Don't leave dangling pointers in the GcalEvent cache

[Michael Catanzaro <mcatanzaro src gnome org>]

commit 4ce65d295a00e9e6ffe18d858883b480a8ea4b63
Author: Michael Catanzaro <mcatanzaro igalia com>
Date:   Tue Jul 16 19:40:06 2019 -0500

    Don't leave dangling pointers in the GcalEvent cache
    
    The cache has an unowned pointer to the GcalEvent's UID. We need to
    update the cache with the GcalEvent's new UID to avoid use-after-free.
    
    Fixes #434

 src/core/gcal-event.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)
---
diff --git a/src/core/gcal-event.c b/src/core/gcal-event.c
index ef16bf04..ee6466dd 100644
--- a/src/core/gcal-event.c
+++ b/src/core/gcal-event.c
@@ -256,13 +256,19 @@ gcal_event_update_uid_internal (GcalEvent *self)
 {
   ECalComponentId *id;
   const gchar *source_id;
+  gboolean should_update_cache = FALSE;
 
   /* Setup event uid */
   source_id = self->calendar ? gcal_calendar_get_id (self->calendar) : "";
   id = e_cal_component_get_id (self->component);
 
-  /* Clear the previous uid */
-  g_clear_pointer (&self->uid, g_free);
+  if (self->uid != NULL)
+    {
+      should_update_cache = TRUE;
+      g_debug ("Removing '%s' (%p) from cache", self->uid, self);
+      g_hash_table_remove (event_cache, self->uid);
+      g_free (self->uid);
+    }
 
   if (e_cal_component_id_get_rid (id) != NULL)
     {
@@ -278,6 +284,12 @@ gcal_event_update_uid_internal (GcalEvent *self)
                                    e_cal_component_id_get_uid (id));
     }
 
+  if (should_update_cache)
+    {
+      g_debug ("Adding %s to the cache", self->uid);
+      g_hash_table_insert (event_cache, self->uid, self);
+    }
+
   e_cal_component_id_free (id);
   g_object_notify_by_pspec (G_OBJECT (self), properties[PROP_UID]);
 }