[gtk/gtk-3-24: 1/3] Fix GtkDragSourceInfo disposal

[Benjamin Otte <otte src gnome org>]

commit 5e00fd25da3014a3f8bb7698623abfbb55fda993
Author: Руслан Ижбулатов <lrn1986 gmail com>
Date:   Tue Oct 16 03:03:33 2018 +0000

    Fix GtkDragSourceInfo disposal
    
    gtk_drag_clear_source_info() immediately unrefs the info attached
    to the context (the very same info we're in the process of destroying
    in gtk_drag_source_info_free()). If that reference was the last one,
    then accessing the info object after that is a use-after-free error.
    Also, change the order a bit to first free the event, and only then
    unref the context.
    
    Fix this by copying all the fields of the info that we need, and
    then working with these copies.

 gtk/gtkdnd.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)
---
diff --git a/gtk/gtkdnd.c b/gtk/gtkdnd.c
index fca79b5d90..dd66413f5d 100644
--- a/gtk/gtkdnd.c
+++ b/gtk/gtkdnd.c
@@ -2768,6 +2768,9 @@ gtk_drag_source_info_free (GtkDragSourceInfo *info)
 static void
 gtk_drag_source_info_destroy (GtkDragSourceInfo *info)
 {
+  GdkDragContext *context;
+  GdkEvent       *last_event;
+
   g_signal_handlers_disconnect_by_func (info->context,
                                         gtk_drag_context_drop_performed_cb,
                                         info);
@@ -2820,12 +2823,15 @@ gtk_drag_source_info_destroy (GtkDragSourceInfo *info)
 
   /* keep the icon_window alive until the (possible) drag cancel animation is done */
   g_object_set_data_full (G_OBJECT (info->context), "former-gtk-source-info", info, 
(GDestroyNotify)gtk_drag_source_info_free);
+  context = info->context;
+  last_event = info->last_event;
 
-  gtk_drag_clear_source_info (info->context);
-  g_object_unref (info->context);
+  gtk_drag_clear_source_info (context);
 
-  if (info->last_event)
-    gdk_event_free (info->last_event);
+  if (last_event)
+    gdk_event_free (last_event);
+
+  g_object_unref (context);
 }
 
 static gboolean