xkbinfo: only insert new layouts, skip over duplicate ones

This matches the behavior to the one in the old code path before
libxkbregistry.

This also fixes a use-after-free bug when a duplicate layout is present. The
same layout struct is a member of multiple hashtables, specifically
priv->layouts_table, priv->layouts_by_language and  priv->layouts_by_country.

When the duplicate layout is added, add_layouts calls g_hash_table_replace
(priv->layouts_table, l->id, l) which frees the original layout - but the
layouts_by_{country|language} still have that now-freed layout.
Immediately afterwards, add_layouts calls add_layout_to_locale_tables () which
calls add_layout_to_table () which triggers a use-after-free.

Avoid all this by simply skipping any duplicate layout.

Reproducible with
  gsettings set org.gnome.desktop.input-sources show-all-sources true
  valgrind /usr/libexec/gnome-desktop-debug/test-xkb-info

Requires xkeyboard-config <= 2.32, it has a duplicate cm(mmuock) entry
(one is marked exotic, hence the need for show-all-sources).

Fixes #190

Bug analysis by Barnabás Pőcze (@pobrn)

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

1 files changed, 6 insertions, 0 deletions

diff --git a/libgnome-desktop/gnome-xkb-info.c b/libgnome-desktop/gnome-xkb-info.c
index b2eca699..f2a3214b 100644
--- a/libgnome-desktop/gnome-xkb-info.c
+++ b/libgnome-desktop/gnome-xkb-info.c
@@ -268,6 +268,12 @@ add_layouts (GnomeXkbInfo        *self,
           l->iso3166Ids = g_slist_prepend (l->iso3166Ids, id);
         }
 
+      if (g_hash_table_contains (priv->layouts_table, l->id))
+        {
+          g_clear_pointer (&l, free_layout);
+          return;
+        }
+
       g_hash_table_replace (priv->layouts_table, l->id, l);
       add_layout_to_locale_tables (l,
                                    priv->layouts_by_language,