wifi: Don't access potentially invalid pointer

When the user launches Settings with a panel passed
as argument, the following things happen:

 1. The Wi-Fi panel starts loading.
 2. The command line arguments are passed and the given
    panel is activated.
 3. The Wi-Fi panel cancels the loading routine, and
    rfkill_proxy_acquired_cb() is called with the GError
    set as G_IO_ERROR_CANCELLED.
 4. Crash in rfkill_proxy_acquired_cb().

The crash is caused because, when rfkill_proxy_acquired_cb()
is called, the CcWifiPanel instance isn't valid anymore. And
yet, the code tries to cast 'gpointer user_data' to a
CcWifiPanel pointer.

Fix that by only trying to cast anything after parsing the
GError set by the callback.

1 files changed, 9 insertions, 3 deletions

diff --git a/panels/network/cc-wifi-panel.c b/panels/network/cc-wifi-panel.c
index f49993851..18ba1bac0 100644
--- a/panels/network/cc-wifi-panel.c
+++ b/panels/network/cc-wifi-panel.c
@@ -404,10 +404,12 @@ rfkill_proxy_acquired_cb (GObject      *source_object,
                           GAsyncResult *res,
                           gpointer      user_data)
 {
-  CcWifiPanel *self = CC_WIFI_PANEL (user_data);
-  GError *error = NULL;
+  CcWifiPanel *self;
+  GDBusProxy *proxy;
+  GError *error;
 
-  self->rfkill_proxy = g_dbus_proxy_new_for_bus_finish (res, &error);
+  error = NULL;
+  proxy = g_dbus_proxy_new_for_bus_finish (res, &error);
 
   if (error)
     {
@@ -418,6 +420,10 @@ rfkill_proxy_acquired_cb (GObject      *source_object,
       return;
     }
 
+  self = CC_WIFI_PANEL (user_data);
+
+  self->rfkill_proxy = proxy;
+
   sync_airplane_mode_switch (self);
 }