libnm: avoid init_async NULL dereference on cancellable=0x0

  (gdb) run c add type bond
  Starting program: /usr/bin/nmcli c add type bond
  Got object file from memory but can't read symbols: File truncated.
  [Thread debugging using libthread_db enabled]
  Using host libthread_db library "/lib64/libthread_db.so.1".
  [New Thread 0x7ffff39b2700 (LWP 13042)]
  [New Thread 0x7fffec4bc700 (LWP 13043)]

  (process:13038): GLib-GObject-CRITICAL **: g_object_ref: assertion 'G_IS_OBJECT (object)' failed

  Program received signal SIGTRAP, Trace/breakpoint trap.
  g_logv (log_domain=0x7ffff5cda224 "GLib-GObject", log_level=G_LOG_LEVEL_CRITICAL, format=<optimized out>, args=args@entry=0x7fffffffd290) at gmessages.c:1046
  1046              g_private_set (&g_log_depth, GUINT_TO_POINTER (depth));
  (gdb) bt
  #0  0x00007ffff59b6c70 in g_logv (log_domain=0x7ffff5cda224 "GLib-GObject", log_level=G_LOG_LEVEL_CRITICAL, format=<optimized out>, args=args@entry=0x7fffffffd290) at gmessages.c:1046
  #1  0x00007ffff59b6eaf in g_log (log_domain=log_domain@entry=0x7ffff5cda224 "GLib-GObject", log_level=log_level@entry=G_LOG_LEVEL_CRITICAL, format=format@entry=0x7ffff5a25a9d "%s: assertion '%s' failed")
      at gmessages.c:1079
  #2  0x00007ffff59b6ee9 in g_return_if_fail_warning (log_domain=log_domain@entry=0x7ffff5cda224 "GLib-GObject", pretty_function=pretty_function@entry=0x7ffff5cdd6b3 <__FUNCTION__.13314> "g_object_ref", expression=expression@entry=0x7ffff5cdc388 "G_IS_OBJECT (object)") at gmessages.c:1088
  #3  0x00007ffff5cb39aa in g_object_ref (_object=_object@entry=0x0) at gobject.c:3041
  #4  0x00007ffff7ad5418 in _nm_dbus_new_connection_async (cancellable=0x0, callback=<optimized out>, user_data=<optimized out>) at nm-dbus-helpers.c:131
  #5  0x00007ffff7ae58f1 in handle_property_changed (synchronously=0, pi=0x5555558a9610, value=0x7fffe40138a0, property_name=<optimized out>, self=0x555555831980 [NMRemoteSettings]) at nm-object.c:1115
  #6  0x00007ffff7ae58f1 in handle_property_changed (self=self@entry=0x555555831980 [NMRemoteSettings], dbus_name=<optimized out>, value=<optimized out>, synchronously=synchronously@entry=0) at nm-object.c:1186
  #7  0x00007ffff7ae59cb in process_properties_changed (self=0x555555831980 [NMRemoteSettings], properties=<optimized out>, synchronously=0) at nm-object.c:1218
  #8  0x00007ffff7ae5a7a in property_proxy_signal (proxy=<optimized out>, sender_name=<optimized out>, signal_name=<optimized out>, parameters=<optimized out>, user_data=0x555555831980) at nm-object.c:1234
  #9  0x00007ffff4d34d60 in ffi_call_unix64 () at ../src/x86/unix64.S:76
  #10 0x00007ffff4d347d1 in ffi_call (cif=cif@entry=0x7fffffffd7e0, fn=<optimized out>, rvalue=0x7fffffffd740, avalue=avalue@entry=0x7fffffffd6c0) at ../src/x86/ffi64.c:525
  #15 0x00007ffff5cca2ef in <emit signal ??? on instance 0x555555881c10 [NMDBusSettingsProxy]> (instance=instance@entry=0x555555881c10, signal_id=<optimized out>, detail=detail@entry=0) at gsignal.c:3365
      #11 0x00007ffff5caf6f4 in g_cclosure_marshal_generic (closure=0x5555558aa400, return_gvalue=0x0, n_param_values=<optimized out>, param_values=<optimized out>, invocation_hint=<optimized out>, marshal_data=0x0) at gclosure.c:1448
      #12 0x00007ffff5caeed5 in g_closure_invoke (closure=0x5555558aa400, return_value=return_value@entry=0x0, n_param_values=4, param_values=param_values@entry=0x7fffffffda10, invocation_hint=invocation_hint@entry=0x7fffffffd9b0) at gclosure.c:768
      #13 0x00007ffff5cc1202 in signal_emit_unlocked_R (node=node@entry=0x555555819270, detail=detail@entry=0, instance=instance@entry=0x555555881c10, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7fffffffda10) at gsignal.c:3553
      #14 0x00007ffff5cca0c1 in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7fffffffdbd0) at gsignal.c:3309
  #16 0x00007ffff63d8bcc in on_signal_received (connection=<optimized out>, sender_name=0x0, object_path=<optimized out>, interface_name=<optimized out>, signal_name=0x7fffe40195b0 "PropertiesChanged", parameters=0x7fffe4031000, user_data=0x5555558a3f30) at gdbusproxy.c:917
  #17 0x00007ffff63c83b4 in emit_signal_instance_in_idle_cb (data=0x7fffe403a6d0) at gdbusconnection.c:3753
  #18 0x00007ffff59afb6b in g_main_context_dispatch (context=0x5555557eb530) at gmain.c:3064
  #19 0x00007ffff59afb6b in g_main_context_dispatch (context=context@entry=0x5555557eb530) at gmain.c:3663
  #20 0x00007ffff59aff08 in g_main_context_iterate (context=0x5555557eb530, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3734
  #21 0x00007ffff59b0232 in g_main_loop_run (loop=0x5555557e3440) at gmain.c:3928
  #22 0x000055555556fd57 in main (argc=<optimized out>, argv=<optimized out>) at nmcli.c:587
  (gdb)

https://bugzilla.gnome.org/show_bug.cgi?id=736962

1 files changed, 4 insertions, 2 deletions

diff --git a/libnm/nm-dbus-helpers.c b/libnm/nm-dbus-helpers.c
index 0d8e0f2be6..fcbbc490df 100644
--- a/libnm/nm-dbus-helpers.c
+++ b/libnm/nm-dbus-helpers.c
@@ -128,8 +128,10 @@ _nm_dbus_new_connection_async (GCancellable *cancellable,
 
 	/* If running as root try the private bus first */
 	if (0 == geteuid ()) {
-		g_object_set_data_full (G_OBJECT (simple), "cancellable",
-		                        g_object_ref (cancellable), g_object_unref);
+		if (cancellable) {
+			g_object_set_data_full (G_OBJECT (simple), "cancellable",
+						g_object_ref (cancellable), g_object_unref);
+		}
 		g_dbus_connection_new_for_address ("unix:path=" NMRUNDIR "/private",
 		                                   G_DBUS_CONNECTION_FLAGS_AUTHENTICATION_CLIENT,
 		                                   NULL,