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keep-alive: avoid race with with D-Bus client disconnecting early

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When we subscribe the signal fo NameOwnerChanged, we are not sure
that the name-owner is currently alive.

Issue a GetNameOwner call to make sure.

Co-authored-by: Thomas Haller <thaller@redhat.com>

Fixes: 37e8c53eee
This commit is contained in:
Benjamin Berg 2018-11-19 14:18:44 +01:00 • committed by Thomas Haller
parent 7420ae8314
commit 5fb24644a1
1 changed files with 54 additions and 2 deletions
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56
src/nm-keep-alive.c
View file

@ -38,6 +38,7 @@ typedef struct {
GDBusConnection *dbus_connection;
char *dbus_client;
GCancellable *dbus_client_confirm_cancellable;
guint subscription_id;
bool floating:1;
@ -65,6 +66,10 @@ G_DEFINE_TYPE (NMKeepAlive, nm_keep_alive, G_TYPE_OBJECT)
/*****************************************************************************/
static void cleanup_dbus_watch (NMKeepAlive *self);
/*****************************************************************************/
static gboolean
_is_alive (NMKeepAlive *self)
{
@ -174,6 +179,40 @@ nm_keep_alive_set_settings_connection_watch_visible (NMKeepAlive *self,
/*****************************************************************************/
static void
get_name_owner_cb (GObject *source_object,
GAsyncResult *res,
gpointer user_data)
{
NMKeepAlive *self = user_data;
NMKeepAlivePrivate *priv;
gs_free_error GError *error = NULL;
gs_unref_variant GVariant *result = NULL;
const char *name_owner;
result = g_dbus_connection_call_finish ((GDBusConnection *) source_object,
res,
&error);
if ( !result
&& g_error_matches (error, G_IO_ERROR, G_IO_ERROR_CANCELLED))
return;
if (result) {
g_variant_get (result, "(&s)", &name_owner);
priv = NM_KEEP_ALIVE_GET_PRIVATE (self);
if (nm_streq (name_owner, priv->dbus_client)) {
/* all good, the name is confirmed. */
return;
}
}
_LOGD ("DBus client for keep alive is not on the bus");
cleanup_dbus_watch (self);
_notify_alive (self);
}
static void
cleanup_dbus_watch (NMKeepAlive *self)
{
@ -184,6 +223,7 @@ cleanup_dbus_watch (NMKeepAlive *self)
_LOGD ("Cleanup DBus client watch");
nm_clear_g_cancellable (&priv->dbus_client_confirm_cancellable);
nm_clear_g_free (&priv->dbus_client);
if (priv->dbus_connection) {
g_dbus_connection_signal_unsubscribe (priv->dbus_connection,
@ -239,8 +279,20 @@ nm_keep_alive_set_dbus_client_watch (NMKeepAlive *self,
name_owner_changed_cb,
self,
NULL);
/* FIXME: is there are race here and is it possible that name-owner is already gone?
* Do we need a GetNameOwner first? */
priv->dbus_client_confirm_cancellable = g_cancellable_new ();
g_dbus_connection_call (priv->dbus_connection,
"org.freedesktop.DBus",
"/org/freedesktop/DBus",
"org.freedesktop.DBus",
"GetNameOwner",
g_variant_new ("(s)", priv->dbus_client),
G_VARIANT_TYPE ("(s)"),
G_DBUS_CALL_FLAGS_NONE,
-1,
priv->dbus_client_confirm_cancellable,
get_name_owner_cb,
self);
}
_notify_alive (self);