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Merge branch '2400-dbus-race' into 'main'

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gdbusconnection: Fix race between method calls and object unregistration

Closes #2400

See merge request GNOME/glib!2265
This commit is contained in:
Philip Withnall 2021-11-01 18:37:17 +00:00
commit 726c44c348
2 changed files with 306 additions and 53 deletions
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179
gio/gdbusconnection.c
View File

@ -466,7 +466,8 @@ typedef struct ExportedObject ExportedObject;
static void exported_object_free (ExportedObject *eo);
typedef struct ExportedSubtree ExportedSubtree;
static void exported_subtree_free (ExportedSubtree *es);
static ExportedSubtree *exported_subtree_ref (ExportedSubtree *es);
static void exported_subtree_unref (ExportedSubtree *es);
enum
{
@ -1096,7 +1097,7 @@ g_dbus_connection_init (GDBusConnection *connection)
connection->map_object_path_to_es = g_hash_table_new_full (g_str_hash,
g_str_equal,
NULL,
(GDestroyNotify) exported_subtree_free);
(GDestroyNotify) exported_subtree_unref);
connection->map_id_to_es = g_hash_table_new (g_direct_hash,
g_direct_equal);
@ -4085,23 +4086,39 @@ typedef struct
{
ExportedObject *eo;
guint id;
gchar *interface_name;
GDBusInterfaceVTable *vtable;
GDBusInterfaceInfo *interface_info;
gint refcount; /* (atomic) */
GMainContext *context;
guint id;
gchar *interface_name; /* (owned) */
GDBusInterfaceVTable *vtable; /* (owned) */
GDBusInterfaceInfo *interface_info; /* (owned) */
GMainContext *context; /* (owned) */
gpointer user_data;
GDestroyNotify user_data_free_func;
} ExportedInterface;
/* called with lock held */
static void
exported_interface_free (ExportedInterface *ei)
static ExportedInterface *
exported_interface_ref (ExportedInterface *ei)
{
g_atomic_int_inc (&ei->refcount);
return ei;
}
/* May be called with lock held */
static void
exported_interface_unref (ExportedInterface *ei)
{
if (!g_atomic_int_dec_and_test (&ei->refcount))
return;
g_dbus_interface_info_cache_release (ei->interface_info);
g_dbus_interface_info_unref ((GDBusInterfaceInfo *) ei->interface_info);
/* All uses of ei->vtable from callbacks scheduled in idle functions must
* have completed by this call_destroy_notify() call, as language bindings
* may destroy function closures in this callback. */
call_destroy_notify (ei->context,
ei->user_data_free_func,
ei->user_data);
@ -4113,36 +4130,95 @@ exported_interface_free (ExportedInterface *ei)
g_free (ei);
}
struct ExportedSubtree
{
gint refcount; /* (atomic) */
guint id;
gchar *object_path; /* (owned) */
GDBusConnection *connection; /* (unowned) */
GDBusSubtreeVTable *vtable; /* (owned) */
GDBusSubtreeFlags flags;
GMainContext *context; /* (owned) */
gpointer user_data;
GDestroyNotify user_data_free_func;
};
static ExportedSubtree *
exported_subtree_ref (ExportedSubtree *es)
{
g_atomic_int_inc (&es->refcount);
return es;
}
/* May be called with lock held */
static void
exported_subtree_unref (ExportedSubtree *es)
{
if (!g_atomic_int_dec_and_test (&es->refcount))
return;
/* All uses of es->vtable from callbacks scheduled in idle functions must
* have completed by this call_destroy_notify() call, as language bindings
* may destroy function closures in this callback. */
call_destroy_notify (es->context,
es->user_data_free_func,
es->user_data);
g_main_context_unref (es->context);
_g_dbus_subtree_vtable_free (es->vtable);
g_free (es->object_path);
g_free (es);
}
/* ---------------------------------------------------------------------------------------------------- */
/* Convenience function to check if @registration_id (if not zero) or
* @subtree_registration_id (if not zero) has been unregistered. If
* so, returns %TRUE.
*
* If not, sets @out_ei and/or @out_es to a strong reference to the relevant
* #ExportedInterface/#ExportedSubtree and returns %FALSE.
*
* May be called by any thread. Caller must *not* hold lock.
*/
static gboolean
has_object_been_unregistered (GDBusConnection *connection,
guint registration_id,
guint subtree_registration_id)
has_object_been_unregistered (GDBusConnection *connection,
guint registration_id,
ExportedInterface **out_ei,
guint subtree_registration_id,
ExportedSubtree **out_es)
{
gboolean ret;
ExportedInterface *ei = NULL;
gpointer es = NULL;
g_return_val_if_fail (G_IS_DBUS_CONNECTION (connection), FALSE);
ret = FALSE;
CONNECTION_LOCK (connection);
if (registration_id != 0 && g_hash_table_lookup (connection->map_id_to_ei,
GUINT_TO_POINTER (registration_id)) == NULL)
if (registration_id != 0)
{
ret = TRUE;
ei = g_hash_table_lookup (connection->map_id_to_ei, GUINT_TO_POINTER (registration_id));
if (ei == NULL)
ret = TRUE;
else if (out_ei != NULL)
*out_ei = exported_interface_ref (ei);
}
else if (subtree_registration_id != 0 && g_hash_table_lookup (connection->map_id_to_es,
GUINT_TO_POINTER (subtree_registration_id)) == NULL)
if (subtree_registration_id != 0)
{
ret = TRUE;
es = g_hash_table_lookup (connection->map_id_to_es, GUINT_TO_POINTER (subtree_registration_id));
if (es == NULL)
ret = TRUE;
else if (out_es != NULL)
*out_es = exported_subtree_ref (es);
}
CONNECTION_UNLOCK (connection);
return ret;
@ -4179,10 +4255,14 @@ invoke_get_property_in_idle_cb (gpointer _data)
GVariant *value;
GError *error;
GDBusMessage *reply;
ExportedInterface *ei = NULL;
ExportedSubtree *es = NULL;
if (has_object_been_unregistered (data->connection,
data->registration_id,
data->subtree_registration_id))
&ei,
data->subtree_registration_id,
&es))
{
reply = g_dbus_message_new_method_error (data->message,
"org.freedesktop.DBus.Error.UnknownMethod",
@ -4229,6 +4309,9 @@ invoke_get_property_in_idle_cb (gpointer _data)
}
out:
g_clear_pointer (&ei, exported_interface_unref);
g_clear_pointer (&es, exported_subtree_unref);
return FALSE;
}
@ -4526,10 +4609,14 @@ invoke_get_all_properties_in_idle_cb (gpointer _data)
GVariantBuilder builder;
GDBusMessage *reply;
guint n;
ExportedInterface *ei = NULL;
ExportedSubtree *es = NULL;
if (has_object_been_unregistered (data->connection,
data->registration_id,
data->subtree_registration_id))
&ei,
data->subtree_registration_id,
&es))
{
reply = g_dbus_message_new_method_error (data->message,
"org.freedesktop.DBus.Error.UnknownMethod",
@ -4582,6 +4669,9 @@ invoke_get_all_properties_in_idle_cb (gpointer _data)
g_object_unref (reply);
out:
g_clear_pointer (&ei, exported_interface_unref);
g_clear_pointer (&es, exported_subtree_unref);
return FALSE;
}
@ -4891,13 +4981,17 @@ call_in_idle_cb (gpointer user_data)
GDBusInterfaceVTable *vtable;
guint registration_id;
guint subtree_registration_id;
ExportedInterface *ei = NULL;
ExportedSubtree *es = NULL;
registration_id = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (invocation), "g-dbus-registration-id"));
subtree_registration_id = GPOINTER_TO_UINT (g_object_get_data (G_OBJECT (invocation), "g-dbus-subtree-registration-id"));
if (has_object_been_unregistered (g_dbus_method_invocation_get_connection (invocation),
registration_id,
subtree_registration_id))
&ei,
subtree_registration_id,
&es))
{
GDBusMessage *reply;
reply = g_dbus_message_new_method_error (g_dbus_method_invocation_get_message (invocation),
@ -4923,6 +5017,9 @@ call_in_idle_cb (gpointer user_data)
g_dbus_method_invocation_get_user_data (invocation));
out:
g_clear_pointer (&ei, exported_interface_unref);
g_clear_pointer (&es, exported_subtree_unref);
return FALSE;
}
@ -5224,7 +5321,7 @@ g_dbus_connection_register_object (GDBusConnection *connection,
eo->map_if_name_to_ei = g_hash_table_new_full (g_str_hash,
g_str_equal,
NULL,
(GDestroyNotify) exported_interface_free);
(GDestroyNotify) exported_interface_unref);
g_hash_table_insert (connection->map_object_path_to_eo, eo->object_path, eo);
}
@ -5241,6 +5338,7 @@ g_dbus_connection_register_object (GDBusConnection *connection,
}
ei = g_new0 (ExportedInterface, 1);
ei->refcount = 1;
ei->id = (guint) g_atomic_int_add (&_global_registration_id, 1); /* TODO: overflow etc. */
ei->eo = eo;
ei->user_data = user_data;
@ -6401,33 +6499,6 @@ g_dbus_connection_call_with_unix_fd_list_sync (GDBusConnection *connection,
/* ---------------------------------------------------------------------------------------------------- */
struct ExportedSubtree
{
guint id;
gchar *object_path;
GDBusConnection *connection;
GDBusSubtreeVTable *vtable;
GDBusSubtreeFlags flags;
GMainContext *context;
gpointer user_data;
GDestroyNotify user_data_free_func;
};
static void
exported_subtree_free (ExportedSubtree *es)
{
call_destroy_notify (es->context,
es->user_data_free_func,
es->user_data);
g_main_context_unref (es->context);
_g_dbus_subtree_vtable_free (es->vtable);
g_free (es->object_path);
g_free (es);
}
/* called without lock held in the thread where the caller registered
* the subtree
*/
@ -6753,14 +6824,15 @@ handle_subtree_method_invocation (GDBusConnection *connection,
typedef struct
{
GDBusMessage *message;
ExportedSubtree *es;
GDBusMessage *message; /* (owned) */
ExportedSubtree *es; /* (owned) */
} SubtreeDeferredData;
static void
subtree_deferred_data_free (SubtreeDeferredData *data)
{
g_object_unref (data->message);
exported_subtree_unref (data->es);
g_free (data);
}
@ -6819,7 +6891,7 @@ subtree_message_func (GDBusConnection *connection,
data = g_new0 (SubtreeDeferredData, 1);
data->message = g_object_ref (message);
data->es = es;
data->es = exported_subtree_ref (es);
/* defer this call to an idle handler in the right thread */
idle_source = g_idle_source_new ();
@ -6924,6 +6996,7 @@ g_dbus_connection_register_subtree (GDBusConnection *connection,
}
es = g_new0 (ExportedSubtree, 1);
es->refcount = 1;
es->object_path = g_strdup (object_path);
es->connection = connection;

180
gio/tests/gdbus-export.c
View File

@ -1792,6 +1792,184 @@ test_async_properties (void)
g_object_unref (c);
}
typedef struct
{
GDBusConnection *connection; /* (owned) */
guint registration_id;
guint subtree_registration_id;
} ThreadedUnregistrationData;
static gpointer
unregister_thread_cb (gpointer user_data)
{
ThreadedUnregistrationData *data = user_data;
/* Sleeping here makes the race more likely to be hit, as it balances the
* time taken to set up the thread and unregister, with the time taken to
* make and handle the D-Bus call. This will likely change with future kernel
* versions, but there isn’t a more deterministic synchronisation point that
* I can think of to use instead. */
usleep (330);
if (data->registration_id > 0)
g_assert_true (g_dbus_connection_unregister_object (data->connection, data->registration_id));
if (data->subtree_registration_id > 0)
g_assert_true (g_dbus_connection_unregister_subtree (data->connection, data->subtree_registration_id));
return NULL;
}
static void
async_result_cb (GObject *source_object,
GAsyncResult *result,
gpointer user_data)
{
GAsyncResult **result_out = user_data;
*result_out = g_object_ref (result);
g_main_context_wakeup (NULL);
}
/* Returns %TRUE if this iteration resolved the race with the unregistration
* first, %FALSE if the call handler was invoked first. */
static gboolean
test_threaded_unregistration_iteration (gboolean subtree)
{
ThreadedUnregistrationData data = { NULL, 0, 0 };
ObjectRegistrationData object_registration_data = { 0, 0, 2 };
GError *local_error = NULL;
GThread *unregister_thread = NULL;
const gchar *object_path;
GVariant *value = NULL;
const gchar *value_str;
GAsyncResult *call_result = NULL;
gboolean unregistration_was_first;
data.connection = g_bus_get_sync (G_BUS_TYPE_SESSION, NULL, &local_error);
g_assert_no_error (local_error);
g_assert_nonnull (data.connection);
/* Register an object or a subtree */
if (!subtree)
{
data.registration_id = g_dbus_connection_register_object (data.connection,
"/foo/boss",
(GDBusInterfaceInfo *) &foo_interface_info,
&foo_vtable,
&object_registration_data,
on_object_unregistered,
&local_error);
g_assert_no_error (local_error);
g_assert_cmpint (data.registration_id, >, 0);
object_path = "/foo/boss";
}
else
{
data.subtree_registration_id = g_dbus_connection_register_subtree (data.connection,
"/foo/boss/executives",
&subtree_vtable,
G_DBUS_SUBTREE_FLAGS_NONE,
&object_registration_data,
on_subtree_unregistered,
&local_error);
g_assert_no_error (local_error);
g_assert_cmpint (data.subtree_registration_id, >, 0);
object_path = "/foo/boss/executives/vp0";
}
/* Allow the registrations to go through. */
g_main_context_iteration (NULL, FALSE);
/* Spawn a thread to unregister the object/subtree. This will race with
* the call we subsequently make. */
unregister_thread = g_thread_new ("unregister-object",
unregister_thread_cb, &data);
/* Call a method on the object (or an object in the subtree). The callback
* will be invoked in this main context. */
g_dbus_connection_call (data.connection,
g_dbus_connection_get_unique_name (data.connection),
object_path,
"org.example.Foo",
"Method1",
g_variant_new ("(s)", "winwinwin"),
NULL,
G_DBUS_CALL_FLAGS_NONE,
-1,
NULL,
async_result_cb,
&call_result);
while (call_result == NULL)
g_main_context_iteration (NULL, TRUE);
value = g_dbus_connection_call_finish (data.connection, call_result, &local_error);
/* The result of the method could either be an error (that the object doesn’t
* exist) or a valid result, depending on how the thread was scheduled
* relative to the call. */
unregistration_was_first = (value == NULL);
if (value != NULL)
{
g_assert_no_error (local_error);
g_assert_true (g_variant_is_of_type (value, G_VARIANT_TYPE ("(s)")));
g_variant_get (value, "(&s)", &value_str);
g_assert_cmpstr (value_str, ==, "You passed the string 'winwinwin'. Jolly good!");
}
else
{
g_assert_null (value);
g_assert_error (local_error, G_DBUS_ERROR, G_DBUS_ERROR_UNKNOWN_METHOD);
}
g_clear_pointer (&value, g_variant_unref);
g_clear_error (&local_error);
/* Tidy up. */
g_thread_join (g_steal_pointer (&unregister_thread));
g_clear_object (&call_result);
g_clear_object (&data.connection);
return unregistration_was_first;
}
static void
test_threaded_unregistration (gconstpointer test_data)
{
gboolean subtree = GPOINTER_TO_INT (test_data);
guint i;
guint n_iterations_unregistration_first = 0;
guint n_iterations_call_first = 0;
g_test_bug ("https://gitlab.gnome.org/GNOME/glib/-/issues/2400");
g_test_summary ("Test that object/subtree unregistration from one thread "
"doesn’t cause problems when racing with method callbacks "
"in another thread for that object or subtree");
/* Run iterations of the test until it’s likely we’ve hit the race. Limit the
* number of iterations so the test doesn’t run forever if not. The choice of
* 100 is arbitrary. */
for (i = 0; i < 1000 && (n_iterations_unregistration_first < 100 || n_iterations_call_first < 100); i++)
{
if (test_threaded_unregistration_iteration (subtree))
n_iterations_unregistration_first++;
else
n_iterations_call_first++;
}
/* If the condition below is met, we probably failed to reproduce the race.
* Don’t fail the test, though, as we can’t always control whether we hit the
* race, and spurious test failures are annoying. */
if (n_iterations_unregistration_first < 100 ||
n_iterations_call_first < 100)
g_test_skip_printf ("Failed to reproduce race (%u iterations with unregistration first, %u with call first); skipping test",
n_iterations_unregistration_first, n_iterations_call_first);
}
/* ---------------------------------------------------------------------------------------------------- */
int
@ -1809,6 +1987,8 @@ main (int argc,
g_test_add_func ("/gdbus/object-registration-with-closures", test_object_registration_with_closures);
g_test_add_func ("/gdbus/registered-interfaces", test_registered_interfaces);
g_test_add_func ("/gdbus/async-properties", test_async_properties);
g_test_add_data_func ("/gdbus/threaded-unregistration/object", GINT_TO_POINTER (FALSE), test_threaded_unregistration);
g_test_add_data_func ("/gdbus/threaded-unregistration/subtree", GINT_TO_POINTER (TRUE), test_threaded_unregistration);
/* TODO: check that we spit out correct introspection data */
/* TODO: check that registering a whole subtree works */