dbus: don't send cgroup agent messages directly to system bus to avoid dbus activation loop

2 files changed, 41 insertions, 30 deletions

diff --git a/src/cgroups-agent.c b/src/cgroups-agent.c
index 30aeede943..3fd0de698f 100644
--- a/src/cgroups-agent.c
+++ b/src/cgroups-agent.c
@@ -43,22 +43,20 @@ int main(int argc, char *argv[]) {
         log_parse_environment();
         log_open();
 
-        /* If possible we go via the system bus, to make sure that
-         * session instances get the messages. If not possible we talk
-         * to the system instance directly. */
-        if (!(bus = dbus_bus_get_private(DBUS_BUS_SYSTEM, &error))) {
-
-                dbus_error_free(&error);
-
-                if (!(bus = dbus_connection_open_private("unix:abstract=/org/freedesktop/systemd1/private", &error))) {
-                        log_error("Failed to get D-Bus connection: %s", bus_error_message(&error));
-                        goto finish;
-                }
-
-                if (bus_check_peercred(bus) < 0) {
-                        log_error("Bus owner not root.");
-                        goto finish;
-                }
+
+        /* We send this event to the private D-Bus socket and then the
+         * system instance will forward this to the system bus. We do
+         * this to avoid an actviation loop when we start dbus when we
+         * are called when the dbus service is shut down. */
+
+        if (!(bus = dbus_connection_open_private("unix:abstract=/org/freedesktop/systemd1/private", &error))) {
+                log_error("Failed to get D-Bus connection: %s", bus_error_message(&error));
+                goto finish;
+        }
+
+        if (bus_check_peercred(bus) < 0) {
+                log_error("Bus owner not root.");
+                goto finish;
         }
 
         if (!(m = dbus_message_new_signal("/org/freedesktop/systemd1/agent", "org.freedesktop.systemd1.Agent", "Released"))) {
@@ -74,7 +72,7 @@ int main(int argc, char *argv[]) {
         }
 
         if (!dbus_connection_send(bus, m, NULL)) {
-                log_error("Failed to send signal message.");
+                log_error("Failed to send signal message on private connection.");
                 goto finish;
         }
 
@@ -87,6 +85,7 @@ finish:
                 dbus_connection_unref(bus);
         }
 
+
         if (m)
                 dbus_message_unref(m);
 
diff --git a/src/dbus.c b/src/dbus.c
index 8c969eab63..85284324b3 100644
--- a/src/dbus.c
+++ b/src/dbus.c
@@ -464,7 +464,9 @@ static DBusHandlerResult system_bus_message_filter(DBusConnection *connection, D
                 log_debug("System D-Bus connection terminated.");
                 bus_done_system(m);
 
-        } else if (dbus_message_is_signal(message, "org.freedesktop.systemd1.Agent", "Released")) {
+        } else if (m->running_as != MANAGER_SYSTEM &&
+                   dbus_message_is_signal(message, "org.freedesktop.systemd1.Agent", "Released")) {
+
                 const char *cgroup;
 
                 if (!dbus_message_get_args(message, &error,
@@ -498,7 +500,9 @@ static DBusHandlerResult private_bus_message_filter(DBusConnection *connection,
 
         if (dbus_message_is_signal(message, DBUS_INTERFACE_LOCAL, "Disconnected"))
                 shutdown_connection(m, connection);
-        else if (dbus_message_is_signal(message, "org.freedesktop.systemd1.Agent", "Released")) {
+        else if (m->running_as == MANAGER_SYSTEM &&
+                 dbus_message_is_signal(message, "org.freedesktop.systemd1.Agent", "Released")) {
+
                 const char *cgroup;
 
                 if (!dbus_message_get_args(message, &error,
@@ -507,6 +511,12 @@ static DBusHandlerResult private_bus_message_filter(DBusConnection *connection,
                         log_error("Failed to parse Released message: %s", error.message);
                 else
                         cgroup_notify_empty(m, cgroup);
+
+                /* Forward the message to the system bus, so that user
+                 * instances are notified as well */
+
+                if (m->system_bus)
+                        dbus_connection_send(m->system_bus, message, NULL);
         }
 
         dbus_error_free(&error);
@@ -808,17 +818,19 @@ static int bus_init_system(Manager *m) {
                 goto fail;
         }
 
-        dbus_bus_add_match(m->system_bus,
-                           "type='signal',"
-                           "interface='org.freedesktop.systemd1.Agent',"
-                           "member='Released',"
-                           "path='/org/freedesktop/systemd1/agent'",
-                           &error);
-
-        if (dbus_error_is_set(&error)) {
-                log_error("Failed to register match: %s", error.message);
-                r = -EIO;
-                goto fail;
+        if (m->running_as != MANAGER_SYSTEM) {
+                dbus_bus_add_match(m->system_bus,
+                                   "type='signal',"
+                                   "interface='org.freedesktop.systemd1.Agent',"
+                                   "member='Released',"
+                                   "path='/org/freedesktop/systemd1/agent'",
+                                   &error);
+
+                if (dbus_error_is_set(&error)) {
+                        log_error("Failed to register match: %s", error.message);
+                        r = -EIO;
+                        goto fail;
+                }
         }
 
         if (m->api_bus != m->system_bus) {