dbus-unit: always load the unit before handling a message for it

We need to be able to show the properties even of inactive units.
systemctl loads the unit before getting its properties, but this is racy
as the garbage collector may kick in right after the loading.

Fix it by always loading the unit before handling a message for it.

https://bugzilla.redhat.com/show_bug.cgi?id=814966#c6

3 files changed, 18 insertions, 19 deletions

diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index b8d661698b..834fbd7693 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -558,12 +558,15 @@ static DBusHandlerResult bus_unit_message_handler(DBusConnection *connection, DB
         Manager *m = data;
         Unit *u;
         int r;
-        DBusMessage *reply;
+        DBusMessage *reply = NULL;
+        DBusError error;
 
         assert(connection);
         assert(message);
         assert(m);
 
+        dbus_error_init(&error);
+
         if (streq(dbus_message_get_path(message), "/org/freedesktop/systemd1/unit")) {
                 /* Be nice to gdbus and return introspection data for our mid-level paths */
 
@@ -638,20 +641,12 @@ static DBusHandlerResult bus_unit_message_handler(DBusConnection *connection, DB
                 return DBUS_HANDLER_RESULT_NOT_YET_HANDLED;
         }
 
-        if ((r = manager_get_unit_from_dbus_path(m, dbus_message_get_path(message), &u)) < 0) {
-
+        r = manager_load_unit_from_dbus_path(m, dbus_message_get_path(message), &error, &u);
+        if (r < 0) {
                 if (r == -ENOMEM)
-                        return DBUS_HANDLER_RESULT_NEED_MEMORY;
-
-                if (r == -ENOENT) {
-                        DBusError e;
-
-                        dbus_error_init(&e);
-                        dbus_set_error_const(&e, DBUS_ERROR_UNKNOWN_OBJECT, "Unknown unit");
-                        return bus_send_error_reply(connection, message, &e, r);
-                }
+                        goto oom;
 
-                return bus_send_error_reply(connection, message, NULL, r);
+                return bus_send_error_reply(connection, message, &error, r);
         }
 
         return bus_unit_message_dispatch(u, connection, message);
@@ -660,6 +655,8 @@ oom:
         if (reply)
                 dbus_message_unref(reply);
 
+        dbus_error_free(&error);
+
         return DBUS_HANDLER_RESULT_NEED_MEMORY;
 }
 
diff --git a/src/core/manager.c b/src/core/manager.c
index bd86f89d53..f8fb8a23e7 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -1490,9 +1490,10 @@ int manager_loop(Manager *m) {
         return m->exit_code;
 }
 
-int manager_get_unit_from_dbus_path(Manager *m, const char *s, Unit **_u) {
+int manager_load_unit_from_dbus_path(Manager *m, const char *s, DBusError *e, Unit **_u) {
         char *n;
         Unit *u;
+        int r;
 
         assert(m);
         assert(s);
@@ -1501,14 +1502,15 @@ int manager_get_unit_from_dbus_path(Manager *m, const char *s, Unit **_u) {
         if (!startswith(s, "/org/freedesktop/systemd1/unit/"))
                 return -EINVAL;
 
-        if (!(n = bus_path_unescape(s+31)))
+        n = bus_path_unescape(s+31);
+        if (!n)
                 return -ENOMEM;
 
-        u = manager_get_unit(m, n);
+        r = manager_load_unit(m, n, NULL, e, &u);
         free(n);
 
-        if (!u)
-                return -ENOENT;
+        if (r < 0)
+                return r;
 
         *_u = u;
 
diff --git a/src/core/manager.h b/src/core/manager.h
index 92dc75db55..046540d896 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -249,11 +249,11 @@ int manager_startup(Manager *m, FILE *serialization, FDSet *fds);
 Job *manager_get_job(Manager *m, uint32_t id);
 Unit *manager_get_unit(Manager *m, const char *name);
 
-int manager_get_unit_from_dbus_path(Manager *m, const char *s, Unit **_u);
 int manager_get_job_from_dbus_path(Manager *m, const char *s, Job **_j);
 
 int manager_load_unit_prepare(Manager *m, const char *name, const char *path, DBusError *e, Unit **_ret);
 int manager_load_unit(Manager *m, const char *name, const char *path, DBusError *e, Unit **_ret);
+int manager_load_unit_from_dbus_path(Manager *m, const char *s, DBusError *e, Unit **_u);
 
 int manager_add_job(Manager *m, JobType type, Unit *unit, JobMode mode, bool force, DBusError *e, Job **_ret);
 int manager_add_job_by_name(Manager *m, JobType type, const char *name, JobMode mode, bool force, DBusError *e, Job **_ret);