logind: enforce a limit on inhibitors we hand out

For similar reasons as the recent addition of a limit on sessions.

Note that we don't enforce a limit on inhibitors per-user currently, but
there's an implicit one, since each inhibitor takes up one fd, and fds are
limited via RLIMIT_NOFILE, and the limit on the number of processes per user.

2 files changed, 24 insertions, 0 deletions

diff --git a/src/login/logind-dbus.c b/src/login/logind-dbus.c
index 1a49a3128..0a30dfd16 100644
--- a/src/login/logind-dbus.c
+++ b/src/login/logind-dbus.c
@@ -283,6 +283,24 @@ static int property_get_current_sessions(
         return sd_bus_message_append(reply, "t", (uint64_t) hashmap_size(m->sessions));
 }
 
+static int property_get_current_inhibitors(
+                sd_bus *bus,
+                const char *path,
+                const char *interface,
+                const char *property,
+                sd_bus_message *reply,
+                void *userdata,
+                sd_bus_error *error) {
+
+        Manager *m = userdata;
+
+        assert(bus);
+        assert(reply);
+        assert(m);
+
+        return sd_bus_message_append(reply, "t", (uint64_t) hashmap_size(m->inhibitors));
+}
+
 static int method_get_session(sd_bus_message *message, void *userdata, sd_bus_error *error) {
         _cleanup_free_ char *p = NULL;
         Manager *m = userdata;
@@ -2522,6 +2540,9 @@ static int method_inhibit(sd_bus_message *message, void *userdata, sd_bus_error
         if (r < 0)
                 return r;
 
+        if (hashmap_size(m->inhibitors) >= m->inhibitors_max)
+                return sd_bus_error_setf(error, SD_BUS_ERROR_LIMITS_EXCEEDED, "Maximum number of inhibitors (%" PRIu64 ") reached, refusing further inhibitors.", m->inhibitors_max);
+
         do {
                 id = mfree(id);
 
@@ -2594,6 +2615,8 @@ const sd_bus_vtable manager_vtable[] = {
         SD_BUS_PROPERTY("Docked", "b", property_get_docked, 0, 0),
         SD_BUS_PROPERTY("RemoveIPC", "b", bus_property_get_bool, offsetof(Manager, remove_ipc), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("RuntimeDirectorySize", "t", bus_property_get_size, offsetof(Manager, runtime_dir_size), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("InhibitorsMax", "t", NULL, offsetof(Manager, inhibitors_max), SD_BUS_VTABLE_PROPERTY_CONST),
+        SD_BUS_PROPERTY("NCurrentInhibitors", "t", property_get_current_inhibitors, 0, 0),
         SD_BUS_PROPERTY("SessionsMax", "t", NULL, offsetof(Manager, sessions_max), SD_BUS_VTABLE_PROPERTY_CONST),
         SD_BUS_PROPERTY("NCurrentSessions", "t", property_get_current_sessions, 0, 0),
         SD_BUS_PROPERTY("UserTasksMax", "t", NULL, offsetof(Manager, user_tasks_max), SD_BUS_VTABLE_PROPERTY_CONST),
diff --git a/src/login/logind.h b/src/login/logind.h
index 3a9ccb6e5..752d4e399 100644
--- a/src/login/logind.h
+++ b/src/login/logind.h
@@ -163,6 +163,7 @@ struct Manager {
         size_t runtime_dir_size;
         uint64_t user_tasks_max;
         uint64_t sessions_max;
+        uint64_t inhibitors_max;
 };
 
 int manager_add_device(Manager *m, const char *sysfs, bool master, Device **_device);