Make taking a global lock automatically initialize locking if needed

This lets them be thread-safe by default, at the cost that they can
now fail.

init_uninitialized_locks() and init_global_locks() must now both
reimplement the equivalent of _dbus_register_shutdown_func(), by using
_dbus_platform_rmutex_lock() on the same underlying mutex around a call
to _dbus_register_shutdown_func_unlocked().

This is because if they used the usual _DBUS_LOCK() API (as
_dbus_register_shutdown_func() does), it would automatically try to
initialize global locking, leading to infinite recursion.

Bug: https://bugs.freedesktop.org/show_bug.cgi?id=54972
Signed-off-by: Simon McVittie <simon.mcvittie@collabora.co.uk>
Reviewed-by: Alban Crequy <alban.crequy@collabora.co.uk>
Reviewed-by: Anas Nashif <anas.nashif@intel.com>

1 files changed, 16 insertions, 4 deletions

diff --git a/dbus/dbus-userdb-util.c b/dbus/dbus-userdb-util.c
index 5af00922..38ea4ef0 100644
--- a/dbus/dbus-userdb-util.c
+++ b/dbus/dbus-userdb-util.c
@@ -104,7 +104,11 @@ _dbus_is_console_user (dbus_uid_t uid,
 
 #endif /* HAVE_CONSOLE_OWNER_FILE */
 
-  _dbus_user_database_lock_system ();
+  if (!_dbus_user_database_lock_system ())
+    {
+      _DBUS_SET_OOM (error);
+      return FALSE;
+    }
 
   db = _dbus_user_database_get_system ();
   if (db == NULL)
@@ -158,7 +162,10 @@ _dbus_get_group_id (const DBusString  *groupname,
 {
   DBusUserDatabase *db;
   const DBusGroupInfo *info;
-  _dbus_user_database_lock_system ();
+
+  /* FIXME: this can't distinguish ENOMEM from other errors */
+  if (!_dbus_user_database_lock_system ())
+    return FALSE;
 
   db = _dbus_user_database_get_system ();
   if (db == NULL)
@@ -195,7 +202,10 @@ _dbus_get_user_id_and_primary_group (const DBusString  *username,
 {
   DBusUserDatabase *db;
   const DBusUserInfo *info;
-  _dbus_user_database_lock_system ();
+
+  /* FIXME: this can't distinguish ENOMEM from other errors */
+  if (!_dbus_user_database_lock_system ())
+    return FALSE;
 
   db = _dbus_user_database_get_system ();
   if (db == NULL)
@@ -388,7 +398,9 @@ _dbus_groups_from_uid (dbus_uid_t         uid,
   *group_ids = NULL;
   *n_group_ids = 0;
 
-  _dbus_user_database_lock_system ();
+  /* FIXME: this can't distinguish ENOMEM from other errors */
+  if (!_dbus_user_database_lock_system ())
+    return FALSE;
 
   db = _dbus_user_database_get_system ();
   if (db == NULL)