+
+int cg_controller_from_attr(const char *attr, char **controller) {
+ const char *dot;
+ char *c;
+
+ assert(attr);
+ assert(controller);
+
+ if (!filename_is_safe(attr))
+ return -EINVAL;
+
+ dot = strchr(attr, '.');
+ if (!dot) {
+ *controller = NULL;
+ return 0;
+ }
+
+ c = strndup(attr, dot - attr);
+ if (!c)
+ return -ENOMEM;
+
+ if (!filename_is_safe(c)) {
+ free(c);
+ return -EINVAL;
+ }
+
+ *controller = c;
+ return 1;
+}