[PATCH 4.14 014/118] cgroup: fix css_task_iter crash on CSS_TASK_ITER_PROC

4.14-stable review patch. If anyone has any objections, please let me know. -- From: Tejun Heo commit 74d0833c659a8a54735e5efdd44f4b225af68586 upstream. While teaching css_task_iter to handle skipping over tasks which aren't group leaders, bc2fb7ed089f

[PATCH 4.14 014/118] cgroup: fix css_task_iter crash on CSS_TASK_ITER_PROC

4.14-stable review patch. If anyone has any objections, please let me know. -- From: Tejun Heo commit 74d0833c659a8a54735e5efdd44f4b225af68586 upstream. While teaching css_task_iter to handle skipping over tasks which aren't group leaders, bc2fb7ed089f ("cgroup: add @flags to