Re: [PATCH] mm: memcontrol: fix possible css ref leak on oom

[Johannes Weiner]

On Mon, May 23, 2016 at 07:02:10PM +0300, Vladimir Davydov wrote:
> mem_cgroup_oom may be invoked multiple times while a process is handling
> a page fault, in which case current->memcg_in_oom will be overwritten
> leaking the previously taken css reference.

There is a task_in_memcg_oom() check before calling mem_cgroup_oom().

How can this happen?