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

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Message-ID: <20160527173629.GE2531@cmpxchg.org>
Date:	Fri, 27 May 2016 13:36:29 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Michal Hocko <mhocko@...nel.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: memcontrol: fix possible css ref leak on oom

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?