linux-kernel - Re: [PATCH cgroup/for-4.4] cgroup: fix race condition around termination check in css_task_iter

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Message-ID: <20151029030217.GC27115@mtj.duckdns.org>
Date:	Thu, 29 Oct 2015 12:02:17 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Li Zefan <lizefan@...wei.com>, Johannes Weiner <hannes@...xchg.org>
Cc:	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	Calvin Owens <calvinowens@...com>, kernel-team@...com
Subject: Re: [PATCH cgroup/for-4.4] cgroup: fix race condition around
 termination check in css_task_iter_next()

On Tue, Oct 27, 2015 at 05:45:04PM +0900, Tejun Heo wrote:
> css_task_iter_next() checked @it->cur_task before grabbing
> css_set_lock and assumed that the result won't change afterwards;
> however, tasks could leave the cgroup being iterated terminating the
> iterator before css_task_lock is acquired.  If this happens,
> css_task_iter_next() tries to calculate the current task from NULL
> cg_list pointer leading to the following oops.

Applied to cgroup/for-4.4.  Thanks.

-- 
tejun
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