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From: Tejun Heo <tj@kernel.org>
To: Zhang Qiao <zhangqiao22@huawei.com>
Cc: peterz@infradead.org, juri.lelli@redhat.com,
	linux-kernel@vger.kernel.org, mingo@redhat.com,
	vincent.guittot@linaro.org
Subject: Re: [PATCH] kernel/sched: Fix sched_fork() access an invalid sched_task_group
Date: Tue, 31 Aug 2021 12:59:27 -1000	[thread overview]
Message-ID: <YS60T2bfLpxb6SUY@slm.duckdns.org> (raw)
In-Reply-To: <1f0cd867-9c6d-4e22-cadd-06af9f852f7a@huawei.com>

Hello,

On Tue, Aug 31, 2021 at 03:58:42PM +0800, Zhang Qiao wrote:
> > I think this would allow cgroup migrations to take place before
> > sched_post_fork() is run, which likely will break stuff. The right
> > thing to do likely is taking sched_task_group (and whatever other
> > fields) after cgroup_can_fork(), which fixates the cgroup memberships,
>
> But it still seems possible that it accessed an invalid sched_task_group?
> because the child process does not update its sched_task_group util
> cgroup_post_fork().

Between cgroup_can_fork() and cgroup_post_fork(), the cgroup membership and
thus sched_task_group can't change, so if the child sets it to the parent's
inbetween, the sched_task_group can't go away.

Thanks.

-- 
tejun

  reply	other threads:[~2021-08-31 22:59 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26 11:26 Zhang Qiao
2021-08-30 11:49 ` Zhang Qiao
2021-08-30 14:39 ` Peter Zijlstra
2021-08-30 17:32   ` Tejun Heo
2021-08-31  7:58     ` Zhang Qiao
2021-08-31 22:59       ` Tejun Heo [this message]
2021-09-01  7:43         ` Zhang Qiao
2021-09-01 16:45           ` Tejun Heo
2021-09-02  7:42             ` Zhang Qiao
2021-09-07 17:01               ` Tejun Heo
2021-09-08 11:32                 ` Zhang Qiao
2021-09-08 16:29                   ` Tejun Heo
2021-09-09  9:45                     ` Zhang Qiao

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