Re: [PATCH v2] kernel/sched: Fix sched_fork() access an invalid sched_task_group

[Tejun Heo]

Hello,

On Sat, Sep 11, 2021 at 03:50:54PM +0800, Zhang Qiao wrote:
> Between cgroup_can_fork() and cgroup_post_fork(), the cgroup
> membership is fixed and thus sched_task_group can't change. So
> call sched_fork() after cgroup_can_fork() and update the child's
> sched_task_group before it is used.

The part being fixed looks correct to me but it's difficult to for me to
assess whether the whole relocation of the sched_fork() hook doesn't change
anything else. Besides, even if we decide to relocate the sched_fork hook, I
think it'd be better to separate the two changes - one is a relatively safe
bug fix, the other is a code reorganization with possibly subtle side
effects. So, I think it'd be better to produce a patch which just fixes the
bug even if that ends up introducing another function in the flow.

Thanks.

-- 
tejun