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

[Zhang Qiao]

在 2021/9/14 2:01, Tejun Heo 写道:
> 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

Indeed is this, although I checked and tested it many times.

> 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.

Perhaps we can fix this bug at sched_post_fork(), which is executed between cgroup_can_fork()
and cgroup_post_fork(). Relocate the fectching of task_group and access it at sched_post_fork().

thanks.

> 
> Thanks.
>