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SubjectRe: sched: fair: NULL ptr deref in check_preempt_wakeup
On Mon, Feb 17, 2014 at 04:11:09PM +0800, Michael wang wrote:
> > While fuzzing with trinity inside a KVM tools guest running latest -next
> > kernel, I've
> > stumbled on the following:
>
> I've reproduced the same issue with tip/master, and below patch fixed the
> problem on my box along with some rcu stall info disappeared, would you
> like to have a try?
>
> BTW, I reproduced it by steps:
> 1. change current to RT
> 2. move to a different depth cpu-cgroup
> 3. change it back to FAIR
>
> Seems like it was caused by that RT has no task_move_group() implemented
> which could maintain depth, and that lead to a wrong depth after switched
> back to FAIR...
>
> Regards,
> Michael Wang
>
>
>
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 235cfa7..4445e56 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -7317,7 +7317,11 @@ static void switched_from_fair(struct rq *rq, struct task_struct *p)
> */
> static void switched_to_fair(struct rq *rq, struct task_struct *p)
> {
> - if (!p->se.on_rq)
> + struct sched_entity *se = &p->se;
> +#ifdef CONFIG_FAIR_GROUP_SCHED
> + se->depth = se->parent ? se->parent->depth + 1 : 0;
> +#endif
> + if (!se->on_rq)
> return;
>
> /*


Michael, do you think you can send a proper patch for this?


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