linux-kernel - Re: sched: fair: NULL ptr deref in check_preempt

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Message-ID: <5304F38E.3090701@oracle.com>
Date:	Wed, 19 Feb 2014 13:10:22 -0500
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Michael wang <wangyun@...ux.vnet.ibm.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Ingo Molnar <mingo@...nel.org>, Dave Jones <davej@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: sched: fair: NULL ptr deref in check_preempt_wakeup

On 02/17/2014 09:26 PM, Michael wang wrote:
> On 02/17/2014 05:20 PM, Peter Zijlstra wrote:
> [snip]
>>> >>  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;
>>> >>
>>> >>  	/*
>> >
>> >Yes indeed. My first idea yesterday was to put it in set_task_rq() to be
>> >absolutely sure we catch all; but if this is sufficient its better.
> Agree, let's wait for Sasha's testing result then:)

I took my time with testing it seems I'm hitting new issues with both sched and mm, and I've wanted 
to confirm I don't see this one any more.

It does seem like this patch fixes the problem for me, so:

	Tested-by: Sasha Levin <sasha.levin@...cle.com>


Thanks,
Sasha
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