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

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Message-ID: <530566DE.3090508@linux.vnet.ibm.com>
Date:	Thu, 20 Feb 2014 10:22:22 +0800
From:	Michael wang <wangyun@...ux.vnet.ibm.com>
To:	Sasha Levin <sasha.levin@...cle.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 02/20/2014 02:10 AM, Sasha Levin wrote:
> 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 for the testing :) will post the patch later.

Regards,
Michael Wang

> 
> 
> Thanks,
> Sasha
> 

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