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

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Message-ID: <20140216191909.GL14089@laptop.programming.kicks-ass.net>
Date:	Sun, 16 Feb 2014 20:19:09 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Sasha Levin <sasha.levin@...cle.com>
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 Sat, Feb 15, 2014 at 06:27:52PM -0500, Sasha Levin wrote:
> Hi folks,
> 
> While fuzzing with trinity inside a KVM tools guest running latest -next kernel, I've
> stumbled on the following:
> 
> [  522.645288] BUG: unable to handle kernel NULL pointer dereference at 0000000000000150
> [  522.646271] IP: [<ffffffff81186c6f>] check_preempt_wakeup+0x11f/0x210
> 
> Since it's pretty inlined, the code points to:
> 
> 	check_preempt_wakeup()
> 		find_matching_se()
> 			find_matching_se()
> 				check_preempt_wakeup()
> 
> 
> 	static inline struct cfs_rq *
> 	is_same_group(struct sched_entity *se, struct sched_entity *pse)
> 	{
> 	        if (se->cfs_rq == pse->cfs_rq)	<=== HERE
> 	                return se->cfs_rq;
> 	
> 	        return NULL;
> 	}

Hrm.. that means we got se->depth wrong. I'll have a poke tomorrow.
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