linux-kernel - Re: [PATCH v6 2/8] debugfs: prevent access to removed files' private data

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Message-ID: <573C87B8.902@oracle.com>
Date:	Wed, 18 May 2016 11:18:16 -0400
From:	Sasha Levin <sasha.levin@...cle.com>
To:	Nicolai Stange <nicstange@...il.com>
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jonathan Corbet <corbet@....net>, Jan Kara <jack@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Julia Lawall <Julia.Lawall@...6.fr>,
	Gilles Muller <Gilles.Muller@...6.fr>,
	Nicolas Palix <nicolas.palix@...g.fr>,
	Michal Marek <mmarek@...e.com>, linux-kernel@...r.kernel.org,
	cocci@...teme.lip6.fr
Subject: Re: [PATCH v6 2/8] debugfs: prevent access to removed files' private
 data

On 05/18/2016 11:01 AM, Nicolai Stange wrote:
> Thanks a million for reporting!
> 
> 1.) Do you have lockdep enabled?

Yup, nothing there.

> 2.) Does this happen before or after userspace init has been spawned,
>     i.e. does the lockup happen at debugfs file creation time or
>     possibly at usage time?

So I looked closer, and it seems to happen after starting syzkaller, which
as far as I know tries to open many different debugfs files.

Is there debug code I can add it that'll help us figure out what's up?


Thanks,
Sasha