linux-kernel - RE: [PATCH] Fix the race between the fget() and close()

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Date:	Tue, 27 Aug 2013 00:53:37 +0000
From:	"Liu, Chuansheng" <chuansheng.liu@...el.com>
To:	Al Viro <viro@...IV.linux.org.uk>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] Fix the race between the fget() and close()

Thanks Al.

> -----Original Message-----
> From: Al Viro [mailto:viro@....linux.org.uk] On Behalf Of Al Viro
> Sent: Tuesday, August 27, 2013 8:43 AM
> To: Liu, Chuansheng
> Cc: Eric Dumazet; linux-fsdevel@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: Re: [PATCH] Fix the race between the fget() and close()
> 
> On Mon, Aug 26, 2013 at 11:56:43PM +0000, Liu, Chuansheng wrote:
> 
> 
> Hell, might be buggered refcounting on descriptor table - binder is playing
I also suspected binder do some strange thing there, but in the panic log, there is another
process causes this case during vfs_read(), maybe it is not related with binder totally.
<1>[  392.669816] BUG: unable to handle kernel NULL pointer dereference at 00000020
<1>[  392.678055] IP: [<c131c8a7>] vfs_read+0x97/0x160

> interesting games there.  Try to reproduce that with
> CONFIG_DEBUG_KMEMLEAK
> and slab debugging turned on, see if you hit anything from those; if it's
> more or less readily reproducible, I would start with that - too many
> scenarios involve broken refcounting of one sort or another.
It is not easy to hit, will try with CONFIG_DEBUG_KMEMLEAK and SLAB DEBUGGING on.
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