linux-kernel - Re: [RFC PATCH] tun: don't zeroize sock->file on detach

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Date:	Wed, 08 Aug 2012 14:34:10 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ycheng@...gle.com
Cc:	skinsbursky@...allels.com, netdev@...r.kernel.org,
	ruanzhijie@...mail.com, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk
Subject: Re: [RFC PATCH] tun: don't zeroize sock->file on detach

From: Yuchung Cheng <ycheng@...gle.com>
Date: Wed, 8 Aug 2012 10:48:32 -0700

> On Wed, Aug 8, 2012 at 5:53 AM, Stanislav Kinsbursky
> <skinsbursky@...allels.com> wrote:
>> Hi, Dave.
>> What about this patch?
>>
>>
>> On Wed, Jul 11, 2012 at 03:48:20PM +0400, Stanislav Kinsbursky wrote:
>>>
>>> This is a fix for bug, introduced in 3.4 kernel by commit
>>> 1ab5ecb90cb6a3df1476e052f76a6e8f6511cb3d, which, among other things,
>>> replaced
>>> simple sock_put() by sk_release_kernel(). Below is sequence, which leads
>>> to
>>> oops for non-persistent devices:
>>>
>>> tun_chr_close()
>>> tun_detach()                            <== tun->socket.file = NULL
>>> tun_free_netdev()
>>> sk_release_sock()
>>> sock_release(sock->file == NULL)
>>> iput(SOCK_INODE(sock))                  <== dereference on NULL pointer
>>>
>>> This patch just removes zeroing of socket's file from __tun_detach().
>>> sock_release() will do this.
>>>
>>> Signed-off-by: Stanislav Kinsbursky <skinsbursky@...allels.com>
> Acked-by: Yuchung Cheng <ycheng@...gle.com>
> 
> I has tested this patch and it works (so my kernel stops crashing
> using tun devices).

This patch needs to be formally resubmitted to netdev.
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