netdev - Re: [PATCH net -v2] [BUGFIX] bonding: use local function pointer of bond->recv_probe in bond_handle

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Date:	Wed, 19 Oct 2011 10:59:07 -0700
From:	Jay Vosburgh <fubar@...ibm.com>
To:	David Miller <davem@...emloft.net>
cc:	mitsuo.hayasaka.hu@...achi.com, andy@...yhouse.net,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	yrl.pp-manager.tt@...achi.com, eric.dumazet@...il.com,
	xiyou.wangcong@...il.com
Subject: Re: [PATCH net -v2] [BUGFIX] bonding: use local function pointer of bond->recv_probe in bond_handle_frame

David Miller <davem@...emloft.net> wrote:

>From: Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
>Date: Thu, 13 Oct 2011 11:04:29 +0900
>
>> The bond->recv_probe is called in bond_handle_frame() when
>> a packet is received, but bond_close() sets it to NULL. So,
>> a panic occurs when both functions work in parallel.
>> 
>> Why this happen:
>> After null pointer check of bond->recv_probe, an sk_buff is
>> duplicated and bond->recv_probe is called in bond_handle_frame.
>> So, a panic occurs when bond_close() is called between the
>> check and call of bond->recv_probe.
>> 
>> Patch:
>> This patch uses a local function pointer of bond->recv_probe
>> in bond_handle_frame(). So, it can avoid the null pointer
>> dereference.
>> 
>> 
>> Signed-off-by: Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
>> Cc: Jay Vosburgh <fubar@...ibm.com>
>> Cc: Andy Gospodarek <andy@...yhouse.net>
>> Cc: Eric Dumazet <eric.dumazet@...il.com>
>> Cc: WANG Cong <xiyou.wangcong@...il.com>
>
>Bonding folks please review this, thanks.
>

	Looks reasonable.  Even if by some quirk of timing the
recv_probe function ends up being entered after bond_close has
completed, it doesn't look like there is a risk of those functions
misbehaving (because bond_close doesn't deallocate the data structures).

	-J

Signed-off-by: Jay Vosburgh <fubar@...ibm.com>

---
	-Jay Vosburgh, IBM Linux Technology Center, fubar@...ibm.com

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