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 06:05:27 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Mitsuo Hayasaka <mitsuo.hayasaka.hu@...achi.com>
Cc:	Jay Vosburgh <fubar@...ibm.com>,
	Andy Gospodarek <andy@...yhouse.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, yrl.pp-manager.tt@...achi.com,
	WANG Cong <xiyou.wangcong@...il.com>
Subject: Re: [PATCH net -v2] [BUGFIX] bonding: use local function pointer of
 bond->recv_probe in bond_handle_frame

Le jeudi 13 octobre 2011 à 11:04 +0900, Mitsuo Hayasaka a écrit :
> 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>
> ---
> 
>  drivers/net/bonding/bond_main.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 6d79b78..de3d351 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1435,6 +1435,8 @@ static rx_handler_result_t bond_handle_frame(struct sk_buff **pskb)
>  	struct sk_buff *skb = *pskb;
>  	struct slave *slave;
>  	struct bonding *bond;
> +	void (*recv_probe)(struct sk_buff *, struct bonding *,
> +				struct slave *);
>  
>  	skb = skb_share_check(skb, GFP_ATOMIC);
>  	if (unlikely(!skb))
> @@ -1448,11 +1450,12 @@ static rx_handler_result_t bond_handle_frame(struct sk_buff **pskb)
>  	if (bond->params.arp_interval)
>  		slave->dev->last_rx = jiffies;
>  
> -	if (bond->recv_probe) {
> +	recv_probe = ACCESS_ONCE(bond->recv_probe);
> +	if (recv_probe) {
>  		struct sk_buff *nskb = skb_clone(skb, GFP_ATOMIC);
>  
>  		if (likely(nskb)) {
> -			bond->recv_probe(nskb, bond, slave);
> +			recv_probe(nskb, bond, slave);
>  			dev_kfree_skb(nskb);
>  		}
>  	}
> 

Sorry, I forgot to add my official ack. Even if not a perfect patch, its
a step into right direction.

Acked-by: Eric Dumazet <eric.dumazet@...il.com>


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