Subject: Re: [PATCH v4 net-next 01/12] bonding: remove bond->lock from bond_arp_rcv

From: Ding Tianhong <[email-masked]>
Date: Tue, 18 Feb 2014 15:07:46 +0800

On 2014/2/18 14:12, Veaceslav Falico wrote:
> On Tue, Feb 18, 2014 at 12:02:41PM +0800, Ding Tianhong wrote:
>> On 2014/2/17 22:41, Veaceslav Falico wrote:
>>> We're always called with rcu_read_lock() held (bond_arp_rcv() is only
>>> called from bond_handle_frame(), which is rx_handler and always called
>>> under rcu from __netif_receive_skb_core() ).
>>>
>>> The slave active/passive and/or bonding params can change in-flight, however
>>> we don't really care about that - we only modify the last time packet was
>>> received, which is harmless.
>>>
>>> CC: Jay Vosburgh <[email-masked]>
>>> CC: Andy Gospodarek <[email-masked]>
>>> Signed-off-by: Veaceslav Falico <[email-masked]>
>>> ---
>>>  drivers/net/bonding/bond_main.c | 3 ---
>>>  1 file changed, 3 deletions(-)
>>>
>>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>>> index 3bce855..3c50bec 100644
>>> --- a/drivers/net/bonding/bond_main.c
>>> +++ b/drivers/net/bonding/bond_main.c
>>> @@ -2260,8 +2260,6 @@ int bond_arp_rcv(const struct sk_buff *skb, struct bonding *bond,
>>>      if (skb->protocol != __cpu_to_be16(ETH_P_ARP))
>>>          return RX_HANDLER_ANOTHER;
>>>
>>> -    read_lock(&bond->lock);
>>> -
>>>      if (!slave_do_arp_validate(bond, slave))
>>>          goto out_unlock;
>>>
>>> @@ -2318,7 +2316,6 @@ int bond_arp_rcv(const struct sk_buff *skb, struct bonding *bond,
>>>          bond_validate_arp(bond, slave, tip, sip);
>>>
>>>  out_unlock:
>>> -    read_unlock(&bond->lock);
>>>      if (arp != (struct arphdr *)skb->data)
>>>          kfree(arp);
>>>      return RX_HANDLER_ANOTHER;
>>>
>>
>> I think it is not enough, you should add rcu_dereference for bond->curr_active_slave, it may be changed during
>> the recv processing.
> 
> bond->lock has absolutely nothing to du with bond->curr_active_slave .
> 
Yep, this problem is introduced by commit aeea64ac7， there is no way to protect the curr_active_slave, so
I think you could fix it in this patch together.
 
	else if (bond->curr_active_slave &&
		 time_after(slave_last_rx(bond, bond->curr_active_slave),
			    bond->curr_active_slave->jiffies))
>> Regards
>> Ding