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Subject: Re: [PATCH] vrf: Fix possible NULL pointer oops when delete nic
To:     "wangxiaogang (F)" <wangxiaogang3@huawei.com>, dsahern@kernel.org,
        shrijeet@gmail.com, davem@davemloft.net
Cc:     netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        hujunwei4@huawei.com, xuhanbing@huawei.com
References: <60e827cb-2bba-2b7e-55dc-651103e9905f@huawei.com>
 <7fe948a8-debd-e336-9584-e66153e90701@gmail.com>
 <bead86fd-ae33-219f-0601-d80b57695d3c@huawei.com>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <a9efbb8a-4f48-9208-0615-087fb9e8e2d9@gmail.com>
Date:   Sun, 17 Nov 2019 20:21:12 -0700
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On 11/17/19 8:16 PM, wangxiaogang (F) wrote:
> 
> 
> On 2019/11/16 0:59, David Ahern wrote:
>> On 11/14/19 11:22 PM, wangxiaogang (F) wrote:
>>> diff --git a/drivers/net/vrf.c b/drivers/net/vrf.c
>>> index b8228f5..86c4b8c 100644
>>> --- a/drivers/net/vrf.c
>>> +++ b/drivers/net/vrf.c
>>> @@ -1427,6 +1427,9 @@ static int vrf_device_event(struct notifier_block *unused,
>>>  			goto out;
>>>
>>>  		vrf_dev = netdev_master_upper_dev_get(dev);
>>> +		if (!vrf_dev)
>>> +			goto out;
>>> +
>>>  		vrf_del_slave(vrf_dev, dev);
>>>  	}
>>>  out:
>>
>> BTW, I believe this is the wrong fix. A device can not be a VRF slave
>> AND not have an upper device. Something is fundamentally wrong.
>>
>>
> 
> this problem occurs when our testers deleted the NIC and vrf in parallel.
> I will try to recurring this problem later.
> 

The deletes are serial in the kernel due to the rtnl, but dev changes
are under rcu...