Subject: Re: [PATCH -net] netpoll: fix NULL pointer dereference in netpoll_cleanup

From: Nikolay Aleksandrov <[email-masked]>
Date: Wed, 18 Sep 2013 23:06:57 +0200

On 09/18/2013 06:15 PM, David Miller wrote:
> From: Nikolay Aleksandrov <[email-masked]>
> Date: Tue, 17 Sep 2013 16:12:35 +0200
> 
>> @@ -1284,15 +1284,15 @@ EXPORT_SYMBOL_GPL(__netpoll_free_async);
>>  
>>  void netpoll_cleanup(struct netpoll *np)
>>  {
>> -	if (!np->dev)
>> -		return;
>> -
>>  	rtnl_lock();
>> +	if (!np->dev) {
>> +		rtnl_unlock();
>> +		return;
>> +	}
>>  	__netpoll_cleanup(np);
>> -	rtnl_unlock();
>> -
>>  	dev_put(np->dev);
>>  	np->dev = NULL;
>> +	rtnl_unlock();
>>  }
>>  EXPORT_SYMBOL(netpoll_cleanup);
> 
> I know it seems arbitrary, but please do this like:
> 
> 	lock();
> 	if (condition) {
> 		...
> 	}
> 	unlock();
> 
> rather than having multiple return/unlock code paths.
> 
> This style I am suggesting is easier to audit for locking problems.
> 
> Thanks.
> 
Got it, I'll edit it and re-post.

Thanks,
 Nik