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

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Message-Id: <20130918.121539.1213515779326200577.davem@davemloft.net>
Date:	Wed, 18 Sep 2013 12:15:39 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	nikolay@...hat.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH -net] netpoll: fix NULL pointer dereference in
 netpoll_cleanup

From: Nikolay Aleksandrov <nikolay@...hat.com>
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.
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