From mboxrd@z Thu Jan  1 00:00:00 1970
From: Joe Perches <joe@perches.com>
Subject: Re: [PATCH -net] netpoll: fix NULL pointer dereference in
 netpoll_cleanup
Date: Wed, 18 Sep 2013 09:25:24 -0700
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References: <1379427155-8561-1-git-send-email-nikolay@redhat.com>
	 <20130918.121539.1213515779326200577.davem@davemloft.net>
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Cc: nikolay@redhat.com, netdev@vger.kernel.org
To: David Miller <davem@davemloft.net>
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On Wed, 2013-09-18 at 12:15 -0400, David Miller wrote:
> From: Nikolay Aleksandrov <nikolay@redhat.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.

Another alternative is:

	lock();

	if (!condition)
		goto out;

	...

out:
	unlock();
	return ...;
}