linux-kernel - Re: [PATCH 4.3] vrf: Fix memory leak on registration failure in vrf

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Date:	Tue, 15 Dec 2015 15:26:21 +0000
From:	Ben Hutchings <ben@...adent.org.uk>
To:	David Ahern <dsa@...ulusnetworks.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	Nikolay Aleksandrov <nikolay@...ulusnetworks.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 4.3] vrf: Fix memory leak on registration failure in
 vrf_newlink()

On Tue, 2015-12-15 at 08:15 -0700, David Ahern wrote:
> On 12/15/15 8:12 AM, Ben Hutchings wrote:
> > @@ -598,7 +599,10 @@ static int vrf_newlink(struct net *src_net, struct net_device *dev,
> > 
> >   	rcu_assign_pointer(dev->vrf_ptr, vrf_ptr);
> > 
> > -	return register_netdev(dev);
> > +	err = register_netdev(dev);
> > +	if (err)
> > +		kfree(vrf_ptr);
> > +	return err;
> >   }
> > 
> >   static size_t vrf_nl_getsize(const struct net_device *dev)
> > 
> 
> The rcu_assign_pointer should only be done if the register_netdev succeeded.

Oh, yes I see.  I though that no other task could access an
unregistered device, but register_netdev() can still fail after listing
the device.

Wait, it's worse, this is calling register_netdev() which will deadlock
as we already hold the RTNL lock.

Ben.

> Thanks for creating the patch.
> 
-- 
Ben Hutchings
Logic doesn't apply to the real world. - Marvin Minsky
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