netdev - Re: net_device leak after "bridge: allow creating bridge devices with netlink"?

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Message-ID: <20110822085532.2ff4479c@nehalam.ftrdhcpuser.net>
Date:	Mon, 22 Aug 2011 08:55:32 -0700
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Jan Beulich <JBeulich@...ell.com>, davem@...emloft.net,
	netdev@...r.kernel.org
Subject: Re: net_device leak after "bridge: allow creating bridge devices
 with netlink"?

On Mon, 22 Aug 2011 14:50:01 +0200
Eric Dumazet <eric.dumazet@...il.com> wrote:

> Le lundi 22 août 2011 à 12:34 +0100, Jan Beulich a écrit :
> > Stephen,
> > 
> > directly returning the result of register_netdev() from br_add_bridge()
> > would - to me - appear to be leaking "dev" in case of failure. Or am I
> > overlooking some implicit mechanism by which this would get freed?
> > 
> > Thanks, Jan
> 
> You're 100 % right, there is a leak here.
> 
> (But "ip" or "brctl" commands first check link already exist before
> trying create it, so you need to tweak them to actually hit this bug)
> 
> We have to add a free_netdev() call to free the net_device.
> 
> 
> 
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index 2cdf007..e738154 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -231,6 +231,7 @@ static struct net_bridge_port *new_nbp(struct net_bridge *br,
>  int br_add_bridge(struct net *net, const char *name)
>  {
>  	struct net_device *dev;
> +	int res;
>  
>  	dev = alloc_netdev(sizeof(struct net_bridge), name,
>  			   br_dev_setup);
> @@ -240,7 +241,10 @@ int br_add_bridge(struct net *net, const char *name)
>  
>  	dev_net_set(dev, net);
>  
> -	return register_netdev(dev);
> +	res = register_netdev(dev);
> +	if (res)
> +		free_netdev(dev);
> +	return res;
>  }
>  
>  int br_del_bridge(struct net *net, const char *name)

Missing Signed-off-by:?

Acked-by: Stephen Hemminger <shemminger@...tta.com>
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