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

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Date:	Mon, 22 Aug 2011 18:05:59 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Stephen Hemminger <shemminger@...tta.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"?

Le lundi 22 août 2011 à 08:55 -0700, Stephen Hemminger a écrit :
> 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>

Well, its only a direct coding of Jan report ;)

Thanks

[PATCH] bridge: fix a possible net_device leak

Jan Beulich reported a possible net_device leak in bridge code after
commit bb900b27a2f4 (bridge: allow creating bridge devices with netlink)

Reported-by: Jan Beulich <JBeulich@...ell.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
Acked-by: Stephen Hemminger <shemminger@...tta.com>
---
 net/bridge/br_if.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletion(-)

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)


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