[patch -next] ipip: potential race in ip_tunnel_init_net()

Dan Carpenter
2013-08-23T08:15:37Z

Eric Dumazet says that my previous fix for an ERR_PTR dereference
(ea857f28ab 'ipip: dereferencing an ERR_PTR in ip_tunnel_init_net()')
could be racy and suggests the following fix instead.

Reported-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 24549b4..830de3f 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -854,16 +854,14 @@ int ip_tunnel_init_net(struct net *net, int ip_tnl_net_id,

rtnl_lock();
itn->fb_tunnel_dev = __ip_tunnel_create(net, ops, &parms);
- rtnl_unlock();
-
- if (IS_ERR(itn->fb_tunnel_dev))
- return PTR_ERR(itn->fb_tunnel_dev);
/* FB netdevice is special: we have one, and only one per netns.
* Allowing to move it to another netns is clearly unsafe.
*/
- itn->fb_tunnel_dev->features |= NETIF_F_NETNS_LOCAL;
+ if (!IS_ERR(itn->fb_tunnel_dev))
+ itn->fb_tunnel_dev->features |= NETIF_F_NETNS_LOCAL;
+ rtnl_unlock();

- return 0;
+ return PTR_RET(itn->fb_tunnel_dev);
}
EXPORT_SYMBOL_GPL(ip_tunnel_init_net);