[patch -next v2] ipip: dereferencing an ERR_PTR in ip_tunnel_init_net()

[Dan Carpenter <dan.carpenter@oracle.com>]

The __ip_tunnel_create() function returns an ERR_PTR on error so we need
to check for that before dereferencing.  This bug was added in commit
6c742e714d8c2 ("ipip: add x-netns support").

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: Eric Dumazet said v1 patch looked racy and suggested the v2 fix.

diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index a4d9126..830de3f 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -857,13 +857,11 @@ int ip_tunnel_init_net(struct net *net, int ip_tnl_net_id,
 	/* 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();
 
-	if (IS_ERR(itn->fb_tunnel_dev))
-		return PTR_ERR(itn->fb_tunnel_dev);
-
-	return 0;
+	return PTR_RET(itn->fb_tunnel_dev);
 }
 EXPORT_SYMBOL_GPL(ip_tunnel_init_net);