Re: net/ipv6: double free in ipip6_dev_free

On Wed, Feb 8, 2017 at 5:56 AM, Dmitry Vyukov [off-list ref] wrote:

First dev->tstats was freed here:

1376 static int ipip6_tunnel_init(struct net_device *dev)
1377 {
1378         struct ip_tunnel *tunnel = netdev_priv(dev);
1379         int err;
1380
1381         tunnel->dev = dev;
1382         tunnel->net = dev_net(dev);
1383         strcpy(tunnel->parms.name, dev->name);
1384
1385         ipip6_tunnel_bind_dev(dev);
1386         dev->tstats = netdev_alloc_pcpu_stats(struct pcpu_sw_netstats);
1387         if (!dev->tstats)
1388                 return -ENOMEM;
1389
1390         err = dst_cache_init(&tunnel->dst_cache, GFP_KERNEL);
1391         if (err) {
1392                 free_percpu(dev->tstats);
1393                 return err;
1394         }
1395
1396         return 0;
1397 }

And then again here:

1342 static void ipip6_dev_free(struct net_device *dev)
1343 {
1344         struct ip_tunnel *tunnel = netdev_priv(dev);
1345
1346         dst_cache_destroy(&tunnel->dst_cache);
1347         free_percpu(dev->tstats);
1348         free_netdev(dev);
1349 }

Probably we need to NULL dev->tstats in the ndo_init(),
and ipip6 tunnel seems not the only one missing it.