[NET]: Take dev_base_lock when moving device name hash list entry

When we added name-based hashing the dev_base_lock was designated as the
lock to take when changing the name hash list.  Unfortunately, because
it was a preexisting lock that just happened to be taken in the right
spots we neglected to take it in dev_change_name.

The race can affect calles of __dev_get_by_name that do so without taking
the RTNL.  They may end up walking down the wrong hash chain and end up
missing the device that they're looking for.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/dev.c

@@ -839,8 +839,12 @@ int dev_change_name(struct net_device *dev, char *newname)
 		strlcpy(dev->name, newname, IFNAMSIZ);
 
 	device_rename(&dev->dev, dev->name);
+
+	write_lock_bh(&dev_base_lock);
 	hlist_del(&dev->name_hlist);
 	hlist_add_head(&dev->name_hlist, dev_name_hash(dev->name));
+	write_unlock_bh(&dev_base_lock);
+
 	raw_notifier_call_chain(&netdev_chain, NETDEV_CHANGENAME, dev);
 
 	return err;