We need to unregister the netdevice if config failed.
.ndo_uninit takes care of most of the heavy lifting.

This was uncovered by recent commit c269a24ce057 ("net: make
free_netdev() more lenient with unregistering devices").
Previously the partially-initialized device would be left
in the system.

Reported-and-tested-by: syzbot+2393580080a2da190f04@syzkaller.appspotmail.com
Fixes: e2f1f072db8d ("sit: allow to configure 6rd tunnels via netlink")
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 net/ipv6/sit.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
index 2da0ee703779..440175bc2e89 100644
--- a/net/ipv6/sit.c
+++ b/net/ipv6/sit.c

@@ -1645,8 +1645,11 @@ static int ipip6_newlink(struct net *src_net, struct net_device *dev,
 	}
 
 #ifdef CONFIG_IPV6_SIT_6RD
-	if (ipip6_netlink_6rd_parms(data, &ip6rd))
+	if (ipip6_netlink_6rd_parms(data, &ip6rd)) {
 		err = ipip6_tunnel_update_6rd(nt, &ip6rd);
+		if (err)
+			unregister_netdevice_queue(dev, NULL);
+	}
 #endif
 
 	return err;

-- 
2.26.2