gre: fix netns vs proto registration ordering

commit c2892f02712e9516d72841d5c019ed6916329794 upstream.

GRE protocol receive hook can be called right after protocol addition is done.
If netns stuff is not yet initialized, we're going to oops in
net_generic().

This is remotely oopsable if ip_gre is compiled as module and packet
comes at unfortunate moment of module loading.

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index aa70db1ccce54de81ebfc98635408ab1a58d3fa6..f8b72dbf85f54ade4298de53ec8a1e2cdbe823c6 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1667,14 +1667,15 @@ static int __init ipgre_init(void)
 
        printk(KERN_INFO "GRE over IPv4 tunneling driver\n");
 
-       if (inet_add_protocol(&ipgre_protocol, IPPROTO_GRE) < 0) {
-               printk(KERN_INFO "ipgre init: can't add protocol\n");
-               return -EAGAIN;
-       }
-
        err = register_pernet_device(&ipgre_net_ops);
        if (err < 0)
-               goto gen_device_failed;
+               return err;
+
+       err = inet_add_protocol(&ipgre_protocol, IPPROTO_GRE);
+       if (err < 0) {
+               printk(KERN_INFO "ipgre init: can't add protocol\n");
+               goto add_proto_failed;
+       }
 
        err = rtnl_link_register(&ipgre_link_ops);
        if (err < 0)
@@ -1690,9 +1691,9 @@ out:
 tap_ops_failed:
        rtnl_link_unregister(&ipgre_link_ops);
 rtnl_link_failed:
-       unregister_pernet_device(&ipgre_net_ops);
-gen_device_failed:
        inet_del_protocol(&ipgre_protocol, IPPROTO_GRE);
+add_proto_failed:
+       unregister_pernet_device(&ipgre_net_ops);
        goto out;
 }
 
@@ -1700,9 +1701,9 @@ static void __exit ipgre_fini(void)
 {
        rtnl_link_unregister(&ipgre_tap_ops);
        rtnl_link_unregister(&ipgre_link_ops);
-       unregister_pernet_device(&ipgre_net_ops);
        if (inet_del_protocol(&ipgre_protocol, IPPROTO_GRE) < 0)
                printk(KERN_INFO "ipgre close: can't remove protocol\n");
+       unregister_pernet_device(&ipgre_net_ops);
 }
 
 module_init(ipgre_init);