[PATCH 3.16 061/204] netfilter: ipset: pernet ops must be unregistered last

[Ben Hutchings]

3.16.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Florian Westphal <f...@strlen.de>

commit e23ed762db7ed1950a6408c3be80bc56909ab3d4 upstream.

Removing the ipset module leaves a small window where one cpu performs
module removal while another runs a command like 'ipset flush'.

ipset uses net_generic(), unregistering the pernet ops frees this
storage area.

Fix it by first removing the user-visible api handlers and the pernet
ops last.

Fixes: 1785e8f473082 ("netfiler: ipset: Add net namespace for ipset")
Reported-by: Li Shuang <shu...@redhat.com>
Signed-off-by: Florian Westphal <f...@strlen.de>
Acked-by: Jozsef Kadlecsik <kad...@blackhole.kfki.hu>
Signed-off-by: Pablo Neira Ayuso <pa...@netfilter.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
---
--- a/net/netfilter/ipset/ip_set_core.c
+++ b/net/netfilter/ipset/ip_set_core.c
@@ -1982,24 +1982,28 @@ static struct pernet_operations ip_set_n
 static int __init
 ip_set_init(void)
 {
-       int ret = nfnetlink_subsys_register(&ip_set_netlink_subsys);
+       int ret = register_pernet_subsys(&ip_set_net_ops);
+
+       if (ret) {
+               pr_err("ip_set: cannot register pernet_subsys.\n");
+               return ret;
+       }
+
+       ret = nfnetlink_subsys_register(&ip_set_netlink_subsys);
        if (ret != 0) {
                pr_err("ip_set: cannot register with nfnetlink.\n");
+               unregister_pernet_subsys(&ip_set_net_ops);
                return ret;
        }
+
        ret = nf_register_sockopt(&so_set);
        if (ret != 0) {
                pr_err("SO_SET registry failed: %d\n", ret);
                nfnetlink_subsys_unregister(&ip_set_netlink_subsys);
+               unregister_pernet_subsys(&ip_set_net_ops);
                return ret;
        }
-       ret = register_pernet_subsys(&ip_set_net_ops);
-       if (ret) {
-               pr_err("ip_set: cannot register pernet_subsys.\n");
-               nf_unregister_sockopt(&so_set);
-               nfnetlink_subsys_unregister(&ip_set_netlink_subsys);
-               return ret;
-       }
+
        pr_info("ip_set: protocol %u\n", IPSET_PROTOCOL);
        return 0;
 }
@@ -2007,9 +2011,10 @@ ip_set_init(void)
 static void __exit
 ip_set_fini(void)
 {
-       unregister_pernet_subsys(&ip_set_net_ops);
        nf_unregister_sockopt(&so_set);
        nfnetlink_subsys_unregister(&ip_set_netlink_subsys);
+
+       unregister_pernet_subsys(&ip_set_net_ops);
        pr_debug("these are the famous last words\n");
 }