ipv6: Register some net/ipv6/ core sysctls at read-only root.

There are some sysctls left to be switched to read-only,
but they are all in ipv6, so complete with them.
Signed-off-by: NPavel Emelyanov <xemul@openvz.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv6/sysctl_net_ipv6.c

@@ -37,6 +37,10 @@ static ctl_table ipv6_table_template[] = {
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec
 	},
+	{ .ctl_name = 0 }
+};
+
+static ctl_table ipv6_table[] = {
 	{
 		.ctl_name	= NET_IPV6_MLD_MAX_MSF,
 		.procname	= "mld_max_msf",
@@ -80,12 +84,6 @@ static int ipv6_sysctl_net_init(struct net *net)
 
 	ipv6_table[2].data = &net->ipv6.sysctl.bindv6only;
 
-	/* We don't want this value to be per namespace, it should be global
-	   to all namespaces, so make it read-only when we are not in the
-	   init network namespace */
-	if (net != &init_net)
-		ipv6_table[3].mode = 0444;
-
 	net->ipv6.sysctl.table = register_net_sysctl_table(net, net_ipv6_ctl_path,
 							   ipv6_table);
 	if (!net->ipv6.sysctl.table)
@@ -126,12 +124,29 @@ static struct pernet_operations ipv6_sysctl_net_ops = {
 	.exit = ipv6_sysctl_net_exit,
 };
 
+static struct ctl_table_header *ip6_header;
+
 int ipv6_sysctl_register(void)
 {
-	return register_pernet_subsys(&ipv6_sysctl_net_ops);
+	int err = -ENOMEM;;
+
+	ip6_header = register_net_sysctl_rotable(net_ipv6_ctl_path, ipv6_table);
+	if (ip6_header == NULL)
+		goto out;
+
+	err = register_pernet_subsys(&ipv6_sysctl_net_ops);
+	if (err)
+		goto err_pernet;
+out:
+	return err;
+
+err_pernet:
+	unregister_net_sysctl_table(ip6_header);
+	goto out;
 }
 
 void ipv6_sysctl_unregister(void)
 {
+	unregister_net_sysctl_table(ip6_header);
 	unregister_pernet_subsys(&ipv6_sysctl_net_ops);
 }