inet: Register fragmentation some ctls at read-only root.

Parts of fragments-related sysctls are read-only, but this is
done by cloning all the tables and dropping write-bits from
mode. Do the same but with read-only root.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 48 insertions, 3 deletions

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 7f102eeb618e..be1cb89a8d5a 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -624,6 +624,10 @@ static struct ctl_table ip4_frags_ns_ctl_table[] = {
                 .proc_handler   = &proc_dointvec_jiffies,
                 .strategy       = &sysctl_jiffies
         },
+        { }
+};
+
+static struct ctl_table ip4_frags_ctl_table[] = {
         {
                 .ctl_name       = NET_IPV4_IPFRAG_SECRET_INTERVAL,
                 .procname       = "ipfrag_secret_interval",
@@ -658,8 +662,6 @@ static int ip4_frags_ns_ctl_register(struct net *net)
                 table[0].data = &net->ipv4.frags.high_thresh;
                 table[1].data = &net->ipv4.frags.low_thresh;
                 table[2].data = &net->ipv4.frags.timeout;
-                table[3].mode &= ~0222;
-                table[4].mode &= ~0222;
         }
 
         hdr = register_net_sysctl_table(net, net_ipv4_ctl_path, table);
@@ -684,6 +686,11 @@ static void ip4_frags_ns_ctl_unregister(struct net *net)
         unregister_net_sysctl_table(net->ipv4.frags_hdr);
         kfree(table);
 }
+
+static void ip4_frags_ctl_register(void)
+{
+        register_net_sysctl_rotable(net_ipv4_ctl_path, ip4_frags_ctl_table);
+}
 #else
 static inline int ip4_frags_ns_ctl_register(struct net *net)
 {
@@ -693,6 +700,10 @@ static inline int ip4_frags_ns_ctl_register(struct net *net)
 static inline void ip4_frags_ns_ctl_unregister(struct net *net)
 {
 }
+
+static inline void ip4_frags_ctl_register(void)
+{
+}
 #endif
 
 static int ipv4_frags_init_net(struct net *net)
@@ -730,6 +741,7 @@ static struct pernet_operations ip4_frags_ops = {
 
 void __init ipfrag_init(void)
 {
+        ip4_frags_ctl_register();
         register_pernet_subsys(&ip4_frags_ops);
         ip4_frags.hashfn = ip4_hashfn;
         ip4_frags.constructor = ip4_frag_init;
diff --git a/net/ipv6/reassembly.c b/net/ipv6/reassembly.c
index 130d6f6b6a6e..9391a6949b96 100644
--- a/net/ipv6/reassembly.c
+++ b/net/ipv6/reassembly.c
@@ -658,6 +658,10 @@ static struct ctl_table ip6_frags_ns_ctl_table[] = {
                 .proc_handler   = &proc_dointvec_jiffies,
                 .strategy       = &sysctl_jiffies,
         },
+        { }
+};
+
+static struct ctl_table ip6_frags_ctl_table[] = {
         {
                 .ctl_name       = NET_IPV6_IP6FRAG_SECRET_INTERVAL,
                 .procname       = "ip6frag_secret_interval",
@@ -684,7 +688,6 @@ static int ip6_frags_ns_sysctl_register(struct net *net)
                 table[0].data = &net->ipv6.frags.high_thresh;
                 table[1].data = &net->ipv6.frags.low_thresh;
                 table[2].data = &net->ipv6.frags.timeout;
-                table[3].mode &= ~0222;
         }
 
         hdr = register_net_sysctl_table(net, net_ipv6_ctl_path, table);
@@ -709,6 +712,20 @@ static void ip6_frags_ns_sysctl_unregister(struct net *net)
         unregister_net_sysctl_table(net->ipv6.sysctl.frags_hdr);
         kfree(table);
 }
+
+static struct ctl_table_header *ip6_ctl_header;
+
+static int ip6_frags_sysctl_register(void)
+{
+        ip6_ctl_header = register_net_sysctl_rotable(net_ipv6_ctl_path,
+                        ip6_frags_ctl_table);
+        return ip6_ctl_header == NULL ? -ENOMEM : 0;
+}
+
+static void ip6_frags_sysctl_unregister(void)
+{
+        unregister_net_sysctl_table(ip6_ctl_header);
+}
 #else
 static inline int ip6_frags_ns_sysctl_register(struct net *net)
 {
@@ -718,6 +735,15 @@ static inline int ip6_frags_ns_sysctl_register(struct net *net)
 static inline void ip6_frags_ns_sysctl_unregister(struct net *net)
 {
 }
+
+static inline int ip6_frags_sysctl_register(void)
+{
+        return 0;
+}
+
+static inline void ip6_frags_sysctl_unregister(void)
+{
+}
 #endif
 
 static int ipv6_frags_init_net(struct net *net)
@@ -750,6 +776,10 @@ int __init ipv6_frag_init(void)
         if (ret)
                 goto out;
 
+        ret = ip6_frags_sysctl_register();
+        if (ret)
+                goto err_sysctl;
+
         ret = register_pernet_subsys(&ip6_frags_ops);
         if (ret)
                 goto err_pernet;
@@ -767,6 +797,8 @@ out:
         return ret;
 
 err_pernet:
+        ip6_frags_sysctl_unregister();
+err_sysctl:
         inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
         goto out;
 }
@@ -774,6 +806,7 @@ err_pernet:
 void ipv6_frag_exit(void)
 {
         inet_frags_fini(&ip6_frags);
+        ip6_frags_sysctl_unregister();
         unregister_pernet_subsys(&ip6_frags_ops);
         inet6_del_protocol(&frag_protocol, IPPROTO_FRAGMENT);
 }