netfilter: nf_conntrack: use l4proto->users as refcount for per-net data

Currently, nf_proto_net's l4proto->users meaning is quite confusing
since it depends on the compilation tweaks.

To resolve this, we cleanup this code to regard it as the refcount
for l4proto's per-net data, since there may be two l4protos use the
same per-net data.

Thus, we increment pn->users when nf_conntrack_l4proto_register
successfully, and decrement it for nf_conntrack_l4_unregister case.

The users refcnt is not required form layer 3 protocol trackers.

Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 46 insertions, 30 deletions

diff --git a/net/netfilter/nf_conntrack_proto.c b/net/netfilter/nf_conntrack_proto.c
index 9d6b6ab193a9..63612e6d7238 100644
--- a/net/netfilter/nf_conntrack_proto.c
+++ b/net/netfilter/nf_conntrack_proto.c
@@ -39,16 +39,13 @@ static int
 nf_ct_register_sysctl(struct net *net,
                       struct ctl_table_header **header,
                       const char *path,
-                      struct ctl_table *table,
-                      unsigned int *users)
+                      struct ctl_table *table)
 {
         if (*header == NULL) {
                 *header = register_net_sysctl(net, path, table);
                 if (*header == NULL)
                         return -ENOMEM;
         }
-        if (users != NULL)
-                (*users)++;
 
         return 0;
 }
@@ -56,9 +53,9 @@ nf_ct_register_sysctl(struct net *net,
 static void
 nf_ct_unregister_sysctl(struct ctl_table_header **header,
                         struct ctl_table **table,
-                        unsigned int *users)
+                        unsigned int users)
 {
-        if (users != NULL && --*users > 0)
+        if (users > 0)
                 return;
 
         unregister_net_sysctl_table(*header);
@@ -191,8 +188,7 @@ static int nf_ct_l3proto_register_sysctl(struct net *net,
                 err = nf_ct_register_sysctl(net,
                                             &in->ctl_table_header,
                                             l3proto->ctl_table_path,
-                                            in->ctl_table,
-                                            NULL);
+                                            in->ctl_table);
                 if (err < 0) {
                         kfree(in->ctl_table);
                         in->ctl_table = NULL;
@@ -213,7 +209,7 @@ static void nf_ct_l3proto_unregister_sysctl(struct net *net,
         if (in->ctl_table_header != NULL)
                 nf_ct_unregister_sysctl(&in->ctl_table_header,
                                         &in->ctl_table,
-                                        NULL);
+                                        0);
 #endif
 }
 
@@ -329,20 +325,17 @@ static struct nf_proto_net *nf_ct_l4proto_net(struct net *net,
 
 static
 int nf_ct_l4proto_register_sysctl(struct net *net,
+                                  struct nf_proto_net *pn,
                                   struct nf_conntrack_l4proto *l4proto)
 {
         int err = 0;
-        struct nf_proto_net *pn = nf_ct_l4proto_net(net, l4proto);
-        if (pn == NULL)
-                return 0;
 
 #ifdef CONFIG_SYSCTL
         if (pn->ctl_table != NULL) {
                 err = nf_ct_register_sysctl(net,
                                             &pn->ctl_table_header,
                                             "net/netfilter",
-                                            pn->ctl_table,
-                                            &pn->users);
+                                            pn->ctl_table);
                 if (err < 0) {
                         if (!pn->users) {
                                 kfree(pn->ctl_table);
@@ -356,15 +349,14 @@ int nf_ct_l4proto_register_sysctl(struct net *net,
                 err = nf_ct_register_sysctl(net,
                                             &pn->ctl_compat_header,
                                             "net/ipv4/netfilter",
-                                            pn->ctl_compat_table,
-                                            NULL);
+                                            pn->ctl_compat_table);
                 if (err == 0)
                         goto out;
 
                 nf_ct_kfree_compat_sysctl_table(pn);
                 nf_ct_unregister_sysctl(&pn->ctl_table_header,
                                         &pn->ctl_table,
-                                        &pn->users);
+                                        pn->users);
         }
 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
 out:
@@ -374,25 +366,21 @@ out:
 
 static
 void nf_ct_l4proto_unregister_sysctl(struct net *net,
+                                     struct nf_proto_net *pn,
                                      struct nf_conntrack_l4proto *l4proto)
 {
-        struct nf_proto_net *pn = nf_ct_l4proto_net(net, l4proto);
-        if (pn == NULL)
-                return;
 #ifdef CONFIG_SYSCTL
         if (pn->ctl_table_header != NULL)
                 nf_ct_unregister_sysctl(&pn->ctl_table_header,
                                         &pn->ctl_table,
-                                        &pn->users);
+                                        pn->users);
 
 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
         if (l4proto->l3proto != AF_INET6 && pn->ctl_compat_header != NULL)
                 nf_ct_unregister_sysctl(&pn->ctl_compat_header,
                                         &pn->ctl_compat_table,
-                                        NULL);
+                                        0);
 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
-#else
-        pn->users--;
 #endif /* CONFIG_SYSCTL */
 }
 
@@ -458,23 +446,32 @@ int nf_conntrack_l4proto_register(struct net *net,
                                   struct nf_conntrack_l4proto *l4proto)
 {
         int ret = 0;
+        struct nf_proto_net *pn = NULL;
 
         if (l4proto->init_net) {
                 ret = l4proto->init_net(net, l4proto->l3proto);
                 if (ret < 0)
-                        return ret;
+                        goto out;
         }
 
-        ret = nf_ct_l4proto_register_sysctl(net, l4proto);
+        pn = nf_ct_l4proto_net(net, l4proto);
+        if (pn == NULL)
+                goto out;
+
+        ret = nf_ct_l4proto_register_sysctl(net, pn, l4proto);
         if (ret < 0)
-                return ret;
+                goto out;
 
         if (net == &init_net) {
                 ret = nf_conntrack_l4proto_register_net(l4proto);
-                if (ret < 0)
-                        nf_ct_l4proto_unregister_sysctl(net, l4proto);
+                if (ret < 0) {
+                        nf_ct_l4proto_unregister_sysctl(net, pn, l4proto);
+                        goto out;
+                }
         }
 
+        pn->users++;
+out:
         return ret;
 }
 EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_register);
@@ -499,10 +496,18 @@ nf_conntrack_l4proto_unregister_net(struct nf_conntrack_l4proto *l4proto)
 void nf_conntrack_l4proto_unregister(struct net *net,
                                      struct nf_conntrack_l4proto *l4proto)
 {
+        struct nf_proto_net *pn = NULL;
+
         if (net == &init_net)
                 nf_conntrack_l4proto_unregister_net(l4proto);
 
-        nf_ct_l4proto_unregister_sysctl(net, l4proto);
+        pn = nf_ct_l4proto_net(net, l4proto);
+        if (pn == NULL)
+                return;
+
+        pn->users--;
+        nf_ct_l4proto_unregister_sysctl(net, pn, l4proto);
+
         /* Remove all contrack entries for this protocol */
         rtnl_lock();
         nf_ct_iterate_cleanup(net, kill_l4proto, l4proto);
@@ -514,11 +519,15 @@ int nf_conntrack_proto_init(struct net *net)
 {
         unsigned int i;
         int err;
+        struct nf_proto_net *pn = nf_ct_l4proto_net(net,
+                                        &nf_conntrack_l4proto_generic);
+
         err = nf_conntrack_l4proto_generic.init_net(net,
                                         nf_conntrack_l4proto_generic.l3proto);
         if (err < 0)
                 return err;
         err = nf_ct_l4proto_register_sysctl(net,
+                                            pn,
                                             &nf_conntrack_l4proto_generic);
         if (err < 0)
                 return err;
@@ -528,13 +537,20 @@ int nf_conntrack_proto_init(struct net *net)
                         rcu_assign_pointer(nf_ct_l3protos[i],
                                            &nf_conntrack_l3proto_generic);
         }
+
+        pn->users++;
         return 0;
 }
 
 void nf_conntrack_proto_fini(struct net *net)
 {
         unsigned int i;
+        struct nf_proto_net *pn = nf_ct_l4proto_net(net,
+                                        &nf_conntrack_l4proto_generic);
+
+        pn->users--;
         nf_ct_l4proto_unregister_sysctl(net,
+                                        pn,
                                         &nf_conntrack_l4proto_generic);
         if (net == &init_net) {
                 /* free l3proto protocol tables */