netfilter: nfacct: per network namespace support

- Move the nfnl_acct_list into the network namespace, initialize
and destroy it per namespace
- Keep track of refcnt on nfacct objects, the old logic does not
longer work with a per namespace list
- Adjust xt_nfacct to pass the namespace when registring objects

Signed-off-by: Andreas Schultz <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

include/linux/netfilter/nfnetlink_acct.h

···
 #define _NFNL_ACCT_H_
 
 #include <uapi/linux/netfilter/nfnetlink_acct.h>
+#include <net/net_namespace.h>
 
 enum {
 	NFACCT_NO_QUOTA		= -1,
···
 
 struct nf_acct;
 
-struct nf_acct *nfnl_acct_find_get(const char *filter_name);
+struct nf_acct *nfnl_acct_find_get(struct net *net, const char *filter_name);
 void nfnl_acct_put(struct nf_acct *acct);
 void nfnl_acct_update(const struct sk_buff *skb, struct nf_acct *nfacct);
 extern int nfnl_acct_overquota(const struct sk_buff *skb,

include/net/net_namespace.h

···
 #endif
 	struct sock		*nfnl;
 	struct sock		*nfnl_stash;
+#if IS_ENABLED(CONFIG_NETFILTER_NETLINK_ACCT)
+	struct list_head        nfnl_acct_list;
+#endif
 #endif
 #ifdef CONFIG_WEXT_CORE
 	struct sk_buff_head	wext_nlevents;

net/netfilter/nfnetlink_acct.c

···
 MODULE_AUTHOR("Pablo Neira Ayuso <[e-mail]>");
 MODULE_DESCRIPTION("nfacct: Extended Netfilter accounting infrastructure");
 
-static LIST_HEAD(nfnl_acct_list);
-
 struct nf_acct {
 	atomic64_t		pkts;
 	atomic64_t		bytes;
···
 	     const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
 	struct nf_acct *nfacct, *matching = NULL;
+	struct net *net = sock_net(nfnl);
 	char *acct_name;
 	unsigned int size = 0;
 	u32 flags = 0;
···
 	if (strlen(acct_name) == 0)
 		return -EINVAL;
 
-	list_for_each_entry(nfacct, &nfnl_acct_list, head) {
+	list_for_each_entry(nfacct, &net->nfnl_acct_list, head) {
 		if (strncmp(nfacct->name, acct_name, NFACCT_NAME_MAX) != 0)
 			continue;
 
···
 			     be64_to_cpu(nla_get_be64(tb[NFACCT_PKTS])));
 	}
 	atomic_set(&nfacct->refcnt, 1);
-	list_add_tail_rcu(&nfacct->head, &nfnl_acct_list);
+	list_add_tail_rcu(&nfacct->head, &net->nfnl_acct_list);
 	return 0;
 }
 
···
 static int
 nfnl_acct_dump(struct sk_buff *skb, struct netlink_callback *cb)
 {
+	struct net *net = sock_net(skb->sk);
 	struct nf_acct *cur, *last;
 	const struct nfacct_filter *filter = cb->data;
 
···
 		cb->args[1] = 0;
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(cur, &nfnl_acct_list, head) {
+	list_for_each_entry_rcu(cur, &net->nfnl_acct_list, head) {
 		if (last) {
 			if (cur != last)
 				continue;
···
 nfnl_acct_get(struct sock *nfnl, struct sk_buff *skb,
 	     const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
+	struct net *net = sock_net(nfnl);
 	int ret = -ENOENT;
 	struct nf_acct *cur;
 	char *acct_name;
···
 		return -EINVAL;
 	acct_name = nla_data(tb[NFACCT_NAME]);
 
-	list_for_each_entry(cur, &nfnl_acct_list, head) {
+	list_for_each_entry(cur, &net->nfnl_acct_list, head) {
 		struct sk_buff *skb2;
 
 		if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
···
 nfnl_acct_del(struct sock *nfnl, struct sk_buff *skb,
 	     const struct nlmsghdr *nlh, const struct nlattr * const tb[])
 {
+	struct net *net = sock_net(nfnl);
 	char *acct_name;
 	struct nf_acct *cur;
 	int ret = -ENOENT;
 
 	if (!tb[NFACCT_NAME]) {
-		list_for_each_entry(cur, &nfnl_acct_list, head)
+		list_for_each_entry(cur, &net->nfnl_acct_list, head)
 			nfnl_acct_try_del(cur);
 
 		return 0;
 	}
 	acct_name = nla_data(tb[NFACCT_NAME]);
 
-	list_for_each_entry(cur, &nfnl_acct_list, head) {
+	list_for_each_entry(cur, &net->nfnl_acct_list, head) {
 		if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX) != 0)
 			continue;
 
···
 
 MODULE_ALIAS_NFNL_SUBSYS(NFNL_SUBSYS_ACCT);
 
-struct nf_acct *nfnl_acct_find_get(const char *acct_name)
+struct nf_acct *nfnl_acct_find_get(struct net *net, const char *acct_name)
 {
 	struct nf_acct *cur, *acct = NULL;
 
 	rcu_read_lock();
-	list_for_each_entry_rcu(cur, &nfnl_acct_list, head) {
+	list_for_each_entry_rcu(cur, &net->nfnl_acct_list, head) {
 		if (strncmp(cur->name, acct_name, NFACCT_NAME_MAX)!= 0)
 			continue;
 
···
 
 void nfnl_acct_put(struct nf_acct *acct)
 {
-	atomic_dec(&acct->refcnt);
+	if (atomic_dec_and_test(&acct->refcnt))
+		kfree_rcu(acct, rcu_head);
+
 	module_put(THIS_MODULE);
 }
 EXPORT_SYMBOL_GPL(nfnl_acct_put);
···
 }
 EXPORT_SYMBOL_GPL(nfnl_acct_overquota);
 
+static int __net_init nfnl_acct_net_init(struct net *net)
+{
+	INIT_LIST_HEAD(&net->nfnl_acct_list);
+
+	return 0;
+}
+
+static void __net_exit nfnl_acct_net_exit(struct net *net)
+{
+	struct nf_acct *cur, *tmp;
+
+	list_for_each_entry_safe(cur, tmp, &net->nfnl_acct_list, head) {
+		list_del_rcu(&cur->head);
+
+		if (atomic_dec_and_test(&cur->refcnt))
+			kfree_rcu(cur, rcu_head);
+	}
+}
+
+static struct pernet_operations nfnl_acct_ops = {
+        .init   = nfnl_acct_net_init,
+        .exit   = nfnl_acct_net_exit,
+};
+
 static int __init nfnl_acct_init(void)
 {
 	int ret;
+
+	ret = register_pernet_subsys(&nfnl_acct_ops);
+	if (ret < 0) {
+		pr_err("nfnl_acct_init: failed to register pernet ops\n");
+		goto err_out;
+	}
 
 	pr_info("nfnl_acct: registering with nfnetlink.\n");
 	ret = nfnetlink_subsys_register(&nfnl_acct_subsys);
 	if (ret < 0) {
 		pr_err("nfnl_acct_init: cannot register with nfnetlink.\n");
-		goto err_out;
+		goto cleanup_pernet;
 	}
 	return 0;
+
+cleanup_pernet:
+	unregister_pernet_subsys(&nfnl_acct_ops);
 err_out:
 	return ret;
 }
 
 static void __exit nfnl_acct_exit(void)
 {
-	struct nf_acct *cur, *tmp;
-
 	pr_info("nfnl_acct: unregistering from nfnetlink.\n");
 	nfnetlink_subsys_unregister(&nfnl_acct_subsys);
-
-	list_for_each_entry_safe(cur, tmp, &nfnl_acct_list, head) {
-		list_del_rcu(&cur->head);
-		/* We are sure that our objects have no clients at this point,
-		 * it's safe to release them all without checking refcnt. */
-		kfree_rcu(cur, rcu_head);
-	}
+	unregister_pernet_subsys(&nfnl_acct_ops);
 }
 
 module_init(nfnl_acct_init);

net/netfilter/xt_nfacct.c

···
 	struct xt_nfacct_match_info *info = par->matchinfo;
 	struct nf_acct *nfacct;
 
-	nfacct = nfnl_acct_find_get(info->name);
+	nfacct = nfnl_acct_find_get(par->net, info->name);
 	if (nfacct == NULL) {
 		pr_info("xt_nfacct: accounting object with name `%s' "
 			"does not exists\n", info->name);