netfilter: ip_tables: pass table pointer via nf_hook_ops

iptable_x modules rely on 'struct net' to contain a pointer to the
table that should be evaluated.

In order to remove these pointers from struct net, pass them via
the 'priv' pointer in a similar fashion as nf_tables passes the
rule data.

To do that, duplicate the nf_hook_info array passed in from the
iptable_x modules, update the ops->priv pointers of the copy to
refer to the table and then change the hookfn implementations to
just pass the 'priv' argument to the traverser.

After this patch, the xt_table pointers can already be removed
from struct net.

However, changes to struct net result in re-compile of the entire
network stack, so do the removal after arptables and ip6tables
have been converted as well.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 36 insertions, 17 deletions

diff --git a/net/ipv4/netfilter/ip_tables.c b/net/ipv4/netfilter/ip_tables.c
index 0b859ec2d3f8..d6caaed5dd45 100644
--- a/net/ipv4/netfilter/ip_tables.c
+++ b/net/ipv4/netfilter/ip_tables.c
@@ -1716,9 +1716,11 @@ static void __ipt_unregister_table(struct net *net, struct xt_table *table)
 
 int ipt_register_table(struct net *net, const struct xt_table *table,
 		       const struct ipt_replace *repl,
-		       const struct nf_hook_ops *ops, struct xt_table **res)
+		       const struct nf_hook_ops *template_ops)
 {
-	int ret;
+	struct nf_hook_ops *ops;
+	unsigned int num_ops;
+	int ret, i;
 	struct xt_table_info *newinfo;
 	struct xt_table_info bootstrap = {0};
 	void *loc_cpu_entry;
@@ -1732,40 +1734,57 @@ int ipt_register_table(struct net *net, const struct xt_table *table,
 	memcpy(loc_cpu_entry, repl->entries, repl->size);
 
 	ret = translate_table(net, newinfo, loc_cpu_entry, repl);
-	if (ret != 0)
-		goto out_free;
+	if (ret != 0) {
+		xt_free_table_info(newinfo);
+		return ret;
+	}
 
 	new_table = xt_register_table(net, table, &bootstrap, newinfo);
 	if (IS_ERR(new_table)) {
-		ret = PTR_ERR(new_table);
-		goto out_free;
+		xt_free_table_info(newinfo);
+		return PTR_ERR(new_table);
 	}
 
-	/* set res now, will see skbs right after nf_register_net_hooks */
-	WRITE_ONCE(*res, new_table);
-	if (!ops)
+	/* No template? No need to do anything. This is used by 'nat' table, it registers
+	 * with the nat core instead of the netfilter core.
+	 */
+	if (!template_ops)
 		return 0;
 
-	ret = nf_register_net_hooks(net, ops, hweight32(table->valid_hooks));
-	if (ret != 0) {
-		__ipt_unregister_table(net, new_table);
-		*res = NULL;
+	num_ops = hweight32(table->valid_hooks);
+	if (num_ops == 0) {
+		ret = -EINVAL;
+		goto out_free;
 	}
 
+	ops = kmemdup(template_ops, sizeof(*ops) * num_ops, GFP_KERNEL);
+	if (!ops) {
+		ret = -ENOMEM;
+		goto out_free;
+	}
+
+	for (i = 0; i < num_ops; i++)
+		ops[i].priv = new_table;
+
+	new_table->ops = ops;
+
+	ret = nf_register_net_hooks(net, ops, num_ops);
+	if (ret != 0)
+		goto out_free;
+
 	return ret;
 
 out_free:
-	xt_free_table_info(newinfo);
+	__ipt_unregister_table(net, new_table);
 	return ret;
 }
 
-void ipt_unregister_table_pre_exit(struct net *net, const char *name,
-				   const struct nf_hook_ops *ops)
+void ipt_unregister_table_pre_exit(struct net *net, const char *name)
 {
 	struct xt_table *table = xt_find_table(net, NFPROTO_IPV4, name);
 
 	if (table)
-		nf_unregister_net_hooks(net, ops, hweight32(table->valid_hooks));
+		nf_unregister_net_hooks(net, table->ops, hweight32(table->valid_hooks));
 }
 
 void ipt_unregister_table_exit(struct net *net, const char *name)