[PATCH v3 nf 7/8] netfilter: ebtables: close dangling table module init race

[Florian Westphal <fw@strlen.de>]

sashiko reported for a related patch:
 In modules like iptable_raw.c, [..], if register_pernet_subsys() fails,
 the rollback might call kfree(rawtable_ops) before [..]
 During this window, could a concurrent userspace process find the globally
 visible template, trigger table_init(), [..]

The table init functions must always register the template last.

Otherwise, set/getsockopt can instantiate a table in a namespace
while the required pernet ops (contain the destructor) isn't available.
This change is also required in x_tables, handled in followup change.

Fixes: 87663c39f898 ("netfilter: ebtables: do not hook tables by default")
Reviewed-by: Tristan Madani <tristan@talencesecurity.com>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 v3: no changes.
 net/bridge/netfilter/ebtable_broute.c | 12 +++++-------
 net/bridge/netfilter/ebtable_filter.c | 12 +++++-------
 net/bridge/netfilter/ebtable_nat.c    | 10 ++++------
 3 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/net/bridge/netfilter/ebtable_broute.c b/net/bridge/netfilter/ebtable_broute.c
index e6f9e343b41f..f05c79f215ea 100644
--- a/net/bridge/netfilter/ebtable_broute.c
+++ b/net/bridge/netfilter/ebtable_broute.c
@@ -112,18 +112,16 @@ static struct pernet_operations broute_net_ops = {
 
 static int __init ebtable_broute_init(void)
 {
-	int ret = ebt_register_template(&broute_table, broute_table_init);
+	int ret = register_pernet_subsys(&broute_net_ops);
 
 	if (ret)
 		return ret;
 
-	ret = register_pernet_subsys(&broute_net_ops);
-	if (ret) {
-		ebt_unregister_template(&broute_table);
-		return ret;
-	}
+	ret = ebt_register_template(&broute_table, broute_table_init);
+	if (ret)
+		unregister_pernet_subsys(&broute_net_ops);
 
-	return 0;
+	return ret;
 }
 
 static void __exit ebtable_broute_fini(void)
diff --git a/net/bridge/netfilter/ebtable_filter.c b/net/bridge/netfilter/ebtable_filter.c
index 02b6501c15a5..0fc03b07e62a 100644
--- a/net/bridge/netfilter/ebtable_filter.c
+++ b/net/bridge/netfilter/ebtable_filter.c
@@ -93,18 +93,16 @@ static struct pernet_operations frame_filter_net_ops = {
 
 static int __init ebtable_filter_init(void)
 {
-	int ret = ebt_register_template(&frame_filter, frame_filter_table_init);
+	int ret = register_pernet_subsys(&frame_filter_net_ops);
 
 	if (ret)
 		return ret;
 
-	ret = register_pernet_subsys(&frame_filter_net_ops);
-	if (ret) {
-		ebt_unregister_template(&frame_filter);
-		return ret;
-	}
+	ret = ebt_register_template(&frame_filter, frame_filter_table_init);
+	if (ret)
+		unregister_pernet_subsys(&frame_filter_net_ops);
 
-	return 0;
+	return ret;
 }
 
 static void __exit ebtable_filter_fini(void)
diff --git a/net/bridge/netfilter/ebtable_nat.c b/net/bridge/netfilter/ebtable_nat.c
index 9985a82555c4..8a10375d8909 100644
--- a/net/bridge/netfilter/ebtable_nat.c
+++ b/net/bridge/netfilter/ebtable_nat.c
@@ -93,16 +93,14 @@ static struct pernet_operations frame_nat_net_ops = {
 
 static int __init ebtable_nat_init(void)
 {
-	int ret = ebt_register_template(&frame_nat, frame_nat_table_init);
+	int ret = register_pernet_subsys(&frame_nat_net_ops);
 
 	if (ret)
 		return ret;
 
-	ret = register_pernet_subsys(&frame_nat_net_ops);
-	if (ret) {
-		ebt_unregister_template(&frame_nat);
-		return ret;
-	}
+	ret = ebt_register_template(&frame_nat, frame_nat_table_init);
+	if (ret)
+		unregister_pernet_subsys(&frame_nat_net_ops);
 
 	return ret;
 }
-- 
2.53.0