[PATCH nf,v2] netfilter: nf_tables: release flowtable after rcu grace period on error

[Pablo Neira Ayuso <pablo@netfilter.org>]

Call synchronize_rcu() after unregistering the hooks from error path,
since a hook that already refers to this flowtable can be already
registered, exposing this flowtable to packet path and nfnetlink_hook
control plane.

This error path is rare, it should only happen by reaching the maximum
number hooks or by failing to set up to hardware offload, just call
synchronize_rcu(). There is a check for duplicates but the hook parser
already checks this.

Uncovered by KASAN reported as use-after-free from nfnetlink_hook path
when dumping hooks.

Fixes: 3b49e2e94e6e ("netfilter: nf_tables: add flow table netlink frontend")
Reported-by: Yiming Qian <yimingqian591@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
---
v2: use synchronize_rcu()

 net/netfilter/nf_tables_api.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 72c1db7738dc..da82a754ba33 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -9155,6 +9155,7 @@ static int nf_tables_newflowtable(struct sk_buff *skb,
 	return 0;
 
 err_flowtable_hooks:
+	synchronize_rcu();
 	nft_trans_destroy(trans);
 err_flowtable_trans:
 	nft_hooks_destroy(&flowtable->hook_list);
-- 
2.47.3