From 2a6586ecfa4ce1413daaafee250d2590e05f1a33 Mon Sep 17 00:00:00 2001 From: Inseo An Date: Tue, 17 Feb 2026 21:14:40 +0900 Subject: netfilter: nf_tables: fix use-after-free in nf_tables_addchain() [ Upstream commit 71e99ee20fc3f662555118cf1159443250647533 ] nf_tables_addchain() publishes the chain to table->chains via list_add_tail_rcu() (in nft_chain_add()) before registering hooks. If nf_tables_register_hook() then fails, the error path calls nft_chain_del() (list_del_rcu()) followed by nf_tables_chain_destroy() with no RCU grace period in between. This creates two use-after-free conditions: 1) Control-plane: nf_tables_dump_chains() traverses table->chains under rcu_read_lock(). A concurrent dump can still be walking the chain when the error path frees it. 2) Packet path: for NFPROTO_INET, nf_register_net_hook() briefly installs the IPv4 hook before IPv6 registration fails. Packets entering nft_do_chain() via the transient IPv4 hook can still be dereferencing chain->blob_gen_X when the error path frees the chain. Add synchronize_rcu() between nft_chain_del() and the chain destroy so that all RCU readers -- both dump threads and in-flight packet evaluation -- have finished before the chain is freed. Fixes: 91c7b38dc9f0 ("netfilter: nf_tables: use new transaction infrastructure to handle chain") Signed-off-by: Inseo An Signed-off-by: Florian Westphal Signed-off-by: Sasha Levin --- net/netfilter/nf_tables_api.c | 1 + 1 file changed, 1 insertion(+) (limited to 'net') diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c index 67729d7c913a..ac3618395651 100644 --- a/net/netfilter/nf_tables_api.c +++ b/net/netfilter/nf_tables_api.c @@ -2510,6 +2510,7 @@ static int nf_tables_addchain(struct nft_ctx *ctx, u8 family, u8 genmask, err_register_hook: nft_chain_del(chain); + synchronize_rcu(); err_chain_add: nft_trans_destroy(trans); err_trans: -- cgit v1.2.3