[Devel] [PATCH vz9] netfilter: nf_tables: netlink notifier might race to release objects

[Alexander Atanasov]

From: Pablo Neira Ayuso <pablo at netfilter.org>

commit release path is invoked via call_rcu and it runs lockless to
release the objects after rcu grace period. The netlink notifier handler
might win race to remove objects that the transaction context is still
referencing from the commit release path.

Call rcu_barrier() to ensure pending rcu callbacks run to completion
if the list of transactions to be destroyed is not empty.

Fixes: 6001a930ce03 ("netfilter: nftables: introduce table ownership")
Reported-by: syzbot+8f747f62763bc6c32916 at syzkaller.appspotmail.com
Signed-off-by: Pablo Neira Ayuso <pablo at netfilter.org>
(cherry picked from commit d4bc8271db21ea9f1c86a1ca4d64999f184d4aae)
https://jira.sw.ru/browse/PSBM-144955
Signed-off-by: Alexander Atanasov <alexander.atanasov at virtuozzo.com>
---
 net/netfilter/nf_tables_api.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 77446ce9548d..b22854e34427 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -9821,6 +9821,8 @@ static int nft_rcv_nl_event(struct notifier_block *this, unsigned long event,
 	nft_net = nft_pernet(net);
 	deleted = 0;
 	mutex_lock(&nft_net->commit_mutex);
+	if (!list_empty(&nf_tables_destroy_list))
+		rcu_barrier();
 again:
 	list_for_each_entry(table, &nft_net->tables, list) {
 		if (nft_table_has_owner(table) &&
-- 
2.31.1