[PATCH 5.4 147/215] netfilter: nf_tables: Fix potential data-race in __nft_flowtable_type_get()

Greg Kroah-Hartman
2024-04-11T10:23:36Z

From: Ziyang Xuan <william.xuanziyang@huawei.com>

commit 24225011d81b471acc0e1e315b7d9905459a6304 upstream.

nft_unregister_flowtable_type() within nf_flow_inet_module_exit() can
concurrent with __nft_flowtable_type_get() within nf_tables_newflowtable().
And thhere is not any protection when iterate over nf_tables_flowtables
list in __nft_flowtable_type_get(). Therefore, there is pertential
data-race of nf_tables_flowtables list entry.

Use list_for_each_entry_rcu() to iterate over nf_tables_flowtables list
in __nft_flowtable_type_get(), and use rcu_read_lock() in the caller
nft_flowtable_type_get() to protect the entire type query process.

Fixes: 3b49e2e94e6e ("netfilter: nf_tables: add flow table netlink frontend")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/netfilter/nf_tables_api.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -6041,11 +6041,12 @@ static int nf_tables_flowtable_parse_hoo
return err;
}

+/* call under rcu_read_lock */
static const struct nf_flowtable_type *__nft_flowtable_type_get(u8 family)
{
const struct nf_flowtable_type *type;

- list_for_each_entry(type, &nf_tables_flowtables, list) {
+ list_for_each_entry_rcu(type, &nf_tables_flowtables, list) {
if (family == type->family)
return type;
}
@@ -6057,9 +6058,13 @@ nft_flowtable_type_get(struct net *net,
{
const struct nf_flowtable_type *type;

+ rcu_read_lock();
type = __nft_flowtable_type_get(family);
- if (type != NULL && try_module_get(type->owner))
+ if (type != NULL && try_module_get(type->owner)) {
+ rcu_read_unlock();
return type;
+ }
+ rcu_read_unlock();

lockdep_nfnl_nft_mutex_not_held();
#ifdef CONFIG_MODULES