[PATCH 6.6 033/158] netfilter: nf_tables: Fix potential data-race in __nft_expr_type_get()

Greg Kroah-Hartman
2024-04-23T21:42:58Z

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

[ Upstream commit f969eb84ce482331a991079ab7a5c4dc3b7f89bf ]

nft_unregister_expr() can concurrent with __nft_expr_type_get(),
and there is not any protection when iterate over nf_tables_expressions
list in __nft_expr_type_get(). Therefore, there is potential data-race
of nf_tables_expressions list entry.

Use list_for_each_entry_rcu() to iterate over nf_tables_expressions
list in __nft_expr_type_get(), and use rcu_read_lock() in the caller
nft_expr_type_get() to protect the entire type query process.

Fixes: ef1f7df9170d ("netfilter: nf_tables: expression ops overloading")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_tables_api.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 2a4649df8f086..fe6ee16e2dbf4 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3047,7 +3047,7 @@ static const struct nft_expr_type *__nft_expr_type_get(u8 family,
{
const struct nft_expr_type *type, *candidate = NULL;

- list_for_each_entry(type, &nf_tables_expressions, list) {
+ list_for_each_entry_rcu(type, &nf_tables_expressions, list) {
if (!nla_strcmp(nla, type->name)) {
if (!type->family && !candidate)
candidate = type;
@@ -3079,9 +3079,13 @@ static const struct nft_expr_type *nft_expr_type_get(struct net *net,
if (nla == NULL)
return ERR_PTR(-EINVAL);

+ rcu_read_lock();
type = __nft_expr_type_get(family, nla);
- 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
--
2.43.0