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 pertential
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@xxxxxxxxxx>
---
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 47e1a22e8fb1..646d59685cfd 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3056,7 +3056,7 @@ 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;
@@ -3088,9 +3088,13 @@ 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
--
2.25.1
