netfilter: nf_tables: Fix potential data-race in __nft_obj_type_get()

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

Use list_for_each_entry_rcu() to iterate over nf_tables_objects
list in __nft_obj_type_get(), and use rcu_read_lock() in the caller
nft_obj_type_get() to protect the entire type query process.

Fixes: e50092404c1b ("netfilter: nf_tables: add stateful objects")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 53b8c00863ad214ad89aa8e85531dff98cc455f3..f11d0c0a2c7352bb3419e3de14778555e25c5f39 100644 (file)
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -7611,7 +7611,7 @@ static const struct nft_object_type *__nft_obj_type_get(u32 objtype, u8 family)
 {
        const struct nft_object_type *type;
 
-       list_for_each_entry(type, &nf_tables_objects, list) {
+       list_for_each_entry_rcu(type, &nf_tables_objects, list) {
                if (type->family != NFPROTO_UNSPEC &&
                    type->family != family)
                        continue;
@@ -7627,9 +7627,13 @@ nft_obj_type_get(struct net *net, u32 objtype, u8 family)
 {
        const struct nft_object_type *type;
 
+       rcu_read_lock();
        type = __nft_obj_type_get(objtype, 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