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

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: ef1f7df917 ("netfilter: nf_tables: expression ops overloading")
Signed-off-by: Ziyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Ziyang Xuan 2024-04-07 14:56:04 +08:00 committed by Pablo Neira Ayuso
parent 19fa4f2a85
commit f969eb84ce
1 changed files with 6 additions and 2 deletions
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8
net/netfilter/nf_tables_api.c
View File

@ -3060,7 +3060,7 @@ 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;
@ -3092,9 +3092,13 @@ 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