Commit f969eb84 authored by Ziyang Xuan's avatar Ziyang Xuan Committed by Pablo Neira Ayuso
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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: ef1f7df9 ("netfilter: nf_tables: expression ops overloading")
Signed-off-by: default avatarZiyang Xuan <william.xuanziyang@huawei.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 19fa4f2a

net/netfilter/nf_tables_api.c

+6 −2
Original line number Diff line number Diff line
@@ -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