Commit b38a133d authored Apr 07, 2024 by Ziyang Xuan Committed by Greg Kroah-Hartman May 02, 2024

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



[ 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: ef1f7df9 ("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>

parent 2450a69d

net/netfilter/nf_tables_api.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -2239,7 +2239,7 @@ 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;
		@@ -2271,9 +2271,13 @@ 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