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

jira LE-3201
cve CVE-2024-35898
Rebuild_History Non-Buildable kernel-rt-4.18.0-553.27.1.rt7.368.el8_10
commit-author Ziyang Xuan <[email protected]>
commit 2422501

nft_unregister_flowtable_type() within nf_flow_inet_module_exit() can
concurrent with __nft_flowtable_type_get() within nf_tables_newflowtable().
And thhere is not any protection when iterate over nf_tables_flowtables
list in __nft_flowtable_type_get(). Therefore, there is pertential
data-race of nf_tables_flowtables list entry.

Use list_for_each_entry_rcu() to iterate over nf_tables_flowtables list
in __nft_flowtable_type_get(), and use rcu_read_lock() in the caller
nft_flowtable_type_get() to protect the entire type query process.

Fixes: 3b49e2e ("netfilter: nf_tables: add flow table netlink frontend")
	Signed-off-by: Ziyang Xuan <[email protected]>
	Signed-off-by: Pablo Neira Ayuso <[email protected]>
(cherry picked from commit 2422501)
	Signed-off-by: Jonathan Maple <[email protected]>

Author: PlaidCat

net/netfilter/nf_tables_api.c

@@ -6819,11 +6819,12 @@ static int nf_tables_flowtable_parse_hook(const struct nft_ctx *ctx,
 	return err;
 }
 
+/* call under rcu_read_lock */
 static const struct nf_flowtable_type *__nft_flowtable_type_get(u8 family)
 {
 	const struct nf_flowtable_type *type;
 
-	list_for_each_entry(type, &nf_tables_flowtables, list) {
+	list_for_each_entry_rcu(type, &nf_tables_flowtables, list) {
 		if (family == type->family)
 			return type;
 	}
@@ -6835,9 +6836,13 @@ nft_flowtable_type_get(struct net *net, u8 family)
 {
 	const struct nf_flowtable_type *type;
 
+	rcu_read_lock();
 	type = __nft_flowtable_type_get(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