net: Add ops_undo_single for module load/unload.

If ops_init() fails while loading a module or we unload the
module, free_exit_list() rolls back the changes.

The rollback sequence is the same as ops_undo_list().

The ops is already removed from pernet_list before calling
free_exit_list().  If we link the ops to a temporary list,
we can reuse ops_undo_list().

Let's add a wrapper of ops_undo_list() and use it instead
of free_exit_list().

Now, we have the central place to roll back ops_init().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://patch.msgid.link/20250411205258.63164-3-kuniyu@amazon.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 2612339efd7149d1c526635ae81b69d757c77089..37026776ae4e93a64d799773ba336a0e433760da 100644 (file)
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -235,6 +235,17 @@ static void ops_undo_list(const struct list_head *ops_list,
                ops_free_list(ops, net_exit_list);
 }
 
+static void ops_undo_single(struct pernet_operations *ops,
+                           struct list_head *net_exit_list)
+{
+       bool hold_rtnl = !!ops->exit_batch_rtnl;
+       LIST_HEAD(ops_list);
+
+       list_add(&ops->list, &ops_list);
+       ops_undo_list(&ops_list, NULL, net_exit_list, false, hold_rtnl);
+       list_del(&ops->list);
+}
+
 /* should be called with nsid_lock held */
 static int alloc_netid(struct net *net, struct net *peer, int reqid)
 {
@@ -1235,31 +1246,13 @@ void __init net_ns_init(void)
        rtnl_register_many(net_ns_rtnl_msg_handlers);
 }
 
-static void free_exit_list(struct pernet_operations *ops, struct list_head *net_exit_list)
-{
-       ops_pre_exit_list(ops, net_exit_list);
-       synchronize_rcu();
-
-       if (ops->exit_batch_rtnl) {
-               LIST_HEAD(dev_kill_list);
-
-               rtnl_lock();
-               ops->exit_batch_rtnl(net_exit_list, &dev_kill_list);
-               unregister_netdevice_many(&dev_kill_list);
-               rtnl_unlock();
-       }
-       ops_exit_list(ops, net_exit_list);
-
-       ops_free_list(ops, net_exit_list);
-}
-
 #ifdef CONFIG_NET_NS
 static int __register_pernet_operations(struct list_head *list,
                                        struct pernet_operations *ops)
 {
+       LIST_HEAD(net_exit_list);
        struct net *net;
        int error;
-       LIST_HEAD(net_exit_list);
 
        list_add_tail(&ops->list, list);
        if (ops->init || ops->id) {
@@ -1278,21 +1271,21 @@ static int __register_pernet_operations(struct list_head *list,
 out_undo:
        /* If I have an error cleanup all namespaces I initialized */
        list_del(&ops->list);
-       free_exit_list(ops, &net_exit_list);
+       ops_undo_single(ops, &net_exit_list);
        return error;
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
-       struct net *net;
        LIST_HEAD(net_exit_list);
+       struct net *net;
 
-       list_del(&ops->list);
        /* See comment in __register_pernet_operations() */
        for_each_net(net)
                list_add_tail(&net->exit_list, &net_exit_list);
 
-       free_exit_list(ops, &net_exit_list);
+       list_del(&ops->list);
+       ops_undo_single(ops, &net_exit_list);
 }
 
 #else
@@ -1300,22 +1293,23 @@ static void __unregister_pernet_operations(struct pernet_operations *ops)
 static int __register_pernet_operations(struct list_head *list,
                                        struct pernet_operations *ops)
 {
-       if (!init_net_initialized) {
-               list_add_tail(&ops->list, list);
+       list_add_tail(&ops->list, list);
+
+       if (!init_net_initialized)
                return 0;
-       }
 
        return ops_init(ops, &init_net);
 }
 
 static void __unregister_pernet_operations(struct pernet_operations *ops)
 {
-       if (!init_net_initialized) {
-               list_del(&ops->list);
-       } else {
+       list_del(&ops->list);
+
+       if (init_net_initialized) {
                LIST_HEAD(net_exit_list);
+
                list_add(&init_net.exit_list, &net_exit_list);
-               free_exit_list(ops, &net_exit_list);
+               ops_undo_single(ops, &net_exit_list);
        }
 }