Merge branch 'rtnetlink-handle-error-of-rtnl_register_module'

Kuniyuki Iwashima says:

====================
rtnetlink: Handle error of rtnl_register_module().

While converting phonet to per-netns RTNL, I found a weird comment

  /* Further rtnl_register_module() cannot fail */

that was true but no longer true after commit addf9b9 ("net:
rtnetlink: use rcu to free rtnl message handlers").

Many callers of rtnl_register_module() just ignore the returned
value but should handle them properly.

This series introduces two helpers, rtnl_register_many() and
rtnl_unregister_many(), to do that easily and fix such callers.

All rtnl_register() and rtnl_register_module() will be converted
to _many() variant and some rtnl_lock() will be saved in _many()
later in net-next.

Changes:
  v4:
    * Add more context in changelog of each patch

  v3: https://lore.kernel.org/all/20241007124459.5727-1-kuniyu@amazon.com/
    * Move module *owner to struct rtnl_msg_handler
    * Make struct rtnl_msg_handler args/vars const
    * Update mctp goto labels

  v2: https://lore.kernel.org/netdev/20241004222358.79129-1-kuniyu@amazon.com/
    * Remove __exit from mctp_neigh_exit().

  v1: https://lore.kernel.org/netdev/20241003205725.5612-1-kuniyu@amazon.com/
====================

Link: https://patch.msgid.link/20241008184737.9619-1-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

drivers/net/vxlan/vxlan_core.c

@@ -4913,9 +4913,13 @@ static int __init vxlan_init_module(void)
 	if (rc)
 		goto out4;
 
-	vxlan_vnifilter_init();
+	rc = vxlan_vnifilter_init();
+	if (rc)
+		goto out5;
 
 	return 0;
+out5:
+	rtnl_link_unregister(&vxlan_link_ops);
 out4:
 	unregister_switchdev_notifier(&vxlan_switchdev_notifier_block);
 out3:

drivers/net/vxlan/vxlan_private.h

@@ -202,7 +202,7 @@ int vxlan_vni_in_use(struct net *src_net, struct vxlan_dev *vxlan,
 int vxlan_vnigroup_init(struct vxlan_dev *vxlan);
 void vxlan_vnigroup_uninit(struct vxlan_dev *vxlan);
 
-void vxlan_vnifilter_init(void);
+int vxlan_vnifilter_init(void);
 void vxlan_vnifilter_uninit(void);
 void vxlan_vnifilter_count(struct vxlan_dev *vxlan, __be32 vni,
 			   struct vxlan_vni_node *vninode,

drivers/net/vxlan/vxlan_vnifilter.c

@@ -992,19 +992,18 @@ static int vxlan_vnifilter_process(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return err;
 }
 
-void vxlan_vnifilter_init(void)
+static const struct rtnl_msg_handler vxlan_vnifilter_rtnl_msg_handlers[] = {
+	{THIS_MODULE, PF_BRIDGE, RTM_GETTUNNEL, NULL, vxlan_vnifilter_dump, 0},
+	{THIS_MODULE, PF_BRIDGE, RTM_NEWTUNNEL, vxlan_vnifilter_process, NULL, 0},
+	{THIS_MODULE, PF_BRIDGE, RTM_DELTUNNEL, vxlan_vnifilter_process, NULL, 0},
+};
+
+int vxlan_vnifilter_init(void)
 {
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_GETTUNNEL, NULL,
-			     vxlan_vnifilter_dump, 0);
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_NEWTUNNEL,
-			     vxlan_vnifilter_process, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_DELTUNNEL,
-			     vxlan_vnifilter_process, NULL, 0);
+	return rtnl_register_many(vxlan_vnifilter_rtnl_msg_handlers);
 }
 
 void vxlan_vnifilter_uninit(void)
 {
-	rtnl_unregister(PF_BRIDGE, RTM_GETTUNNEL);
-	rtnl_unregister(PF_BRIDGE, RTM_NEWTUNNEL);
-	rtnl_unregister(PF_BRIDGE, RTM_DELTUNNEL);
+	rtnl_unregister_many(vxlan_vnifilter_rtnl_msg_handlers);
 }

include/net/mctp.h

@@ -295,7 +295,7 @@ void mctp_neigh_remove_dev(struct mctp_dev *mdev);
 int mctp_routes_init(void);
 void mctp_routes_exit(void);
 
-void mctp_device_init(void);
+int mctp_device_init(void);
 void mctp_device_exit(void);
 
 #endif /* __NET_MCTP_H */

include/net/rtnetlink.h

@@ -29,13 +29,30 @@ static inline enum rtnl_kinds rtnl_msgtype_kind(int msgtype)
 	return msgtype & RTNL_KIND_MASK;
 }
 
+struct rtnl_msg_handler {
+	struct module *owner;
+	int protocol;
+	int msgtype;
+	rtnl_doit_func doit;
+	rtnl_dumpit_func dumpit;
+	int flags;
+};
+
 void rtnl_register(int protocol, int msgtype,
 		   rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);
 int rtnl_register_module(struct module *owner, int protocol, int msgtype,
 			 rtnl_doit_func, rtnl_dumpit_func, unsigned int flags);
 int rtnl_unregister(int protocol, int msgtype);
 void rtnl_unregister_all(int protocol);
 
+int __rtnl_register_many(const struct rtnl_msg_handler *handlers, int n);
+void __rtnl_unregister_many(const struct rtnl_msg_handler *handlers, int n);
+
+#define rtnl_register_many(handlers)				\
+	__rtnl_register_many(handlers, ARRAY_SIZE(handlers))
+#define rtnl_unregister_many(handlers)				\
+	__rtnl_unregister_many(handlers, ARRAY_SIZE(handlers))
+
 static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
 {
 	if (nlmsg_len(nlh) >= sizeof(struct rtgenmsg))

net/bridge/br_netlink.c

@@ -1920,7 +1920,10 @@ int __init br_netlink_init(void)
 {
 	int err;
 
-	br_vlan_rtnl_init();
+	err = br_vlan_rtnl_init();
+	if (err)
+		goto out;
+
 	rtnl_af_register(&br_af_ops);
 
 	err = rtnl_link_register(&br_link_ops);
@@ -1931,6 +1934,7 @@ int __init br_netlink_init(void)
 
 out_af:
 	rtnl_af_unregister(&br_af_ops);
+out:
 	return err;
 }
 

net/bridge/br_private.h

@@ -1571,7 +1571,7 @@ void br_vlan_get_stats(const struct net_bridge_vlan *v,
 void br_vlan_port_event(struct net_bridge_port *p, unsigned long event);
 int br_vlan_bridge_event(struct net_device *dev, unsigned long event,
 			 void *ptr);
-void br_vlan_rtnl_init(void);
+int br_vlan_rtnl_init(void);
 void br_vlan_rtnl_uninit(void);
 void br_vlan_notify(const struct net_bridge *br,
 		    const struct net_bridge_port *p,
@@ -1802,8 +1802,9 @@ static inline int br_vlan_bridge_event(struct net_device *dev,
 	return 0;
 }
 
-static inline void br_vlan_rtnl_init(void)
+static inline int br_vlan_rtnl_init(void)
 {
+	return 0;
 }
 
 static inline void br_vlan_rtnl_uninit(void)

net/bridge/br_vlan.c

@@ -2296,19 +2296,18 @@ static int br_vlan_rtm_process(struct sk_buff *skb, struct nlmsghdr *nlh,
 	return err;
 }
 
-void br_vlan_rtnl_init(void)
+static const struct rtnl_msg_handler br_vlan_rtnl_msg_handlers[] = {
+	{THIS_MODULE, PF_BRIDGE, RTM_NEWVLAN, br_vlan_rtm_process, NULL, 0},
+	{THIS_MODULE, PF_BRIDGE, RTM_DELVLAN, br_vlan_rtm_process, NULL, 0},
+	{THIS_MODULE, PF_BRIDGE, RTM_GETVLAN, NULL, br_vlan_rtm_dump, 0},
+};
+
+int br_vlan_rtnl_init(void)
 {
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_GETVLAN, NULL,
-			     br_vlan_rtm_dump, 0);
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_NEWVLAN,
-			     br_vlan_rtm_process, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_BRIDGE, RTM_DELVLAN,
-			     br_vlan_rtm_process, NULL, 0);
+	return rtnl_register_many(br_vlan_rtnl_msg_handlers);
 }
 
 void br_vlan_rtnl_uninit(void)
 {
-	rtnl_unregister(PF_BRIDGE, RTM_GETVLAN);
-	rtnl_unregister(PF_BRIDGE, RTM_NEWVLAN);
-	rtnl_unregister(PF_BRIDGE, RTM_DELVLAN);
+	rtnl_unregister_many(br_vlan_rtnl_msg_handlers);
 }

net/core/rtnetlink.c

@@ -384,6 +384,35 @@ void rtnl_unregister_all(int protocol)
 }
 EXPORT_SYMBOL_GPL(rtnl_unregister_all);
 
+int __rtnl_register_many(const struct rtnl_msg_handler *handlers, int n)
+{
+	const struct rtnl_msg_handler *handler;
+	int i, err;
+
+	for (i = 0, handler = handlers; i < n; i++, handler++) {
+		err = rtnl_register_internal(handler->owner, handler->protocol,
+					     handler->msgtype, handler->doit,
+					     handler->dumpit, handler->flags);
+		if (err) {
+			__rtnl_unregister_many(handlers, i);
+			break;
+		}
+	}
+
+	return err;
+}
+EXPORT_SYMBOL_GPL(__rtnl_register_many);
+
+void __rtnl_unregister_many(const struct rtnl_msg_handler *handlers, int n)
+{
+	const struct rtnl_msg_handler *handler;
+	int i;
+
+	for (i = n - 1, handler = handlers + n - 1; i >= 0; i--, handler--)
+		rtnl_unregister(handler->protocol, handler->msgtype);
+}
+EXPORT_SYMBOL_GPL(__rtnl_unregister_many);
+
 static LIST_HEAD(link_ops);
 
 static const struct rtnl_link_ops *rtnl_link_ops_get(const char *kind)

net/mctp/af_mctp.c

@@ -756,10 +756,14 @@ static __init int mctp_init(void)
 	if (rc)
 		goto err_unreg_routes;
 
-	mctp_device_init();
+	rc = mctp_device_init();
+	if (rc)
+		goto err_unreg_neigh;
 
 	return 0;
 
+err_unreg_neigh:
+	mctp_neigh_exit();
 err_unreg_routes:
 	mctp_routes_exit();
 err_unreg_proto:

net/mctp/device.c

@@ -524,25 +524,31 @@ static struct notifier_block mctp_dev_nb = {
 	.priority = ADDRCONF_NOTIFY_PRIORITY,
 };
 
-void __init mctp_device_init(void)
+static const struct rtnl_msg_handler mctp_device_rtnl_msg_handlers[] = {
+	{THIS_MODULE, PF_MCTP, RTM_NEWADDR, mctp_rtm_newaddr, NULL, 0},
+	{THIS_MODULE, PF_MCTP, RTM_DELADDR, mctp_rtm_deladdr, NULL, 0},
+	{THIS_MODULE, PF_MCTP, RTM_GETADDR, NULL, mctp_dump_addrinfo, 0},
+};
+
+int __init mctp_device_init(void)
 {
-	register_netdevice_notifier(&mctp_dev_nb);
+	int err;
 
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_GETADDR,
-			     NULL, mctp_dump_addrinfo, 0);
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_NEWADDR,
-			     mctp_rtm_newaddr, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_DELADDR,
-			     mctp_rtm_deladdr, NULL, 0);
+	register_netdevice_notifier(&mctp_dev_nb);
 	rtnl_af_register(&mctp_af_ops);
+
+	err = rtnl_register_many(mctp_device_rtnl_msg_handlers);
+	if (err) {
+		rtnl_af_unregister(&mctp_af_ops);
+		unregister_netdevice_notifier(&mctp_dev_nb);
+	}
+
+	return err;
 }
 
 void __exit mctp_device_exit(void)
 {
+	rtnl_unregister_many(mctp_device_rtnl_msg_handlers);
 	rtnl_af_unregister(&mctp_af_ops);
-	rtnl_unregister(PF_MCTP, RTM_DELADDR);
-	rtnl_unregister(PF_MCTP, RTM_NEWADDR);
-	rtnl_unregister(PF_MCTP, RTM_GETADDR);
-
 	unregister_netdevice_notifier(&mctp_dev_nb);
 }

net/mctp/neigh.c

@@ -322,22 +322,29 @@ static struct pernet_operations mctp_net_ops = {
 	.exit = mctp_neigh_net_exit,
 };
 
+static const struct rtnl_msg_handler mctp_neigh_rtnl_msg_handlers[] = {
+	{THIS_MODULE, PF_MCTP, RTM_NEWNEIGH, mctp_rtm_newneigh, NULL, 0},
+	{THIS_MODULE, PF_MCTP, RTM_DELNEIGH, mctp_rtm_delneigh, NULL, 0},
+	{THIS_MODULE, PF_MCTP, RTM_GETNEIGH, NULL, mctp_rtm_getneigh, 0},
+};
+
 int __init mctp_neigh_init(void)
 {
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_NEWNEIGH,
-			     mctp_rtm_newneigh, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_DELNEIGH,
-			     mctp_rtm_delneigh, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_GETNEIGH,
-			     NULL, mctp_rtm_getneigh, 0);
-
-	return register_pernet_subsys(&mctp_net_ops);
+	int err;
+
+	err = register_pernet_subsys(&mctp_net_ops);
+	if (err)
+		return err;
+
+	err = rtnl_register_many(mctp_neigh_rtnl_msg_handlers);
+	if (err)
+		unregister_pernet_subsys(&mctp_net_ops);
+
+	return err;
 }
 
-void __exit mctp_neigh_exit(void)
+void mctp_neigh_exit(void)
 {
+	rtnl_unregister_many(mctp_neigh_rtnl_msg_handlers);
 	unregister_pernet_subsys(&mctp_net_ops);
-	rtnl_unregister(PF_MCTP, RTM_GETNEIGH);
-	rtnl_unregister(PF_MCTP, RTM_DELNEIGH);
-	rtnl_unregister(PF_MCTP, RTM_NEWNEIGH);
 }

net/mctp/route.c

@@ -1474,26 +1474,39 @@ static struct pernet_operations mctp_net_ops = {
 	.exit = mctp_routes_net_exit,
 };
 
+static const struct rtnl_msg_handler mctp_route_rtnl_msg_handlers[] = {
+	{THIS_MODULE, PF_MCTP, RTM_NEWROUTE, mctp_newroute, NULL, 0},
+	{THIS_MODULE, PF_MCTP, RTM_DELROUTE, mctp_delroute, NULL, 0},
+	{THIS_MODULE, PF_MCTP, RTM_GETROUTE, NULL, mctp_dump_rtinfo, 0},
+};
+
 int __init mctp_routes_init(void)
 {
+	int err;
+
 	dev_add_pack(&mctp_packet_type);
 
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_GETROUTE,
-			     NULL, mctp_dump_rtinfo, 0);
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_NEWROUTE,
-			     mctp_newroute, NULL, 0);
-	rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_DELROUTE,
-			     mctp_delroute, NULL, 0);
+	err = register_pernet_subsys(&mctp_net_ops);
+	if (err)
+		goto err_pernet;
+
+	err = rtnl_register_many(mctp_route_rtnl_msg_handlers);
+	if (err)
+		goto err_rtnl;
 
-	return register_pernet_subsys(&mctp_net_ops);
+	return 0;
+
+err_rtnl:
+	unregister_pernet_subsys(&mctp_net_ops);
+err_pernet:
+	dev_remove_pack(&mctp_packet_type);
+	return err;
 }
 
 void mctp_routes_exit(void)
 {
+	rtnl_unregister_many(mctp_route_rtnl_msg_handlers);
 	unregister_pernet_subsys(&mctp_net_ops);
-	rtnl_unregister(PF_MCTP, RTM_DELROUTE);
-	rtnl_unregister(PF_MCTP, RTM_NEWROUTE);
-	rtnl_unregister(PF_MCTP, RTM_GETROUTE);
 	dev_remove_pack(&mctp_packet_type);
 }