Merge branch 'net-hold-instance-lock-during-netdev_up-register'

Stanislav Fomichev says:

====================
net: hold instance lock during NETDEV_UP/REGISTER

Solving the issue reported by Cosmin in [0] requires consistent
lock during NETDEV_UP/REGISTER notifiers. This series
addresses that (along with some other fixes in net/ipv4/devinet.c
and net/ipv6/addrconf.c) and appends the patches from Jakub
that were conditional on consistent locking in NETDEV_UNREGISTER.

0: https://lore.kernel.org/[e-mail]
====================

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

Documentation/networking/netdevices.rst

···
 acquiring the instance lock themselves, while the ``netif_xxx`` functions
 assume that the driver has already acquired the instance lock.
 
+Notifiers and netdev instance lock
+==================================
+
+For device drivers that implement shaping or queue management APIs,
+some of the notifiers (``enum netdev_cmd``) are running under the netdev
+instance lock.
+
+For devices with locked ops, currently only the following notifiers are
+running under the lock:
+* ``NETDEV_REGISTER``
+* ``NETDEV_UP``
+
+The following notifiers are running without the lock:
+* ``NETDEV_UNREGISTER``
+
+There are no clear expectations for the remaining notifiers. Notifiers not on
+the list may run with or without the instance lock, potentially even invoking
+the same notifier type with and without the lock from different code paths.
+The goal is to eventually ensure that all (or most, with a few documented
+exceptions) notifiers run under the instance lock. Please extend this
+documentation whenever you make explicit assumption about lock being held
+from a notifier.
+
 NETDEV_INTERNAL symbol namespace
 ================================
 

drivers/net/dummy.c

···
 	dev->netdev_ops = &dummy_netdev_ops;
 	dev->ethtool_ops = &dummy_ethtool_ops;
 	dev->needs_free_netdev = true;
+	dev->request_ops_lock = true;
 
 	/* Fill in device structure with ethernet-generic values. */
 	dev->flags |= IFF_NOARP;

drivers/net/netdevsim/netdev.c

···
 	ns->netdev->netdev_ops = &nsim_netdev_ops;
 	ns->netdev->stat_ops = &nsim_stat_ops;
 	ns->netdev->queue_mgmt_ops = &nsim_queue_mgmt_ops;
+	netdev_lockdep_set_classes(ns->netdev);
 
 	err = nsim_udp_tunnels_info_create(ns->nsim_dev, ns->netdev);
 	if (err)
···
 	if (err)
 		goto err_ipsec_teardown;
 	rtnl_unlock();
+
+	if (IS_ENABLED(CONFIG_DEBUG_NET)) {
+		ns->nb.notifier_call = netdev_debug_event;
+		if (register_netdevice_notifier_dev_net(ns->netdev, &ns->nb,
+							&ns->nn))
+			ns->nb.notifier_call = NULL;
+	}
+
 	return 0;
 
 err_ipsec_teardown:
···
 
 	debugfs_remove(ns->qr_dfs);
 	debugfs_remove(ns->pp_dfs);
+
+	if (ns->nb.notifier_call)
+		unregister_netdevice_notifier_dev_net(ns->netdev, &ns->nb,
+						      &ns->nn);
 
 	rtnl_lock();
 	peer = rtnl_dereference(ns->peer);

drivers/net/netdevsim/netdevsim.h

···
 
 	struct nsim_ethtool ethtool;
 	struct netdevsim __rcu *peer;
+
+	struct notifier_block nb;
+	struct netdev_net_notifier nn;
 };
 
 struct netdevsim *

include/linux/netdevice.h

···
 int netif_set_alias(struct net_device *dev, const char *alias, size_t len);
 int dev_set_alias(struct net_device *, const char *, size_t);
 int dev_get_alias(const struct net_device *, char *, size_t);
-int netif_change_net_namespace(struct net_device *dev, struct net *net,
+int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 			       const char *pat, int new_ifindex,
 			       struct netlink_ext_ack *extack);
 int dev_change_net_namespace(struct net_device *dev, struct net *net,

include/net/ip.h

···
 		memcpy(buf, &naddr, sizeof(naddr));
 }
 
-#if IS_MODULE(CONFIG_IPV6)
-#define EXPORT_IPV6_MOD(X) EXPORT_SYMBOL(X)
-#define EXPORT_IPV6_MOD_GPL(X) EXPORT_SYMBOL_GPL(X)
-#else
-#define EXPORT_IPV6_MOD(X)
-#define EXPORT_IPV6_MOD_GPL(X)
-#endif
-
 #if IS_ENABLED(CONFIG_IPV6)
 #include <linux/ipv6.h>
 #endif
···
 #endif
 }
 
+#endif
+
+#if IS_MODULE(CONFIG_IPV6)
+#define EXPORT_IPV6_MOD(X) EXPORT_SYMBOL(X)
+#define EXPORT_IPV6_MOD_GPL(X) EXPORT_SYMBOL_GPL(X)
+#else
+#define EXPORT_IPV6_MOD(X)
+#define EXPORT_IPV6_MOD_GPL(X)
 #endif
 
 static inline unsigned int ipv4_addr_hash(__be32 ip)

include/net/netdev_lock.h

···
 				  &qdisc_xmit_lock_key);	\
 }
 
+int netdev_debug_event(struct notifier_block *nb, unsigned long event,
+		       void *ptr);
+
 #endif

net/core/Makefile

···
 obj-$(CONFIG_OF)	+= of_net.o
 obj-$(CONFIG_NET_TEST) += net_test.o
 obj-$(CONFIG_NET_DEVMEM) += devmem.o
-obj-$(CONFIG_DEBUG_NET_SMALL_RTNL) += rtnl_net_debug.o
+obj-$(CONFIG_DEBUG_NET) += lock_debug.o
 obj-$(CONFIG_FAIL_SKB_REALLOC) += skb_fault_injection.o

net/core/dev.c

···
 		netdev_unlock_ops(lower_dev);
 	}
 }
+EXPORT_IPV6_MOD(netif_disable_lro);
 
 /**
  *	dev_disable_gro_hw - disable HW Generic Receive Offload on a device
···
 	int err;
 
 	for_each_netdev(net, dev) {
+		netdev_lock_ops(dev);
 		err = call_netdevice_register_notifiers(nb, dev);
+		netdev_unlock_ops(dev);
 		if (err)
 			goto rollback;
 	}
···
 		memcpy(dev->perm_addr, dev->dev_addr, dev->addr_len);
 
 	/* Notify protocols, that a new device appeared. */
+	netdev_lock_ops(dev);
 	ret = call_netdevice_notifiers(NETDEV_REGISTER, dev);
+	netdev_unlock_ops(dev);
 	ret = notifier_to_errno(ret);
 	if (ret) {
 		/* Expect explicit free_netdev() on failure */
···
 }
 EXPORT_SYMBOL(unregister_netdev);
 
-int netif_change_net_namespace(struct net_device *dev, struct net *net,
+int __dev_change_net_namespace(struct net_device *dev, struct net *net,
 			       const char *pat, int new_ifindex,
 			       struct netlink_ext_ack *extack)
 {
···
 	 * And now a mini version of register_netdevice unregister_netdevice.
 	 */
 
+	netdev_lock_ops(dev);
 	/* If device is running close it first. */
 	netif_close(dev);
-
 	/* And unlink it from device chain */
 	unlist_netdevice(dev);
+	netdev_unlock_ops(dev);
 
 	synchronize_net();
 
···
 	err = netdev_change_owner(dev, net_old, net);
 	WARN_ON(err);
 
+	netdev_lock_ops(dev);
 	/* Add the device back in the hashes */
 	list_netdevice(dev);
-
 	/* Notify protocols, that a new device appeared. */
 	call_netdevice_notifiers(NETDEV_REGISTER, dev);
+	netdev_unlock_ops(dev);
 
 	/*
 	 *	Prevent userspace races by waiting until the network

net/core/dev_api.c

···
 int dev_change_net_namespace(struct net_device *dev, struct net *net,
 			     const char *pat)
 {
-	int ret;
-
-	netdev_lock_ops(dev);
-	ret = netif_change_net_namespace(dev, net, pat, 0, NULL);
-	netdev_unlock_ops(dev);
-
-	return ret;
+	return __dev_change_net_namespace(dev, net, pat, 0, NULL);
 }
 EXPORT_SYMBOL_GPL(dev_change_net_namespace);
 

net/core/rtnetlink.c

···
 	char ifname[IFNAMSIZ];
 	int err;
 
-	netdev_lock_ops(dev);
-
 	err = validate_linkmsg(dev, tb, extack);
 	if (err < 0)
 		goto errout;
···
 
 		new_ifindex = nla_get_s32_default(tb[IFLA_NEW_IFINDEX], 0);
 
-		err = netif_change_net_namespace(dev, tgt_net, pat,
+		err = __dev_change_net_namespace(dev, tgt_net, pat,
 						 new_ifindex, extack);
 		if (err)
-			goto errout;
+			return err;
 
 		status |= DO_SETLINK_MODIFIED;
 	}
+
+	netdev_lock_ops(dev);
 
 	if (tb[IFLA_MAP]) {
 		struct rtnl_link_ifmap *u_map;

net/core/rtnl_net_debug.c net/core/lock_debug.c

···
 #include <linux/notifier.h>
 #include <linux/rtnetlink.h>
 #include <net/net_namespace.h>
+#include <net/netdev_lock.h>
 #include <net/netns/generic.h>
 
-static int rtnl_net_debug_event(struct notifier_block *nb,
-				unsigned long event, void *ptr)
+int netdev_debug_event(struct notifier_block *nb, unsigned long event,
+		       void *ptr)
 {
 	struct net_device *dev = netdev_notifier_info_to_dev(ptr);
 	struct net *net = dev_net(dev);
···
 
 	/* Keep enum and don't add default to trigger -Werror=switch */
 	switch (cmd) {
+	case NETDEV_REGISTER:
 	case NETDEV_UP:
+		netdev_ops_assert_locked(dev);
+		fallthrough;
 	case NETDEV_DOWN:
 	case NETDEV_REBOOT:
 	case NETDEV_CHANGE:
-	case NETDEV_REGISTER:
 	case NETDEV_UNREGISTER:
 	case NETDEV_CHANGEMTU:
 	case NETDEV_CHANGEADDR:
···
 
 	return NOTIFY_DONE;
 }
+EXPORT_SYMBOL_NS_GPL(netdev_debug_event, "NETDEV_INTERNAL");
 
 static int rtnl_net_debug_net_id;
 
···
 	struct notifier_block *nb;
 
 	nb = net_generic(net, rtnl_net_debug_net_id);
-	nb->notifier_call = rtnl_net_debug_event;
+	nb->notifier_call = netdev_debug_event;
 
 	return register_netdevice_notifier_net(net, nb);
 }
···
 };
 
 static struct notifier_block rtnl_net_debug_block = {
-	.notifier_call = rtnl_net_debug_event,
+	.notifier_call = netdev_debug_event,
 };
 
 static int __init rtnl_net_debug_init(void)

net/ipv4/devinet.c

···
 	if (!in_dev->arp_parms)
 		goto out_kfree;
 	if (IPV4_DEVCONF(in_dev->cnf, FORWARDING))
-		dev_disable_lro(dev);
+		netif_disable_lro(dev);
 	/* Reference in_dev->dev */
 	netdev_hold(dev, &in_dev->dev_tracker, GFP_KERNEL);
 	/* Account for reference dev->ip_ptr (below) */

net/ipv6/addrconf.c

···
 #include <net/netlink.h>
 #include <net/pkt_sched.h>
 #include <net/l3mdev.h>
+#include <net/netdev_lock.h>
 #include <linux/if_tunnel.h>
 #include <linux/rtnetlink.h>
 #include <linux/netconf.h>
···
 	int err = -ENOMEM;
 
 	ASSERT_RTNL();
+	netdev_ops_assert_locked(dev);
 
 	if (dev->mtu < IPV6_MIN_MTU && dev != blackhole_netdev)
 		return ERR_PTR(-EINVAL);
···
 		return ERR_PTR(err);
 	}
 	if (ndev->cnf.forwarding)
-		dev_disable_lro(dev);
+		netif_disable_lro(dev);
 	/* We refer to the device */
 	netdev_hold(dev, &ndev->dev_tracker, GFP_KERNEL);
 
···
 
 	rtnl_net_lock(net);
 	dev = __dev_get_by_index(net, ireq.ifr6_ifindex);
+	netdev_lock_ops(dev);
 	if (dev)
 		err = inet6_addr_add(net, dev, &cfg, 0, 0, NULL);
 	else
 		err = -ENODEV;
+	netdev_unlock_ops(dev);
 	rtnl_net_unlock(net);
 	return err;
 }
···
 	if (!dev) {
 		NL_SET_ERR_MSG_MOD(extack, "Unable to find the interface");
 		err = -ENODEV;
-		goto unlock;
+		goto unlock_rtnl;
 	}
 
+	netdev_lock_ops(dev);
 	idev = ipv6_find_idev(dev);
 	if (IS_ERR(idev)) {
 		err = PTR_ERR(idev);
···
 
 	in6_ifa_put(ifa);
 unlock:
+	netdev_unlock_ops(dev);
+unlock_rtnl:
 	rtnl_net_unlock(net);
 
 	return err;
···
 
 			if (idev->cnf.addr_gen_mode != new_val) {
 				WRITE_ONCE(idev->cnf.addr_gen_mode, new_val);
+				netdev_lock_ops(idev->dev);
 				addrconf_init_auto_addrs(idev->dev);
+				netdev_unlock_ops(idev->dev);
 			}
 		} else if (&net->ipv6.devconf_all->addr_gen_mode == ctl->data) {
 			struct net_device *dev;
···
 				    idev->cnf.addr_gen_mode != new_val) {
 					WRITE_ONCE(idev->cnf.addr_gen_mode,
 						  new_val);
+					netdev_lock_ops(idev->dev);
 					addrconf_init_auto_addrs(idev->dev);
+					netdev_unlock_ops(idev->dev);
 				}
 			}
 		}

tools/testing/selftests/net/lib.sh

···
 	NS_LIST+=("${ns_list[@]}")
 }
 
+# Create netdevsim with given id and net namespace.
+create_netdevsim() {
+    local id="$1"
+    local ns="$2"
+
+    modprobe netdevsim &> /dev/null
+    udevadm settle
+
+    echo "$id 1" | ip netns exec $ns tee /sys/bus/netdevsim/new_device >/dev/null
+    local dev=$(ip netns exec $ns ls /sys/bus/netdevsim/devices/netdevsim$id/net)
+    ip -netns $ns link set dev $dev name nsim$id
+    ip -netns $ns link set dev nsim$id up
+
+    echo nsim$id
+}
+
+# Remove netdevsim with given id.
+cleanup_netdevsim() {
+    local id="$1"
+
+    if [ -d "/sys/bus/netdevsim/devices/netdevsim$id/net" ]; then
+        echo "$id" > /sys/bus/netdevsim/del_device
+    fi
+}
+
 tc_rule_stats_get()
 {
 	local dev=$1; shift

tools/testing/selftests/net/netns-name.sh

···
 DEV=dummy-dev0
 DEV2=dummy-dev1
 ALT_NAME=some-alt-name
+NSIM_ADDR=2025
 
 RET_CODE=0
 
 cleanup() {
+    cleanup_netdevsim $NSIM_ADDR
     cleanup_ns $NS $test_ns
 }
 
···
 
 #
 # Test basic move without a rename
+# Use netdevsim because it has extra asserts for notifiers.
 #
-ip -netns $NS link add name $DEV type dummy || fail
-ip -netns $NS link set dev $DEV netns $test_ns ||
+
+nsim=$(create_netdevsim $NSIM_ADDR $NS)
+ip -netns $NS link set dev $nsim netns $test_ns ||
     fail "Can't perform a netns move"
-ip -netns $test_ns link show dev $DEV >> /dev/null || fail "Device not found after move"
-ip -netns $test_ns link del $DEV || fail
+ip -netns $test_ns link show dev $nsim >> /dev/null ||
+    fail "Device not found after move"
+cleanup_netdevsim $NSIM_ADDR
 
 #
 # Test move with a conflict