net: reinstate rtnl in call_netdevice_notifiers()

Eric Biederman pointed out that not holding RTNL while calling
call_netdevice_notifiers() was racy.

This patch is a direct transcription his feedback
against commit 0115e8e30d6fc (net: remove delay at device dismantle)

Thanks Eric !

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Tom Herbert <therbert@google.com>
Cc: Mahesh Bandewar <maheshb@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Gao feng <gaofeng@cn.fujitsu.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

5 files changed, 12 insertions, 19 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 0640d2a859c6..bc857fead8c8 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1466,8 +1466,7 @@ EXPORT_SYMBOL(unregister_netdevice_notifier);
 
 int call_netdevice_notifiers(unsigned long val, struct net_device *dev)
 {
-        if (val != NETDEV_UNREGISTER_FINAL)
-                ASSERT_RTNL();
+        ASSERT_RTNL();
         return raw_notifier_call_chain(&netdev_chain, val, dev);
 }
 EXPORT_SYMBOL(call_netdevice_notifiers);
@@ -5782,7 +5781,11 @@ static void netdev_wait_allrefs(struct net_device *dev)
 
                         /* Rebroadcast unregister notification */
                         call_netdevice_notifiers(NETDEV_UNREGISTER, dev);
+
+                        __rtnl_unlock();
                         rcu_barrier();
+                        rtnl_lock();
+
                         call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
                         if (test_bit(__LINK_STATE_LINKWATCH_PENDING,
                                      &dev->state)) {
@@ -5855,7 +5858,9 @@ void netdev_run_todo(void)
                         = list_first_entry(&list, struct net_device, todo_list);
                 list_del(&dev->todo_list);
 
+                rtnl_lock();
                 call_netdevice_notifiers(NETDEV_UNREGISTER_FINAL, dev);
+                __rtnl_unlock();
 
                 if (unlikely(dev->reg_state != NETREG_UNREGISTERING)) {
                         pr_err("network todo '%s' but state %d\n",
diff --git a/net/core/fib_rules.c b/net/core/fib_rules.c
index 585093755c23..ab7db83236c9 100644
--- a/net/core/fib_rules.c
+++ b/net/core/fib_rules.c
@@ -711,16 +711,15 @@ static int fib_rules_event(struct notifier_block *this, unsigned long event,
         struct net *net = dev_net(dev);
         struct fib_rules_ops *ops;
 
+        ASSERT_RTNL();
 
         switch (event) {
         case NETDEV_REGISTER:
-                ASSERT_RTNL();
                 list_for_each_entry(ops, &net->rules_ops, list)
                         attach_rules(&ops->rules_list, dev);
                 break;
 
         case NETDEV_UNREGISTER:
-                ASSERT_RTNL();
                 list_for_each_entry(ops, &net->rules_ops, list)
                         detach_rules(&ops->rules_list, dev);
                 break;
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 6a5e6e4b142c..adf273f8ad2e 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1147,12 +1147,8 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
                          void *ptr)
 {
         struct net_device *dev = ptr;
-        struct in_device *in_dev;
-
-        if (event == NETDEV_UNREGISTER_FINAL)
-                goto out;
+        struct in_device *in_dev = __in_dev_get_rtnl(dev);
 
-        in_dev = __in_dev_get_rtnl(dev);
         ASSERT_RTNL();
 
         if (!in_dev) {
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index fd7d9ae64f16..acdee325d972 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1050,9 +1050,6 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
                 return NOTIFY_DONE;
         }
 
-        if (event == NETDEV_UNREGISTER_FINAL)
-                return NOTIFY_DONE;
-
         in_dev = __in_dev_get_rtnl(dev);
 
         switch (event) {
@@ -1064,14 +1061,14 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
                 fib_sync_up(dev);
 #endif
                 atomic_inc(&net->ipv4.dev_addr_genid);
-                rt_cache_flush(dev_net(dev), -1);
+                rt_cache_flush(net, -1);
                 break;
         case NETDEV_DOWN:
                 fib_disable_ip(dev, 0, 0);
                 break;
         case NETDEV_CHANGEMTU:
         case NETDEV_CHANGE:
-                rt_cache_flush(dev_net(dev), 0);
+                rt_cache_flush(net, 0);
                 break;
         }
         return NOTIFY_DONE;
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index e581009cb09e..6bc85f7c31e3 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -2566,14 +2566,10 @@ static int addrconf_notify(struct notifier_block *this, unsigned long event,
                            void *data)
 {
         struct net_device *dev = (struct net_device *) data;
-        struct inet6_dev *idev;
+        struct inet6_dev *idev = __in6_dev_get(dev);
         int run_pending = 0;
         int err;
 
-        if (event == NETDEV_UNREGISTER_FINAL)
-                return NOTIFY_DONE;
-
-        idev = __in6_dev_get(dev);
         switch (event) {
         case NETDEV_REGISTER:
                 if (!idev && dev->mtu >= IPV6_MIN_MTU) {