net: force a list_del() in unregister_netdevice_many()

unregister_netdevice_many() API is error prone and we had too
many bugs because of dangling LIST_HEAD on stacks.

See commit f87e6f47933e3e ("net: dont leave active on stack LIST_HEAD")

In fact, instead of making sure no caller leaves an active list_head,
just force a list_del() in the callee. No one seems to need to access
the list after unregister_netdevice_many()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 4 insertions, 4 deletions

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index d53e299ae1d9..7eec598c5cb6 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -1036,7 +1036,6 @@ static int macvlan_device_event(struct notifier_block *unused,
                 list_for_each_entry_safe(vlan, next, &port->vlans, list)
                         vlan->dev->rtnl_link_ops->dellink(vlan->dev, &list_kill);
                 unregister_netdevice_many(&list_kill);
-                list_del(&list_kill);
                 break;
         case NETDEV_PRE_TYPE_CHANGE:
                 /* Forbid underlaying device to change its type. */
diff --git a/net/core/dev.c b/net/core/dev.c
index fb8b0546485b..a30bef1882f5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6613,6 +6613,9 @@ EXPORT_SYMBOL(unregister_netdevice_queue);
 /**
  *      unregister_netdevice_many - unregister many devices
  *      @head: list of devices
+ *
+ *  Note: As most callers use a stack allocated list_head,
+ *  we force a list_del() to make sure stack wont be corrupted later.
  */
 void unregister_netdevice_many(struct list_head *head)
 {
@@ -6622,6 +6625,7 @@ void unregister_netdevice_many(struct list_head *head)
                 rollback_registered_many(head);
                 list_for_each_entry(dev, head, unreg_list)
                         net_set_todo(dev);
+                list_del(head);
         }
 }
 EXPORT_SYMBOL(unregister_netdevice_many);
@@ -7077,7 +7081,6 @@ static void __net_exit default_device_exit_batch(struct list_head *net_list)
                 }
         }
         unregister_netdevice_many(&dev_kill_list);
-        list_del(&dev_kill_list);
         rtnl_unlock();
 }
 
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index f4e9037f9a0c..fbdb1556b0db 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1744,7 +1744,6 @@ static int rtnl_dellink(struct sk_buff *skb, struct nlmsghdr *nlh)
 
         ops->dellink(dev, &list_kill);
         unregister_netdevice_many(&list_kill);
-        list_del(&list_kill);
         return 0;
 }
 
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index b8d331e7d883..34799e06ee01 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -1758,7 +1758,6 @@ void ieee80211_remove_interfaces(struct ieee80211_local *local)
         }
         mutex_unlock(&local->iflist_mtx);
         unregister_netdevice_many(&unreg_list);
-        list_del(&unreg_list);
 
         list_for_each_entry_safe(sdata, tmp, &wdev_list, list) {
                 list_del(&sdata->list);