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net: Do not take net_rwsem in __rtnl_link_unregister()
This function calls call_netdevice_notifier(), which also may take net_rwsem. So, we can't use net_rwsem here. This patch makes callers of this functions take pernet_ops_rwsem, like register_netdevice_notifier() does. This will protect the modifications of net_namespace_list, and allows notifiers to take it (they won't have to care about context). Since __rtnl_link_unregister() is used on module load and unload (which are not frequent operations), this looks for me better, than make all call_netdevice_notifier() always executing in "protected net_namespace_list" context. Also, this fixes the problem we had a deal in 328fbe747ad4 "Close race between {un, }register_netdevice_notifier and ...", and guarantees __rtnl_link_unregister() does not skip exitting net. Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -219,6 +219,7 @@ static int __init dummy_init_module(void)
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{
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int i, err = 0;
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down_write(&pernet_ops_rwsem);
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rtnl_lock();
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err = __rtnl_link_register(&dummy_link_ops);
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if (err < 0)
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@ -233,6 +234,7 @@ static int __init dummy_init_module(void)
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out:
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rtnl_unlock();
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up_write(&pernet_ops_rwsem);
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return err;
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}
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@ -330,6 +330,7 @@ static int __init ifb_init_module(void)
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{
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int i, err;
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down_write(&pernet_ops_rwsem);
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rtnl_lock();
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err = __rtnl_link_register(&ifb_link_ops);
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if (err < 0)
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@ -344,6 +345,7 @@ static int __init ifb_init_module(void)
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out:
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rtnl_unlock();
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up_write(&pernet_ops_rwsem);
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return err;
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}
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@ -51,6 +51,7 @@ static bool init_net_initialized;
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* outside.
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*/
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DECLARE_RWSEM(pernet_ops_rwsem);
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EXPORT_SYMBOL_GPL(pernet_ops_rwsem);
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#define MIN_PERNET_OPS_ID \
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((sizeof(struct net_generic) + sizeof(void *) - 1) / sizeof(void *))
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@ -412,17 +412,17 @@ static void __rtnl_kill_links(struct net *net, struct rtnl_link_ops *ops)
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* __rtnl_link_unregister - Unregister rtnl_link_ops from rtnetlink.
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* @ops: struct rtnl_link_ops * to unregister
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*
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* The caller must hold the rtnl_mutex.
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* The caller must hold the rtnl_mutex and guarantee net_namespace_list
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* integrity (hold pernet_ops_rwsem for writing to close the race
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* with setup_net() and cleanup_net()).
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*/
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void __rtnl_link_unregister(struct rtnl_link_ops *ops)
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{
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struct net *net;
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down_read(&net_rwsem);
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for_each_net(net) {
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__rtnl_kill_links(net, ops);
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}
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up_read(&net_rwsem);
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list_del(&ops->list);
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}
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EXPORT_SYMBOL_GPL(__rtnl_link_unregister);
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