Commit 554873e5 authored by Kirill Tkhai's avatar Kirill Tkhai Committed by David S. Miller
Browse files

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 328fbe74
"Close race between {un, }register_netdevice_notifier and ...",
and guarantees __rtnl_link_unregister() does not skip
exitting net.

Signed-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fc1dd369

drivers/net/dummy.c

+2 −0
Original line number Diff line number Diff line
@@ -219,6 +219,7 @@ static int __init dummy_init_module(void) 
{

	int i, err = 0;



	down_write(&pernet_ops_rwsem);

	rtnl_lock();

	err = __rtnl_link_register(&dummy_link_ops);

	if (err < 0)
@@ -233,6 +234,7 @@ static int __init dummy_init_module(void) 


out:

	rtnl_unlock();

	up_write(&pernet_ops_rwsem);



	return err;

}

drivers/net/ifb.c

+2 −0
Original line number Diff line number Diff line
@@ -330,6 +330,7 @@ static int __init ifb_init_module(void) 
{

	int i, err;



	down_write(&pernet_ops_rwsem);

	rtnl_lock();

	err = __rtnl_link_register(&ifb_link_ops);

	if (err < 0)
@@ -344,6 +345,7 @@ static int __init ifb_init_module(void) 


out:

	rtnl_unlock();

	up_write(&pernet_ops_rwsem);



	return err;

}

net/core/net_namespace.c

+1 −0
Original line number Diff line number Diff line
@@ -51,6 +51,7 @@ static bool init_net_initialized; 
 * outside.

 */

DECLARE_RWSEM(pernet_ops_rwsem);

EXPORT_SYMBOL_GPL(pernet_ops_rwsem);



#define MIN_PERNET_OPS_ID	\

	((sizeof(struct net_generic) + sizeof(void *) - 1) / sizeof(void *))

net/core/rtnetlink.c

+3 −3
Original line number Diff line number Diff line
@@ -412,17 +412,17 @@ static void __rtnl_kill_links(struct net *net, struct rtnl_link_ops *ops) 
 * __rtnl_link_unregister - Unregister rtnl_link_ops from rtnetlink.

 * @ops: struct rtnl_link_ops * to unregister

 *

 * The caller must hold the rtnl_mutex.

 * The caller must hold the rtnl_mutex and guarantee net_namespace_list

 * integrity (hold pernet_ops_rwsem for writing to close the race

 * with setup_net() and cleanup_net()).

 */

void __rtnl_link_unregister(struct rtnl_link_ops *ops)

{

	struct net *net;



	down_read(&net_rwsem);

	for_each_net(net) {

		__rtnl_kill_links(net, ops);

	}

	up_read(&net_rwsem);

	list_del(&ops->list);

}

EXPORT_SYMBOL_GPL(__rtnl_link_unregister);

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