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net: Do not take net_rwsem in __rtnl_link_unregister()

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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 328fbe747a
"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>
This commit is contained in:
Kirill Tkhai 2018-03-30 19:38:37 +03:00 committed by David S. Miller
parent fc1dd36992
commit 554873e517
4 changed files with 8 additions and 3 deletions
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2
drivers/net/dummy.c
View File

@ -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;
}

2
drivers/net/ifb.c
View File

@ -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;
}

1
net/core/net_namespace.c
View File

@ -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 *))

6
net/core/rtnetlink.c
View File

@ -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);