[NETNS]: Simplify the network namespace list locking rules.
Denis V. Lunev <den@sw.ru> noticed that the locking rules
for the network namespace list are over complicated and broken.
In particular the current register_netdev_notifier currently
does not take any lock making the for_each_net iteration racy
with network namespace creation and destruction. Oops.
The fact that we need to use for_each_net in rtnl_unlock() when
the rtnetlink support becomes per network namespace makes designing
the proper locking tricky. In addition we need to be able to call
rtnl_lock() and rtnl_unlock() when we have the net_mutex held.
After thinking about it and looking at the alternatives carefully
it looks like the simplest and most maintainable solution is
to remove net_list_mutex altogether, and to use the rtnl_mutex instead.
Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 13b0e3b..934c840 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -96,9 +96,6 @@
#endif
}
-extern void net_lock(void);
-extern void net_unlock(void);
-
#define for_each_net(VAR) \
list_for_each_entry(VAR, &net_namespace_list, list)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index e478e35..0e0ca6d 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -15,7 +15,6 @@
static struct list_head *first_device = &pernet_list;
static DEFINE_MUTEX(net_mutex);
-static DEFINE_MUTEX(net_list_mutex);
LIST_HEAD(net_namespace_list);
static struct kmem_cache *net_cachep;
@@ -23,16 +22,6 @@
struct net init_net;
EXPORT_SYMBOL_GPL(init_net);
-void net_lock(void)
-{
- mutex_lock(&net_list_mutex);
-}
-
-void net_unlock(void)
-{
- mutex_unlock(&net_list_mutex);
-}
-
static struct net *net_alloc(void)
{
return kmem_cache_alloc(net_cachep, GFP_KERNEL);
@@ -62,9 +51,9 @@
mutex_lock(&net_mutex);
/* Don't let anyone else find us. */
- net_lock();
+ rtnl_lock();
list_del(&net->list);
- net_unlock();
+ rtnl_unlock();
/* Run all of the network namespace exit methods */
list_for_each_entry_reverse(ops, &pernet_list, list) {
@@ -151,9 +140,9 @@
if (err)
goto out_unlock;
- net_lock();
+ rtnl_lock();
list_add_tail(&new_net->list, &net_namespace_list);
- net_unlock();
+ rtnl_unlock();
out_unlock:
@@ -178,9 +167,9 @@
mutex_lock(&net_mutex);
err = setup_net(&init_net);
- net_lock();
+ rtnl_lock();
list_add_tail(&init_net.list, &net_namespace_list);
- net_unlock();
+ rtnl_unlock();
mutex_unlock(&net_mutex);
if (err)
