@@ -71,7 +71,7 @@ static inline int rtnl_msg_family(const struct nlmsghdr *nlh)
/**
* struct rtnl_link_ops - rtnetlink link operations
*
- * @list: Used internally, protected by RTNL and SRCU
+ * @list: Used internally, protected by link_ops_mutex and SRCU
* @srcu: Used internally
* @kind: Identifier
* @netns_refund: Physical device, move to init_net on netns exit
@@ -466,6 +466,7 @@ void __rtnl_unregister_many(const struct rtnl_msg_handler *handlers, int n)
}
EXPORT_SYMBOL_GPL(__rtnl_unregister_many);
+static DEFINE_MUTEX(link_ops_mutex);
static LIST_HEAD(link_ops);
static struct rtnl_link_ops *rtnl_link_ops_get(const char *kind, int *srcu_index)
@@ -508,14 +509,6 @@ int __rtnl_link_register(struct rtnl_link_ops *ops)
struct rtnl_link_ops *tmp;
int err;
- /* When RTNL is removed, add lock for link_ops. */
- ASSERT_RTNL();
-
- list_for_each_entry(tmp, &link_ops, list) {
- if (!strcmp(ops->kind, tmp->kind))
- return -EEXIST;
- }
-
/* The check for alloc/setup is here because if ops
* does not have that filled up, it is not possible
* to use the ops for creating device. So do not
@@ -528,9 +521,20 @@ int __rtnl_link_register(struct rtnl_link_ops *ops)
if (err)
return err;
+ mutex_lock(&link_ops_mutex);
+
+ list_for_each_entry(tmp, &link_ops, list) {
+ if (!strcmp(ops->kind, tmp->kind)) {
+ err = -EEXIST;
+ goto unlock;
+ }
+ }
+
list_add_tail_rcu(&ops->list, &link_ops);
+unlock:
+ mutex_unlock(&link_ops_mutex);
- return 0;
+ return err;
}
EXPORT_SYMBOL_GPL(__rtnl_link_register);
@@ -598,14 +602,17 @@ void rtnl_link_unregister(struct rtnl_link_ops *ops)
{
struct net *net;
- /* Close the race with setup_net() and cleanup_net() */
- down_write(&pernet_ops_rwsem);
- rtnl_lock_unregistering_all();
-
+ mutex_lock(&link_ops_mutex);
list_del_rcu(&ops->list);
+ mutex_unlock(&link_ops_mutex);
+
synchronize_srcu(&ops->srcu);
cleanup_srcu_struct(&ops->srcu);
+ /* Close the race with setup_net() and cleanup_net() */
+ down_write(&pernet_ops_rwsem);
+ rtnl_lock_unregistering_all();
+
for_each_net(net)
__rtnl_kill_links(net, ops);
rtnl_link_unregister() holds RTNL and calls synchronize_srcu(), but rtnl_newlink() will acquire SRCU frist and then RTNL. Then, we need to unlink ops and call synchronize_srcu() outside of RTNL to avoid the deadlock. rtnl_link_unregister() rtnl_newlink() ---- ---- lock(rtnl_mutex); lock(&ops->srcu); lock(rtnl_mutex); sync(&ops->srcu); Let's move as such and add a mutex to protect link_ops. Now, link_ops is protected by its dedicated mutex and rtnl_link_register() no longer needs to hold RTNL. While at it, we move the initialisation of ops->dellink and ops->srcu out of the mutex scope. Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> --- include/net/rtnetlink.h | 2 +- net/core/rtnetlink.c | 33 ++++++++++++++++++++------------- 2 files changed, 21 insertions(+), 14 deletions(-)