Message ID | 151066746546.14355.8649773749613206923.stgit@localhost.localdomain |
---|---|
State | Accepted, archived |
Delegated to: | David Miller |
Headers | show |
Series | net: Protect iterations over net::fib_notifier_ops in fib_seq_sum() | expand |
From: Kirill Tkhai <ktkhai@virtuozzo.com> Date: Tue, 14 Nov 2017 16:51:56 +0300 > There is at least unlocked deletion of net->ipv4.fib_notifier_ops > from net::fib_notifier_ops: > > ip_fib_net_exit() > rtnl_unlock() > fib4_notifier_exit() > fib_notifier_ops_unregister(net->ipv4.notifier_ops) > list_del_rcu(&ops->list) > > So fib_seq_sum() can't use rtnl_lock() only for protection. > > The possible solution could be to use rtnl_lock() > in fib_notifier_ops_unregister(), but this adds > a possible delay during net namespace creation, > so we better use rcu_read_lock() till someone > really needs the mutex (if that happens). > > Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> Applied.
diff --git a/net/core/fib_notifier.c b/net/core/fib_notifier.c index 4fc202dbdfb6..fd5c613aea56 100644 --- a/net/core/fib_notifier.c +++ b/net/core/fib_notifier.c @@ -34,12 +34,14 @@ static unsigned int fib_seq_sum(void) rtnl_lock(); for_each_net(net) { - list_for_each_entry(ops, &net->fib_notifier_ops, list) { + rcu_read_lock(); + list_for_each_entry_rcu(ops, &net->fib_notifier_ops, list) { if (!try_module_get(ops->owner)) continue; fib_seq += ops->fib_seq_read(net); module_put(ops->owner); } + rcu_read_unlock(); } rtnl_unlock();
There is at least unlocked deletion of net->ipv4.fib_notifier_ops from net::fib_notifier_ops: ip_fib_net_exit() rtnl_unlock() fib4_notifier_exit() fib_notifier_ops_unregister(net->ipv4.notifier_ops) list_del_rcu(&ops->list) So fib_seq_sum() can't use rtnl_lock() only for protection. The possible solution could be to use rtnl_lock() in fib_notifier_ops_unregister(), but this adds a possible delay during net namespace creation, so we better use rcu_read_lock() till someone really needs the mutex (if that happens). Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com> --- net/core/fib_notifier.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)