net: Protect iterations over net::fib_notifier_ops in fib_seq_sum()
authorKirill Tkhai <ktkhai@virtuozzo.com>
Tue, 14 Nov 2017 13:51:56 +0000 (16:51 +0300)
committerDavid S. Miller <davem@davemloft.net>
Wed, 15 Nov 2017 05:01:30 +0000 (14:01 +0900)
commit11bf284f81b46f59d5f4a4522c13aa7852cfd560
treeef75ac5dfa27442a19b463937088e7f2eeca87fb
parent094009531612246d9e13f9e0c3ae2205d7f63a0a
net: Protect iterations over net::fib_notifier_ops in fib_seq_sum()

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>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/core/fib_notifier.c