net_sched: reorder pernet ops and act ops registrations
Krister reported a kernel NULL pointer dereference after
tcf_action_init_1() invokes a_o->init(), it is a race condition
where one thread calling tcf_register_action() to initialize
the netns data after putting act ops in the global list and
the other thread searching the list and then calling
a_o->init(net, ...).
Fix this by moving the pernet ops registration before making
the action ops visible. This is fine because: a) we don't
rely on act_base in pernet ops->init(), b) in the worst case we
have a fully initialized netns but ops is still not ready so
new actions still can't be created.
Reported-by: Krister Johansen <kjlx@templeofstupid.com>
Tested-by: Krister Johansen <kjlx@templeofstupid.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index c910217..a512b18 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -341,22 +341,25 @@
if (!act->act || !act->dump || !act->init || !act->walk || !act->lookup)
return -EINVAL;
+ /* We have to register pernet ops before making the action ops visible,
+ * otherwise tcf_action_init_1() could get a partially initialized
+ * netns.
+ */
+ ret = register_pernet_subsys(ops);
+ if (ret)
+ return ret;
+
write_lock(&act_mod_lock);
list_for_each_entry(a, &act_base, head) {
if (act->type == a->type || (strcmp(act->kind, a->kind) == 0)) {
write_unlock(&act_mod_lock);
+ unregister_pernet_subsys(ops);
return -EEXIST;
}
}
list_add_tail(&act->head, &act_base);
write_unlock(&act_mod_lock);
- ret = register_pernet_subsys(ops);
- if (ret) {
- tcf_unregister_action(act, ops);
- return ret;
- }
-
return 0;
}
EXPORT_SYMBOL(tcf_register_action);
@@ -367,8 +370,6 @@
struct tc_action_ops *a;
int err = -ENOENT;
- unregister_pernet_subsys(ops);
-
write_lock(&act_mod_lock);
list_for_each_entry(a, &act_base, head) {
if (a == act) {
@@ -378,6 +379,8 @@
}
}
write_unlock(&act_mod_lock);
+ if (!err)
+ unregister_pernet_subsys(ops);
return err;
}
EXPORT_SYMBOL(tcf_unregister_action);