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authorWANG Cong <xiyou.wangcong@gmail.com>2016-10-11 10:56:45 -0700
committerDavid S. Miller <davem@davemloft.net>2016-10-13 10:26:43 -0400
commitab102b80cef28c20b3ef7794806c3a982c6444fc (patch)
treef1f4ef200fb7180cccc07d88978c1d4ff42aae92
parentd1ef006dc116bf6487426b0b50c1bf2bf51e6423 (diff)
downloadlinux-ab102b80cef28c20b3ef7794806c3a982c6444fc.tar.bz2
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>
-rw-r--r--net/sched/act_api.c19
1 files changed, 11 insertions, 8 deletions
diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index c9102172ce3b..a512b18c0088 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -341,22 +341,25 @@ int tcf_register_action(struct tc_action_ops *act,
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 @@ int tcf_unregister_action(struct tc_action_ops *act,
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 @@ int tcf_unregister_action(struct tc_action_ops *act,
}
}
write_unlock(&act_mod_lock);
+ if (!err)
+ unregister_pernet_subsys(ops);
return err;
}
EXPORT_SYMBOL(tcf_unregister_action);