[Patch net 12/15] net_sched: remove RCU callbacks in sample action

[Cong Wang]

The ->cleanup() now can block, it is okay to change
it to synchronize_rcu(). This could also fix a use-after-free
in module unloading.

Cc: Yotam Gigi <yot...@mellanox.com>
Cc: Jiri Pirko <j...@resnulli.us>
Cc: Jamal Hadi Salim <j...@mojatatu.com>
Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com>
Signed-off-by: Cong Wang <xiyou.wangc...@gmail.com>
---
 include/net/tc_act/tc_sample.h |  1 -
 net/sched/act_sample.c         | 12 +++---------
 2 files changed, 3 insertions(+), 10 deletions(-)

diff --git a/include/net/tc_act/tc_sample.h b/include/net/tc_act/tc_sample.h
index 89e9305be880..eb44804ff5f0 100644
--- a/include/net/tc_act/tc_sample.h
+++ b/include/net/tc_act/tc_sample.h
@@ -13,7 +13,6 @@ struct tcf_sample {
        struct psample_group __rcu *psample_group;
        u32 psample_group_num;
        struct list_head tcfm_list;
-       struct rcu_head rcu;
 };
 #define to_sample(a) ((struct tcf_sample *)a)
 
diff --git a/net/sched/act_sample.c b/net/sched/act_sample.c
index ec986ae52808..b8863e3f6776 100644
--- a/net/sched/act_sample.c
+++ b/net/sched/act_sample.c
@@ -96,23 +96,17 @@ static int tcf_sample_init(struct net *net, struct nlattr 
*nla,
        return ret;
 }
 
-static void tcf_sample_cleanup_rcu(struct rcu_head *rcu)
+static void tcf_sample_cleanup(struct tc_action *a, int bind)
 {
-       struct tcf_sample *s = container_of(rcu, struct tcf_sample, rcu);
+       struct tcf_sample *s = to_sample(a);
        struct psample_group *psample_group;
 
+       synchronize_rcu();
        psample_group = rcu_dereference_protected(s->psample_group, 1);
        RCU_INIT_POINTER(s->psample_group, NULL);
        psample_group_put(psample_group);
 }
 
-static void tcf_sample_cleanup(struct tc_action *a, int bind)
-{
-       struct tcf_sample *s = to_sample(a);
-
-       call_rcu(&s->rcu, tcf_sample_cleanup_rcu);
-}
-
 static bool tcf_sample_dev_ok_push(struct net_device *dev)
 {
        switch (dev->type) {
-- 
2.13.0