[Patch net 08/16] net_sched: use tcf_queue_work() in matchall filter

[Cong Wang]

Defer the tcf_exts_destroy() in RCU callback to
tc filter workqueue and get RTNL lock.

Reported-by: Chris Mi <chr...@mellanox.com>
Cc: Daniel Borkmann <dan...@iogearbox.net>
Cc: Jiri Pirko <j...@resnulli.us>
Cc: John Fastabend <john.fastab...@gmail.com>
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>
---
 net/sched/cls_matchall.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_matchall.c b/net/sched/cls_matchall.c
index eeac606c95ab..c33f711b9019 100644
--- a/net/sched/cls_matchall.c
+++ b/net/sched/cls_matchall.c
@@ -21,7 +21,10 @@ struct cls_mall_head {
        struct tcf_result res;
        u32 handle;
        u32 flags;
-       struct rcu_head rcu;
+       union {
+               struct work_struct work;
+               struct rcu_head rcu;
+       };
 };
 
 static int mall_classify(struct sk_buff *skb, const struct tcf_proto *tp,
@@ -41,13 +44,23 @@ static int mall_init(struct tcf_proto *tp)
        return 0;
 }
 
+static void mall_destroy_work(struct work_struct *work)
+{
+       struct cls_mall_head *head = container_of(work, struct cls_mall_head,
+                                                 work);
+       rtnl_lock();
+       tcf_exts_destroy(&head->exts);
+       kfree(head);
+       rtnl_unlock();
+}
+
 static void mall_destroy_rcu(struct rcu_head *rcu)
 {
        struct cls_mall_head *head = container_of(rcu, struct cls_mall_head,
                                                  rcu);
 
-       tcf_exts_destroy(&head->exts);
-       kfree(head);
+       INIT_WORK(&head->work, mall_destroy_work);
+       tcf_queue_work(&head->work);
 }
 
 static int mall_replace_hw_filter(struct tcf_proto *tp,
-- 
2.13.0