[Patch net 04/16] net_sched: use tcf_queue_work() in cgroup 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_cgroup.c | 22 ++++++++++++++++++----
 1 file changed, 18 insertions(+), 4 deletions(-)

diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index d48452f87975..a97e069bee89 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -23,7 +23,10 @@ struct cls_cgroup_head {
        struct tcf_exts         exts;
        struct tcf_ematch_tree  ematches;
        struct tcf_proto        *tp;
-       struct rcu_head         rcu;
+       union {
+               struct work_struct      work;
+               struct rcu_head         rcu;
+       };
 };
 
 static int cls_cgroup_classify(struct sk_buff *skb, const struct tcf_proto *tp,
@@ -57,15 +60,26 @@ static const struct nla_policy cgroup_policy[TCA_CGROUP_MAX 
+ 1] = {
        [TCA_CGROUP_EMATCHES]   = { .type = NLA_NESTED },
 };
 
+static void cls_cgroup_destroy_work(struct work_struct *work)
+{
+       struct cls_cgroup_head *head = container_of(work,
+                                                   struct cls_cgroup_head,
+                                                   work);
+       rtnl_lock();
+       tcf_exts_destroy(&head->exts);
+       tcf_em_tree_destroy(&head->ematches);
+       kfree(head);
+       rtnl_unlock();
+}
+
 static void cls_cgroup_destroy_rcu(struct rcu_head *root)
 {
        struct cls_cgroup_head *head = container_of(root,
                                                    struct cls_cgroup_head,
                                                    rcu);
 
-       tcf_exts_destroy(&head->exts);
-       tcf_em_tree_destroy(&head->ematches);
-       kfree(head);
+       INIT_WORK(&head->work, cls_cgroup_destroy_work);
+       tcf_queue_work(&head->work);
 }
 
 static int cls_cgroup_change(struct net *net, struct sk_buff *in_skb,
-- 
2.13.0