net_sched: use tcf_queue_work() in cgroup filter

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

Reported-by: Chris Mi <chrism@mellanox.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files 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,