From: Vlad Buslov <vladbu@mellanox.com>
Date: Thu, 5 Jul 2018 17:24:31 +0300
Subject: net: sched: use reference counting action init
Patch-mainline: v4.19-rc1
Git-commit: cae422f379f37fe9105d2a113259788f989e7df5
References: bsc#1109837

Change action API to assume that action init function always takes
reference to action, even when overwriting existing action. This is
necessary because action API continues to use action pointer after init
function is done. At this point action becomes accessible for concurrent
modifications, so user must always hold reference to it.

Implement helper put list function to atomically release list of actions
after action API init code is done using them.

Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/sched/act_api.c |   35 +++++++++++++++++------------------
 1 file changed, 17 insertions(+), 18 deletions(-)

--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -628,6 +628,18 @@ static int tcf_action_put(struct tc_acti
 	return __tcf_action_put(p, false);
 }
 
+static void tcf_action_put_lst(struct list_head *actions)
+{
+	struct tc_action *a, *tmp;
+
+	list_for_each_entry_safe(a, tmp, actions, list) {
+		const struct tc_action_ops *ops = a->ops;
+
+		if (tcf_action_put(a))
+			module_put(ops->owner);
+	}
+}
+
 int
 tcf_action_dump_old(struct sk_buff *skb, struct tc_action *a, int bind, int ref)
 {
@@ -836,17 +848,6 @@ err_out:
 	return ERR_PTR(err);
 }
 
-static void cleanup_a(struct list_head *actions, int ovr)
-{
-	struct tc_action *a;
-
-	if (!ovr)
-		return;
-
-	list_for_each_entry(a, actions, list)
-		refcount_dec(&a->tcfa_refcnt);
-}
-
 int tcf_action_init(struct net *net, struct tcf_proto *tp, struct nlattr *nla,
 		    struct nlattr *est, char *name, int ovr, int bind,
 		    struct list_head *actions, size_t *attr_size,
@@ -875,11 +876,6 @@ int tcf_action_init(struct net *net, str
 	}
 
 	*attr_size = tcf_action_full_attrs_size(sz);
-
-	/* Remove the temp refcnt which was necessary to protect against
-	 * destroying an existing action which was being replaced
-	 */
-	cleanup_a(actions, ovr);
 	return 0;
 
 err:
@@ -1210,7 +1206,7 @@ tca_action_gd(struct net *net, struct nl
 		return ret;
 	}
 err:
-	tcf_action_destroy(&actions, 0);
+	tcf_action_put_lst(&actions);
 	return ret;
 }
 
@@ -1252,8 +1248,11 @@ static int tcf_action_add(struct net *ne
 			      &attr_size, true, extack);
 	if (ret)
 		return ret;
+	ret = tcf_add_notify(net, n, &actions, portid, attr_size, extack);
+	if (ovr)
+		tcf_action_put_lst(&actions);
 
-	return tcf_add_notify(net, n, &actions, portid, attr_size, extack);
+	return ret;
 }
 
 static u32 tcaa_root_flags_allowed = TCA_FLAG_LARGE_DUMP_ON;