netdev - [PATCH v2 net 1/1] net sched actions: fix GETing actions

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Date:   Mon, 12 Sep 2016 06:21:32 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     davem@...emloft.net
Cc:     xiyou.wangcong@...il.com, netdev@...r.kernel.org,
        Jamal Hadi Salim <jhs@...atatu.com>
Subject: [PATCH v2 net 1/1] net sched actions: fix GETing actions

From: Jamal Hadi Salim <jhs@...atatu.com>

With the batch changes that translated transient actions into
a temporary list we lost in the translation the fact that
tcf_action_destroy() will eventually delete the action from
the permanent location if the refcount is zero.

Example of what broke:
...add a gact action to drop
sudo $TC actions add action drop index 10
...now retrieve it, looks good
sudo $TC actions get action gact index 10
...retrieve it again and find it is gone!
sudo $TC actions get action gact index 10

Fixes:
22dc13c837c3 ("net_sched: convert tcf_exts from list to pointer array"),
824a7e8863b3 ("net_sched: remove an unnecessary list_del()")
f07fed82ad79 ("net_sched: remove the leftover cleanup_a()")

Signed-off-by: Jamal Hadi Salim <jhs@...atatu.com>
---
 net/sched/act_api.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index d09d068..63b8167 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -592,6 +592,16 @@ err_out:
 	return ERR_PTR(err);
 }
 
+static void cleanup_a(struct list_head *actions, int ovr)
+{
+	struct tc_action *a, *tmp;
+
+	list_for_each_entry_safe(a, tmp, actions, list) {
+		if (ovr)
+			a->tcfa_refcnt-=1;
+	}
+}
+
 int tcf_action_init(struct net *net, struct nlattr *nla,
 				  struct nlattr *est, char *name, int ovr,
 				  int bind, struct list_head *actions)
@@ -612,8 +622,15 @@ int tcf_action_init(struct net *net, struct nlattr *nla,
 			goto err;
 		}
 		act->order = i;
+		if (ovr)
+			act->tcfa_refcnt+=1;
 		list_add_tail(&act->list, actions);
 	}
+
+	/* 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:
@@ -883,6 +900,8 @@ tca_action_gd(struct net *net, struct nlattr *nla, struct nlmsghdr *n,
 			goto err;
 		}
 		act->order = i;
+		if (event == RTM_GETACTION)
+			act->tcfa_refcnt+=1;
 		list_add_tail(&act->list, &actions);
 	}
 
-- 
1.9.1