[PATCH v4 net 1/1] net sched actions: fix GETing actions

[PATCH v4 net 1/1] net sched actions: fix GETing actions

[Jamal Hadi Salim]

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

With the batch changes that translated transient actions into
a temporary list lost in the translation was 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:
commit 22dc13c837c3 ("net_sched: convert tcf_exts from list to pointer array"),
commit 824a7e8863b3 ("net_sched: remove an unnecessary list_del()")
commit f07fed82ad79 ("net_sched: remove the leftover cleanup_a()")

Signed-off-by: Jamal Hadi Salim <jhs@mojatatu.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.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..e1c0ce1 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;
+
+	list_for_each_entry(a, actions, list) {
+		if (ovr)
+			a->tcfa_refcnt--;
+	}
+}
+
 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++;
 		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++;
 		list_add_tail(&act->list, &actions);
 	}
 
-- 
1.9.1

Re: [PATCH v4 net 1/1] net sched actions: fix GETing actions

[David Miller]

From: Jamal Hadi Salim <jhs@mojatatu.com>
Date: Fri, 16 Sep 2016 16:27:04 -0400

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

Please use multiple "Fixes: " lines to reference multiple commits, like so:


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

> +static void cleanup_a(struct list_head *actions, int ovr)
> +{
> +	struct tc_action *a;
> +
> +	list_for_each_entry(a, actions, list) {
> +		if (ovr)
> +			a->tcfa_refcnt--;
> +	}
> +}

Please move the invariant test outside of the loop, like so:

	if (!ovr)
		return;
	list_for_each_entry(a, actions, list)
		a->tcfa_refcnt--;

Thanks.