netdev - [PATCH net 1/1] cls_api.c: Fix dumping of non-existing actions' stats.

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Date:	Tue, 3 Feb 2015 18:32:51 +0100
From:	Ignacy Gawędzki 
	<ignacy.gawedzki@...en-communications.fr>
To:	netdev@...r.kernel.org
Subject: [PATCH net 1/1] cls_api.c: Fix dumping of non-existing actions'
 stats.

In tcf_exts_dump_stats(), ensure that exts->actions is not empty before
accessing the first element of that list and calling tcf_action_copy_stats()
on it.  This fixes some random segvs when adding filters of type "basic" with
no particular action.

This also fixes the dumping of those "no-action" filters, which more often
than not made calls to tcf_action_copy_stats() fail and consequently netlink
attributes added by the caller to be removed by a call to nla_nest_cancel().

Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@...en-communications.fr>
---
 net/sched/cls_api.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index aad6a67..30e6967 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -602,9 +602,12 @@ EXPORT_SYMBOL(tcf_exts_dump);
 int tcf_exts_dump_stats(struct sk_buff *skb, struct tcf_exts *exts)
 {
 #ifdef CONFIG_NET_CLS_ACT
-	struct tc_action *a = tcf_exts_first_act(exts);
-	if (tcf_action_copy_stats(skb, a, 1) < 0)
-		return -1;
+	struct tc_action *a;
+	if (!list_empty(&exts->actions)) {
+		a = tcf_exts_first_act(exts);
+		if (tcf_action_copy_stats(skb, a, 1) < 0)
+			return -1;
+	}
 #endif
 	return 0;
 }
-- 
2.1.0
--
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