releases/3.18.78/cls_api.c-fix-dumping-of-non-existing-actions-stats.patch

From b057df24a7536cce6c372efe9d0e3d1558afedf4 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ignacy=20Gaw=C4=99dzki?=
 <ignacy.gawedzki@green-communications.fr>
Date: Tue, 3 Feb 2015 19:05:18 +0100
Subject: cls_api.c: Fix dumping of non-existing actions' stats.
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From: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>

commit b057df24a7536cce6c372efe9d0e3d1558afedf4 upstream.

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().

Fixes: 33be62715991 ("net_sched: act: use standard struct list_head")
Signed-off-by: Ignacy Gawędzki <ignacy.gawedzki@green-communications.fr>
Acked-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: J Pommnitz <jpo234@outlook.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 net/sched/cls_api.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -563,8 +563,9 @@ void tcf_exts_change(struct tcf_proto *t
 }
 EXPORT_SYMBOL(tcf_exts_change);
 
-#define tcf_exts_first_act(ext) \
-		list_first_entry(&(exts)->actions, struct tc_action, list)
+#define tcf_exts_first_act(ext)					\
+	list_first_entry_or_null(&(exts)->actions,		\
+				 struct tc_action, list)
 
 int tcf_exts_dump(struct sk_buff *skb, struct tcf_exts *exts)
 {
@@ -610,7 +611,7 @@ int tcf_exts_dump_stats(struct sk_buff *
 {
 #ifdef CONFIG_NET_CLS_ACT
 	struct tc_action *a = tcf_exts_first_act(exts);
-	if (tcf_action_copy_stats(skb, a, 1) < 0)
+	if (a != NULL && tcf_action_copy_stats(skb, a, 1) < 0)
 		return -1;
 #endif
 	return 0;