[PATCH 1/1] openvswitch: check return value of nla_nest_start

[Pan Bian <bianpan2016-9Onoh4P/yGk@public.gmane.org>]

Function nla_nest_start() will return a NULL pointer on error, and its
return value should be validated before it is used. However, in function
queue_userspace_packet(), its return value is ignored. This may result
in NULL dereference when calling nla_nest_end(). This patch fixes the
bug.

Signed-off-by: Pan Bian <bianpan2016-9Onoh4P/yGk@public.gmane.org>
---
 net/openvswitch/datapath.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 9c62b63..34c0fbd 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -489,7 +489,8 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 		err = ovs_nla_put_tunnel_info(user_skb,
 					      upcall_info->egress_tun_info);
 		BUG_ON(err);
-		nla_nest_end(user_skb, nla);
+		if (nla)
+			nla_nest_end(user_skb, nla);
 	}
 
 	if (upcall_info->actions_len) {
@@ -497,7 +498,7 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 		err = ovs_nla_put_actions(upcall_info->actions,
 					  upcall_info->actions_len,
 					  user_skb);
-		if (!err)
+		if (!err && nla)
 			nla_nest_end(user_skb, nla);
 		else
 			nla_nest_cancel(user_skb, nla);
-- 
1.9.1