[PATCH] datapath.c: fix missing return value check of nla_nest_start()

[Jiecheng Wu <jasonwood2031@gmail.com>]

Function queue_userspace_packet() defined in net/openvswitch/datapath.c calls nla_nest_start() to allocate memory for struct nlattr which is dereferenced immediately. As nla_nest_start() may return NULL on failure, this code piece may cause NULL pointer dereference bug.
---
 net/openvswitch/datapath.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index 0f5ce77..ff4457d 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -460,6 +460,8 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 
 	if (upcall_info->egress_tun_info) {
 		nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_EGRESS_TUN_KEY);
+		if (!nla)
+			return -EMSGSIZE;
 		err = ovs_nla_put_tunnel_info(user_skb,
 					      upcall_info->egress_tun_info);
 		BUG_ON(err);
@@ -468,6 +470,8 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
 
 	if (upcall_info->actions_len) {
 		nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_ACTIONS);
+		if (!nla)
+			return -EMSGSIZE;
 		err = ovs_nla_put_actions(upcall_info->actions,
 					  upcall_info->actions_len,
 					  user_skb);
-- 
2.6.4