net: openvswitch: fix missing checks for nla_nest_start

mainline inclusion
from mainline-5.1
commit a734d1f4c2fc
category: bugfix
bugzilla: 15155
CVE: NA

-------------------------------------------------

nla_nest_start may fail and thus deserves a check.
The fix returns -EMSGSIZE when it fails.
Signed-off-by: NKangjie Lu <kjlu@umn.edu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NZhiqiang Liu <liuzhiqiang26@huawei.com>
Reviewed-by: NWenan Mao <maowenan@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/openvswitch/datapath.c

@@ -464,6 +464,10 @@ 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) {
+			err = -EMSGSIZE;
+			goto out;
+		}
 		err = ovs_nla_put_tunnel_info(user_skb,
 					      upcall_info->egress_tun_info);
 		BUG_ON(err);
@@ -472,6 +476,10 @@ 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) {
+			err = -EMSGSIZE;
+			goto out;
+		}
 		err = ovs_nla_put_actions(upcall_info->actions,
 					  upcall_info->actions_len,
 					  user_skb);