net_sched: properly cancel netlink dump on failure

When nla_put*() fails after nla_nest_start(), we need
to call nla_nest_cancel() to cancel the message, otherwise
we end up calling nla_nest_end() like a success.

Fixes: 0ed5269f ("net/sched: add tunnel option support to act_tunnel_key")
Cc: Davide Caratti <dcaratti@redhat.com>
Cc: Simon Horman <simon.horman@netronome.com>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/sched/act_tunnel_key.c

@@ -412,8 +412,10 @@ static int tunnel_key_geneve_opts_dump(struct sk_buff *skb,
 		    nla_put_u8(skb, TCA_TUNNEL_KEY_ENC_OPT_GENEVE_TYPE,
 			       opt->type) ||
 		    nla_put(skb, TCA_TUNNEL_KEY_ENC_OPT_GENEVE_DATA,
-			    opt->length * 4, opt + 1))
+			    opt->length * 4, opt + 1)) {
+			nla_nest_cancel(skb, start);
 			return -EMSGSIZE;
+		}
 
 		len -= sizeof(struct geneve_opt) + opt->length * 4;
 		src += sizeof(struct geneve_opt) + opt->length * 4;
@@ -427,7 +429,7 @@ static int tunnel_key_opts_dump(struct sk_buff *skb,
 				const struct ip_tunnel_info *info)
 {
 	struct nlattr *start;
-	int err;
+	int err = -EINVAL;
 
 	if (!info->options_len)
 		return 0;
@@ -439,9 +441,11 @@ static int tunnel_key_opts_dump(struct sk_buff *skb,
 	if (info->key.tun_flags & TUNNEL_GENEVE_OPT) {
 		err = tunnel_key_geneve_opts_dump(skb, info);
 		if (err)
-			return err;
+			goto err_out;
 	} else {
-		return -EINVAL;
+err_out:
+		nla_nest_cancel(skb, start);
+		return err;
 	}
 
 	nla_nest_end(skb, start);