skmsg: Fix a memory leak in sk_psock_verdict_apply()

If the dest psock does not set SK_PSOCK_TX_ENABLED,
the skb can't be queued anywhere so must be dropped.

This one is found during code review.

Fixes: 799aa7f ("skmsg: Avoid lock_sock() in sk_psock_backlog()")
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20210615021342.7416-6-xiyou.wangcong@gmail.com

net/core/skmsg.c

@@ -924,8 +924,13 @@ static void sk_psock_verdict_apply(struct sk_psock *psock,
 			if (sk_psock_test_state(psock, SK_PSOCK_TX_ENABLED)) {
 				skb_queue_tail(&psock->ingress_skb, skb);
 				schedule_work(&psock->work);
+				err = 0;
 			}
 			spin_unlock_bh(&psock->ingress_lock);
+			if (err < 0) {
+				skb_bpf_redirect_clear(skb);
+				goto out_free;
+			}
 		}
 		break;
 	case __SK_REDIRECT: