Merge: [s390] s390/iucv: MSG_PEEK causes memory leak in iucv_sock_destruct()

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-10/-/merge_requests/215

JIRA: https://issues.redhat.com/browse/RHEL-74386
Tested-by: IBM

commits:
```
ebaf813
```

Signed-off-by: Mete Durlu <mdurlu@redhat.com>

Approved-by: Steve Best <sbest@redhat.com>
Approved-by: Tony Camuso <tcamuso@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Jan Stancek <jstancek@redhat.com>

Author: jstancek

net/iucv/af_iucv.c

@@ -1236,7 +1236,9 @@ static int iucv_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 		return -EOPNOTSUPP;
 
 	/* receive/dequeue next skb:
-	 * the function understands MSG_PEEK and, thus, does not dequeue skb */
+	 * the function understands MSG_PEEK and, thus, does not dequeue skb
+	 * only refcount is increased.
+	 */
 	skb = skb_recv_datagram(sk, flags, &err);
 	if (!skb) {
 		if (sk->sk_shutdown & RCV_SHUTDOWN)
@@ -1252,9 +1254,8 @@ static int iucv_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 
 	cskb = skb;
 	if (skb_copy_datagram_msg(cskb, offset, msg, copied)) {
-		if (!(flags & MSG_PEEK))
-			skb_queue_head(&sk->sk_receive_queue, skb);
-		return -EFAULT;
+		err = -EFAULT;
+		goto err_out;
 	}
 
 	/* SOCK_SEQPACKET: set MSG_TRUNC if recv buf size is too small */
@@ -1271,11 +1272,8 @@ static int iucv_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 	err = put_cmsg(msg, SOL_IUCV, SCM_IUCV_TRGCLS,
 		       sizeof(IUCV_SKB_CB(skb)->class),
 		       (void *)&IUCV_SKB_CB(skb)->class);
-	if (err) {
-		if (!(flags & MSG_PEEK))
-			skb_queue_head(&sk->sk_receive_queue, skb);
-		return err;
-	}
+	if (err)
+		goto err_out;
 
 	/* Mark read part of skb as used */
 	if (!(flags & MSG_PEEK)) {
@@ -1331,8 +1329,18 @@ static int iucv_sock_recvmsg(struct socket *sock, struct msghdr *msg,
 	/* SOCK_SEQPACKET: return real length if MSG_TRUNC is set */
 	if (sk->sk_type == SOCK_SEQPACKET && (flags & MSG_TRUNC))
 		copied = rlen;
+	if (flags & MSG_PEEK)
+		skb_unref(skb);
 
 	return copied;
+
+err_out:
+	if (!(flags & MSG_PEEK))
+		skb_queue_head(&sk->sk_receive_queue, skb);
+	else
+		skb_unref(skb);
+
+	return err;
 }
 
 static inline __poll_t iucv_accept_poll(struct sock *parent)