sctp_do_peeloff() calls sock_create() to allocate and initialise
struct sock, inet_sock, and sctp_sock, but later sctp_copy_sock()
and sctp_sock_migrate() overwrite most fields.

What sctp_do_peeloff() does is more like accept().

Let's use sock_create_lite() and sctp_clone_sock().

Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
---
v2: Export __inet_accept()
---
 net/ipv4/af_inet.c |  1 +
 net/sctp/socket.c  | 36 +++++++++++++++---------------------
 2 files changed, 16 insertions(+), 21 deletions(-)

diff --git a/net/ipv4/af_inet.c b/net/ipv4/af_inet.c
index 77f6ae0fc231..0784e2a873a1 100644
--- a/net/ipv4/af_inet.c
+++ b/net/ipv4/af_inet.c
@@ -788,6 +788,7 @@ void __inet_accept(struct socket *sock, struct socket *newsock, struct sock *new
 
 	newsock->state = SS_CONNECTED;
 }
+EXPORT_SYMBOL_GPL(__inet_accept);
 
 /*
  *	Accept a pending connection. The TCP layer now gives BSD semantics.
diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 826f17747f17..60d3e340dfed 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -5671,11 +5671,11 @@ static int sctp_getsockopt_autoclose(struct sock *sk, int len, char __user *optv
 
 /* Helper routine to branch off an association to a new socket.  */
 static int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id,
-		struct socket **sockp)
+			   struct socket **sockp)
 {
 	struct sctp_association *asoc = sctp_id2assoc(sk, id);
-	struct sctp_sock *sp = sctp_sk(sk);
 	struct socket *sock;
+	struct sock *newsk;
 	int err = 0;
 
 	/* Do not peel off from one netns to another one. */
@@ -5691,30 +5691,24 @@ static int sctp_do_peeloff(struct sock *sk, sctp_assoc_t id,
 	if (!sctp_style(sk, UDP))
 		return -EINVAL;
 
-	/* Create a new socket.  */
-	err = sock_create(sk->sk_family, SOCK_SEQPACKET, IPPROTO_SCTP, &sock);
-	if (err < 0)
+	err = sock_create_lite(sk->sk_family, SOCK_SEQPACKET, IPPROTO_SCTP, &sock);
+	if (err)
 		return err;
 
-	sctp_copy_sock(sock->sk, sk, asoc);
-
-	/* Make peeled-off sockets more like 1-1 accepted sockets.
-	 * Set the daddr and initialize id to something more random and also
-	 * copy over any ip options.
-	 */
-	sp->pf->to_sk_daddr(&asoc->peer.primary_addr, sock->sk);
-	sp->pf->copy_ip_options(sk, sock->sk);
-
-	/* Populate the fields of the newsk from the oldsk and migrate the
-	 * asoc to the newsk.
-	 */
-	err = sctp_sock_migrate(sk, sock->sk, asoc,
-				SCTP_SOCKET_UDP_HIGH_BANDWIDTH);
-	if (err) {
+	newsk = sctp_clone_sock(sk, asoc, SCTP_SOCKET_UDP_HIGH_BANDWIDTH);
+	if (IS_ERR(newsk)) {
 		sock_release(sock);
-		sock = NULL;
+		*sockp = NULL;
+		return PTR_ERR(newsk);
 	}
 
+	lock_sock_nested(newsk, SINGLE_DEPTH_NESTING);
+	__inet_accept(sk->sk_socket, sock, newsk);
+	release_sock(newsk);
+
+	sock->ops = sk->sk_socket->ops;
+	__module_get(sock->ops->owner);
+
 	*sockp = sock;
 
 	return err;
-- 
2.51.1.851.g4ebd6896fd-goog