sctp: not bind the socket in sctp_connect

Now when sctp_connect() is called with a wrong sa_family, it binds
to a port but doesn't set bp->port, then sctp_get_af_specific will
return NULL and sctp_connect() returns -EINVAL.

Then if sctp_bind() is called to bind to another port, the last
port it has bound will leak due to bp->port is NULL by then.

sctp_connect() doesn't need to bind ports, as later __sctp_connect
will do it if bp->port is NULL. So remove it from sctp_connect().
While at it, remove the unnecessary sockaddr.sa_family len check
as it's already done in sctp_inet_connect.

Fixes: 644fbdea ("sctp: fix the issue that flags are ignored when using kernel_connect")
Reported-by: syzbot+079bf326b38072f849d9@syzkaller.appspotmail.com
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sctp/socket.c

@@ -4816,35 +4816,17 @@ static int sctp_setsockopt(struct sock *sk, int level, int optname,
 static int sctp_connect(struct sock *sk, struct sockaddr *addr,
 			int addr_len, int flags)
 {
-	struct inet_sock *inet = inet_sk(sk);
 	struct sctp_af *af;
-	int err = 0;
+	int err = -EINVAL;
 
 	lock_sock(sk);
-
 	pr_debug("%s: sk:%p, sockaddr:%p, addr_len:%d\n", __func__, sk,
 		 addr, addr_len);
 
-	/* We may need to bind the socket. */
-	if (!inet->inet_num) {
-		if (sk->sk_prot->get_port(sk, 0)) {
-			release_sock(sk);
-			return -EAGAIN;
-		}
-		inet->inet_sport = htons(inet->inet_num);
-	}
-
 	/* Validate addr_len before calling common connect/connectx routine. */
-	af = addr_len < offsetofend(struct sockaddr, sa_family) ? NULL :
-		sctp_get_af_specific(addr->sa_family);
-	if (!af || addr_len < af->sockaddr_len) {
-		err = -EINVAL;
-	} else {
-		/* Pass correct addr len to common routine (so it knows there
-		 * is only one address being passed.
-		 */
+	af = sctp_get_af_specific(addr->sa_family);
+	if (af && addr_len >= af->sockaddr_len)
 		err = __sctp_connect(sk, addr, af->sockaddr_len, flags, NULL);
-	}
 
 	release_sock(sk);
 	return err;