scsi: iscsi: Fail session and connection on transport registration failure

If the transport cannot be registered, the session/connection creation
needs to be failed early to let the initiator know.  Otherwise, the system
will have an outstanding connection that cannot be used nor removed by
open-iscsi. The result is similar to the error below, triggered by
injecting a failure in the transport's registration path.

openiscsi reports success:

root@debian-vm:~#  iscsiadm -m node -T iqn:lun1 -p 127.0.0.1 -l
Logging in to [iface: default, target: iqn:lun1, portal: 127.0.0.1,3260]
Login to [iface: default, target: iqn:lun1, portal:127.0.0.1,3260] successful.

But cannot remove the session afterwards, since the kernel is in an
inconsistent state.

root@debian-vm:~#  iscsiadm -m node -T iqn:lun1 -p 127.0.0.1 -u
iscsiadm: No matching sessions found

Link: https://lore.kernel.org/r/20200106185817.640331-4-krisman@collabora.comSigned-off-by: Gabriel Krisman Bertazi <krisman@collabora.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_transport_iscsi.c

@@ -2093,7 +2093,12 @@ int iscsi_add_session(struct iscsi_cls_session *session, unsigned int target_id)
 					 "could not register session's dev\n");
 		goto release_ida;
 	}
-	transport_register_device(&session->dev);
+	err = transport_register_device(&session->dev);
+	if (err) {
+		iscsi_cls_session_printk(KERN_ERR, session,
+					 "could not register transport's dev\n");
+		goto release_dev;
+	}
 
 	spin_lock_irqsave(&sesslock, flags);
 	list_add(&session->sess_list, &sesslist);
@@ -2103,6 +2108,8 @@ int iscsi_add_session(struct iscsi_cls_session *session, unsigned int target_id)
 	ISCSI_DBG_TRANS_SESSION(session, "Completed session adding\n");
 	return 0;
 
+release_dev:
+	device_del(&session->dev);
 release_ida:
 	if (session->ida_used)
 		ida_simple_remove(&iscsi_sess_ida, session->target_id);
@@ -2263,7 +2270,12 @@ iscsi_create_conn(struct iscsi_cls_session *session, int dd_size, uint32_t cid)
 					 "register connection's dev\n");
 		goto release_parent_ref;
 	}
-	transport_register_device(&conn->dev);
+	err = transport_register_device(&conn->dev);
+	if (err) {
+		iscsi_cls_session_printk(KERN_ERR, session, "could not "
+					 "register transport's dev\n");
+		goto release_conn_ref;
+	}
 
 	spin_lock_irqsave(&connlock, flags);
 	list_add(&conn->conn_list, &connlist);
@@ -2272,6 +2284,8 @@ iscsi_create_conn(struct iscsi_cls_session *session, int dd_size, uint32_t cid)
 	ISCSI_DBG_TRANS_CONN(conn, "Completed conn creation\n");
 	return conn;
 
+release_conn_ref:
+	put_device(&conn->dev);
 release_parent_ref:
 	put_device(&session->dev);
 free_conn: