scsi: libiscsi: Teardown iscsi_cls_conn gracefully

Commit 1b8d0300a3e9 ("scsi: libiscsi: Fix UAF in
iscsi_conn_get_param()/iscsi_conn_teardown()") fixed an UAF in
iscsi_conn_get_param() and introduced 2 tmp_xxx varibles.

We can gracefully fix this UAF with the help of device_del(). Calling
iscsi_remove_conn() at the beginning of iscsi_conn_teardown would make
userspace unable to see iscsi_cls_conn. This way we we can free memory
safely.

Remove iscsi_destroy_conn() since it is no longer used.

Link: https://lore.kernel.org/r/20220310015759.3296841-4-haowenchao@huawei.com
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Wenchao Hao <haowenchao@huawei.com>
Signed-off-by: Wu Bo <wubo40@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

1 files changed, 5 insertions, 22 deletions

diff --git a/drivers/scsi/scsi_transport_iscsi.c b/drivers/scsi/scsi_transport_iscsi.c
index 803b6b06d83b..27951ea05dd4 100644
--- a/drivers/scsi/scsi_transport_iscsi.c
+++ b/drivers/scsi/scsi_transport_iscsi.c
@@ -2137,7 +2137,11 @@ static int iscsi_iter_destroy_conn_fn(struct device *dev, void *data)
 {
 	if (!iscsi_is_conn_dev(dev))
 		return 0;
-	return iscsi_destroy_conn(iscsi_dev_to_conn(dev));
+
+	iscsi_remove_conn(iscsi_dev_to_conn(dev));
+	iscsi_put_conn(iscsi_dev_to_conn(dev));
+
+	return 0;
 }
 
 void iscsi_remove_session(struct iscsi_cls_session *session)
@@ -2414,27 +2418,6 @@ void iscsi_remove_conn(struct iscsi_cls_conn *conn)
 }
 EXPORT_SYMBOL_GPL(iscsi_remove_conn);
 
-/**
- * iscsi_destroy_conn - destroy iscsi class connection
- * @conn: iscsi cls session
- *
- * This can be called from a LLD or iscsi_transport.
- */
-int iscsi_destroy_conn(struct iscsi_cls_conn *conn)
-{
-	unsigned long flags;
-
-	spin_lock_irqsave(&connlock, flags);
-	list_del(&conn->conn_list);
-	spin_unlock_irqrestore(&connlock, flags);
-
-	transport_unregister_device(&conn->dev);
-	ISCSI_DBG_TRANS_CONN(conn, "Completing conn destruction\n");
-	device_unregister(&conn->dev);
-	return 0;
-}
-EXPORT_SYMBOL_GPL(iscsi_destroy_conn);
-
 void iscsi_put_conn(struct iscsi_cls_conn *conn)
 {
 	put_device(&conn->dev);