scsi: libiscsi: Fix use-after-free race during iscsi_session_teardown

Session attributes exposed through sysfs were freed before the device
was destroyed, resulting in a potential use-after-free. Free these
attributes after removing the device.
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
Acked-by: Chris Leech <cleech@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/libiscsi.c

@@ -2851,9 +2851,6 @@ EXPORT_SYMBOL_GPL(iscsi_session_setup);
 /**
  * iscsi_session_teardown - destroy session, host, and cls_session
  * @cls_session: iscsi session
- *
- * The driver must have called iscsi_remove_session before
- * calling this.
  */
 void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
 {
@@ -2863,6 +2860,8 @@ void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
 
 	iscsi_pool_free(&session->cmdpool);
 
+	iscsi_remove_session(cls_session);
+
 	kfree(session->password);
 	kfree(session->password_in);
 	kfree(session->username);
@@ -2877,7 +2876,8 @@ void iscsi_session_teardown(struct iscsi_cls_session *cls_session)
 	kfree(session->portal_type);
 	kfree(session->discovery_parent_type);
 
-	iscsi_destroy_session(cls_session);
+	iscsi_free_session(cls_session);
+
 	iscsi_host_dec_session_cnt(shost);
 	module_put(owner);
 }