From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755726AbcAOAgb (ORCPT ); Thu, 14 Jan 2016 19:36:31 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:54960 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753365AbcAOAga (ORCPT ); Thu, 14 Jan 2016 19:36:30 -0500 X-Original-SENDERIP: 156.147.1.126 X-Original-MAILFROM: junil0814.lee@lge.com X-Original-SENDERIP: 165.244.98.203 X-Original-MAILFROM: junil0814.lee@lge.com X-Original-SENDERIP: 10.168.177.123 X-Original-MAILFROM: junil0814.lee@lge.com From: Junil Lee To: , CC: sergey.senozhatsky.work@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Junil Lee Subject: [PATCH] zsmalloc: fix migrate_zspage-zs_free race condition Date: Fri, 15 Jan 2016 09:36:24 +0900 Message-ID: <1452818184-2994-1-git-send-email-junil0814.lee@lge.com> X-Mailer: git-send-email 2.6.2 X-MIMETrack: Itemize by SMTP Server on LGEKRMHUB03/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2016/01/15 09:36:26, Serialize by Router on LGEKRMHUB03/LGE/LG Group(Release 8.5.3FP6|November 21, 2013) at 2016/01/15 09:36:26, Serialize complete at 2016/01/15 09:36:26 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org To prevent unlock at the not correct situation, tagging the new obj to assure lock in migrate_zspage() before right unlock path. Two functions are in race condition by tag which set 1 on last bit of obj, however unlock succrently when update new obj to handle before call unpin_tag() which is right unlock path. summarize this problem by call flow as below: CPU0 CPU1 migrate_zspage find_alloced_obj() trypin_tag() -- obj |= HANDLE_PIN_BIT obj_malloc() -- new obj is not set zs_free record_obj() -- unlock and break sync pin_tag() -- get lock unpin_tag() Signed-off-by: Junil Lee --- mm/zsmalloc.c | 1 + 1 file changed, 1 insertion(+) diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c index e7414ce..bb459ef 100644 --- a/mm/zsmalloc.c +++ b/mm/zsmalloc.c @@ -1635,6 +1635,7 @@ static int migrate_zspage(struct zs_pool *pool, struct size_class *class, free_obj = obj_malloc(d_page, class, handle); zs_object_copy(free_obj, used_obj, class); index++; + free_obj |= BIT(HANDLE_PIN_BIT); record_obj(handle, free_obj); unpin_tag(handle); obj_free(pool, class, used_obj); -- 2.6.2