From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 35035C25B08 for ; Tue, 23 Aug 2022 05:11:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239454AbiHWFLW (ORCPT ); Tue, 23 Aug 2022 01:11:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44298 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229811AbiHWFLT (ORCPT ); Tue, 23 Aug 2022 01:11:19 -0400 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2ED91BF7F; Mon, 22 Aug 2022 22:11:13 -0700 (PDT) X-UUID: e23580cfd354418cb259c541853515fd-20220823 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=mediatek.com; s=dk; h=Content-Transfer-Encoding:Content-Type:MIME-Version:Message-ID:Date:Subject:CC:To:From; bh=ijokMmJKsT0+CBQ8Gdmv6lUHjb9/6ryw7rMwmSGnkVw=; b=GByrc0r3KGPbaCEiHMyIryxylUl/rH/AF3p/EIBetbHVoteuc28GINy4DQQZhC3G2vtFfGpjEJ+1SbHZR1GNitPZLcOFZVjjvOA0V8hjwNaJS4C1FSSXg/ilHhI1NBN5o83jhC6g0jQfHM9dOU72A7+kJD5dJRLpoxhkAXvsodU=; X-CID-P-RULE: Release_Ham X-CID-O-INFO: VERSION:1.1.10,REQID:90c676c6-7bd7-47ce-bdb3-a80e92190630,OB:0,L OB:0,IP:0,URL:0,TC:0,Content:-5,EDM:0,RT:0,SF:100,FILE:0,BULK:0,RULE:Relea se_Ham,ACTION:release,TS:95 X-CID-INFO: VERSION:1.1.10,REQID:90c676c6-7bd7-47ce-bdb3-a80e92190630,OB:0,LOB :0,IP:0,URL:0,TC:0,Content:-5,EDM:0,RT:0,SF:100,FILE:0,BULK:0,RULE:Spam_GS 981B3D,ACTION:quarantine,TS:95 X-CID-META: VersionHash:84eae18,CLOUDID:69ca0168-a9d9-4672-a3c8-12721739a220,C OID:973335c3ec86,Recheck:0,SF:28|17|19|48,TC:nil,Content:0,EDM:-3,IP:nil,U RL:0,File:nil,Bulk:nil,QS:nil,BEC:nil,COL:0 X-UUID: e23580cfd354418cb259c541853515fd-20220823 Received: from mtkcas11.mediatek.inc [(172.21.101.40)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 498602566; Tue, 23 Aug 2022 13:11:08 +0800 Received: from mtkmbs11n1.mediatek.inc (172.21.101.186) by mtkmbs10n1.mediatek.inc (172.21.101.34) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.792.15; Tue, 23 Aug 2022 13:11:06 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkmbs11n1.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.2.792.15 via Frontend Transport; Tue, 23 Aug 2022 13:11:06 +0800 From: Jing-Ting Wu To: =?UTF-8?q?Michal=20Koutn=C3=BD?= , Tejun Heo , Zefan Li , Johannes Weiner , Matthias Brugger CC: , , , , Jing-Ting Wu , , , , Subject: [PATCH 1/1] cgroup: Fix race condition at rebind_subsystems() Date: Tue, 23 Aug 2022 13:09:41 +0800 Message-ID: <20220823050943.28619-1-Jing-Ting.Wu@mediatek.com> X-Mailer: git-send-email 2.18.0 MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Root cause: The rebind_subsystems() is no lock held when move css object from A list to B list,then let B's head be treated as css node at list_for_each_entry_rcu(). Solution: Add grace period before invalidating the removed rstat_css_node. Suggested-by: Michal Koutný Signed-off-by: Jing-Ting Wu --- kernel/cgroup/cgroup.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index ffaccd6373f1..0d0c959966ed 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1820,6 +1820,7 @@ int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask) if (ss->css_rstat_flush) { list_del_rcu(&css->rstat_css_node); + synchronize_rcu(); list_add_rcu(&css->rstat_css_node, &dcgrp->rstat_css_list); } -- 2.18.0