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 X-Spam-Level: X-Spam-Status: No, score=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 36BD7C33CB6 for ; Thu, 23 Jan 2020 02:14:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 12AB724125 for ; Thu, 23 Jan 2020 02:14:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726231AbgAWCOI (ORCPT ); Wed, 22 Jan 2020 21:14:08 -0500 Received: from lgeamrelo11.lge.com ([156.147.23.51]:36456 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725911AbgAWCOI (ORCPT ); Wed, 22 Jan 2020 21:14:08 -0500 Received: from unknown (HELO lgemrelse6q.lge.com) (156.147.1.121) by 156.147.23.51 with ESMTP; 23 Jan 2020 11:14:05 +0900 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: chanho.min@lge.com Received: from unknown (HELO ?10.178.36.63?) (10.178.36.63) by 156.147.1.121 with ESMTP; 23 Jan 2020 11:14:05 +0900 X-Original-SENDERIP: 10.178.36.63 X-Original-MAILFROM: chanho.min@lge.com Subject: Re: [PATCH] PM: core: Fix handling of devices deleted during system-wide resume To: "Rafael J. Wysocki" , Linux PM Cc: LKML , Greg Kroah-Hartman , Daewoong Kim , Lee Gunho , "Rafael J. Wysocki" References: <2601275.1tEomSadG4@kreacher> From: Chanho Min Message-ID: Date: Thu, 23 Jan 2020 11:14:04 +0900 User-Agent: Mozilla/5.0 (X11; Linux i686; rv:60.0) Gecko/20100101 Thunderbird/60.9.0 MIME-Version: 1.0 In-Reply-To: <2601275.1tEomSadG4@kreacher> Content-Type: text/plain; charset=euc-kr; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > From: Rafael J. Wysocki > > If a device is deleted by one of its system-wide resume callbacks > (for example, because it does not appear to be present or accessible > any more) along with its children, the resume of the children may > continue leading to use-after-free errors and other issues > (potentially). > > Namely, if the device's children are resumed asynchronously, their > resume may have been scheduled already before the device's callback > runs and so the device may be deleted while dpm_wait_for_superior() > is being executed for them. The memory taken up by the parent device > object may be freed then while dpm_wait() is waiting for the parent's > resume callback to complete, which leads to a use-after-free. > Moreover, the resume of the children is really not expected to > continue after they have been unregistered, so it must be terminated > right away in that case.Seokjoo Lee > > To address this problem, modify dpm_wait_for_superior() to check > if the target device is still there in the system-wide PM list of > devices and if so, to increment its parent's reference counter, both > under dpm_list_mtx which prevents device_del() running for the child > from dropping the parent's reference counter prematurely. > > If the device is not present in the system-wide PM list of devices > any more, the resume of it cannot continue, so check that again after > dpm_wait() returns, which means that the parent's callback has been > completed, and pass the result of that check to the caller of > dpm_wait_for_superior() to allow it to abort the device's resume > if it is not there any more. > > Link: https://lore.kernel.org/linux-pm/1579568452-27253-1-git-send-email-chanho.min@lge.com > Reported-by: Chanho Min > Signed-off-by: Rafael J. Wysocki > --- > drivers/base/power/main.c | 42 +++++++++++++++++++++++++++++++++++++----- > 1 file changed, 37 insertions(+), 5 deletions(-) > > Index: linux-pm/drivers/base/power/main.c > =================================================================== > --- linux-pm.orig/drivers/base/power/main.cSeokjoo Lee > +++ linux-pm/drivers/base/power/main.c20. 1. 23. 오전 8:11에 Rafael J. Wysocki 이(가) 쓴 글: > @@ -273,10 +273,38 @@ static void dpm_wait_for_suppliers(struc > device_links_read_unlock(idx); > } > > -static void dpm_wait_for_superior(struct device *dev, bool async) > +static bool dpm_wait_for_superior(struct device *dev, bool async) > { > - dpm_wait(dev->parent, async); > + struct device *parent;board > + > + /* > + * If the device is resumed asynchronously and the parent's callback > + * deletes both the device and the parent itself, the parent object may > + * be freed while this function is running, so avoid that by reference > + * counting the parent once more unless the device has been deleted > + * already (in which case return right away). > + */ > + mutex_lock(&dpm_list_mtx); > + > + if (!device_pm_initialized(dev)) {20. 1. 23. 오전 8:11에 Rafael J. Wysocki 이(가) 쓴 글: > + mutex_unlock(&dpm_list_mtx); > + return false; > + } > + > + parent = get_device(dev->parent); > + > + mutex_unlock(&dpm_list_mtx); > + > + dpm_wait(parent, async); > + put_device(parent); > + > dpm_wait_for_suppliers(dev, async); > + > + /* > + * If the parent's callback has deleted the device, attempting to resume > + * it would be invalid, so avoid doing that then. > + */ > + return device_pm_initialized(dev);20. 1. 23. 오전 8:11에 Rafael J. Wysocki 이(가) 쓴 글: > } > > static void dpm_wait_for_consumers(struct device *dev, bool async) > @@ -621,7 +649,8 @@ static int device_resume_noirq(struct de > if (!dev->power.is_noirq_suspended) > goto Out; > > - dpm_wait_for_superior(dev, async); > + if (!dpm_wait_for_superior(dev, async)) > + goto Out; > > skip_resume = dev_pm_may_skip_resume(dev); > > @@ -829,7 +858,8 @@ static int device_resume_early(struct de > if (!dev->power.is_late_suspended) > goto Out; > > - dpm_wait_for_superior(dev, async);Seokjoo Lee > + if (!dpm_wait_for_superior(dev, async)) > + goto Out; > > callback = dpm_subsys_resume_early_cb(dev, state, &info); > > @@ -944,7 +974,9 @@ static int device_resume(struct device * > goto Complete; > } > > - dpm_wait_for_superior(dev, async); > + if (!dpm_wait_for_superior(dev, async)) > + goto Complete; > + > dpm_watchdog_set(&wd, dev); > device_lock(dev);Thanks, This seems to solve the rare hang on our target. Actually, the problem is occurred in v4.4. Shouldn't it apply to -stable? Chanho