From patchwork Mon Jan 13 01:03:16 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 3473341 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: X-Original-To: patchwork-linux-pci@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 4E10A9F169 for ; Mon, 13 Jan 2014 00:49:25 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 5C20A2011E for ; Mon, 13 Jan 2014 00:49:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6598220121 for ; Mon, 13 Jan 2014 00:49:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751102AbaAMAtW (ORCPT ); Sun, 12 Jan 2014 19:49:22 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:50862 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1751019AbaAMAtV (ORCPT ); Sun, 12 Jan 2014 19:49:21 -0500 Received: from afcd9.neoplus.adsl.tpnet.pl [95.49.55.9] (HELO vostro.rjw.lan) by serwer1319399.home.pl [79.96.170.134] with SMTP (IdeaSmtpServer v0.80) id 64c760026b20266c; Mon, 13 Jan 2014 01:49:19 +0100 From: "Rafael J. Wysocki" To: Yinghai Lu Cc: Bjorn Helgaas , "Rafael J. Wysocki" , Gu Zheng , Guo Chao , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Mika Westerberg , Myron Stowe Subject: [PATCH] PCI / remove: Check parent kobject in pci_destroy_dev() (was: Re: [PATCH v2 04/10] PCI: Destroy pci dev only once) Date: Mon, 13 Jan 2014 02:03:16 +0100 Message-ID: <3407940.L2vvqCPqy4@vostro.rjw.lan> User-Agent: KMail/4.11.3 (Linux/3.13.0-rc8+; KDE/4.11.3; x86_64; ; ) In-Reply-To: <1519414.GDlGZFCTSR@vostro.rjw.lan> References: <1385429290-25397-1-git-send-email-yinghai@kernel.org> <1519414.GDlGZFCTSR@vostro.rjw.lan> MIME-Version: 1.0 Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Spam-Status: No, score=-7.0 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Saturday, December 07, 2013 02:27:51 AM Rafael J. Wysocki wrote: > On Thursday, December 05, 2013 10:52:36 PM Yinghai Lu wrote: > > On Mon, Dec 2, 2013 at 6:49 AM, Rafael J. Wysocki wrote: > > > > > > Scenario 5: pci_stop_and_remove_bus_device() is run concurrently > > > for a device and its parent bridge via remove_callback(). > > > > > > In that case both code paths attempt to acquire > > > pci_remove_rescan_mutex. If the child device removal acquires > > > it first, there will be no problems. However, if the parent > > > bridge removal acquires it first, it will eventually execute > > > pci_destroy_dev() for the child device, but that device will > > > not be freed yet due to the reference held by the concurrent > > > child removal. Consequently, both pci_stop_bus_device() and > > > pci_remove_bus_device() will be executed for that device > > > unnecessarily and pci_destroy_dev() will see a corrupted list > > > head in that object. Moreover, an excess put_device() will > > > be executed for that device in that case which may lead to a > > > use-after-free in the final kobject_put() done by > > > sysfs_schedule_callback_work(). > > > > > > Index: linux-pm/include/linux/pci.h > > > =================================================================== > > > --- linux-pm.orig/include/linux/pci.h > > > +++ linux-pm/include/linux/pci.h > > > @@ -321,6 +321,7 @@ struct pci_dev { > > > unsigned int multifunction:1;/* Part of multi-function device */ > > > /* keep track of device state */ > > > unsigned int is_added:1; > > > + unsigned int is_gone:1; > > > unsigned int is_busmaster:1; /* device is busmaster */ > > > unsigned int no_msi:1; /* device may not use msi */ > > > unsigned int block_cfg_access:1; /* config space access is blocked */ > > > Index: linux-pm/drivers/pci/remove.c > > > =================================================================== > > > --- linux-pm.orig/drivers/pci/remove.c > > > +++ linux-pm/drivers/pci/remove.c > > > @@ -34,6 +34,7 @@ static void pci_stop_dev(struct pci_dev > > > > > > static void pci_destroy_dev(struct pci_dev *dev) > > > { > > > + dev->is_gone = 1; > > > device_del(&dev->dev); > > > > > > down_write(&pci_bus_sem); > > > @@ -109,8 +110,10 @@ static void pci_remove_bus_device(struct > > > */ > > > void pci_stop_and_remove_bus_device(struct pci_dev *dev) > > > { > > > - pci_stop_bus_device(dev); > > > - pci_remove_bus_device(dev); > > > + if (!dev->is_gone) { > > > + pci_stop_bus_device(dev); > > > + pci_remove_bus_device(dev); > > > + } > > > } > > > EXPORT_SYMBOL(pci_stop_and_remove_bus_device); > > > > > > > Yes, above change should address sys double remove problem. > > I've just realized that we don't need a new flag for that, though. > > It looks like we only need to check dev->dev.kobj.parent and return if that is > NULL, because that means pci_destroy_dev() has run for that device already > (I'm wondering why device_del() doesn't clear dev->parent, BTW, it looks like > it should do that?). > > Of course, that still is going to be racy if we don't hold > pci_remove_rescan_mutex around pci_stop_and_remove_bus_device() in every code > path using it (or use another similar synchronization mechanism). Before I forget about this, on top of the series I sent out on Friday. Thanks, Rafael --- From: Rafael J. Wysocki Subject: PCI / remove: Check parent kobject in pci_destroy_dev() If pci_stop_and_remove_bus_device() is run concurrently for a device and its parent bridge via remove_callback(), both code paths attempt to acquire pci_rescan_remove_lock. If the child device removal acquires it first, there will be no problems. However, if the parent bridge removal acquires it first, it will eventually execute pci_destroy_dev() for the child device, but that device object will not be freed yet due to the reference held by the concurrent child removal. Consequently, both pci_stop_bus_device() and pci_remove_bus_device() will be executed for that device unnecessarily and pci_destroy_dev() will see a corrupted list head in that object. Moreover, an excess put_device() will be executed for that device in that case which may lead to a use-after-free in the final kobject_put() done by sysfs_schedule_callback_work(). To avoid that problem, make pci_destroy_dev() check if the device's parent kobject is NULL, which only happens after device_del() has already run for it. Make pci_destroy_dev() return immediately whithout doing anything in that case. Signed-off-by: Rafael J. Wysocki --- drivers/pci/remove.c | 3 +++ 1 file changed, 3 insertions(+) -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Index: linux-pm/drivers/pci/remove.c =================================================================== --- linux-pm.orig/drivers/pci/remove.c +++ linux-pm/drivers/pci/remove.c @@ -34,6 +34,9 @@ static void pci_stop_dev(struct pci_dev static void pci_destroy_dev(struct pci_dev *dev) { + if (!dev->dev.kobj.parent) + return; + device_del(&dev->dev); down_write(&pci_bus_sem);