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=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 D4A04C433DF for ; Wed, 8 Jul 2020 13:38:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B636C2065F for ; Wed, 8 Jul 2020 13:38:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729675AbgGHNh7 (ORCPT ); Wed, 8 Jul 2020 09:37:59 -0400 Received: from mailout1.hostsharing.net ([83.223.95.204]:48223 "EHLO mailout1.hostsharing.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729136AbgGHNh7 (ORCPT ); Wed, 8 Jul 2020 09:37:59 -0400 X-Greylist: delayed 650 seconds by postgrey-1.27 at vger.kernel.org; Wed, 08 Jul 2020 09:37:57 EDT Received: from h08.hostsharing.net (h08.hostsharing.net [IPv6:2a01:37:1000::53df:5f1c:0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client CN "*.hostsharing.net", Issuer "COMODO RSA Domain Validation Secure Server CA" (not verified)) by mailout1.hostsharing.net (Postfix) with ESMTPS id 14E1010190FA4; Wed, 8 Jul 2020 15:37:57 +0200 (CEST) Received: from localhost (pd95be530.dip0.t-ipconnect.de [217.91.229.48]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by h08.hostsharing.net (Postfix) with ESMTPSA id B1E906106EC8; Wed, 8 Jul 2020 15:37:56 +0200 (CEST) X-Mailbox-Line: From f2d349b5ba67b5ca70cb19577725167642eb69c5 Mon Sep 17 00:00:00 2001 Message-Id: In-Reply-To: References: From: Lukas Wunner Date: Wed, 8 Jul 2020 15:27:03 +0200 Subject: [PATCH 3/3] driver core: Avoid adding children below a dead parent To: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" , Dan Williams , Geert Uytterhoeven , Pantelis Antoniou , Alexander Duyck , Mark Brown , linux-kernel@vger.kernel.org, linux-spi@vger.kernel.org Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org If CONFIG_OF_DYNAMIC or CONFIG_ACPI is enabled, SPI devices may be added below a controller at runtime by a DeviceTree overlay or DSDT patch. But there are no precautions to prevent adding a device below a controller that's being removed. This seems like something that should be guarded against in the driver core because it's not specific to SPI: Adding a child below a parent that's going away seems like a bad idea regardless of the bus type. Take advantage of kill_device() which was added by commit 00289cd87676 ("drivers/base: Introduce kill_device()"), call it upon removal of an SPI controller and teach the driver core to refuse device addition below a killed parent. To make this race-free, device_add() needs to take the parent's dead_sem before checking its "dead" flag and until the child device has been added to the parent's klist_children. Signed-off-by: Lukas Wunner Cc: Dan Williams Cc: Geert Uytterhoeven Cc: Pantelis Antoniou Cc: Alexander Duyck --- drivers/base/core.c | 18 ++++++++++++++++-- drivers/spi/spi.c | 3 +++ 2 files changed, 19 insertions(+), 2 deletions(-) diff --git a/drivers/base/core.c b/drivers/base/core.c index 057da42b1a660..1d4e39696f996 100644 --- a/drivers/base/core.c +++ b/drivers/base/core.c @@ -2597,6 +2597,14 @@ int device_add(struct device *dev) pr_debug("device: '%s': %s\n", dev_name(dev), __func__); parent = get_device(dev->parent); + if (parent) { + down_read(&parent->p->dead_sem); + if (parent->p->dead) { + error = -ENODEV; + goto parent_error; + } + } + kobj = get_device_parent(dev, parent); if (IS_ERR(kobj)) { error = PTR_ERR(kobj); @@ -2679,9 +2687,11 @@ int device_add(struct device *dev) } bus_probe_device(dev); - if (parent) + if (parent) { klist_add_tail(&dev->p->knode_parent, &parent->p->klist_children); + up_read(&parent->p->dead_sem); + } if (dev->class) { mutex_lock(&dev->class->p->mutex); @@ -2722,6 +2732,8 @@ int device_add(struct device *dev) Error: cleanup_glue_dir(dev, glue_dir); parent_error: + if (parent) + up_read(&parent->p->dead_sem); put_device(parent); name_error: kfree(dev->p); @@ -2785,7 +2797,9 @@ EXPORT_SYMBOL_GPL(put_device); * kill_device - declare device dead * @dev: device in question * - * Declare @dev dead to prevent it from binding to a driver. + * Declare @dev dead to prevent it from binding to a driver and + * to prevent addition of children. + * * Return true if it was killed or false if it was already dead. */ bool kill_device(struct device *dev) diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 8158e281f3540..005eca4bae089 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -2764,6 +2764,9 @@ void spi_unregister_controller(struct spi_controller *ctlr) struct spi_controller *found; int id = ctlr->bus_num; + /* Prevent addition of new children, then remove existing ones */ + if (IS_ENABLED(CONFIG_OF_DYNAMIC) || IS_ENABLED(CONFIG_ACPI)) + kill_device(&ctlr->dev); device_for_each_child(&ctlr->dev, NULL, __unregister); /* First make sure that this controller was ever added */ -- 2.27.0