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=-12.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 15BFDC433E1 for ; Mon, 17 Aug 2020 19:36:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DD29520716 for ; Mon, 17 Aug 2020 19:36:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597693012; bh=LQsR3dnBfeULtjAcQHnXV69le54pY/011/AqbEmrMsw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=ZsmFWMDklhYFWfF01qNKbyiF8XSONUhgtnHB6xBsgMjQbG0DXcnEXnEYH1qgI392B MMXGvxHCINwOG2E884PmzOnr5M4R+x90xiEdUtODPizxZOoigPh5KvvWO5f/r9US0Z hl0FkT16OBUut6AWltVZ1Fggok9jnz43MulrowII= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732388AbgHQTgv (ORCPT ); Mon, 17 Aug 2020 15:36:51 -0400 Received: from mail.kernel.org ([198.145.29.99]:42484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729984AbgHQP2S (ORCPT ); Mon, 17 Aug 2020 11:28:18 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 46F9923B5F; Mon, 17 Aug 2020 15:28:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597678097; bh=LQsR3dnBfeULtjAcQHnXV69le54pY/011/AqbEmrMsw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=VXb9ARegsIFaFE+3QRKD56+U7y9SyTIlGczd/rlQYtR6J1HdNGu+auomTkpLySho3 FJUV5jv0/GDGUSsZ2Wg8n17jbh4gyKdN4uawSwWnXTnKU1zvThJfo+rGUcuncrzjvf NEUCuN0GNUg2QPNAaogzHWxOXosAcIgxDVpVevS8= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Bjorn Helgaas , Xiang Zheng , Heyi Guo , Biaoxiang Ye , Sasha Levin Subject: [PATCH 5.8 216/464] PCI: Fix pci_cfg_wait queue locking problem Date: Mon, 17 Aug 2020 17:12:49 +0200 Message-Id: <20200817143844.155715857@linuxfoundation.org> X-Mailer: git-send-email 2.28.0 In-Reply-To: <20200817143833.737102804@linuxfoundation.org> References: <20200817143833.737102804@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Bjorn Helgaas [ Upstream commit 2a7e32d0547f41c5ce244f84cf5d6ca7fccee7eb ] The pci_cfg_wait queue is used to prevent user-space config accesses to devices while they are recovering from reset. Previously we used these operations on pci_cfg_wait: __add_wait_queue(&pci_cfg_wait, ...) __remove_wait_queue(&pci_cfg_wait, ...) wake_up_all(&pci_cfg_wait) The wake_up acquires the wait queue lock, but the add and remove do not. Originally these were all protected by the pci_lock, but cdcb33f98244 ("PCI: Avoid possible deadlock on pci_lock and p->pi_lock"), moved wake_up_all() outside pci_lock, so it could race with add/remove operations, which caused occasional kernel panics, e.g., during vfio-pci hotplug/unplug testing: Unable to handle kernel read from unreadable memory at virtual address ffff802dac469000 Resolve this by using wait_event() instead of __add_wait_queue() and __remove_wait_queue(). The wait queue lock is held by both wait_event() and wake_up_all(), so it provides mutual exclusion. Fixes: cdcb33f98244 ("PCI: Avoid possible deadlock on pci_lock and p->pi_lock") Link: https://lore.kernel.org/linux-pci/79827f2f-9b43-4411-1376-b9063b67aee3@huawei.com/T/#u Based-on: https://lore.kernel.org/linux-pci/20191210031527.40136-1-zhengxiang9@huawei.com/ Based-on-patch-by: Xiang Zheng Signed-off-by: Bjorn Helgaas Tested-by: Xiang Zheng Cc: Heyi Guo Cc: Biaoxiang Ye Signed-off-by: Sasha Levin --- drivers/pci/access.c | 8 ++------ 1 file changed, 2 insertions(+), 6 deletions(-) diff --git a/drivers/pci/access.c b/drivers/pci/access.c index 79c4a2ef269a7..9793f17fa1843 100644 --- a/drivers/pci/access.c +++ b/drivers/pci/access.c @@ -204,17 +204,13 @@ EXPORT_SYMBOL(pci_bus_set_ops); static DECLARE_WAIT_QUEUE_HEAD(pci_cfg_wait); static noinline void pci_wait_cfg(struct pci_dev *dev) + __must_hold(&pci_lock) { - DECLARE_WAITQUEUE(wait, current); - - __add_wait_queue(&pci_cfg_wait, &wait); do { - set_current_state(TASK_UNINTERRUPTIBLE); raw_spin_unlock_irq(&pci_lock); - schedule(); + wait_event(pci_cfg_wait, !dev->block_cfg_access); raw_spin_lock_irq(&pci_lock); } while (dev->block_cfg_access); - __remove_wait_queue(&pci_cfg_wait, &wait); } /* Returns 0 on success, negative values indicate error. */ -- 2.25.1