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=-9.8 required=3.0 tests=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 1AA4BC35642 for ; Fri, 21 Feb 2020 08:18:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D911A24692 for ; Fri, 21 Feb 2020 08:18:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582273093; bh=JH7Jqxn+2yA5s6yASEVbvRqf0qXawno/wfcdV5ZkVDI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=2fuwgeyGWvU0Kwj4vSfNcaFbhFGTyli/wqNC3K3UHY+TqH4aQzOYAi5fr5nkHTD74 bmMTsn2+wKvkWI4EkS35hIzqESp8ixeaahXze7Uuf2FybGnlvof1K3Aix9q5h0+5Wu 8l7SqMXZ/9DhjbhBwRC1ijDZcagmmmY0JexzwrT0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387789AbgBUISL (ORCPT ); Fri, 21 Feb 2020 03:18:11 -0500 Received: from mail.kernel.org ([198.145.29.99]:55786 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1733038AbgBUISD (ORCPT ); Fri, 21 Feb 2020 03:18:03 -0500 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 8C89124682; Fri, 21 Feb 2020 08:18:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1582273083; bh=JH7Jqxn+2yA5s6yASEVbvRqf0qXawno/wfcdV5ZkVDI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=wiiG9x+wBzL/i5PF47W/9r57Dnk4AvC8K78qHvBUZThYSsu6Dfo2Xr41bWyZXJSz/ bOlJePiwNm4VMMU8flLs2qCYehMw1VPRANkLicDKWHh2btWaNjqdqlCsXCkWaR15qk loS2b0HSbGVFCP6cq34dUrPUnvzE7a67GgGtErnM= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Niklas Schnelle , Peter Oberparleiter , Vasily Gorbik , Sasha Levin Subject: [PATCH 4.19 039/191] s390/pci: Fix possible deadlock in recover_store() Date: Fri, 21 Feb 2020 08:40:12 +0100 Message-Id: <20200221072256.273568918@linuxfoundation.org> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20200221072250.732482588@linuxfoundation.org> References: <20200221072250.732482588@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: Niklas Schnelle [ Upstream commit 576c75e36c689bec6a940e807bae27291ab0c0de ] With zpci_disable() working, lockdep detected a potential deadlock (lockdep output at the end). The deadlock is between recovering a PCI function via the /sys/bus/pci/devices//recover attribute vs powering it off via /sys/bus/pci/slots//power. The fix is analogous to the changes in commit 0ee223b2e1f6 ("scsi: core: Avoid that SCSI device removal through sysfs triggers a deadlock") that fixed a potential deadlock on removing a SCSI device via sysfs. [ 204.830107] ====================================================== [ 204.830109] WARNING: possible circular locking dependency detected [ 204.830111] 5.5.0-rc2-06072-gbc03ecc9a672 #6 Tainted: G W [ 204.830112] ------------------------------------------------------ [ 204.830113] bash/1034 is trying to acquire lock: [ 204.830115] 0000000192a1a610 (kn->count#200){++++}, at: kernfs_remove_by_name_ns+0x5c/0xa8 [ 204.830122] but task is already holding lock: [ 204.830123] 00000000c16134a8 (pci_rescan_remove_lock){+.+.}, at: pci_stop_and_remove_bus_device_locked+0x26/0x48 [ 204.830128] which lock already depends on the new lock. [ 204.830129] the existing dependency chain (in reverse order) is: [ 204.830130] -> #1 (pci_rescan_remove_lock){+.+.}: [ 204.830134] validate_chain+0x93a/0xd08 [ 204.830136] __lock_acquire+0x4ae/0x9d0 [ 204.830137] lock_acquire+0x114/0x280 [ 204.830140] __mutex_lock+0xa2/0x960 [ 204.830142] mutex_lock_nested+0x32/0x40 [ 204.830145] recover_store+0x4c/0xa8 [ 204.830147] kernfs_fop_write+0xe6/0x218 [ 204.830151] vfs_write+0xb0/0x1b8 [ 204.830152] ksys_write+0x6c/0xf8 [ 204.830154] system_call+0xd8/0x2d8 [ 204.830155] -> #0 (kn->count#200){++++}: [ 204.830187] check_noncircular+0x1e6/0x240 [ 204.830189] check_prev_add+0xfc/0xdb0 [ 204.830190] validate_chain+0x93a/0xd08 [ 204.830192] __lock_acquire+0x4ae/0x9d0 [ 204.830193] lock_acquire+0x114/0x280 [ 204.830194] __kernfs_remove.part.0+0x2e4/0x360 [ 204.830196] kernfs_remove_by_name_ns+0x5c/0xa8 [ 204.830198] remove_files.isra.0+0x4c/0x98 [ 204.830199] sysfs_remove_group+0x66/0xc8 [ 204.830201] sysfs_remove_groups+0x46/0x68 [ 204.830204] device_remove_attrs+0x52/0x90 [ 204.830207] device_del+0x182/0x418 [ 204.830208] pci_remove_bus_device+0x8a/0x130 [ 204.830210] pci_stop_and_remove_bus_device_locked+0x3a/0x48 [ 204.830212] disable_slot+0x68/0x100 [ 204.830213] power_write_file+0x7c/0x130 [ 204.830215] kernfs_fop_write+0xe6/0x218 [ 204.830217] vfs_write+0xb0/0x1b8 [ 204.830218] ksys_write+0x6c/0xf8 [ 204.830220] system_call+0xd8/0x2d8 [ 204.830221] other info that might help us debug this: [ 204.830223] Possible unsafe locking scenario: [ 204.830224] CPU0 CPU1 [ 204.830225] ---- ---- [ 204.830226] lock(pci_rescan_remove_lock); [ 204.830227] lock(kn->count#200); [ 204.830229] lock(pci_rescan_remove_lock); [ 204.830231] lock(kn->count#200); [ 204.830233] *** DEADLOCK *** [ 204.830234] 4 locks held by bash/1034: [ 204.830235] #0: 00000001b6fbc498 (sb_writers#4){.+.+}, at: vfs_write+0x158/0x1b8 [ 204.830239] #1: 000000018c9f5090 (&of->mutex){+.+.}, at: kernfs_fop_write+0xaa/0x218 [ 204.830242] #2: 00000001f7da0810 (kn->count#235){.+.+}, at: kernfs_fop_write+0xb6/0x218 [ 204.830245] #3: 00000000c16134a8 (pci_rescan_remove_lock){+.+.}, at: pci_stop_and_remove_bus_device_locked+0x26/0x48 [ 204.830248] stack backtrace: [ 204.830250] CPU: 2 PID: 1034 Comm: bash Tainted: G W 5.5.0-rc2-06072-gbc03ecc9a672 #6 [ 204.830252] Hardware name: IBM 8561 T01 703 (LPAR) [ 204.830253] Call Trace: [ 204.830257] [<00000000c05e10c0>] show_stack+0x88/0xf0 [ 204.830260] [<00000000c112dca4>] dump_stack+0xa4/0xe0 [ 204.830261] [<00000000c0694c06>] check_noncircular+0x1e6/0x240 [ 204.830263] [<00000000c0695bec>] check_prev_add+0xfc/0xdb0 [ 204.830264] [<00000000c06971da>] validate_chain+0x93a/0xd08 [ 204.830266] [<00000000c06994c6>] __lock_acquire+0x4ae/0x9d0 [ 204.830267] [<00000000c069867c>] lock_acquire+0x114/0x280 [ 204.830269] [<00000000c09ca15c>] __kernfs_remove.part.0+0x2e4/0x360 [ 204.830270] [<00000000c09cb5c4>] kernfs_remove_by_name_ns+0x5c/0xa8 [ 204.830272] [<00000000c09cee14>] remove_files.isra.0+0x4c/0x98 [ 204.830274] [<00000000c09cf2ae>] sysfs_remove_group+0x66/0xc8 [ 204.830276] [<00000000c09cf356>] sysfs_remove_groups+0x46/0x68 [ 204.830278] [<00000000c0e3dfe2>] device_remove_attrs+0x52/0x90 [ 204.830280] [<00000000c0e40382>] device_del+0x182/0x418 [ 204.830281] [<00000000c0dcfd7a>] pci_remove_bus_device+0x8a/0x130 [ 204.830283] [<00000000c0dcfe92>] pci_stop_and_remove_bus_device_locked+0x3a/0x48 [ 204.830285] [<00000000c0de7190>] disable_slot+0x68/0x100 [ 204.830286] [<00000000c0de6514>] power_write_file+0x7c/0x130 [ 204.830288] [<00000000c09cc846>] kernfs_fop_write+0xe6/0x218 [ 204.830290] [<00000000c08f3480>] vfs_write+0xb0/0x1b8 [ 204.830291] [<00000000c08f378c>] ksys_write+0x6c/0xf8 [ 204.830293] [<00000000c1154374>] system_call+0xd8/0x2d8 [ 204.830294] INFO: lockdep is turned off. Signed-off-by: Niklas Schnelle Reviewed-by: Peter Oberparleiter Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin --- arch/s390/pci/pci_sysfs.c | 63 ++++++++++++++++++++++++++------------- 1 file changed, 42 insertions(+), 21 deletions(-) diff --git a/arch/s390/pci/pci_sysfs.c b/arch/s390/pci/pci_sysfs.c index 430c14b006d17..0e11fc023fe78 100644 --- a/arch/s390/pci/pci_sysfs.c +++ b/arch/s390/pci/pci_sysfs.c @@ -13,6 +13,8 @@ #include #include +#include "../../../drivers/pci/pci.h" + #include #define zpci_attr(name, fmt, member) \ @@ -40,31 +42,50 @@ zpci_attr(segment3, "0x%02x\n", pfip[3]); static ssize_t recover_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { + struct kernfs_node *kn; struct pci_dev *pdev = to_pci_dev(dev); struct zpci_dev *zdev = to_zpci(pdev); - int ret; - - if (!device_remove_file_self(dev, attr)) - return count; - + int ret = 0; + + /* Can't use device_remove_self() here as that would lead us to lock + * the pci_rescan_remove_lock while holding the device' kernfs lock. + * This would create a possible deadlock with disable_slot() which is + * not directly protected by the device' kernfs lock but takes it + * during the device removal which happens under + * pci_rescan_remove_lock. + * + * This is analogous to sdev_store_delete() in + * drivers/scsi/scsi_sysfs.c + */ + kn = sysfs_break_active_protection(&dev->kobj, &attr->attr); + WARN_ON_ONCE(!kn); + /* device_remove_file() serializes concurrent calls ignoring all but + * the first + */ + device_remove_file(dev, attr); + + /* A concurrent call to recover_store() may slip between + * sysfs_break_active_protection() and the sysfs file removal. + * Once it unblocks from pci_lock_rescan_remove() the original pdev + * will already be removed. + */ pci_lock_rescan_remove(); - pci_stop_and_remove_bus_device(pdev); - ret = zpci_disable_device(zdev); - if (ret) - goto error; - - ret = zpci_enable_device(zdev); - if (ret) - goto error; - - pci_rescan_bus(zdev->bus); + if (pci_dev_is_added(pdev)) { + pci_stop_and_remove_bus_device(pdev); + ret = zpci_disable_device(zdev); + if (ret) + goto out; + + ret = zpci_enable_device(zdev); + if (ret) + goto out; + pci_rescan_bus(zdev->bus); + } +out: pci_unlock_rescan_remove(); - - return count; - -error: - pci_unlock_rescan_remove(); - return ret; + if (kn) + sysfs_unbreak_active_protection(kn); + return ret ? ret : count; } static DEVICE_ATTR_WO(recover); -- 2.20.1