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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 495D3C433F5 for ; Thu, 7 Apr 2022 01:24:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236480AbiDGB0U (ORCPT ); Wed, 6 Apr 2022 21:26:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60736 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239633AbiDGBTY (ORCPT ); Wed, 6 Apr 2022 21:19:24 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C29F91ACA67; Wed, 6 Apr 2022 18:14:51 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 3D612B81E7F; Thu, 7 Apr 2022 01:14:50 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D24ECC385A6; Thu, 7 Apr 2022 01:14:47 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1649294089; bh=DZk+WXcnW8g/8vZtd8VD3Srcm77n05xo5TSm9bOHfNo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kqeMKdYMEQYBlPv48zQtzTq01QJOSpz0KtSFk/QUbSJ0/UfXqyVpksn93RtqgFfWH tEtMnrO8BzhD6hcpctNsW7xdkXnrzgp8i//OgxG/JKH0fj9ZvZNdXrpKlKOMQtPrUJ OZtS4DoEbMvX9y/QyoFTo3plFOUVZp2XoJsQIjmkPKGLR9O9BSlE2qV8fZ7+zlPQ+L qKGxHKpTtFp1r7FzrvU63F38TmK/G7HU0rUUHTFjgeb01bOX/Vec7RAyHjSOQnbZ7P uJr/DFx/gIfbt05po7iobp47kKszEFiqwcH+dp1kkREYzeel9UIQDQ4KFllmzpAkAc R63rKyvXgxytg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Niklas Schnelle , Matthew Rosato , Vasily Gorbik , Sasha Levin , gerald.schaefer@linux.ibm.com, hca@linux.ibm.com, agordeev@linux.ibm.com, linux-s390@vger.kernel.org Subject: [PATCH AUTOSEL 5.10 14/25] s390/pci: improve zpci_dev reference counting Date: Wed, 6 Apr 2022 21:14:02 -0400 Message-Id: <20220407011413.114662-14-sashal@kernel.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220407011413.114662-1-sashal@kernel.org> References: <20220407011413.114662-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Niklas Schnelle [ Upstream commit c122383d221dfa2f41cfe5e672540595de986fde ] Currently zpci_dev uses kref based reference counting but only accounts for one original reference plus one reference from an added pci_dev to its underlying zpci_dev. Counting just the original reference worked until the pci_dev reference was added in commit 2a671f77ee49 ("s390/pci: fix use after free of zpci_dev") because once a zpci_dev goes away, i.e. enters the reserved state, it would immediately get released. However with the pci_dev reference this is no longer the case and the zpci_dev may still appear in multiple availability events indicating that it was reserved. This was solved by detecting when the zpci_dev is already on its way out but still hanging around. This has however shown some light on how unusual our zpci_dev reference counting is. Improve upon this by modelling zpci_dev reference counting on pci_dev. Analogous to pci_get_slot() increment the reference count in get_zdev_by_fid(). Thus all users of get_zdev_by_fid() must drop the reference once they are done with the zpci_dev. Similar to pci_scan_single_device(), zpci_create_device() returns the device with an initial count of 1 and the device added to the zpci_list (analogous to the PCI bus' device_list). In turn users of zpci_create_device() must only drop the reference once the device is gone from the point of view of the zPCI subsystem, it might still be referenced by the common PCI subsystem though. Reviewed-by: Matthew Rosato Signed-off-by: Niklas Schnelle Signed-off-by: Vasily Gorbik Signed-off-by: Sasha Levin --- arch/s390/pci/pci.c | 1 + arch/s390/pci/pci_bus.h | 3 ++- arch/s390/pci/pci_clp.c | 9 +++++++-- arch/s390/pci/pci_event.c | 7 ++++++- 4 files changed, 16 insertions(+), 4 deletions(-) diff --git a/arch/s390/pci/pci.c b/arch/s390/pci/pci.c index e14e4a3a647a..74799439b259 100644 --- a/arch/s390/pci/pci.c +++ b/arch/s390/pci/pci.c @@ -69,6 +69,7 @@ struct zpci_dev *get_zdev_by_fid(u32 fid) list_for_each_entry(tmp, &zpci_list, entry) { if (tmp->fid == fid) { zdev = tmp; + zpci_zdev_get(zdev); break; } } diff --git a/arch/s390/pci/pci_bus.h b/arch/s390/pci/pci_bus.h index 55c9488e504c..8d2fcd091ca7 100644 --- a/arch/s390/pci/pci_bus.h +++ b/arch/s390/pci/pci_bus.h @@ -13,7 +13,8 @@ void zpci_bus_device_unregister(struct zpci_dev *zdev); void zpci_release_device(struct kref *kref); static inline void zpci_zdev_put(struct zpci_dev *zdev) { - kref_put(&zdev->kref, zpci_release_device); + if (zdev) + kref_put(&zdev->kref, zpci_release_device); } static inline void zpci_zdev_get(struct zpci_dev *zdev) diff --git a/arch/s390/pci/pci_clp.c b/arch/s390/pci/pci_clp.c index 0a0e8b8293be..d1a5c80a41cb 100644 --- a/arch/s390/pci/pci_clp.c +++ b/arch/s390/pci/pci_clp.c @@ -22,6 +22,8 @@ #include #include +#include "pci_bus.h" + bool zpci_unique_uid; void update_uid_checking(bool new) @@ -372,8 +374,11 @@ static void __clp_add(struct clp_fh_list_entry *entry, void *data) return; zdev = get_zdev_by_fid(entry->fid); - if (!zdev) - zpci_create_device(entry->fid, entry->fh, entry->config_state); + if (zdev) { + zpci_zdev_put(zdev); + return; + } + zpci_create_device(entry->fid, entry->fh, entry->config_state); } int clp_scan_pci_devices(void) diff --git a/arch/s390/pci/pci_event.c b/arch/s390/pci/pci_event.c index b7cfde7e80a8..6ced44b5be8a 100644 --- a/arch/s390/pci/pci_event.c +++ b/arch/s390/pci/pci_event.c @@ -61,10 +61,12 @@ static void __zpci_event_error(struct zpci_ccdf_err *ccdf) pdev ? pci_name(pdev) : "n/a", ccdf->pec, ccdf->fid); if (!pdev) - return; + goto no_pdev; pdev->error_state = pci_channel_io_perm_failure; pci_dev_put(pdev); +no_pdev: + zpci_zdev_put(zdev); } void zpci_event_error(void *data) @@ -76,6 +78,7 @@ void zpci_event_error(void *data) static void __zpci_event_availability(struct zpci_ccdf_avail *ccdf) { struct zpci_dev *zdev = get_zdev_by_fid(ccdf->fid); + bool existing_zdev = !!zdev; enum zpci_state state; struct pci_dev *pdev; int ret; @@ -161,6 +164,8 @@ static void __zpci_event_availability(struct zpci_ccdf_avail *ccdf) default: break; } + if (existing_zdev) + zpci_zdev_put(zdev); } void zpci_event_availability(void *data) -- 2.35.1