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 05807C3F2D1 for ; Mon, 2 Mar 2020 13:57:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D912B2166E for ; Mon, 2 Mar 2020 13:57:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726925AbgCBN5n (ORCPT ); Mon, 2 Mar 2020 08:57:43 -0500 Received: from mga03.intel.com ([134.134.136.65]:39949 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726451AbgCBN5n (ORCPT ); Mon, 2 Mar 2020 08:57:43 -0500 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by orsmga103.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 02 Mar 2020 05:57:42 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,507,1574150400"; d="scan'208";a="351545030" Received: from kuha.fi.intel.com ([10.237.72.53]) by fmsmga001.fm.intel.com with SMTP; 02 Mar 2020 05:57:39 -0800 Received: by kuha.fi.intel.com (sSMTP sendmail emulation); Mon, 02 Mar 2020 15:57:38 +0200 Date: Mon, 2 Mar 2020 15:57:38 +0200 From: Heikki Krogerus To: Brendan Higgins Cc: gregkh@linuxfoundation.org, rafael@kernel.org, linux-kernel@vger.kernel.org, davidgow@google.com, Heidi Fahim , Hans de Goede , "Rafael J . Wysocki" Subject: Re: [PATCH v1] Revert "software node: Simplify software_node_release() function" Message-ID: <20200302135738.GD22243@kuha.fi.intel.com> References: <20200228000001.240428-1-brendanhiggins@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200228000001.240428-1-brendanhiggins@google.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 27, 2020 at 04:00:01PM -0800, Brendan Higgins wrote: > This reverts commit 3df85a1ae51f6b256982fe9d17c2dc5bfb4cc402. > > The reverted commit says "It's possible to release the node ID > immediately when fwnode_remove_software_node() is called, no need to > wait for software_node_release() with that." However, releasing the node > ID before waiting for software_node_release() to be called causes the > node ID to be released before the kobject and the underlying sysfs > entry; this means there is a period of time where a sysfs entry exists > that is associated with an unallocated node ID. > > Once consequence of this is that there is a race condition where it is > possible to call fwnode_create_software_node() with no parent node > specified (NULL) and have it fail with -EEXIST because the node ID that > was assigned is still associated with a stale sysfs entry that hasn't > been cleaned up yet. > > Although it is difficult to reproduce this race condition under normal > conditions, it can be deterministically reproduced with the following > minconfig on UML: > > CONFIG_KUNIT_DRIVER_PE_TEST=y > CONFIG_DEBUG_KERNEL=y > CONFIG_DEBUG_OBJECTS=y > CONFIG_DEBUG_OBJECTS_TIMERS=y > CONFIG_DEBUG_KOBJECT_RELEASE=y > CONFIG_KUNIT=y > > Running the tests with this configuration causes the following failure: > > > kobject: 'node0' ((____ptrval____)): kobject_release, parent (____ptrval____) (delayed 400) > ok 1 - pe_test_uints > sysfs: cannot create duplicate filename '/kernel/software_nodes/node0' > CPU: 0 PID: 28 Comm: kunit_try_catch Not tainted 5.6.0-rc3-next-20200227 #14 > > kobject_add_internal failed for node0 with -EEXIST, don't try to register things with the same name in the same directory. > kobject: 'node0' ((____ptrval____)): kobject_release, parent (____ptrval____) (delayed 100) > # pe_test_uint_arrays: ASSERTION FAILED at drivers/base/test/property-entry-test.c:123 > Expected node is not error, but is: -17 > not ok 2 - pe_test_uint_arrays > > > Reported-by: Heidi Fahim > Signed-off-by: Brendan Higgins > Cc: Heikki Krogerus > Cc: Hans de Goede > Cc: Rafael J. Wysocki Reviewed-by: Heikki Krogerus > --- > drivers/base/swnode.c | 14 +++++++------- > 1 file changed, 7 insertions(+), 7 deletions(-) > > diff --git a/drivers/base/swnode.c b/drivers/base/swnode.c > index 0b081dee1e95c..de8d3543e8fe3 100644 > --- a/drivers/base/swnode.c > +++ b/drivers/base/swnode.c > @@ -608,6 +608,13 @@ static void software_node_release(struct kobject *kobj) > { > struct swnode *swnode = kobj_to_swnode(kobj); > > + if (swnode->parent) { > + ida_simple_remove(&swnode->parent->child_ids, swnode->id); > + list_del(&swnode->entry); > + } else { > + ida_simple_remove(&swnode_root_ids, swnode->id); > + } > + > if (swnode->allocated) { > property_entries_free(swnode->node->properties); > kfree(swnode->node); > @@ -773,13 +780,6 @@ void fwnode_remove_software_node(struct fwnode_handle *fwnode) > if (!swnode) > return; > > - if (swnode->parent) { > - ida_simple_remove(&swnode->parent->child_ids, swnode->id); > - list_del(&swnode->entry); > - } else { > - ida_simple_remove(&swnode_root_ids, swnode->id); > - } > - > kobject_put(&swnode->kobj); > } > EXPORT_SYMBOL_GPL(fwnode_remove_software_node); > -- > 2.25.1.481.gfbce0eb801-goog thanks, -- heikki