From patchwork Mon Aug 17 15:12:52 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 266499 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=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 A897AC433DF for ; Mon, 17 Aug 2020 15:29:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 75E2C23AC3 for ; Mon, 17 Aug 2020 15:29:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597678162; bh=w5U96Fw6mjrn3JpYW7hRBEbu4JgEbS0Dkmw6fue0zYU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=thyjVUE0ABVBfKQhf0Cl0c+mLDk9KqJZ3nvdlC3V3oiue/falEXEkbJyEaVi3Pbx+ gypfR/9nLvmsOaLXAITiv6ohfxSluNUgs/M8vfdf8MA6Hq/gDGfL31TunPIFc8LN3K spDPXcDZZxy/VeYqhJ0Fh4/dtT6v+783TJcp5klI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730054AbgHQP3S (ORCPT ); Mon, 17 Aug 2020 11:29:18 -0400 Received: from mail.kernel.org ([198.145.29.99]:46944 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730082AbgHQP3P (ORCPT ); Mon, 17 Aug 2020 11:29:15 -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 DD8A823A9B; Mon, 17 Aug 2020 15:29:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1597678153; bh=w5U96Fw6mjrn3JpYW7hRBEbu4JgEbS0Dkmw6fue0zYU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=1yCYbC+J9WK3kOhzfac+bmy+2wNi0RZr0HdpyJJY5A17FXp2jHlcHt0+aiIRNLfFi XcbUNMPMtMldOjUkjGv9V2YAIinR2J9XAjBfbUy0m1BFR+d+l+QrZ9VvcDXWib439n ue88nbXR+E2JXxcs0FPo6jIqOn3dGAUmS/jZ54RA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Naresh Kamboju , kernel test robot , "Rafael J. Wysocki" , Heikki Krogerus , "Rafael J. Wysocki" , Sasha Levin Subject: [PATCH 5.8 219/464] kobject: Avoid premature parent object freeing in kobject_cleanup() Date: Mon, 17 Aug 2020 17:12:52 +0200 Message-Id: <20200817143844.294781668@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 Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Heikki Krogerus [ Upstream commit 079ad2fb4bf9eba8a0aaab014b49705cd7f07c66 ] If kobject_del() is invoked by kobject_cleanup() to delete the target kobject, it may cause its parent kobject to be freed before invoking the target kobject's ->release() method, which effectively means freeing the parent before dealing with the child entirely. That is confusing at best and it may also lead to functional issues if the callers of kobject_cleanup() are not careful enough about the order in which these calls are made, so avoid the problem by making kobject_cleanup() drop the last reference to the target kobject's parent at the end, after invoking the target kobject's ->release() method. [ rjw: Rewrite the subject and changelog, make kobject_cleanup() drop the parent reference only when __kobject_del() has been called. ] Reported-by: Naresh Kamboju Reported-by: kernel test robot Fixes: 7589238a8cf3 ("Revert "software node: Simplify software_node_release() function"") Suggested-by: Rafael J. Wysocki Signed-off-by: Heikki Krogerus Signed-off-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/1908555.IiAGLGrh1Z@kreacher Signed-off-by: Greg Kroah-Hartman Signed-off-by: Sasha Levin --- lib/kobject.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/lib/kobject.c b/lib/kobject.c index 1e4b7382a88ed..3afb939f2a1cc 100644 --- a/lib/kobject.c +++ b/lib/kobject.c @@ -599,14 +599,7 @@ int kobject_move(struct kobject *kobj, struct kobject *new_parent) } EXPORT_SYMBOL_GPL(kobject_move); -/** - * kobject_del() - Unlink kobject from hierarchy. - * @kobj: object. - * - * This is the function that should be called to delete an object - * successfully added via kobject_add(). - */ -void kobject_del(struct kobject *kobj) +static void __kobject_del(struct kobject *kobj) { struct kernfs_node *sd; const struct kobj_type *ktype; @@ -632,9 +625,23 @@ void kobject_del(struct kobject *kobj) kobj->state_in_sysfs = 0; kobj_kset_leave(kobj); - kobject_put(kobj->parent); kobj->parent = NULL; } + +/** + * kobject_del() - Unlink kobject from hierarchy. + * @kobj: object. + * + * This is the function that should be called to delete an object + * successfully added via kobject_add(). + */ +void kobject_del(struct kobject *kobj) +{ + struct kobject *parent = kobj->parent; + + __kobject_del(kobj); + kobject_put(parent); +} EXPORT_SYMBOL(kobject_del); /** @@ -670,6 +677,7 @@ EXPORT_SYMBOL(kobject_get_unless_zero); */ static void kobject_cleanup(struct kobject *kobj) { + struct kobject *parent = kobj->parent; struct kobj_type *t = get_ktype(kobj); const char *name = kobj->name; @@ -684,7 +692,10 @@ static void kobject_cleanup(struct kobject *kobj) if (kobj->state_in_sysfs) { pr_debug("kobject: '%s' (%p): auto cleanup kobject_del\n", kobject_name(kobj), kobj); - kobject_del(kobj); + __kobject_del(kobj); + } else { + /* avoid dropping the parent reference unnecessarily */ + parent = NULL; } if (t && t->release) { @@ -698,6 +709,8 @@ static void kobject_cleanup(struct kobject *kobj) pr_debug("kobject: '%s': free name\n", name); kfree_const(name); } + + kobject_put(parent); } #ifdef CONFIG_DEBUG_KOBJECT_RELEASE