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=-3.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS autolearn=no 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 DC674C433E0 for ; Sun, 24 May 2020 15:35:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B40CB20826 for ; Sun, 24 May 2020 15:35:08 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590334508; bh=E8UEpF+FHR7JwtgCX5qsPu9Jts5pgO1PoKNJAS7GS3Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=Ha1otG+G/37u6MbkaLT13y9rPP4L9OT7g3lOMVGr6gCT5l/gWAZmQJxpP8RxNrSdD BWT1wyhhDab0SH4l3kjVXfHExhcFDdlN2Y5sRYEFpU39ZOJiXVbBrt4E/LZaHCf/61 JXi2fV2+1lIRY6UbAb2GyCZQox0zP9+H+f3xdkKs= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387725AbgEXPfI (ORCPT ); Sun, 24 May 2020 11:35:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:38396 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726506AbgEXPfH (ORCPT ); Sun, 24 May 2020 11:35:07 -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 65902207CB; Sun, 24 May 2020 15:35:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1590334506; bh=E8UEpF+FHR7JwtgCX5qsPu9Jts5pgO1PoKNJAS7GS3Q=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=M6uqNT8/6cSvlY8QC7DkkcHqlAqpaYum9jpPhEu0mXK1LVHHNBuvrGN7M4DCImMdT ipkipaSbOYq3CFyOE+xgPxqDEuC6tuyReqA+ju6gma8hpSmVjWhR7Q3xakgJzhGcy0 U2xfk41dxwTNQxMd7qx4Qv5hsjHzATMztDfolRFQ= Date: Sun, 24 May 2020 17:35:04 +0200 From: Greg Kroah-Hartman To: Randy Dunlap Cc: Heikki Krogerus , linux-kernel@vger.kernel.org, Naresh Kamboju , kernel test robot , Brendan Higgins , "Rafael J. Wysocki" Subject: Re: [PATCH] kobject: Make sure the parent does not get released before its children Message-ID: <20200524153504.GA2684@kroah.com> References: <20200513151840.36400-1-heikki.krogerus@linux.intel.com> <20200523153643.GA226270@kroah.com> <7a5e4740-8099-ef70-776f-0d92ce84ab3d@infradead.org> <20200524125727.GA2430@kroah.com> <20200524131405.GA24073@kroah.com> <20200524132812.GA2401@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200524132812.GA2401@kroah.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 24, 2020 at 03:28:12PM +0200, Greg Kroah-Hartman wrote: > On Sun, May 24, 2020 at 03:14:05PM +0200, Greg Kroah-Hartman wrote: > > On Sun, May 24, 2020 at 02:57:27PM +0200, Greg Kroah-Hartman wrote: > > > On Sat, May 23, 2020 at 08:44:06AM -0700, Randy Dunlap wrote: > > > > On 5/23/20 8:36 AM, Greg Kroah-Hartman wrote: > > > > > On Wed, May 13, 2020 at 06:18:40PM +0300, Heikki Krogerus wrote: > > > > >> In the function kobject_cleanup(), kobject_del(kobj) is > > > > >> called before the kobj->release(). That makes it possible to > > > > >> release the parent of the kobject before the kobject itself. > > > > >> > > > > >> To fix that, adding function __kboject_del() that does > > > > >> everything that kobject_del() does except release the parent > > > > >> reference. kobject_cleanup() then calls __kobject_del() > > > > >> instead of kobject_del(), and separately decrements the > > > > >> reference count of the parent kobject after kobj->release() > > > > >> 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 > > > > >> Reviewed-by: Rafael J. Wysocki > > > > >> Reviewed-by: Brendan Higgins > > > > >> Tested-by: Brendan Higgins > > > > >> Acked-by: Randy Dunlap > > > > >> --- > > > > >> lib/kobject.c | 30 ++++++++++++++++++++---------- > > > > >> 1 file changed, 20 insertions(+), 10 deletions(-) > > > > > > > > > > Stepping back, now that it turns out this patch causes more problems > > > > > than it fixes, how is everyone reproducing the original crash here? > > > > > > > > Just load lib/test_printf.ko and boom! > > > > > > Thanks, that helps. > > > > > > Ok, in messing around with the kobject core more, originally we thought > > > this was an issue of the kobject uevent happening for the parent pointer > > > (when the parent was invalid). so, moving things around some more, and > > > now I'm crashing in software_node_release() when we are trying to access > > > swnode->parent->child_ids as parent is invalid there. > > > > > > So I feel like this is a swnode bug, or a use of swnode in a way it > > > shouldn't be that the testing framework is exposing somehow. > > > > > > Let me dig deeper... > > > > Ah, ick, static software nodes trying to be cleaned up in the totally > > wrong order. You can't just try to randomly clean up a kobject anywhere > > in the middle of the hierarchy, that's flat out not going to work > > properly. let me unwind it... > > Ok, the patch below fixes the test, there's not really anything wrong > with the kobject core, except maybe the kobject uevent for removal, > which I'll send a patch for. > > I'll write these up as a real set of patches after a bit. They are now here: https://lore.kernel.org/lkml/20200524153041.2361-1-gregkh@linuxfoundation.org/ thanks, greg k-h