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=-5.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_MUTT 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 919C8C282C4 for ; Mon, 4 Feb 2019 08:58:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6066A217D6 for ; Mon, 4 Feb 2019 08:58:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549270723; bh=WVwPyiHfMHxK+04o9zzyBLrnBS0k4+zBX0dVcJBoZ1o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=10e0dMMMQzYz9bMSdcUYnKjPL2aKyNoWwimoUYQ2IZ3wRbeiUGilGdBJruNvkyKnv GtRm2F0MkGvE8uTZPi4uex2Tx+sjN9a5x1/aGNfpxX/1o7LB90TFTI32UrrnHl1HtH hs9ONy39EioQFthaBT+VaBX4UhvAvlgVoa0AiZ5E= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728472AbfBDI6m (ORCPT ); Mon, 4 Feb 2019 03:58:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:56566 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726502AbfBDI6m (ORCPT ); Mon, 4 Feb 2019 03:58:42 -0500 Received: from localhost (5356596B.cm-6-7b.dynamic.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 B035B214DA; Mon, 4 Feb 2019 08:58:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1549270722; bh=WVwPyiHfMHxK+04o9zzyBLrnBS0k4+zBX0dVcJBoZ1o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=1Z3ApEAUXkF2+y0UIHda42OJN5AWh4c0Cs5I9uUyHOW5oQ5QXQflmG9nyxWbzw3i7 RmZZgYhTx5H4ySovOVyHJqjjBqGoEyoQeKUXZILyyKH9iSQFptqFn2N6X3Pa/avEMX rte2nxgVFxJLv+5ZEZM4gQ5WowyAyorznZcTzUnQ= Date: Mon, 4 Feb 2019 09:58:39 +0100 From: Greg KH To: Zubin Mithra Cc: stable@vger.kernel.org, groeck@chromium.org, benh@kernel.crashing.org, rafael@kernel.org Subject: Re: [PATCH v4.4.y] drivers: core: Remove glue dirs from sysfs earlier Message-ID: <20190204085839.GC2015@kroah.com> References: <20190128173130.22618-1-zsm@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190128173130.22618-1-zsm@chromium.org> User-Agent: Mutt/1.11.3 (2019-02-01) Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On Mon, Jan 28, 2019 at 09:31:30AM -0800, Zubin Mithra wrote: > From: Benjamin Herrenschmidt > > commit 726e41097920a73e4c7c33385dcc0debb1281e18 upstream > > For devices with a class, we create a "glue" directory between > the parent device and the new device with the class name. > > This directory is never "explicitely" removed when empty however, > this is left to the implicit sysfs removal done by kobject_release() > when the object loses its last reference via kobject_put(). > > This is problematic because as long as it's not been removed from > sysfs, it is still present in the class kset and in sysfs directory > structure. > > The presence in the class kset exposes a use after free bug fixed > by the previous patch, but the presence in sysfs means that until > the kobject is released, which can take a while (especially with > kobject debugging), any attempt at re-creating such as binding a > new device for that class/parent pair, will result in a sysfs > duplicate file name error. > > This fixes it by instead doing an explicit kobject_del() when > the glue dir is empty, by keeping track of the number of > child devices of the gluedir. > > This is made easy by the fact that all glue dir operations are > done with a global mutex, and there's already a function > (cleanup_glue_dir) called in all the right places taking that > mutex that can be enhanced for this. It appears that this was > in fact the intent of the function, but the implementation was > wrong. > > Backport Note: kref_read() is not present in 4.4. Hence, > use atomic_read(&kref.refcount) instead of kref_read(&kref). > > Signed-off-by: Benjamin Herrenschmidt > Acked-by: Linus Torvalds > Signed-off-by: Greg Kroah-Hartman > Signed-off-by: Zubin Mithra > --- > drivers/base/core.c | 2 ++ > include/linux/kobject.h | 17 +++++++++++++++++ > 2 files changed, 19 insertions(+) Now queued up everywhere, thanks. greg k-h