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=-5.6 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 BEC1CC282C8 for ; Mon, 28 Jan 2019 19:44:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8CE4021741 for ; Mon, 28 Jan 2019 19:44:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548704674; bh=v/xeE6brfLuyhZtA2on1bwzfflW0vSb0ykr2vN6OZUo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=0tbvr8IOzbLt16Uo3qQNeBVL0/TPzJMMA6w3dhSBUN2AKuN4324kwADb2RUhRuqik VFpe5cDDpyS3/+uq4f5MYksBOSFDw7Z1S6dW17jYVbdFow4MMwx583j8PP37SmJ3Nn H5I3+JhNBb+zWGjhW7QDjINJRJvK7u2fIcBIraWI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727237AbfA1Toe (ORCPT ); Mon, 28 Jan 2019 14:44:34 -0500 Received: from mail.kernel.org ([198.145.29.99]:43860 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727198AbfA1Tod (ORCPT ); Mon, 28 Jan 2019 14:44:33 -0500 Received: from localhost (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (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 BD28E20855; Mon, 28 Jan 2019 19:44:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1548704673; bh=v/xeE6brfLuyhZtA2on1bwzfflW0vSb0ykr2vN6OZUo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=W3AEzn+tUrlsfyRDeL1GJ5MeIAnqVogFPtTNts89wEMnk3XpKaRvDfTqu/Yho/iVY Dya53UiPtMcaYGnKNuFCTpxxo7tiGP9Hp0iQiL4gRQBtD7iq+pijBrbNxFHEZdszpD IPO7GzAyYyn7Z27j4tqWp/nXbHUA7f4qi6tSzOKo= Date: Mon, 28 Jan 2019 14:44:31 -0500 From: Sasha Levin To: Zubin Mithra Cc: stable@vger.kernel.org, gregkh@linuxfoundation.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: <20190128194431.GL3973@sasha-vm> References: <20190128173130.22618-1-zsm@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20190128173130.22618-1-zsm@chromium.org> User-Agent: Mutt/1.10.1 (2018-07-13) 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 Queued for 4.4, thank you. -- Thanks, Sasha