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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7925EC433FE for ; Fri, 21 Oct 2022 08:18:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230086AbiJUISk (ORCPT ); Fri, 21 Oct 2022 04:18:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46716 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229616AbiJUISi (ORCPT ); Fri, 21 Oct 2022 04:18:38 -0400 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDC0B1C2E8C for ; Fri, 21 Oct 2022 01:18:36 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by sin.source.kernel.org (Postfix) with ESMTPS id 4ABB1CE2A1B for ; Fri, 21 Oct 2022 08:18:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3C09FC433D7; Fri, 21 Oct 2022 08:18:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1666340313; bh=8++5V96CRoT3offEW1sfGPjlBhG5kCvkZ9nTWWOETBI=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jgzWKnVMDL4jjfh3rpyIZnQ6lzYGvVQFOfB2Sz0ckbK8TSaMML0PB6ejva6LPIpVh ec2TKJYGoaFx30SX5W4+m5zVlvfmFnd1+qS08e2EpH9AWzJBI41sDGDR+b9qaC68rY UySyAc400Lqb6/UqLIyGB/GHeIBa76ZzCFASzYBo= Date: Fri, 21 Oct 2022 10:18:31 +0200 From: Greg KH To: Luben Tuikov Cc: Yang Yingliang , linux-kernel@vger.kernel.org, qemu-devel@nongnu.org, linux-f2fs-devel@lists.sourceforge.net, linux-erofs@lists.ozlabs.org, ocfs2-devel@oss.oracle.com, linux-mtd@lists.infradead.org, amd-gfx@lists.freedesktop.org, rafael@kernel.org, somlo@cmu.edu, mst@redhat.com, jaegeuk@kernel.org, chao@kernel.org, hsiangkao@linux.alibaba.com, huangjianan@oppo.com, mark@fasheh.com, jlbec@evilplan.org, joseph.qi@linux.alibaba.com, akpm@linux-foundation.org, alexander.deucher@amd.com, richard@nod.at, liushixin2@huawei.com Subject: Re: [PATCH 00/11] fix memory leak while kset_register() fails Message-ID: References: <20221021022102.2231464-1-yangyingliang@huawei.com> <5efd73b0-d634-d34f-3d7a-13d674e40d04@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5efd73b0-d634-d34f-3d7a-13d674e40d04@amd.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Oct 21, 2022 at 03:55:18AM -0400, Luben Tuikov wrote: > On 2022-10-21 01:37, Greg KH wrote: > > On Fri, Oct 21, 2022 at 01:29:31AM -0400, Luben Tuikov wrote: > >> On 2022-10-20 22:20, Yang Yingliang wrote: > >>> The previous discussion link: > >>> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flore.kernel.org%2Flkml%2F0db486eb-6927-927e-3629-958f8f211194%40huawei.com%2FT%2F&data=05%7C01%7Cluben.tuikov%40amd.com%7C65b33f087ef245a9f23708dab3264840%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638019274318153227%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=1ZoieEob62iU9kI8fvpp20qGut9EeHKIHtCAT01t%2Bz8%3D&reserved=0 > >> > >> The very first discussion on this was here: > >> > >> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.spinics.net%2Flists%2Fdri-devel%2Fmsg368077.html&data=05%7C01%7Cluben.tuikov%40amd.com%7C65b33f087ef245a9f23708dab3264840%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C638019274318153227%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C3000%7C%7C%7C&sdata=9joWxGLUxZZMvrfkxCR8KbkoXifsqoMK0vGR%2FyEG62w%3D&reserved=0 > >> > >> Please use this link, and not the that one up there you which quoted above, > >> and whose commit description is taken verbatim from the this link. > >> > >>> > >>> kset_register() is currently used in some places without calling > >>> kset_put() in error path, because the callers think it should be > >>> kset internal thing to do, but the driver core can not know what > >>> caller doing with that memory at times. The memory could be freed > >>> both in kset_put() and error path of caller, if it is called in > >>> kset_register(). > >> > >> As I explained in the link above, the reason there's > >> a memory leak is that one cannot call kset_register() without > >> the kset->kobj.name being set--kobj_add_internal() returns -EINVAL, > >> in this case, i.e. kset_register() fails with -EINVAL. > >> > >> Thus, the most common usage is something like this: > >> > >> kobj_set_name(&kset->kobj, format, ...); > >> kset->kobj.kset = parent_kset; > >> kset->kobj.ktype = ktype; > >> res = kset_register(kset); > >> > >> So, what is being leaked, is the memory allocated in kobj_set_name(), > >> by the common idiom shown above. This needs to be mentioned in > >> the documentation, at least, in case, in the future this is absolved > >> in kset_register() redesign, etc. > > > > Based on this, can kset_register() just clean up from itself when an > > error happens? Ideally that would be the case, as the odds of a kset > > being embedded in a larger structure is probably slim, but we would have > > to search the tree to make sure. > > Looking at kset_register(), we can add kset_put() in the error path, > when kobject_add_internal(&kset->kobj) fails. > > See the attached patch. It needs to be tested with the same error injection > as Yang has been doing. > > Now, struct kset is being embedded in larger structs--see amdgpu_discovery.c > starting at line 575. If you're on an AMD system, it gets you the tree > structure you'll see when you run "tree /sys/class/drm/card0/device/ip_discovery/". > That shouldn't be a problem though. Yes, that shouldn't be an issue as the kobject embedded in a kset is ONLY for that kset itself, the kset structure should not be controling the lifespan of the object it is embedded in, right? Note, the use of ksets by a device driver like you are doing here in the amd driver is BROKEN and will cause problems by userspace tools. Don't do that please, just use a single subdirectory for an attribute. Doing deeper stuff like this is sure to cause problems and be a headache. thanks, greg k-h