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 403D6C433FE for ; Wed, 2 Nov 2022 08:53:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229846AbiKBIxO (ORCPT ); Wed, 2 Nov 2022 04:53:14 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56242 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229548AbiKBIxL (ORCPT ); Wed, 2 Nov 2022 04:53:11 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DC66824F22 for ; Wed, 2 Nov 2022 01:53:10 -0700 (PDT) Received: from dggpemm500023.china.huawei.com (unknown [172.30.72.56]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4N2LF32w9qzJnLD; Wed, 2 Nov 2022 16:50:15 +0800 (CST) Received: from dggpemm100009.china.huawei.com (7.185.36.113) by dggpemm500023.china.huawei.com (7.185.36.83) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 2 Nov 2022 16:53:09 +0800 Received: from [10.174.179.24] (10.174.179.24) by dggpemm100009.china.huawei.com (7.185.36.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 2 Nov 2022 16:53:08 +0800 Subject: Re: [PATCH v2 0/3] Refactor __kmem_cache_create() and fix memory leak To: Hyeonggon Yoo <42.hyeyoo@gmail.com> References: <20221031134747.3049593-1-liushixin2@huawei.com> CC: Christoph Lameter , Pekka Enberg , "David Rientjes" , Joonsoo Kim , "Andrew Morton" , Vlastimil Babka , "Roman Gushchin" , , From: Liu Shixin Message-ID: Date: Wed, 2 Nov 2022 16:53:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.24] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm100009.china.huawei.com (7.185.36.113) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/11/2 15:46, Hyeonggon Yoo wrote: > On Mon, Oct 31, 2022 at 09:47:44PM +0800, Liu Shixin wrote: >> I found a memory leak of kobj->name in sysfs_slab_add() which is introduced >> by 80da026a8e5d ("mm/slub: fix slab double-free in case of duplicate sysfs filename"). >> Following the rules stated in the comment for kobject_init_and_add(): > Thank you for reporting this! Indeed it seems tried to fix double free but > introduced a leak. > >> If this function returns an error, kobject_put() must be called to >> properly clean up the memory associated with the object. >> >> We should use kobject_put() to free kobject. > But what to do if a cache is created early and later sysfs_slab_add() failed? > (Which is unlikely on normal condition) > > With this series it introduces use-after-free if sysfs_slab_add() in > slab_sysfs_init() failed. Should we just call BUG() or something like that? Thanks for your discovery, what I missed. I prefer to panic directly, just as create_boot_cache() does. Of couse, if you want the system to continue booting, I think it's possible to distinguish them by slab_state. Looking forward to your advice. Thanks, > >> But we can't simply add kobject_put() since it will free kmem_cache too. >> If we use kobject_put(), we need to skip other release functions. >> >> In this series, We refactor the code to separate sysfs_slab_add() and >> debugfs_slab_add() from __kmem_cache_create(), and then use kobject_put() >> to free kobject in sysfs_slab_add(). This can fix the memory leak of >> kobject->name. >> >> v1->v2: Fix build error reported by kernel test robot . >> >> Liu Shixin (3): >> mm/slab_common: Move cache_name to create_cache() >> mm/slub: Refactor __kmem_cache_create() >> mm/slub: Fix memory leak of kobj->name in sysfs_slab_add() >> >> include/linux/slub_def.h | 11 +++++++++ >> mm/slab_common.c | 44 ++++++++++++++++++---------------- >> mm/slub.c | 52 ++++++++++------------------------------ >> 3 files changed, 48 insertions(+), 59 deletions(-) >> >> -- >> 2.25.1 >>