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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8FA5C19F2D for ; Thu, 11 Aug 2022 03:52:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 0EB4B8E0002; Wed, 10 Aug 2022 23:52:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 09A768E0001; Wed, 10 Aug 2022 23:52:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id ECCDA8E0002; Wed, 10 Aug 2022 23:52:45 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id DF26B8E0001 for ; Wed, 10 Aug 2022 23:52:45 -0400 (EDT) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay04.hostedemail.com (Postfix) with ESMTP id B151B1A14DF for ; Thu, 11 Aug 2022 03:52:45 +0000 (UTC) X-FDA: 79785940290.28.41965E3 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) by imf08.hostedemail.com (Postfix) with ESMTP id 97421160055 for ; Thu, 11 Aug 2022 03:52:43 +0000 (UTC) X-Alimail-AntiSpam:AC=PASS;BC=-1|-1;BR=01201311R121e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045192;MF=xhao@linux.alibaba.com;NM=1;PH=DS;RN=11;SR=0;TI=SMTPD_---0VLxY2fF_1660189933; Received: from 30.240.98.115(mailfrom:xhao@linux.alibaba.com fp:SMTPD_---0VLxY2fF_1660189933) by smtp.aliyun-inc.com; Thu, 11 Aug 2022 11:52:37 +0800 Message-ID: <66c5a94a-4e6d-7719-7b03-de77a3f18c1b@linux.alibaba.com> Date: Thu, 11 Aug 2022 11:52:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.1.0 Subject: Re: [PATCH] mm/slub: release kobject if kobject_init_and_add failed in sysfs_slab_add To: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, vbabka@suse.cz, roman.gushchin@linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, xhao@linux.alibaba.com References: <20220811025258.68684-1-xhao@linux.alibaba.com> From: haoxin In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660189965; a=rsa-sha256; cv=none; b=LmtOv6VDwtUaxOunvyKjeSzDCW0tqRkj9EUpCyoWpW5eHWR6lawpHjP6D34voKngSbyG1L ar/yRYAH61FHZBMBE0HGgYrCs5PtGnCHwQCwrgrrLe6/1xKZpHQLInd9brFLU0ezaf2YTB umJ5oz93iTIqhxWdUf4IxrNK7s6sJmo= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf08.hostedemail.com: domain of xhao@linux.alibaba.com designates 115.124.30.132 as permitted sender) smtp.mailfrom=xhao@linux.alibaba.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660189965; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=+DbQGsWHHK/7nsrxfQepHteI9PmYNoAol3aw/sMQ5+Y=; b=da3ddNlSUr7kSd21ZN+LLre3j9JvDpCaLMpsjMHzM0GyAaJS/hsYUJQvPITeQciKCv8c3C pWreoJxq3EeJAIRpoJXBnSHdgGw8QqedgWxxC3BJM6b+FJCBIQ5Oujn5Fdf66UxxKX8Kln OXVi8MOd/ImxmLvT9aY5L2Iro3o7ca0= X-Rspam-User: X-Stat-Signature: uq1fg593qpkiexqi66xniwadu61pdj49 X-Rspamd-Queue-Id: 97421160055 Authentication-Results: imf08.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=alibaba.com; spf=pass (imf08.hostedemail.com: domain of xhao@linux.alibaba.com designates 115.124.30.132 as permitted sender) smtp.mailfrom=xhao@linux.alibaba.com X-Rspamd-Server: rspam01 X-HE-Tag: 1660189963-751886 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 在 2022/8/11 上午11:31, Hyeonggon Yoo 写道: > On Thu, Aug 11, 2022 at 10:52:58AM +0800, Xin Hao wrote: >> In kobject_init_and_add() function, the refcount is setted by calling >> kobject_init() function, regardless of whether the return value is zero >> or not, therefore, we must call kobject_del(&s->kobj) to prevent memory > Hello and thanks! > > Should kobject_del() be called when kobject_add() failed? Yes,  I'm afraid think so， you can see the comment about kobject_add() * Return: If this function returns an error, kobject_put() must be  *         called to properly clean up the memory associated with the  *         object.  Under no instance should the kobject that is passed  *         to this function be directly freed with a call to kfree(),  *         that can leak memory.  *  *         If this function returns success, kobject_put() must also be called  *         in order to properly clean up the memory associated with the object.  *  *         In short, once this function is called, kobject_put() MUST be called  *         when the use of the object is finished in order to properly free  *         everything.  */ int kobject_add(struct kobject *kobj, struct kobject *parent,                 const char *fmt, ...) > > its comments says: > > 597 * kobject_del() - Unlink kobject from hierarchy. > 598 * @kobj: object. > 599 * > 600 * This is the function that should be called to delete an object > 601 * successfully added via kobject_add(). > > AFAIK kobject_put() is proper function to call when > kobject_init_and_add() failed as stated in its comment: > > 417 /** > 418 * kobject_init_and_add() - Initialize a kobject structure and add it to > 419 * the kobject hierarchy. > 420 * @kobj: pointer to the kobject to initialize > 421 * @ktype: pointer to the ktype for this kobject. > 422 * @parent: pointer to the parent of this kobject. > 423 * @fmt: the name of the kobject. > 424 * > 425 * This function combines the call to kobject_init() and kobject_add(). > 426 * > 427 * If this function returns an error, kobject_put() must be called to > 428 * properly clean up the memory associated with the object. This is the > 429 * same type of error handling after a call to kobject_add() and kobject > 430 * lifetime rules are the same here. > >> of s->kobj is leaked. >> >> Signed-off-by: Xin Hao >> --- >> mm/slub.c | 7 +++---- >> 1 file changed, 3 insertions(+), 4 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index b1281b8654bd..63b0a8a3a71f 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -5981,19 +5981,18 @@ static int sysfs_slab_add(struct kmem_cache *s) >> >> err = sysfs_create_group(&s->kobj, &slab_attr_group); >> if (err) >> - goto out_del_kobj; >> + goto out; >> >> if (!unmergeable) { >> /* Setup first alias */ >> sysfs_slab_alias(s, s->name); >> } >> + return err; >> out: >> if (!unmergeable) >> kfree(name); >> - return err; >> -out_del_kobj: >> kobject_del(&s->kobj); Maybe there use kobject_put will be better. >> - goto out; >> + return err; >> } >> >> void sysfs_slab_unlink(struct kmem_cache *s) >> -- >> 2.31.0