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 83071C4332F for ; Thu, 20 Oct 2022 02:07:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230054AbiJTCHA (ORCPT ); Wed, 19 Oct 2022 22:07:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52010 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230519AbiJTCGy (ORCPT ); Wed, 19 Oct 2022 22:06:54 -0400 Received: from out30-133.freemail.mail.aliyun.com (out30-133.freemail.mail.aliyun.com [115.124.30.133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E0885159D5F for ; Wed, 19 Oct 2022 19:06:52 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R141e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018046050;MF=joseph.qi@linux.alibaba.com;NM=1;PH=DS;RN=7;SR=0;TI=SMTPD_---0VScf.A8_1666231608; Received: from 30.221.128.181(mailfrom:joseph.qi@linux.alibaba.com fp:SMTPD_---0VScf.A8_1666231608) by smtp.aliyun-inc.com; Thu, 20 Oct 2022 10:06:49 +0800 Message-ID: <30747fd7-fe79-2ed8-ce63-425a008e3e4f@linux.alibaba.com> Date: Thu, 20 Oct 2022 10:06:48 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.3.3 Subject: Re: [PATCH] ocfs2: possible memory leak in mlog_sys_init() Content-Language: en-US To: Yang Yingliang , Greg Kroah-Hartman Cc: mark@fasheh.com, jlbec@evilplan.org, akpm@linux-foundation.org, ocfs2-devel , "linux-kernel@vger.kernel.org" References: <20221018075213.736562-1-yangyingliang@huawei.com> <09bb2844-e20a-98e8-c2af-5b6c4795d48e@huawei.com> <0db486eb-6927-927e-3629-958f8f211194@huawei.com> <1adbbf98-2700-27c8-4aca-9510bca91458@linux.alibaba.com> From: Joseph Qi In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/19/22 10:57 AM, Yang Yingliang wrote: > > On 2022/10/19 10:26, Joseph Qi wrote: >> >> On 10/18/22 10:28 PM, Yang Yingliang wrote: >>> On 2022/10/18 21:39, Joseph Qi wrote: >>>> On 10/18/22 6:33 PM, Yang Yingliang wrote: >>>>> Hi, >>>>> >>>>> On 2022/10/18 17:02, Joseph Qi wrote: >>>>>> Hi, >>>>>> >>>>>> On 10/18/22 3:52 PM, Yang Yingliang wrote: >>>>>>> Inject fault while probing module, kset_register() may fail, >>>>>>> if it fails, but the refcount of kobject is not decreased to >>>>>>> 0, the name allocated in kobject_set_name() is leaked. Fix >>>>>>> this by calling kset_put(), so that name can be freed in >>>>>>> callback function kobject_cleanup(). >>>>>>> >>>>>>> unreferenced object 0xffff888100da9348 (size 8): >>>>>>>      comm "modprobe", pid 257, jiffies 4294701096 (age 33.334s) >>>>>>>      hex dump (first 8 bytes): >>>>>>>        6c 6f 67 6d 61 73 6b 00                          logmask. >>>>>>>      backtrace: >>>>>>>        [<00000000306e441c>] __kmalloc_node_track_caller+0x44/0x1b0 >>>>>>>        [<000000007c491a9e>] kstrdup+0x3a/0x70 >>>>>>>        [<0000000015719a3b>] kstrdup_const+0x63/0x80 >>>>>>>        [<0000000084e458ea>] kvasprintf_const+0x149/0x180 >>>>>>>        [<0000000091302b42>] kobject_set_name_vargs+0x56/0x150 >>>>>>>        [<000000005f48eeac>] kobject_set_name+0xab/0xe0 >>>>>>> >>>>>>> Fixes: 34980ca8faeb ("Drivers: clean up direct setting of the name of a kset") >>>>>>> Signed-off-by: Yang Yingliang >>>>>>> --- >>>>>>>     fs/ocfs2/cluster/masklog.c | 7 ++++++- >>>>>>>     1 file changed, 6 insertions(+), 1 deletion(-) >>>>>>> >>>>>>> diff --git a/fs/ocfs2/cluster/masklog.c b/fs/ocfs2/cluster/masklog.c >>>>>>> index 563881ddbf00..7f9ba816d955 100644 >>>>>>> --- a/fs/ocfs2/cluster/masklog.c >>>>>>> +++ b/fs/ocfs2/cluster/masklog.c >>>>>>> @@ -156,6 +156,7 @@ static struct kset mlog_kset = { >>>>>>>     int mlog_sys_init(struct kset *o2cb_kset) >>>>>>>     { >>>>>>>         int i = 0; >>>>>>> +    int ret; >>>>>>>           while (mlog_attrs[i].attr.mode) { >>>>>>>             mlog_default_attrs[i] = &mlog_attrs[i].attr; >>>>>>> @@ -165,7 +166,11 @@ int mlog_sys_init(struct kset *o2cb_kset) >>>>>>>           kobject_set_name(&mlog_kset.kobj, "logmask"); >>>>>>>         mlog_kset.kobj.kset = o2cb_kset; >>>>>>> -    return kset_register(&mlog_kset); >>>>>>> +    ret = kset_register(&mlog_kset); >>>>>> If register fails, it will call unregister in o2cb_sys_init(), which >>>>>> will put kobject. >>>>> They are different ksets, the kset unregistered in o2cb_sys_init() is 'o2cb_kset', the >>>>> kset used to registered in mlog_sys_init() is 'mlog_kset', and they hold difference >>>>> refcounts. >>>>> Yes, you are right. I've mixed the two ksets up. >>>> In theory, kset_register() may return error because of a NULL kset, so >>>> here we may not call kset_put() directly, I'm not sure if a static >>>> checker will happy. >>>> Though this can't happen since it's already statically allocated... >>> kset_register() may fail if kobject_add_internal() return error (can't allocate memory), the name >>> "logmask" is dynamically alloctated while ocfs2 is compile as module and insert it (if ocfs2 is >>> built in kernel, the name is constant, it won't cause a leak), so the name can be leaked. >> What I mean is kset_register() may fail with many reasons, or even >> without kset_init(). >> I wonder if we have to handle this internal kset_register(), but not >> leave it to caller. This may benefit other callers as well. >> >> Something like: >> err = kobject_add_internal(&k->kobj); >> if (err) { >>     kset_put(k); >>     return err; >> } > I had think about this method to fix this, but some kset is allocated dynamically in driver and > it's freed in callback function which is called after kset_put() and in error path in driver will free > it again, it leads double free in some drivers. > I don't think it's good idea that caller has to take care part of the internal logic of kset_register() in case of error. Hi Greg, what do you think? Thanks, Joseph > I think kset_register() is similar with device_register(), if it fails need another put function to give > up reference in driver. >