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 C1E52C4332F for ; Wed, 19 Oct 2022 02:58:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229769AbiJSC6N (ORCPT ); Tue, 18 Oct 2022 22:58:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229569AbiJSC6L (ORCPT ); Tue, 18 Oct 2022 22:58:11 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B662E6F4A for ; Tue, 18 Oct 2022 19:58:10 -0700 (PDT) Received: from dggpemm500020.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4MsZzn0hW2zmVCH; Wed, 19 Oct 2022 10:53:25 +0800 (CST) Received: from dggpemm500007.china.huawei.com (7.185.36.183) by dggpemm500020.china.huawei.com (7.185.36.49) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 19 Oct 2022 10:57:50 +0800 Received: from [10.174.178.174] (10.174.178.174) by dggpemm500007.china.huawei.com (7.185.36.183) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Wed, 19 Oct 2022 10:57:50 +0800 Subject: Re: [PATCH] ocfs2: possible memory leak in mlog_sys_init() To: Joseph Qi , , CC: , , , 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: Yang Yingliang Message-ID: Date: Wed, 19 Oct 2022 10:57:49 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <1adbbf98-2700-27c8-4aca-9510bca91458@linux.alibaba.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Originating-IP: [10.174.178.174] X-ClientProxiedBy: dggems701-chm.china.huawei.com (10.3.19.178) To dggpemm500007.china.huawei.com (7.185.36.183) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 think kset_register() is similar with device_register(), if it fails need another put function to give up reference in driver. Thanks, Yang > > Thanks, > Joseph > > .