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 0F7DEC38A2D for ; Tue, 25 Oct 2022 13:20:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232793AbiJYNUZ (ORCPT ); Tue, 25 Oct 2022 09:20:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38352 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232494AbiJYNUS (ORCPT ); Tue, 25 Oct 2022 09:20:18 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8F65E09EF; Tue, 25 Oct 2022 06:20:14 -0700 (PDT) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.57]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4MxXc10mGSzHty9; Tue, 25 Oct 2022 21:20:01 +0800 (CST) Received: from dggpemm500007.china.huawei.com (7.185.36.183) by dggpemm500024.china.huawei.com (7.185.36.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Tue, 25 Oct 2022 21:20:13 +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; Tue, 25 Oct 2022 21:20:12 +0800 Subject: Re: [PATCH v2] chardev: fix error handling in cdev_device_add() To: Greg KH CC: , , , , , , References: <20221025113957.693723-1-yangyingliang@huawei.com> From: Yang Yingliang Message-ID: Date: Tue, 25 Oct 2022 21:20:12 +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: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Originating-IP: [10.174.178.174] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) 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 Hi, Greg On 2022/10/25 19:50, Greg KH wrote: > On Tue, Oct 25, 2022 at 07:39:57PM +0800, Yang Yingliang wrote: >> While doing fault injection test, I got the following report: >> >> ------------[ cut here ]------------ >> kobject: '(null)' (0000000039956980): is not initialized, yet kobject_put() is being called. >> WARNING: CPU: 3 PID: 6306 at kobject_put+0x23d/0x4e0 >> CPU: 3 PID: 6306 Comm: 283 Tainted: G W 6.1.0-rc2-00005-g307c1086d7c9 #1253 >> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014 >> RIP: 0010:kobject_put+0x23d/0x4e0 >> Call Trace: >> >> cdev_device_add+0x15e/0x1b0 >> __iio_device_register+0x13b4/0x1af0 [industrialio] >> __devm_iio_device_register+0x22/0x90 [industrialio] >> max517_probe+0x3d8/0x6b4 [max517] >> i2c_device_probe+0xa81/0xc00 >> >> When device_add() is injected fault and returns error, if dev->devt is not set, >> cdev_add() is not called, cdev_del() is not needed. Fix this by checking dev->devt >> in error path. > Nit, please wrap your changelog text at 72 columns. > >> Fixes: 233ed09d7fda ("chardev: add helper function to register char devs with a struct device") >> Signed-off-by: Yang Yingliang >> --- >> v1 -> v2: >> Add information to update commit message. >> v1 link: https://lore.kernel.org/lkml/1959fa74-b06c-b8bc-d14f-b71e5c4290ee@huawei.com/T/ >> --- >> fs/char_dev.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/char_dev.c b/fs/char_dev.c >> index ba0ded7842a7..3f667292608c 100644 >> --- a/fs/char_dev.c >> +++ b/fs/char_dev.c >> @@ -547,7 +547,7 @@ int cdev_device_add(struct cdev *cdev, struct device *dev) >> } >> >> rc = device_add(dev); >> - if (rc) >> + if (rc && dev->devt) > No, this is a layering violation and one that you do not know is really > going to be true or not. the devt being present, or not, should not be > an issue of if the device_add failed or not. This isn't correct, sorry. Do you mean it's not a bug or the warn can be ignored or it's bug in driver ? I see devt is checked before calling cdev_del() in cdev_device_del(). Thanks, Yang > > thanks, > > greg k-h > .