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 2B9ABC4332F for ; Fri, 2 Dec 2022 01:46:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231687AbiLBBqv (ORCPT ); Thu, 1 Dec 2022 20:46:51 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37146 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230209AbiLBBqr (ORCPT ); Thu, 1 Dec 2022 20:46:47 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 56F21D3A3C; Thu, 1 Dec 2022 17:46:46 -0800 (PST) Received: from dggpemm500007.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4NNbPj363qzmWDc; Fri, 2 Dec 2022 09:46:01 +0800 (CST) 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; Fri, 2 Dec 2022 09:46:43 +0800 Subject: Re: [PATCH v2] chardev: fix error handling in cdev_device_add() To: Greg KH CC: , , , , , , References: <20221025113957.693723-1-yangyingliang@huawei.com> <65b29177-6892-7578-b2ae-a09d5adab661@huawei.com> From: Yang Yingliang Message-ID: <83280689-206f-668d-665c-0a2a3b8d8838@huawei.com> Date: Fri, 2 Dec 2022 09:46:43 +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: dggems706-chm.china.huawei.com (10.3.19.183) 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 2022/12/1 20:28, Greg KH wrote: > On Thu, Dec 01, 2022 at 08:06:44PM +0800, Yang Yingliang wrote: >> Hi Greg, >> >> On 2022/10/25 21:37, Greg KH wrote: >>> On Tue, Oct 25, 2022 at 09:20:12PM +0800, Yang Yingliang wrote: >>>> 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(). >>> Ah! The core doesn't set devt, the caller has that set. That makes >>> more sense now, sorry for the confusion on my side. >>> >>> Yes, this looks correct, the diff didn't have the full context and I was >>> confused. >>> >>> I'll go queue this up, very nice work. >>> >>> greg k-h >> I didn't find this patch in your trees, does it been merged? > Hm, is this: > 4634c973096a ("chardev: Fix potential memory leak when cdev_add() failed") > or is this a different patch? If different, it's not in my review queue > anymore, sorry, can you resend it? It's a different patch, I can resend it. Thanks, Yang > > thanks, > > greg k-h > .