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 3696CC43217 for ; Thu, 24 Nov 2022 02:16:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229688AbiKXCQN (ORCPT ); Wed, 23 Nov 2022 21:16:13 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37654 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229555AbiKXCQL (ORCPT ); Wed, 23 Nov 2022 21:16:11 -0500 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF165C6D0C; Wed, 23 Nov 2022 18:16:09 -0800 (PST) Received: from dggpemm500024.china.huawei.com (unknown [172.30.72.57]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4NHhRW5Lp9zmW72; Thu, 24 Nov 2022 10:15:35 +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; Thu, 24 Nov 2022 10:16:08 +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; Thu, 24 Nov 2022 10:16:07 +0800 Subject: Re: [PATCH] powercap: fix possible name leak while device_register() fails To: Greg Kroah-Hartman , "Rafael J. Wysocki" CC: , Linux Kernel Mailing List References: <20221112094048.3614365-1-yangyingliang@huawei.com> From: Yang Yingliang Message-ID: Date: Thu, 24 Nov 2022 10:16:06 +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: 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 2022/11/24 3:25, Greg Kroah-Hartman wrote: > On Wed, Nov 23, 2022 at 08:00:14PM +0100, Rafael J. Wysocki wrote: >> On Sat, Nov 12, 2022 at 10:42 AM Yang Yingliang >> wrote: >>> If device_register() returns error, the name allocated by Sorry, I didn't describe clearly here, it's not only after device_register() failure, but also in the error path before register, the name is not freed, see description below. >>> dev_set_name() need be freed. In technical, we should call >>> put_device() to give up the reference and free the name in >>> driver core, but in some cases the device is not intizalized, >>> put_device() can not be called, so don't complicate the code, >>> just call kfree_const() to free name in the error path. >>> >>> Fixes: 75d2364ea0ca ("PowerCap: Add class driver") >>> Signed-off-by: Yang Yingliang >>> --- >>> drivers/powercap/powercap_sys.c | 2 ++ >>> 1 file changed, 2 insertions(+) >>> >>> diff --git a/drivers/powercap/powercap_sys.c b/drivers/powercap/powercap_sys.c >>> index f0654a932b37..11e742dc83b9 100644 >>> --- a/drivers/powercap/powercap_sys.c >>> +++ b/drivers/powercap/powercap_sys.c >>> @@ -572,6 +572,7 @@ struct powercap_zone *powercap_register_zone( >>> err_name_alloc: >>> idr_remove(power_zone->parent_idr, power_zone->id); >>> err_idr_alloc: >>> + kfree_const(dev_name(&power_zone->dev)); >>> if (power_zone->allocated) >>> kfree(power_zone); >>> mutex_unlock(&control_type->lock); >>> @@ -622,6 +623,7 @@ struct powercap_control_type *powercap_register_control_type( >>> dev_set_name(&control_type->dev, "%s", name); >>> result = device_register(&control_type->dev); >>> if (result) { >>> + kfree_const(dev_name(&control_type->dev)); >> Why is it necessary to free a device name explicitly after a failing >> device_register()? powercap_register_zone() {     ...     dev_set_name() // allocate name     ...     if (!power_zone->constraints)         goto err_const_alloc; //the name is leaked in this path     ...     if (!power_zone->zone_dev_attrs)         goto err_attr_alloc; //the name is leaked in this path     ...     if (result)         goto err_dev_ret; //the name is leaked in this path     result = device_register(&power_zone->dev);     if (result)         goto err_dev_ret;//put_device() is not called, the name is leaked in this path     ... err_dev_ret:     kfree(power_zone->zone_dev_attrs); err_attr_alloc:     kfree(power_zone->constraints); err_const_alloc:     kfree(power_zone->name); err_name_alloc:     idr_remove(power_zone->parent_idr, power_zone->id); err_idr_alloc:     if (power_zone->allocated)         kfree(power_zone); } >> >> If it is really necessary, then there is a problem in >> device_register() itself AFAICS, because it uses dev_set_name() at >> least in the dev->init_name present case. When the dev_set_name() called in device_register(), if register fails, the name is freed in its error path. But in this case, dev_set_name() is called outside the register, it needs call put_device() to free the name. > I think we already fixed this in the driver core, so these types of > patches should not be applied. driver core free the name by calling put_device(), but in these two functions, put_device() is not called. Thanks, Yang > > Yang, can you make sure you respond to all of them and say "this is not > needed anymore!" and if any got merged, send reverts for them? > > thanks, > > greg k-h > .