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 647ABFA373D for ; Tue, 1 Nov 2022 11:58:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230487AbiKAL63 (ORCPT ); Tue, 1 Nov 2022 07:58:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49284 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230311AbiKAL6K (ORCPT ); Tue, 1 Nov 2022 07:58:10 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9CAFA632D for ; Tue, 1 Nov 2022 04:58:03 -0700 (PDT) Received: from kwepemi500016.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4N1pN53HxtzpW4Z; Tue, 1 Nov 2022 19:54:29 +0800 (CST) Received: from [10.174.176.230] (10.174.176.230) by kwepemi500016.china.huawei.com (7.221.188.220) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.31; Tue, 1 Nov 2022 19:58:01 +0800 Message-ID: <5344d255-5186-dc97-89f0-0b8c40f65324@huawei.com> Date: Tue, 1 Nov 2022 19:57:59 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.1.0 Subject: Re: [PATCH] comedi: Fix potential memory leak in comedi_init() To: Ian Abbott , Greg KH CC: , , , References: <20221101032125.27337-1-shangxiaojing@huawei.com> <32c291d7-0e87-ec1f-e2af-28d7f8ca0981@huawei.com> <5b8ee99d-2358-39c5-b663-2d1c80353639@mev.co.uk> From: shangxiaojing In-Reply-To: <5b8ee99d-2358-39c5-b663-2d1c80353639@mev.co.uk> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.176.230] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To kwepemi500016.china.huawei.com (7.221.188.220) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/11/1 19:40, Ian Abbott wrote: > On 01/11/2022 06:16, shangxiaojing wrote: >> >> >> On 2022/11/1 12:45, Greg KH wrote: >>> On Tue, Nov 01, 2022 at 11:21:25AM +0800, Shang XiaoJing wrote: >>>> comedi_init() will goto out_unregister_chrdev_region if cdev_add() >>>> failed, which won't free the resource alloced in kobject_set_name(). >>>> Call kfree_const() to free the leaked name before goto >>>> out_unregister_chrdev_region. >>>> >>>> unreferenced object 0xffff8881000fa8c0 (size 8): >>>>    comm "modprobe", pid 239, jiffies 4294905173 (age 51.308s) >>>>    hex dump (first 8 bytes): >>>>      63 6f 6d 65 64 69 00 ff                          comedi.. >>>>    backtrace: >>>>      [<000000005f9878f7>] __kmalloc_node_track_caller+0x4c/0x1c0 >>>>      [<000000000fd70302>] kstrdup+0x3f/0x70 >>>>      [<000000009428bc33>] kstrdup_const+0x46/0x60 >>>>      [<00000000ed50d9de>] kvasprintf_const+0xdb/0xf0 >>>>      [<00000000b2766964>] kobject_set_name_vargs+0x3c/0xe0 >>>>      [<00000000f2424ef7>] kobject_set_name+0x62/0x90 >>>>      [<000000005d5a125b>] 0xffffffffa0013098 >>>>      [<00000000f331e663>] do_one_initcall+0x7a/0x380 >>>>      [<00000000aa7bac96>] do_init_module+0x5c/0x230 >>>>      [<000000005fd72335>] load_module+0x227d/0x2420 >>>>      [<00000000ad550cf1>] __do_sys_finit_module+0xd5/0x140 >>>>      [<00000000069a60c5>] do_syscall_64+0x3f/0x90 >>>>      [<00000000c5e0d521>] entry_SYSCALL_64_after_hwframe+0x63/0xcd >>>> >>>> Fixes: ed9eccbe8970 ("Staging: add comedi core") >>>> Signed-off-by: Shang XiaoJing >>>> --- >>>>   drivers/comedi/comedi_fops.c | 5 ++++- >>>>   1 file changed, 4 insertions(+), 1 deletion(-) >>>> >>>> diff --git a/drivers/comedi/comedi_fops.c >>>> b/drivers/comedi/comedi_fops.c >>>> index e2114bcf815a..2c508c2cf6f6 100644 >>>> --- a/drivers/comedi/comedi_fops.c >>>> +++ b/drivers/comedi/comedi_fops.c >>>> @@ -3379,8 +3379,11 @@ static int __init comedi_init(void) >>>>       retval = cdev_add(&comedi_cdev, MKDEV(COMEDI_MAJOR, 0), >>>>                 COMEDI_NUM_MINORS); >>>> -    if (retval) >>>> +    if (retval) { >>>> +        kfree_const(comedi_cdev.kobj.name); >>>> +        comedi_cdev.kobj.name = NULL; >>>>           goto out_unregister_chrdev_region; >>>> +    } >>> >>> A driver should never have to poke around in the internals of a cdev >>> object like this.  Please fix the cdev core to not need this if >>> cdev_add() fails. > > Or at least there should be a function that can be called to undo the > allocations of kobject_set_name(). It's ok to add a pair function, but maybe only one place where used cdev_add() need free name. Your mean all "kfree_const(name);" should be replaced to the new function? > >>> >> Hi, >> >> I had checked all 67 places that used cdev_add(), and only the >> following 5 functions set the name before the cdev_add(): >> >> 1. comedi_init(), will memleak and will be fixed by this patch. >> 2. hfi1_cdev_init(), won't memleak. >> 3. qib_cdev_init(), won't memleak. >> 4. uio_major_init(), won't memleak. >> 5. __register_chrdev(), won't memleak. >> >> As the result, I just fix the code in comedi_init(). Should I still >> fix the cdev core code, which is free the name in cdev_add() fail path? > > I'm stuck trying to work out why hfi1_cdev_init() doesn't have the same > problem when cdev_add() returns an error. > Only user_add() calls the hfi1_cdev_init(), and will call user_remove() if hfi1_cdev_init() failed. In user_remove(), hfi1_cdev_cleanup() will call cdev_del(). Thanks, -- Shang XiaoJing