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 1A443C4332F for ; Tue, 1 Nov 2022 16:46:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230075AbiKAQqz (ORCPT ); Tue, 1 Nov 2022 12:46:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49926 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230472AbiKAQqu (ORCPT ); Tue, 1 Nov 2022 12:46:50 -0400 X-Greylist: delayed 313 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Tue, 01 Nov 2022 09:46:46 PDT Received: from smtp83.ord1d.emailsrvr.com (smtp83.ord1d.emailsrvr.com [184.106.54.83]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B11351CFE0 for ; Tue, 1 Nov 2022 09:46:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=mev.co.uk; s=20190130-41we5z8j; t=1667320892; bh=qJLswMUIQnKWy9P1HYXGzQd2kw0D8cZfMy+lK/Mt37Q=; h=Date:Subject:From:To:From; b=DIZoYyzsbNie4DfUWmAfGk5cP+eMAr+A1g2U8ztCcy1Pp5Wclaqs64Ox900NSmtFl RqMUPUG02MmMGtVqTnhETfvNe4E5I/CuDZPL24jJa/OxjvkHjKHW1WP8A1oCugiPdg 42mw7g9GLU/ZmKUxb8V7ZHBY47Pui0Q5cv/vE8sQ= X-Auth-ID: abbotti@mev.co.uk Received: by smtp19.relay.ord1d.emailsrvr.com (Authenticated sender: abbotti-AT-mev.co.uk) with ESMTPSA id A03276010E; Tue, 1 Nov 2022 12:41:31 -0400 (EDT) Message-ID: <04bf1874-77bc-ce73-28e2-04fe4d098e58@mev.co.uk> Date: Tue, 1 Nov 2022 16:41:30 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.3 Subject: Re: [PATCH] comedi: Fix potential memory leak in comedi_init() Content-Language: en-GB From: Ian Abbott To: shangxiaojing , Greg KH Cc: hsweeten@visionengravers.com, zhangxuezhi1@coolpad.com, fmhess@users.sourceforge.net, linux-kernel@vger.kernel.org References: <20221101032125.27337-1-shangxiaojing@huawei.com> <32c291d7-0e87-ec1f-e2af-28d7f8ca0981@huawei.com> <5b8ee99d-2358-39c5-b663-2d1c80353639@mev.co.uk> Organization: MEV Ltd. 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-Classification-ID: 4ff644c6-a677-4628-86f7-04ccb9ec198a-1-1 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 01/11/2022 11:40, 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(). Looking at it a bit more, cdev_init() calls kobject_init(), and kobject_init() requires a matching call to kobject_put(). Nothing is calling kobject_put() in this situation. Calling cdev_del() will call kobject_put(), so is that the correct way to clean up after cdev_init() if the call to cdev_add() fails? -- -=( Ian Abbott || MEV Ltd. is a company )=- -=( registered in England & Wales. Regd. number: 02862268. )=- -=( Regd. addr.: S11 & 12 Building 67, Europa Business Park, )=- -=( Bird Hall Lane, STOCKPORT, SK3 0XA, UK. || www.mev.co.uk )=-