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 46A48C77B75 for ; Thu, 18 May 2023 02:37:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229690AbjERChM (ORCPT ); Wed, 17 May 2023 22:37:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35120 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229576AbjERChL (ORCPT ); Wed, 17 May 2023 22:37:11 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5C4862D77 for ; Wed, 17 May 2023 19:37:09 -0700 (PDT) Received: from kwepemi500009.china.huawei.com (unknown [172.30.72.55]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4QMDZD482NzLqKx; Thu, 18 May 2023 10:34:12 +0800 (CST) Received: from [10.67.110.89] (10.67.110.89) by kwepemi500009.china.huawei.com (7.221.188.199) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Thu, 18 May 2023 10:37:05 +0800 Message-ID: <111fa8ed-9031-a393-401c-0266a9bf7544@huawei.com> Date: Thu, 18 May 2023 10:37:05 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:102.0) Gecko/20100101 Thunderbird/102.4.1 Subject: Re: [PATCH v6] kobject: Fix global-out-of-bounds in kobject_action_type() To: Greg KH CC: , References: <20230517101957.14655-1-xiafukun@huawei.com> <2023051739-shrunk-reopen-b968@gregkh> From: Xia Fukun In-Reply-To: <2023051739-shrunk-reopen-b968@gregkh> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.110.89] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemi500009.china.huawei.com (7.221.188.199) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/5/17 20:17, Greg KH wrote: > On Wed, May 17, 2023 at 06:19:57PM +0800, Xia Fukun wrote: >> --- a/include/linux/kobject.h >> +++ b/include/linux/kobject.h >> @@ -32,6 +32,9 @@ >> #define UEVENT_NUM_ENVP 64 /* number of env pointers */ >> #define UEVENT_BUFFER_SIZE 2048 /* buffer for the variables */ >> >> +/* the maximum length of the string contained in kobject_actions[] */ >> +#define UEVENT_KACT_STRSIZE 16 > > Why does this value need to be in a global .h file when it is only used > in one .c file? > > And how are you going to keep it in sync with kobject_actions if it > changes in the future? And that variable isn't even in this file, how > would anyone know to modify this if the structure changes in a .c file? Your criticism is correct. UEVENT_KACT_STRSIZE should not be defined in the global .h file here. I will move it to that .c file. >> --- a/lib/kobject_uevent.c >> +++ b/lib/kobject_uevent.c >> @@ -66,7 +66,8 @@ static int kobject_action_type(const char *buf, size_t count, >> enum kobject_action action; >> size_t count_first; >> const char *args_start; >> - int ret = -EINVAL; >> + int i, ret = -EINVAL; >> + char kobj_act_buf[UEVENT_KACT_STRSIZE] = ""; > > Why does this need to be initialized? My initialization method has some flaws, which should be done as follows: char kobj_act_buf[UEVENT_KACT_STRSIZE] = {0}; Initialize the string kobj_act_buf to "/0" and parse it using sysfs_match_string after subsequent copy operations. > And are you sure the size is correct? If so, how? UEVENT_KACT_STRSIZE is defined as the maximum length of the string contained in kobject_actions[]. At present, the maximum length of strings in this array is 7. Based on the actual meaning of these strings, these actions will not exceed 16 if there are any subsequent changes. > And how was any of this tested? Based on your prior submissions, we are > going to require some sort of proof. What would you do if you were in > my position? My testing method is to apply the patch, compile the kernel image, and start the QEMU virtual machine. Then compile and execute the code mentioned in the patch that triggers out-of-bounds issues. In addition, the following operations will be performed to verify the functions mentioned by Peter Rajnoha : # echo "add fe4d7c9d-b8c6-4a70-9ef1-3d8a58d18eed A=1 B=abc" > /sys/block/ram0/uevent # udevadm monitor --kernel --env monitor will print the received events for: KERNEL - the kernel uevent KERNEL[189.376386] add /devices/virtual/block/ram0 (block) ACTION=add DEVPATH=/devices/virtual/block/ram0 SUBSYSTEM=block SYNTH_UUID=fe4d7c9d-b8c6-4a70-9ef1-3d8a58d18eed SYNTH_ARG_A=1 SYNTH_ARG_B=abc DEVNAME=/dev/ram0 DEVTYPE=disk DISKSEQ=14 SEQNUM=3781 MAJOR=1 MINOR=0 > thanks, > > greg k-h Thank you for your suggestion. My submission was indeed negligent, and your guidance has benefited me greatly.