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 B31A7EB64DD for ; Thu, 27 Jul 2023 07:09:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232375AbjG0HJ4 (ORCPT ); Thu, 27 Jul 2023 03:09:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55886 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231883AbjG0HId (ORCPT ); Thu, 27 Jul 2023 03:08:33 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ECB3A3C31; Thu, 27 Jul 2023 00:05:00 -0700 (PDT) Received: from kwepemm600005.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4RBM9R3RmrztRjS; Thu, 27 Jul 2023 15:00:43 +0800 (CST) Received: from [10.67.103.158] (10.67.103.158) by kwepemm600005.china.huawei.com (7.193.23.191) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Thu, 27 Jul 2023 15:03:58 +0800 Subject: Re: [PATCH] USB:bugfix a controller halt error To: Alan Stern CC: , , References: <20230721100015.27124-1-liulongfang@huawei.com> From: liulongfang Message-ID: <77a8ecb4-8099-1826-abd8-4f080d80b07d@huawei.com> Date: Thu, 27 Jul 2023 15:03:57 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="gbk" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.103.158] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemm600005.china.huawei.com (7.193.23.191) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/7/26 22:20, Alan Stern wrote: > On Wed, Jul 26, 2023 at 02:58:18PM +0800, liulongfang wrote: >> On 2023/7/21 22:57, Alan Stern Wrote: >>> On Fri, Jul 21, 2023 at 06:00:15PM +0800, liulongfang wrote: >>>> On systems that use ECC memory. The ECC error of the memory will >>>> cause the USB controller to halt. It causes the usb_control_msg() >>>> operation to fail. >>> >>> How often does this happen in real life? (Besides, it seems to me that >>> if your system is getting a bunch of ECC memory errors then you've got >>> much worse problems than a simple USB failure!) >>> >> >> This problem is on ECC memory platform. >> In the test scenario, the problem is 100% reproducible. >> >>> And why do you worry about ECC memory failures in particular? Can't >>> _any_ kind of failure cause the usb_control_msg() operation to fail? >>> >>>> At this point, the returned buffer data is an abnormal value, and >>>> continuing to use it will lead to incorrect results. >>> >>> The driver already contains code to check for abnormal values. The >>> check is not perfect, but it should prevent things from going too >>> badly wrong. >>> >> >> If it is ECC memory error. These parameter checks would also >> actually be invalid. >> >>>> Therefore, it is necessary to judge the return value and exit. >>>> >>>> Signed-off-by: liulongfang >>> >>> There is a flaw in your reasoning. >>> >>> The operation carried out here is deliberately unsafe (for full-speed >>> devices). It is made before we know the actual maxpacket size for ep0, >>> and as a result it might return an error code even when it works okay. >>> This shouldn't happen, but a lot of USB hardware is unreliable. >>> >>> Therefore we must not ignore the result merely because r < 0. If we do >>> that, the kernel might stop working with some devices. >>> >> It may be that the handling solution for ECC errors is different from that >> of the OS platform. On the test platform, after usb_control_msg() fails, >> reading the memory data of buf will directly lead to kernel crash: > > All right, then here's a proposal for a different way to solve the > problem: Change the kernel's handler for the ECC error notification. > Have it clear the affected parts of memory, so that the kernel can go > ahead and use them without crashing. > > It seems to me that something along these lines must be necessary in > any case. Unless the bad memory is cleared somehow, it would never be > usable again. The kernel might deallocate it, then reallocate for > another purpose, and then crash when the new user tries to access it. > > In fact, this scenario could still happen even with your patch, which > means the patch doesn't really fix the problem. > This patch is only used to prevent data in the buffer from being accessed. As long as the data is not accessed, the kernel does not crash. thanks, Longfang. > Alan Stern > > . >