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 X-Spam-Level: X-Spam-Status: No, score=-12.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SPF_HELO_NONE,SPF_PASS,UNPARSEABLE_RELAY,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id AD8FDC4338F for ; Wed, 18 Aug 2021 01:41:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8B9DA60249 for ; Wed, 18 Aug 2021 01:41:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235897AbhHRBlg (ORCPT ); Tue, 17 Aug 2021 21:41:36 -0400 Received: from out30-56.freemail.mail.aliyun.com ([115.124.30.56]:32777 "EHLO out30-56.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234723AbhHRBle (ORCPT ); Tue, 17 Aug 2021 21:41:34 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R341e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04394;MF=xianting.tian@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0UjbJumo_1629250858; Received: from B-LB6YLVDL-0141.local(mailfrom:xianting.tian@linux.alibaba.com fp:SMTPD_---0UjbJumo_1629250858) by smtp.aliyun-inc.com(127.0.0.1); Wed, 18 Aug 2021 09:40:59 +0800 Subject: Re: [PATCH] mailbox: fix a UAF bug in msg_submit() To: Jassi Brar Cc: Linux Kernel Mailing List , guoren@kernel.org References: <20210806121521.124365-1-xianting.tian@linux.alibaba.com> <977740a4-c08d-663d-410e-3375d034d2e8@linux.alibaba.com> <26a45754-4227-5f20-8c7d-c320d3905b60@linux.alibaba.com> From: Xianting TIan Message-ID: <1106a379-72e6-71d8-6529-645d1403c2ed@linux.alibaba.com> Date: Wed, 18 Aug 2021 09:40:58 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2021/8/18 上午7:33, Jassi Brar 写道: > On Tue, Aug 17, 2021 at 3:01 AM Xianting TIan > wrote: >> >> 在 2021/8/17 下午1:58, Xianting TIan 写道: >>> 在 2021/8/17 下午12:29, Jassi Brar 写道: >>>> On Fri, Aug 6, 2021 at 7:15 AM Xianting Tian >>>> wrote: >>>>> We met a UAF issue during our mailbox testing. >>>>> >>>>> In synchronous mailbox, we use mbox_send_message() to send a message >>>>> and wait for completion. mbox_send_message() calls msg_submit() to >>>>> send the message for the first time, if timeout, it will send the >>>>> message in tx_tick() for the second time. >>>>> >>>> Seems like your controller's .send_data() returns error. Can you >>>> please explain why it does so? Because >>>> send_data() only _accepts_ data for further transmission... which >>>> should seldom be a problem. >>> Thanks for the comments, >>> >>> We developed virtio-mailbox for heterogeneous virtualization system. >>> >>> virtio-mailbox is based on the mialbox framework. >>> >>> In virtio framework, its send func 'virtqueue_add_outbuf()' may return >>> error, which caused .send_data() return error. And also contains >>> other csenarios. >>> >>> But I think mailbox framework shouldn't depend on .send_data() always >>> return OK, as .send_data() is implemented by mailbox hardware >>> manufacturer, which is not controlled by mailbox framework itself. >>> > As I said, send_data() is basically "accepted for transfer", and not > "transferred fine". > >>> You said 'seldom', but it still possible we can meet such issue. sucn >>> as flexrm_send_data() of drivers/mailbox/bcm-flexrm-mailbox.c. >>> > The api is used not just in synchronous mode. > And the flexrm driver relies on ACK method, not the synchronous one. > >>> I think mailbox framework should be work normaly no matter >>> .send_data() returns ok or not ok. Do you think so? thanks > Normal is your controller driver should be ready after .startup() and > accepts the first message submitted to it. > If it does that, everything would work. > >> Another solution is to ignore the return value of .send_data() in >> msg_submit(), >> >> change >> >> err = chan->mbox->ops->send_data(chan, data); >> if (!err) { >> chan->active_req = data; >> chan->msg_count--; >> } >> >> to >> >> chan->mbox->ops->send_data(chan, data); >> chan->active_req = data; >> chan->msg_count--; >> > Yes, I also have something like this in mind. Definitely not the hack > in your original post. > >> But the side effect of the solution is obvious, as if send failed in the >> first time, it will have no chance to sent it in tx_tick() for the >> second time. That is to say, no retry. >> > The api doesn't retry. The .last_tx_done() is supposed to tell the > api when is it ok to send a message. > > The following should work for you (though I believe your code needs > fixing), which anyway, should have been there. thanks for the comment, so you apply below solution to kernel code? I will use it as our solution. > > diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > index 3e7d4b20ab34..9824a51b82fa 100644 > --- a/drivers/mailbox/mailbox.c > +++ b/drivers/mailbox/mailbox.c > @@ -75,10 +75,12 @@ static void msg_submit(struct mbox_chan *chan) > chan->cl->tx_prepare(chan->cl, data); > /* Try to submit a message to the MBOX controller */ > err = chan->mbox->ops->send_data(chan, data); > - if (!err) { > + if (!err) > chan->active_req = data; > - chan->msg_count--; > - } > + > + /* done with another message */ > + chan->msg_count--; > + > exit: > spin_unlock_irqrestore(&chan->lock, flags);