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=-15.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,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 91E5EC4338F for ; Tue, 10 Aug 2021 10:45:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6A2EB60EC0 for ; Tue, 10 Aug 2021 10:45:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239896AbhHJKpx (ORCPT ); Tue, 10 Aug 2021 06:45:53 -0400 Received: from out30-44.freemail.mail.aliyun.com ([115.124.30.44]:58212 "EHLO out30-44.freemail.mail.aliyun.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236592AbhHJKpu (ORCPT ); Tue, 10 Aug 2021 06:45:50 -0400 X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R741e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=e01e04423;MF=xianting.tian@linux.alibaba.com;NM=1;PH=DS;RN=3;SR=0;TI=SMTPD_---0UiaH9SV_1628592326; Received: from B-LB6YLVDL-0141.local(mailfrom:xianting.tian@linux.alibaba.com fp:SMTPD_---0UiaH9SV_1628592326) by smtp.aliyun-inc.com(127.0.0.1); Tue, 10 Aug 2021 18:45:27 +0800 Subject: Re: [PATCH] mailbox: fix a UAF bug in msg_submit() To: jassisinghbrar@gmail.com Cc: linux-kernel@vger.kernel.org, guoren@kernel.org References: <20210806121521.124365-1-xianting.tian@linux.alibaba.com> From: Xianting TIan Message-ID: <554d6b8d-0b09-f3cc-8124-b33131d1243f@linux.alibaba.com> Date: Tue, 10 Aug 2021 18:45:26 +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: <20210806121521.124365-1-xianting.tian@linux.alibaba.com> 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 Could I get the comments for the patch, thanks. 在 2021/8/6 下午8:15, Xianting Tian 写道: > 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. > > We assume message sending failed for both two times, then the message > will be still in the internal buffer of a chan(chan->msg_data[idx]). > It will be send again in the same way when mbox_send_message() is > called next time. But, at this time this message (chan->msg_data[idx]) > may be a UAF pointer, as the message is passed to mailbox core by user. > User may free it after last calling of mbox_send_message() returned > or not. Who knows!!! > > In this patch, if the first time sending timeout, we pass timeout > info(-ETIME) to msg_submit() when do the second time sending by > tx_tick(). If it still send failed (chan->mbox->ops->send_data() > returned non-zero value) in the second time, we will give up this > message(chan->msg_count--) sending. It doesn't matter, user can chose > to send it again. > > Actually, the issue I described above doesn't exist if > 'chan->mbox->ops->send_data()' always return 0. Because if it always > returns 0, we will always do 'chan->msg_count—' regardless of message > sending success or failure. We have such mailbox driver, for example, > hi6220_mbox_send_data() always return 0. But we still have mailbox > drivers, which don't always return 0, for example, flexrm_send_data() > of drivers/mailbox/bcm-flexrm-mailbox.c. > > Signed-off-by: Xianting Tian > --- > drivers/mailbox/mailbox.c | 8 ++++---- > 1 file changed, 4 insertions(+), 4 deletions(-) > > diff --git a/drivers/mailbox/mailbox.c b/drivers/mailbox/mailbox.c > index 3e7d4b20a..3e010aafa 100644 > --- a/drivers/mailbox/mailbox.c > +++ b/drivers/mailbox/mailbox.c > @@ -50,7 +50,7 @@ static int add_to_rbuf(struct mbox_chan *chan, void *mssg) > return idx; > } > > -static void msg_submit(struct mbox_chan *chan) > +static void msg_submit(struct mbox_chan *chan, int last_submit) > { > unsigned count, idx; > unsigned long flags; > @@ -75,7 +75,7 @@ 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 || last_submit == -ETIME) { > chan->active_req = data; > chan->msg_count--; > } > @@ -101,7 +101,7 @@ static void tx_tick(struct mbox_chan *chan, int r) > spin_unlock_irqrestore(&chan->lock, flags); > > /* Submit next message */ > - msg_submit(chan); > + msg_submit(chan, r); > > if (!mssg) > return; > @@ -260,7 +260,7 @@ int mbox_send_message(struct mbox_chan *chan, void *mssg) > return t; > } > > - msg_submit(chan); > + msg_submit(chan, 0); > > if (chan->cl->tx_block) { > unsigned long wait;