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Subject: Re: [PATCH] mailbox: fix a UAF bug in msg_submit()
To:     Jassi Brar <jassisinghbrar@gmail.com>
Cc:     Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        guoren@kernel.org
References: <20210806121521.124365-1-xianting.tian@linux.alibaba.com>
 <CABb+yY3i5aZQrimoWLTMQRY5WsOJ1FCGNxBN0Hz_=4qxUvoqSw@mail.gmail.com>
From:   Xianting TIan <xianting.tian@linux.alibaba.com>
Message-ID: <977740a4-c08d-663d-410e-3375d034d2e8@linux.alibaba.com>
Date:   Tue, 17 Aug 2021 13:58:47 +0800
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在 2021/8/17 下午12:29, Jassi Brar 写道:
> On Fri, Aug 6, 2021 at 7:15 AM Xianting Tian
> <xianting.tian@linux.alibaba.com> 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.

You said 'seldom',  but it still possible we can meet such issue.  sucn 
as flexrm_send_data() of drivers/mailbox/bcm-flexrm-mailbox.c.

I think mailbox framework should be work normaly no matter .send_data() 
returns ok or not ok.  Do you think so? thanks

>
> thanks.