Messages in this thread Patch in this message | | | From | Jassi Brar <> | Date | Tue, 17 Aug 2021 18:33:38 -0500 | Subject | Re: [PATCH] mailbox: fix a UAF bug in msg_submit() |
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On Tue, Aug 17, 2021 at 3:01 AM Xianting TIan <xianting.tian@linux.alibaba.com> 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 > >> <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. > > 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.
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);
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