From: Jassi Brar <jassisinghbrar@gmail.com>
To: Xianting TIan <xianting.tian@linux.alibaba.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
guoren@kernel.org
Subject: Re: [PATCH] mailbox: fix a UAF bug in msg_submit()
Date: Tue, 17 Aug 2021 18:33:38 -0500 [thread overview]
Message-ID: <CABb+yY337=BVjHygv7wurj9Hh8-dj2aMyMnh54WL0CovyMfi_w@mail.gmail.com> (raw)
In-Reply-To: <26a45754-4227-5f20-8c7d-c320d3905b60@linux.alibaba.com>
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);
next prev parent reply other threads:[~2021-08-17 23:33 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-06 12:15 [PATCH] mailbox: fix a UAF bug in msg_submit() Xianting Tian
2021-08-10 10:45 ` Xianting TIan
2021-08-11 2:37 ` Guo Ren
2021-08-17 3:40 ` Xianting TIan
2021-08-17 4:29 ` Jassi Brar
2021-08-17 5:40 ` Xianting TIan
2021-08-17 5:58 ` Xianting TIan
2021-08-17 8:01 ` Xianting TIan
2021-08-17 23:33 ` Jassi Brar [this message]
2021-08-18 1:40 ` Xianting TIan
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