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Date: Tue, 10 Aug 2021 18:45:26 +0800 From: Xianting TIan <xianting.tian@...ux.alibaba.com> To: jassisinghbrar@...il.com Cc: linux-kernel@...r.kernel.org, guoren@...nel.org Subject: Re: [PATCH] mailbox: fix a UAF bug in msg_submit() 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 <xianting.tian@...ux.alibaba.com> > --- > 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;
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