Messages in this thread Patch in this message | | | From | Xianting Tian <> | Subject | [PATCH] mailbox: fix a UAF bug in msg_submit() | Date | Fri, 6 Aug 2021 20:15:21 +0800 |
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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@linux.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; -- 2.17.1
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