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* [PATCH] mailbox: fix a UAF bug in msg_submit()
@ 2021-08-06 12:15 Xianting Tian
  2021-08-10 10:45 ` Xianting TIan
                   ` (2 more replies)
  0 siblings, 3 replies; 10+ messages in thread
From: Xianting Tian @ 2021-08-06 12:15 UTC (permalink / raw)
  To: jassisinghbrar; +Cc: linux-kernel, guoren, Xianting Tian

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 <>
 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;
@@ -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)
@@ -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;

^ permalink raw reply	[flat|nested] 10+ messages in thread

end of thread, other threads:[~2021-08-18  1:41 UTC | newest]

Thread overview: 10+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
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
2021-08-18  1:40         ` Xianting TIan

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