[PATCH 4.9 035/105] mailbox: handle empty message in tx_tick

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sudeep Holla <sudeep.holla@xxxxxxx>

commit cb710ab1d8a23f68ff8f45aedf3e552bb90e70de upstream.

We already check if the message is empty before calling the client
tx_done callback. Calling completion on a wait event is also invalid
if the message is empty.

This patch moves the existing empty message check earlier.

Fixes: 2b6d83e2b8b7 ("mailbox: Introduce framework for mailbox")
Signed-off-by: Sudeep Holla <sudeep.holla@xxxxxxx>
Signed-off-by: Jassi Brar <jaswinder.singh@xxxxxxxxxx>
Signed-off-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/mailbox/mailbox.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/mailbox/mailbox.c
+++ b/drivers/mailbox/mailbox.c
@@ -104,8 +104,11 @@ static void tx_tick(struct mbox_chan *ch
 	/* Submit next message */
 	msg_submit(chan);
 
+	if (!mssg)
+		return;
+
 	/* Notify the client */
-	if (mssg && chan->cl->tx_done)
+	if (chan->cl->tx_done)
 		chan->cl->tx_done(chan->cl, mssg, r);
 
 	if (r != -ETIME && chan->cl->tx_block)