USB: serial: keyspan_pda: fix dropped unthrottle interrupts

commit 696c541c8c6cfa05d65aa24ae2b9e720fc01766e upstream.

Commit c528fcb116e6 ("USB: serial: keyspan_pda: fix receive sanity
checks") broke write-unthrottle handling by dropping well-formed
unthrottle-interrupt packets which are precisely two bytes long. This
could lead to blocked writers not being woken up when buffer space again
becomes available.

Instead, stop unconditionally printing the third byte which is
(presumably) only valid on modem-line changes.

Fixes: c528fcb116e6 ("USB: serial: keyspan_pda: fix receive sanity checks")
Cc: stable <stable@vger.kernel.org>     # 4.11
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index f8e8285663a62fbb6accbcec887c3cfcf7914ca2..a4fe3ff8b159c1b799496570a2decfa4c15f0d6d 100644 (file)
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -176,11 +176,11 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
                break;
        case 1:
                /* status interrupt */
-               if (len < 3) {
+               if (len < 2) {
                        dev_warn(&port->dev, "short interrupt message received\n");
                        break;
                }
-               dev_dbg(&port->dev, "rx int, d1=%d, d2=%d\n", data[1], data[2]);
+               dev_dbg(&port->dev, "rx int, d1=%d\n", data[1]);
                switch (data[1]) {
                case 1: /* modemline change */
                        break;