tty: USB: serial/mct_u232, fix tty refcnt

Stanse found a tty refcnt leak in read_int_callback. In fact
it's handled wrong altogether. tty_port_tty_get can return NULL
and it's not checked in that manner.

Fix that by checking the tty_port_tty_get retval and put tty kref
properly.

http://stanse.fi.muni.cz/

Signed-off-by: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index d501aefa2628..ad4998bbf16f 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -566,10 +566,13 @@ static void mct_u232_read_int_callback(struct urb *urb)
          * Work-a-round: handle the 'usual' bulk-in pipe here
          */
         if (urb->transfer_buffer_length > 2) {
-                tty = tty_port_tty_get(&port->port);
                 if (urb->actual_length) {
-                        tty_insert_flip_string(tty, data, urb->actual_length);
-                        tty_flip_buffer_push(tty);
+                        tty = tty_port_tty_get(&port->port);
+                        if (tty) {
+                                tty_insert_flip_string(tty, data,
+                                                urb->actual_length);
+                                tty_flip_buffer_push(tty);
+                        }
                         tty_kref_put(tty);
                 }
                 goto exit;