USB: omninet: fix potential tty NULL dereference

Add check for return value of tty_port_tty_get,
since it can return NULL after port hangup that may happen anytime.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/drivers/usb/serial/omninet.c b/drivers/usb/serial/omninet.c
index d31f661d758c..f524cd910e2c 100644
--- a/drivers/usb/serial/omninet.c
+++ b/drivers/usb/serial/omninet.c
@@ -185,10 +185,12 @@ static void omninet_read_bulk_callback(struct urb *urb)
 
         if (urb->actual_length && header->oh_len) {
                 struct tty_struct *tty = tty_port_tty_get(&port->port);
-                tty_insert_flip_string(tty, data + OMNINET_DATAOFFSET,
+                if (tty) {
+                        tty_insert_flip_string(tty, data + OMNINET_DATAOFFSET,
                                                         header->oh_len);
-                tty_flip_buffer_push(tty);
-                tty_kref_put(tty);
+                        tty_flip_buffer_push(tty);
+                        tty_kref_put(tty);
+                }
         }
 
         /* Continue trying to always read  */