USB: serial: keyspan_pda: fix receive sanity checks

commit c528fcb116e61afc379a2e0a0f70906b937f1e2c upstream.

Make sure to check for short transfers before parsing the receive buffer
to avoid acting on stale data.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
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>

1 files changed, 14 insertions, 5 deletions

diff --git a/drivers/usb/serial/keyspan_pda.c b/drivers/usb/serial/keyspan_pda.c
index 83523fcf6fb9..d2dab2a341b8 100644
--- a/drivers/usb/serial/keyspan_pda.c
+++ b/drivers/usb/serial/keyspan_pda.c
@@ -139,6 +139,7 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
 {
         struct usb_serial_port *port = urb->context;
         unsigned char *data = urb->transfer_buffer;
+        unsigned int len = urb->actual_length;
         int retval;
         int status = urb->status;
         struct keyspan_pda_private *priv;
@@ -159,18 +160,26 @@ static void keyspan_pda_rx_interrupt(struct urb *urb)
                 goto exit;
         }
 
+        if (len < 1) {
+                dev_warn(&port->dev, "short message received\n");
+                goto exit;
+        }
+
         /* see if the message is data or a status interrupt */
         switch (data[0]) {
         case 0:
                  /* rest of message is rx data */
-                if (urb->actual_length) {
-                        tty_insert_flip_string(&port->port, data + 1,
-                                                urb->actual_length - 1);
-                        tty_flip_buffer_push(&port->port);
-                }
+                if (len < 2)
+                        break;
+                tty_insert_flip_string(&port->port, data + 1, len - 1);
+                tty_flip_buffer_push(&port->port);
                 break;
         case 1:
                 /* status interrupt */
+                if (len < 3) {
+                        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]);
                 switch (data[1]) {
                 case 1: /* modemline change */