USB: serial: mct_u232: fix modem-status error handling

Make sure to detect short control-message transfers so that errors are
logged when reading the modem status at open.

Note that while this also avoids initialising the modem status using
uninitialised heap data, these bits could not leak to user space as they
are currently not used.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index 885655315de15a4b28db64da22f5d94bea7c8ea9..edbc81f205c253f41f7afa2d3375ef7818e0ae86 100644 (file)
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -322,8 +322,12 @@ static int mct_u232_get_modem_stat(struct usb_serial_port *port,
                        MCT_U232_GET_REQUEST_TYPE,
                        0, 0, buf, MCT_U232_GET_MODEM_STAT_SIZE,
                        WDR_TIMEOUT);
-       if (rc < 0) {
+       if (rc < MCT_U232_GET_MODEM_STAT_SIZE) {
                dev_err(&port->dev, "Get MODEM STATus failed (error = %d)\n", rc);
+
+               if (rc >= 0)
+                       rc = -EIO;
+
                *msr = 0;
        } else {
                *msr = buf[0];