USB: serial: ftdi_sio: fix latency-timer error handling

Make sure to detect short responses when reading the latency timer to
avoid using stale buffer data.

Note that no heap data would currently leak through sysfs as
ASYNC_LOW_LATENCY is set by default.

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/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 6dee20fc7e455bb83834a371b2a9c90b2627c7f2..b064fad8e3eeed43bcb4675f05333452252552bd 100644 (file)
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1439,10 +1439,13 @@ static int read_latency_timer(struct usb_serial_port *port)
                             FTDI_SIO_GET_LATENCY_TIMER_REQUEST_TYPE,
                             0, priv->interface,
                             buf, 1, WDR_TIMEOUT);
-       if (rv < 0)
+       if (rv < 1) {
                dev_err(&port->dev, "Unable to read latency timer: %i\n", rv);
-       else
+               if (rv >= 0)
+                       rv = -EIO;
+       } else {
                priv->latency = buf[0];
+       }
 
        kfree(buf);