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

commit e3e574ad85a208cb179f33720bb5f12b453de33c upstream.

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>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 43e1c392817c7db4a6751e247f6f2c9c4aa3e48a..b1dae1aa5e1e72dedacd1a22b738420bfb252edc 100644 (file)
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -1475,10 +1475,13 @@ 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);