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

commit 427c3a95e3e29e65f59d99aaf320d7506f3eed57 upstream.

Make sure to detect short responses when fetching the modem status in
order to avoid parsing uninitialised buffer data and having bits of it
leak to user space.

Note that we still allow for short 1-byte responses.

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: Willy Tarreau <w@1wt.eu>

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 4e865664699bbce4233b583f5ad99f6db6265b69..ba043088582ea2d51c3c7a55fbd63e9408348338 100644 (file)
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2452,8 +2452,12 @@ static int ftdi_get_modem_status(struct usb_serial_port *port,
                        FTDI_SIO_GET_MODEM_STATUS_REQUEST_TYPE,
                        0, priv->interface,
                        buf, len, WDR_TIMEOUT);
-       if (ret < 0) {
+
+       /* NOTE: We allow short responses and handle that below. */
+       if (ret < 1) {
                dev_err(&port->dev, "failed to get modem status: %d\n", ret);
+               if (ret >= 0)
+                       ret = -EIO;
                ret = usb_translate_errors(ret);
                goto out;
        }