USB: serial: ssu100: fix control-message error handling

commit 1eac5c244f705182d1552a53e2f74e2775ed95d6 upstream.

Make sure to detect short control-message transfers rather than continue
with zero-initialised data when retrieving modem status and during
device initialisation.

Fixes: 52af95459939 ("USB: add USB serial ssu100 driver")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/usb/serial/ssu100.c b/drivers/usb/serial/ssu100.c
index ad8e5f3..965812b 100644 (file)
--- a/drivers/usb/serial/ssu100.c
+++ b/drivers/usb/serial/ssu100.c
@@ -107,9 +107,17 @@ static inline int ssu100_setdevice(struct usb_device *dev, u8 *data)
 
 static inline int ssu100_getdevice(struct usb_device *dev, u8 *data)
 {
-       return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
-                              QT_SET_GET_DEVICE, 0xc0, 0, 0,
-                              data, 3, 300);
+       int ret;
+
+       ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+                             QT_SET_GET_DEVICE, 0xc0, 0, 0,
+                             data, 3, 300);
+       if (ret < 3) {
+               if (ret >= 0)
+                       ret = -EIO;
+       }
+
+       return ret;
 }
 
 static inline int ssu100_getregister(struct usb_device *dev,
@@ -117,10 +125,17 @@ static inline int ssu100_getregister(struct usb_device *dev,
                                     unsigned short reg,
                                     u8 *data)
 {
-       return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
-                              QT_SET_GET_REGISTER, 0xc0, reg,
-                              uart, data, sizeof(*data), 300);
+       int ret;
+
+       ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+                             QT_SET_GET_REGISTER, 0xc0, reg,
+                             uart, data, sizeof(*data), 300);
+       if (ret < sizeof(*data)) {
+               if (ret >= 0)
+                       ret = -EIO;
+       }
 
+       return ret;
 }
 
 
@@ -322,8 +337,10 @@ static int ssu100_open(struct tty_struct *tty, struct usb_serial_port *port)
                                 QT_OPEN_CLOSE_CHANNEL,
                                 QT_TRANSFER_IN, 0x01,
                                 0, data, 2, 300);
-       if (result < 0) {
+       if (result < 2) {
                dbg("%s - open failed %i", __func__, result);
+               if (result >= 0)
+                       result = -EIO;
                kfree(data);
                return result;
        }