[PATCH 3.2 015/101] USB: serial: ssu100: fix control-message error handling

[Ben Hutchings]

3.2.89-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@xxxxxxxxxx>

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@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Johan Hovold <johan@xxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/usb/serial/ssu100.c | 31 ++++++++++++++++++++++++-------
 1 file changed, 24 insertions(+), 7 deletions(-)

--- a/drivers/usb/serial/ssu100.c
+++ b/drivers/usb/serial/ssu100.c
@@ -107,9 +107,17 @@ static inline int ssu100_setdevice(struc
 
 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(str
 				     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
 				 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;
 	}