USB: serial: kl5kusb105: fix line-state error handling

[ Upstream commit 146cc8a1 ]

The current implementation failed to detect short transfers when
attempting to read the line state, and also, to make things worse,
logged the content of the uninitialised heap transfer buffer.

Fixes: abf492e7 ("USB: kl5kusb105: fix DMA buffers on stack")
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>

drivers/usb/serial/kl5kusb105.c

@@ -192,10 +192,11 @@ static int klsi_105_get_line_state(struct usb_serial_port *port,
 			     status_buf, KLSI_STATUSBUF_LEN,
 			     10000
 			     );
-	if (rc < 0)
-		dev_err(&port->dev, "Reading line status failed (error = %d)\n",
-			rc);
-	else {
+	if (rc != KLSI_STATUSBUF_LEN) {
+		dev_err(&port->dev, "reading line status failed: %d\n", rc);
+		if (rc >= 0)
+			rc = -EIO;
+	} else {
 		status = get_unaligned_le16(status_buf);
 
 		dev_info(&port->serial->dev->dev, "read status %x %x\n",