Staging: lustre: error handling tweaks in obd_ioctl_getdata()

1)  The places which called copy_from_user() were returning the number
of bytes not copied instead of -EFAULT.

2) The user could trigger a memory leak if the condition
"(hdr.ioc_len != data->ioc_len)" was true.  Instead of adding a new call
to OBD_FREE_LARGE(), I created a free_buf label and changed everything
to use that label.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/obdclass/linux/linux-module.c

@@ -83,9 +83,8 @@ int obd_ioctl_getdata(char **buf, int *len, void *arg)
 	int err;
 	int offset = 0;
 
-	err = copy_from_user(&hdr, (void *)arg, sizeof(hdr));
-	if (err)
-		return err;
+	if (copy_from_user(&hdr, (void *)arg, sizeof(hdr)))
+		return -EFAULT;
 
 	if (hdr.ioc_version != OBD_IOCTL_VERSION) {
 		CERROR("Version mismatch kernel (%x) vs application (%x)\n",
@@ -117,18 +116,19 @@ int obd_ioctl_getdata(char **buf, int *len, void *arg)
 	*len = hdr.ioc_len;
 	data = (struct obd_ioctl_data *)*buf;
 
-	err = copy_from_user(*buf, (void *)arg, hdr.ioc_len);
-	if (err) {
-		OBD_FREE_LARGE(*buf, hdr.ioc_len);
-		return err;
+	if (copy_from_user(*buf, (void *)arg, hdr.ioc_len)) {
+		err = -EFAULT;
+		goto free_buf;
+	}
+	if (hdr.ioc_len != data->ioc_len) {
+		err = -EINVAL;
+		goto free_buf;
 	}
-	if (hdr.ioc_len != data->ioc_len)
-		return -EINVAL;
 
 	if (obd_ioctl_is_invalid(data)) {
 		CERROR("ioctl not correctly formatted\n");
-		OBD_FREE_LARGE(*buf, hdr.ioc_len);
-		return -EINVAL;
+		err = -EINVAL;
+		goto free_buf;
 	}
 
 	if (data->ioc_inllen1) {
@@ -151,6 +151,10 @@ int obd_ioctl_getdata(char **buf, int *len, void *arg)
 	}
 
 	return 0;
+
+free_buf:
+	OBD_FREE_LARGE(*buf, hdr.ioc_len);
+	return err;
 }
 EXPORT_SYMBOL(obd_ioctl_getdata);