staging: lustre: obdclass: return -EFAULT if copy_from_user() fails

The copy_from_user() function returns the number of bytes which we
weren't able to copy.  We don't want to return that to the user but
instead we want to return -EFAULT.

Fixes: d7e09d03 ("staging: add Lustre file system client support")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/obdclass/class_obd.c

@@ -180,7 +180,8 @@ int class_handle_ioctl(unsigned int cmd, unsigned long arg)
 			err = -ENOMEM;
 			goto out;
 		}
-		err = copy_from_user(lcfg, data->ioc_pbuf1, data->ioc_plen1);
+		if (copy_from_user(lcfg, data->ioc_pbuf1, data->ioc_plen1))
+			err = -EFAULT;
 		if (!err)
 			err = lustre_cfg_sanity_check(lcfg, data->ioc_plen1);
 		if (!err)