From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751230AbcLDMot (ORCPT ); Sun, 4 Dec 2016 07:44:49 -0500 Received: from mail-pg0-f68.google.com ([74.125.83.68]:35691 "EHLO mail-pg0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750774AbcLDMop (ORCPT ); Sun, 4 Dec 2016 07:44:45 -0500 From: Sergey Senozhatsky To: Andrew Morton Cc: Greg KH , Minchan Kim , Steven Allen , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Sergey Senozhatsky , Sergey Senozhatsky Subject: [PATCHv2] zram: restrict add/remove attributes to root only Date: Sun, 4 Dec 2016 21:44:13 +0900 Message-Id: <20161204124413.22595-1-sergey.senozhatsky@gmail.com> X-Mailer: git-send-email 2.10.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org zram hot_add sysfs attribute is a very 'special' attribute - reading from it creates a new uninitialized zram device. This file, by a mistake, can be read by a 'normal' user at the moment, while only root must be able to create a new zram device, therefore hot_add attribute must have S_IRUSR mode, not S_IRUGO. Fixes: 6566d1a32bf72 ("zram: add dynamic device add/remove functionality") Reported-by: Steven Allen Cc: [4.2+] Signed-off-by: Sergey Senozhatsky --- drivers/block/zram/zram_drv.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 5163c8f..3a0576f 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -1413,9 +1413,16 @@ static ssize_t hot_remove_store(struct class *class, return ret ? ret : count; } +/* + * NOTE: hot_add attribute is not the usual read-only sysfs + * attribute. In a sence that reading from this file does alter + * the state of your system -- it creates a new un-initialized + * zram device and returns back this device's device_id (or an + * error code if it fails to create a new device). + */ static struct class_attribute zram_control_class_attrs[] = { - __ATTR_RO(hot_add), - __ATTR_WO(hot_remove), + __ATTR(hot_add, 0400, hot_add_show, NULL), + __ATTR(hot_remove, 0200, NULL, hot_remove_store), __ATTR_NULL, }; -- 2.10.2