From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751443AbcLEM5m (ORCPT ); Mon, 5 Dec 2016 07:57:42 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:49720 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750998AbcLEM5l (ORCPT ); Mon, 5 Dec 2016 07:57:41 -0500 Date: Mon, 5 Dec 2016 13:57:19 +0100 From: Greg KH To: Sergey Senozhatsky Cc: Andrew Morton , Minchan Kim , Steven Allen , linux-kernel@vger.kernel.org, stable@vger.kernel.org, Sergey Senozhatsky Subject: Re: [PATCHv2] zram: restrict add/remove attributes to root only Message-ID: <20161205125719.GE19696@kroah.com> References: <20161204124413.22595-1-sergey.senozhatsky@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161204124413.22595-1-sergey.senozhatsky@gmail.com> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Dec 04, 2016 at 09:44:13PM +0900, Sergey Senozhatsky wrote: > 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), You can leave hot_remove as __ATTR_WO(), right? Please do so if at all possible. thanks, greg k-h