From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751207AbcLDK2E (ORCPT ); Sun, 4 Dec 2016 05:28:04 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:40770 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750774AbcLDK2C (ORCPT ); Sun, 4 Dec 2016 05:28:02 -0500 Date: Sun, 4 Dec 2016 11:28:07 +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: [PATCH] zram: restrict add/remove attributes to root only Message-ID: <20161204102807.GB15437@kroah.com> References: <20161204023515.7740-1-sergey.senozhatsky@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161204023515.7740-1-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 11:35:15AM +0900, Sergey Senozhatsky wrote: > Only root must be able to create a new zram device, therefore > hot_add attribute must have S_IRUSR mode, not S_IRUGO. Otherwise, > anyone can create a new zram device (device initialization with > the disksize attr requires root permission). > > 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 | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index 5163c8f..ee03464 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -1414,8 +1414,8 @@ static ssize_t hot_remove_store(struct class *class, > } > > 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), Huh? The only change you are making here is that a "normal" user can not read the value, ATTR_WO only allows root to write to the file. This change doesn't match up with your changelog, what really is the problem here with the _RO and _WO values that you can not use them? Why can't a normal user read the attribute? Does a read actually modify something? If so, that's really not a good idea. confused, greg k-h