From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753350AbbLJHKr (ORCPT ); Thu, 10 Dec 2015 02:10:47 -0500 Received: from wtarreau.pck.nerim.net ([62.212.114.60]:14542 "EHLO 1wt.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750975AbbLJHKp (ORCPT ); Thu, 10 Dec 2015 02:10:45 -0500 Date: Thu, 10 Dec 2015 08:10:22 +0100 From: Willy Tarreau To: Kees Cook Cc: Andrew Morton , Jan Kara , yalin wang , "Eric W. Biederman" , Alexander Viro , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v5] fs: clear file privilege bits when mmap writing Message-ID: <20151210071022.GA31969@1wt.eu> References: <20151209225148.GA14794@www.outflux.net> <20151210070635.GC31922@1wt.eu> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20151210070635.GC31922@1wt.eu> User-Agent: Mutt/1.4.2.3i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Dec 10, 2015 at 08:06:35AM +0100, Willy Tarreau wrote: > Hi Kees, > > Why not add a new file flag instead ? > > Something like this (editing your patch by hand to illustrate) : (...) > diff --git a/include/linux/fs.h b/include/linux/fs.h > index 3aa514254161..409bd7047e7e 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -913,3 +913,4 @@ > #define FL_OFDLCK 1024 /* lock is "owned" by struct file */ > #define FL_LAYOUT 2048 /* outstanding pNFS layout */ > +#define FL_DROP_PRIVS 4096 /* lest something weird decides that 2 is OK */ Crap, these ones are for locks, we need to use O_* instead But anyway you get the idea, I mean there are probably many spare bits overthere. Another option I was thinking about was to change f_mode and detect the change on close. But I don't know what to compare it against. Willy