From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756451Ab2CYPgT (ORCPT ); Sun, 25 Mar 2012 11:36:19 -0400 Received: from mail-bk0-f46.google.com ([209.85.214.46]:41660 "EHLO mail-bk0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755960Ab2CYPgS (ORCPT ); Sun, 25 Mar 2012 11:36:18 -0400 Date: Sun, 25 Mar 2012 19:36:12 +0400 From: Vasiliy Kulikov To: Arkadiusz =?utf-8?Q?Mi=C5=9Bkiewicz?= Cc: Andrew Morton , linux-kernel@vger.kernel.org, Alexey Dobriyan Subject: Re: [PATCH] proc: fix mount -t proc -o AAA Message-ID: <20120325153612.GC4391@albatros> References: <201203220903.15360.a.miskiewicz@gmail.com> <20120323171058.GA3279@albatros> <20120323161504.dced28b9.akpm@linux-foundation.org> <201203250924.06908.a.miskiewicz@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <201203250924.06908.a.miskiewicz@gmail.com> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 25, 2012 at 09:24 +0200, Arkadiusz Miśkiewicz wrote: > but there is another problem - unmounting it and mounting without options > causes old option to persist: > > # mount none /proc -t proc -o hidepid=2 > # umount /proc > # mount none /proc -t proc > # grep "/proc" /proc/mounts > none /proc proc rw,relatime,hidepid=2 0 0 > > There should be no hidepid=2 now. No, that's an expected behaviour. Procfs is a special filesystem. Mount options are not reset on each mount(2) as you can mount procfs multiple times at different mount points (/proc/, /aaa/proc/, etc.). Each time you add mount options they are applied to _each_ mount point because there is no per-mount point sb, but there is a per pid_ns superblock: pid_ns itself. All options are stored at pid_ns. When you mount it another time without any option nothing should change at the old mount points. When you umount the last mount point all mount options are still stored. When you mount it again old options are used (unless you override them). Thanks, -- Vasiliy Kulikov http://www.openwall.com - bringing security into open computing environments