Date: Thu, 15 Oct 2009 18:39:48 GMT From: Alexander Haderer <alexander.haderer@loescap.de> To: freebsd-gnats-submit@FreeBSD.org Subject: bin/139651: mount: read-only remount of NFS volume does not work Message-ID: <200910151839.n9FIdm1N092259@www.freebsd.org> Resent-Message-ID: <200910151840.n9FIe2NW070336@freefall.freebsd.org>
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>Number: 139651 >Category: bin >Synopsis: mount: read-only remount of NFS volume does not work >Confidential: no >Severity: serious >Priority: medium >Responsible: freebsd-bugs >State: open >Quarter: >Keywords: >Date-Required: >Class: sw-bug >Submitter-Id: current-users >Arrival-Date: Thu Oct 15 18:40:02 UTC 2009 >Closed-Date: >Last-Modified: >Originator: Alexander Haderer >Release: Freebsd 7.2R >Organization: LoeScap Technology GmbH >Environment: FreeBSD xxxxxxx 7.2-RELEASE-p4 FreeBSD 7.2-RELEASE-p4 #0: Fri Oct 2 12:21:39 UTC 2009 root@i386-builder.daemonology.net:/usr/obj/usr/src/sys/GENERIC i386 >Description: When trying to read-only remount a NFS volume with 'mount -u -r /mnt' the volume will be/remain mounted read-write. Neither the mount command nor the logfiles show any diagnostics, mount's exitcode is 0. Note: This problem is strongly related to PR 136470 kern/136470: [nfs] Cannot mount / in read-only, over NFS PR Summary: A network booted machine has root NFS mounted read-write, although in rc.conf root_rw_mount="NO" is set. Because I run diskless setups, I stumbled over the same problem and found the PR above. My further investigations of such a network boot environment show, that rc.d/root respects the config var set, but later rc.d/mountcritremote calls "mount -a -t nfs", which will silently remount / as read-write. I marked this PR as serious because with the current behaviour of mount one can accidently read-write mount a volume. >How-To-Repeat: Setup an NFS server (here: FreeBSD 4.9 running a NFS server with defaults), then goto 7.2 nfs client machine and do: # mount server:/fs /mnt # mount server:/fs on /mnt (nfs) # mount -u -r /mnt # mount server:/fs on /mnt (nfs) # umount /mnt # mount -r server:/fs /mnt # mount server:/fs on /mnt (nfs, read-only) # mount -u -r /mnt # mount server:/fs on /mnt (nfs) >Fix: Only workarounds: - make the exported filesystem read-only - export the NFS volume as read-only - umount and NFS remount read-only >Release-Note: >Audit-Trail: >Unformatted:
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