stale cifs mount can't be unmounted: "This utility only unmounts cifs filesystems"

Binary package hint: samba

Hello, I think this is superficially similar to #427896 but I am not certain it's the same thing.

On occasion, perhaps all the time (I do not know - will try to find out) I cannot unmount a CIFS mount. I use mount/umount (thus mount.cifs/umount.cifs) in combination with the following line from /etc/fstab

//tower3/home13/njd33 /home/jon/h cifs uid=1000,gid=1000,username=CAMPUS\njd33,user,noauto 0 0

I notice this after resuming from suspend so I presume the mount has become stale. However, I consistently get

# umount ~jon/h
This utility only unmounts cifs filesystems.

the contents of h cannot be enumerated. df -h output shows the mount present, and I believe it is in the mtab but not /proc/mounts (will confirm next time I experience it).

One workaround appears to be to mount something on top of the stale mount, then attempt to remove that. I think. Again, I will confirm this next time I experience it.

package is source samba binary smbfs

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: smbfs 2:3.4.7~dfsg-1ubuntu3.1
ProcVersionSignature: Ubuntu 2.6.32-24.39-generic-pae 2.6.32.15+drm33.5
Uname: Linux 2.6.32-24-generic-pae i686
Architecture: i386
CIFSMounts: Error: command ['mount', '|', 'grep', 'cifs'] failed with exit code 1: mount: only root can do that
Date: Thu Aug 19 09:34:18 2010
EcryptfsInUse: Yes
InstallationMedia: Ubuntu 10.04 LTS "Lucid Lynx" - Release i386 (20100429)
ProcEnviron:
 PATH=(custom, user)
 LANG=en_GB.utf8
 SHELL=/bin/bash
SambaClientRegression: No
SourcePackage: samba