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[Bug 1402834] Re: fuse filesystems get disconnected on container exit

 

I didn't see the irc discussion. Atm we don't have a concept of a owner
or "master" namespace for a super block, though I expect we will see it
in the future. And I agree it doesn't seem to make sense to let a less
privileged userns to do this to a more privileged namespace. However if
we ignore MNT_FORCE if there are mounts in any other namespace this
would allow a lesser privileged namespace to block MNT_FORCE for a more
privileged one, which is also undesirable.

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https://bugs.launchpad.net/bugs/1402834

Title:
  fuse filesystems get disconnected on container exit

Status in linux package in Ubuntu:
  Confirmed

Bug description:
  When bind-mounting a directory from a fuse filesytems into a container,
  then when the container is shut down, the userspace process serving the
  fuse fs is terminated.  The original fuse mountpoint remains busy until it
  is manually unmounted.

  I've tested this with sshfs, git://github.com/stgraber/cgmanagerfs,
  the bbfs example fs from http://www.cs.nmsu.edu/~pfeiffer/fuse-tutorial/,
  or git://github.com/lxc/lxcfs.

  To reproduce:

  Mount a fusefs - say sshfs - with -o allow_other, let's say onto
  /tmp/d.

  sshfs -f -d -o allow_other somehost:$HOME /tmp/d

  Bind that into a container by adding

  lxc.mount.entry = /tmp/d freezer none bind,create=dir 0 0

  to the container's config.

  start the container, stop it.

  the fuse program stops (exits 0 in fact)

  the mount is not cleaned up - ls /tmp/d on the host henceforth
  complains:

  	ls: cannot access /tmp/d Transport endpoint is not connected"
  	
  (sudo umount /tmp/d cleans it up)

  I don't know for sure whether this is a kernel or libfuse bug.

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References