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[AlainKnaff <1397649@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

When remounting root read-only in a private mount namespace, then also
the real root (in default namespace) is read-only.

However, it is then possible to remount the real root read-write, and
this doesn't (fortunately...) affect the other namespace.

How to reproduce:
-----------------------------
(in one console):
# unshare --mount /bin/bash
# mount -o remount -r /

(in other console)
# touch /x
touch: cannot touch `/x': Read-only file system
# mount -o remount -w /
# touch /x

(in first console)
# touch /x
touch: cannot touch `/x': Read-only file system

What happened:
--------------------------
Read-only mount performed in private mount namespace affected main (default) namespace

What should have happened:
-----------------------------------------------
The read-only mount should not have affected the main namespace

(this has been seen in 3.0.0 and also 3.4.0 on precise)

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: Incomplete

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https://bugs.launchpad.net/bugs/1397649

Title:
  remounting root read-only in private mount namespace affects main
  namespace

Status in linux package in Ubuntu:
  Incomplete

Bug description:
  When remounting root read-only in a private mount namespace, then also
  the real root (in default namespace) is read-only.

  However, it is then possible to remount the real root read-write, and
  this doesn't (fortunately...) affect the other namespace.

  How to reproduce:
  -----------------------------
  (in one console):
  # unshare --mount /bin/bash
  # mount -o remount -r /

  (in other console)
  # touch /x
  touch: cannot touch `/x': Read-only file system
  # mount -o remount -w /
  # touch /x

  (in first console)
  # touch /x
  touch: cannot touch `/x': Read-only file system

  What happened:
  --------------------------
  Read-only mount performed in private mount namespace affected main (default) namespace

  What should have happened:
  -----------------------------------------------
  The read-only mount should not have affected the main namespace

  (this has been seen in 3.0.0 and also 3.4.0 on precise)

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