[PATCH 0/3] pidns: Closing the pid namespace exit race.

[ebiederm@xmission.com (Eric W. Biederman)]

I had some patches that broke the circular reference between the
pid_namespace and the proc_mnt by combining the reference counts but the
world has changes and now the proc_mnt reference count is not suitable
to be used that way so that plan is scrapped.

I did play with it and I have found a relatively elegant way of at least
handling the problem of self reaping children escaping from
zap_pid_ns_processess.

The following patches guarantee that the task with pid == 1 will be the
last task reaped in a pid namespace. Making proc_flush_task safe.

The previous patch to call pid_ns_release_proc on fork failure is still
needed.  These patches simply address the other failure mode.

How did it escape my memory that setting SIGCHLD to SIG_IGN caused
children to autoreap?


Eric W. Biederman (3):
      pidns:  Use task_active_pid_ns in do_notify_parent.
      pidns: Guarantee that the pidns init will be the last pidns process reaped.
      pidns: Make killed children autoreap

 kernel/exit.c          |   46 +++++++++++++++++++++++++++++++++++-----------
 kernel/pid_namespace.c |    7 ++++++-
 kernel/signal.c        |   11 +++++------
 3 files changed, 46 insertions(+), 18 deletions(-)