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b64a9f67e0
alloc_pid() checks PIDNS_ADDING only on the leaf pid namespace before
making a new struct pid visible in every ancestor namespace. That is
insufficient when an unborn descendant pid namespace outlives an
ancestor whose init task has already exited. The descendant can still be
initialized later through setns(), and the new pid is then published
into the dead ancestor as well.
Keep the existing ENOMEM behavior, but require PIDNS_ADDING to be set in
every namespace that will receive the new pid before publishing any of
them. This preserves the invariant that free_pid() never decrements
pid_allocated in a namespace whose child_reaper is no longer live.
Fixes: a3bdc23ba8 ("pid_namespace: allow opening pid_for_children before init was created")
Signed-off-by: Jérémy Jean <Jeremy.Jean@oss.cyber.gouv.fr>
Reviewed-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>
Linux kernel ============ The Linux kernel is the core of any Linux operating system. It manages hardware, system resources, and provides the fundamental services for all other software. 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