Commit eaa0d190 authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Linus Torvalds
Browse files

pidns: expose task pid_ns_for_children to userspace 

pid_ns_for_children set by a task is known only to the task itself, and
it's impossible to identify it from outside.

It's a big problem for checkpoint/restore software like CRIU, because it
can't correctly handle tasks, that do setns(CLONE_NEWPID) in proccess of
their work.

This patch solves the problem, and it exposes pid_ns_for_children to ns
directory in standard way with the name "pid_for_children":

  ~# ls /proc/5531/ns -l | grep pid
  lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid -> pid:[4026531836]
  lrwxrwxrwx 1 root root 0 Jan 14 16:38 pid_for_children -> pid:[4026532286]

Link: http://lkml.kernel.org/r/149201123914.6007.2187327078064239572.stgit@localhost.localdomain


Signed-off-by: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Cc: Andrei Vagin <avagin@virtuozzo.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Michael Kerrisk <mtk.manpages@googlemail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Serge Hallyn <serge@hallyn.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 25b14e92

fs/proc/namespaces.c

+1 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = { 
#endif

#ifdef CONFIG_PID_NS

	&pidns_operations,

	&pidns_for_children_operations,

#endif

#ifdef CONFIG_USER_NS

	&userns_operations,

include/linux/proc_ns.h

+1 −0
Original line number Diff line number Diff line
@@ -27,6 +27,7 @@ extern const struct proc_ns_operations netns_operations; 
extern const struct proc_ns_operations utsns_operations;

extern const struct proc_ns_operations ipcns_operations;

extern const struct proc_ns_operations pidns_operations;

extern const struct proc_ns_operations pidns_for_children_operations;

extern const struct proc_ns_operations userns_operations;

extern const struct proc_ns_operations mntns_operations;

extern const struct proc_ns_operations cgroupns_operations;

kernel/pid_namespace.c

+34 −0
Original line number Diff line number Diff line
@@ -374,6 +374,29 @@ static struct ns_common *pidns_get(struct task_struct *task) 
	return ns ? &ns->ns : NULL;

}



static struct ns_common *pidns_for_children_get(struct task_struct *task)

{

	struct pid_namespace *ns = NULL;



	task_lock(task);

	if (task->nsproxy) {

		ns = task->nsproxy->pid_ns_for_children;

		get_pid_ns(ns);

	}

	task_unlock(task);



	if (ns) {

		read_lock(&tasklist_lock);

		if (!ns->child_reaper) {

			put_pid_ns(ns);

			ns = NULL;

		}

		read_unlock(&tasklist_lock);

	}



	return ns ? &ns->ns : NULL;

}



static void pidns_put(struct ns_common *ns)

{

	put_pid_ns(to_pid_ns(ns));
@@ -443,6 +466,17 @@ const struct proc_ns_operations pidns_operations = { 
	.get_parent	= pidns_get_parent,

};



const struct proc_ns_operations pidns_for_children_operations = {

	.name		= "pid_for_children",

	.real_ns_name	= "pid",

	.type		= CLONE_NEWPID,

	.get		= pidns_for_children_get,

	.put		= pidns_put,

	.install	= pidns_install,

	.owner		= pidns_owner,

	.get_parent	= pidns_get_parent,

};



static __init int pid_namespaces_init(void)

{

	pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);

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