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

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.localdomainSigned-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
...@@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = { ...@@ -23,6 +23,7 @@ static const struct proc_ns_operations *ns_entries[] = {
#endif #endif
#ifdef CONFIG_PID_NS #ifdef CONFIG_PID_NS
&pidns_operations, &pidns_operations,
&pidns_for_children_operations,
#endif #endif
#ifdef CONFIG_USER_NS #ifdef CONFIG_USER_NS
&userns_operations, &userns_operations,
......
...@@ -27,6 +27,7 @@ extern const struct proc_ns_operations netns_operations; ...@@ -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 utsns_operations;
extern const struct proc_ns_operations ipcns_operations; extern const struct proc_ns_operations ipcns_operations;
extern const struct proc_ns_operations pidns_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 userns_operations;
extern const struct proc_ns_operations mntns_operations; extern const struct proc_ns_operations mntns_operations;
extern const struct proc_ns_operations cgroupns_operations; extern const struct proc_ns_operations cgroupns_operations;
......
...@@ -374,6 +374,29 @@ static struct ns_common *pidns_get(struct task_struct *task) ...@@ -374,6 +374,29 @@ static struct ns_common *pidns_get(struct task_struct *task)
return ns ? &ns->ns : NULL; 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) static void pidns_put(struct ns_common *ns)
{ {
put_pid_ns(to_pid_ns(ns)); put_pid_ns(to_pid_ns(ns));
...@@ -443,6 +466,17 @@ const struct proc_ns_operations pidns_operations = { ...@@ -443,6 +466,17 @@ const struct proc_ns_operations pidns_operations = {
.get_parent = pidns_get_parent, .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) static __init int pid_namespaces_init(void)
{ {
pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC); pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC);
......
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