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461 lines
11 KiB
461 lines
11 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Pid namespaces |
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* |
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* Authors: |
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* (C) 2007 Pavel Emelyanov <[email protected]>, OpenVZ, SWsoft Inc. |
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* (C) 2007 Sukadev Bhattiprolu <[email protected]>, IBM |
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* Many thanks to Oleg Nesterov for comments and help |
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* |
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*/ |
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#include <linux/pid.h> |
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#include <linux/pid_namespace.h> |
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#include <linux/user_namespace.h> |
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#include <linux/syscalls.h> |
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#include <linux/cred.h> |
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#include <linux/err.h> |
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#include <linux/acct.h> |
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#include <linux/slab.h> |
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#include <linux/proc_ns.h> |
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#include <linux/reboot.h> |
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#include <linux/export.h> |
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#include <linux/sched/task.h> |
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#include <linux/sched/signal.h> |
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#include <linux/idr.h> |
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static DEFINE_MUTEX(pid_caches_mutex); |
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static struct kmem_cache *pid_ns_cachep; |
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/* Write once array, filled from the beginning. */ |
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static struct kmem_cache *pid_cache[MAX_PID_NS_LEVEL]; |
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/* |
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* creates the kmem cache to allocate pids from. |
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* @level: pid namespace level |
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*/ |
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static struct kmem_cache *create_pid_cachep(unsigned int level) |
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{ |
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/* Level 0 is init_pid_ns.pid_cachep */ |
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struct kmem_cache **pkc = &pid_cache[level - 1]; |
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struct kmem_cache *kc; |
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char name[4 + 10 + 1]; |
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unsigned int len; |
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kc = READ_ONCE(*pkc); |
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if (kc) |
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return kc; |
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snprintf(name, sizeof(name), "pid_%u", level + 1); |
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len = sizeof(struct pid) + level * sizeof(struct upid); |
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mutex_lock(&pid_caches_mutex); |
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/* Name collision forces to do allocation under mutex. */ |
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if (!*pkc) |
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*pkc = kmem_cache_create(name, len, 0, |
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SLAB_HWCACHE_ALIGN | SLAB_ACCOUNT, 0); |
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mutex_unlock(&pid_caches_mutex); |
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/* current can fail, but someone else can succeed. */ |
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return READ_ONCE(*pkc); |
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} |
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static struct ucounts *inc_pid_namespaces(struct user_namespace *ns) |
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{ |
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return inc_ucount(ns, current_euid(), UCOUNT_PID_NAMESPACES); |
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} |
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static void dec_pid_namespaces(struct ucounts *ucounts) |
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{ |
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dec_ucount(ucounts, UCOUNT_PID_NAMESPACES); |
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} |
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static struct pid_namespace *create_pid_namespace(struct user_namespace *user_ns, |
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struct pid_namespace *parent_pid_ns) |
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{ |
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struct pid_namespace *ns; |
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unsigned int level = parent_pid_ns->level + 1; |
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struct ucounts *ucounts; |
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int err; |
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err = -EINVAL; |
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if (!in_userns(parent_pid_ns->user_ns, user_ns)) |
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goto out; |
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err = -ENOSPC; |
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if (level > MAX_PID_NS_LEVEL) |
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goto out; |
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ucounts = inc_pid_namespaces(user_ns); |
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if (!ucounts) |
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goto out; |
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err = -ENOMEM; |
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ns = kmem_cache_zalloc(pid_ns_cachep, GFP_KERNEL); |
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if (ns == NULL) |
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goto out_dec; |
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idr_init(&ns->idr); |
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ns->pid_cachep = create_pid_cachep(level); |
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if (ns->pid_cachep == NULL) |
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goto out_free_idr; |
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err = ns_alloc_inum(&ns->ns); |
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if (err) |
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goto out_free_idr; |
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ns->ns.ops = &pidns_operations; |
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refcount_set(&ns->ns.count, 1); |
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ns->level = level; |
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ns->parent = get_pid_ns(parent_pid_ns); |
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ns->user_ns = get_user_ns(user_ns); |
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ns->ucounts = ucounts; |
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ns->pid_allocated = PIDNS_ADDING; |
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return ns; |
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out_free_idr: |
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idr_destroy(&ns->idr); |
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kmem_cache_free(pid_ns_cachep, ns); |
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out_dec: |
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dec_pid_namespaces(ucounts); |
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out: |
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return ERR_PTR(err); |
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} |
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static void delayed_free_pidns(struct rcu_head *p) |
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{ |
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struct pid_namespace *ns = container_of(p, struct pid_namespace, rcu); |
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dec_pid_namespaces(ns->ucounts); |
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put_user_ns(ns->user_ns); |
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kmem_cache_free(pid_ns_cachep, ns); |
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} |
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static void destroy_pid_namespace(struct pid_namespace *ns) |
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{ |
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ns_free_inum(&ns->ns); |
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idr_destroy(&ns->idr); |
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call_rcu(&ns->rcu, delayed_free_pidns); |
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} |
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struct pid_namespace *copy_pid_ns(unsigned long flags, |
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struct user_namespace *user_ns, struct pid_namespace *old_ns) |
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{ |
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if (!(flags & CLONE_NEWPID)) |
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return get_pid_ns(old_ns); |
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if (task_active_pid_ns(current) != old_ns) |
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return ERR_PTR(-EINVAL); |
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return create_pid_namespace(user_ns, old_ns); |
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} |
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void put_pid_ns(struct pid_namespace *ns) |
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{ |
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struct pid_namespace *parent; |
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while (ns != &init_pid_ns) { |
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parent = ns->parent; |
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if (!refcount_dec_and_test(&ns->ns.count)) |
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break; |
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destroy_pid_namespace(ns); |
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ns = parent; |
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} |
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} |
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EXPORT_SYMBOL_GPL(put_pid_ns); |
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void zap_pid_ns_processes(struct pid_namespace *pid_ns) |
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{ |
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int nr; |
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int rc; |
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struct task_struct *task, *me = current; |
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int init_pids = thread_group_leader(me) ? 1 : 2; |
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struct pid *pid; |
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/* Don't allow any more processes into the pid namespace */ |
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disable_pid_allocation(pid_ns); |
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/* |
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* Ignore SIGCHLD causing any terminated children to autoreap. |
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* This speeds up the namespace shutdown, plus see the comment |
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* below. |
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*/ |
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spin_lock_irq(&me->sighand->siglock); |
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me->sighand->action[SIGCHLD - 1].sa.sa_handler = SIG_IGN; |
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spin_unlock_irq(&me->sighand->siglock); |
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/* |
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* The last thread in the cgroup-init thread group is terminating. |
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* Find remaining pid_ts in the namespace, signal and wait for them |
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* to exit. |
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* |
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* Note: This signals each threads in the namespace - even those that |
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* belong to the same thread group, To avoid this, we would have |
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* to walk the entire tasklist looking a processes in this |
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* namespace, but that could be unnecessarily expensive if the |
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* pid namespace has just a few processes. Or we need to |
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* maintain a tasklist for each pid namespace. |
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* |
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*/ |
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rcu_read_lock(); |
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read_lock(&tasklist_lock); |
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nr = 2; |
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idr_for_each_entry_continue(&pid_ns->idr, pid, nr) { |
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task = pid_task(pid, PIDTYPE_PID); |
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if (task && !__fatal_signal_pending(task)) |
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group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX); |
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} |
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read_unlock(&tasklist_lock); |
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rcu_read_unlock(); |
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/* |
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* Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD. |
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* kernel_wait4() will also block until our children traced from the |
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* parent namespace are detached and become EXIT_DEAD. |
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*/ |
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do { |
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clear_thread_flag(TIF_SIGPENDING); |
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rc = kernel_wait4(-1, NULL, __WALL, NULL); |
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} while (rc != -ECHILD); |
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/* |
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* kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE |
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* process whose parents processes are outside of the pid |
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* namespace. Such processes are created with setns()+fork(). |
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* |
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* If those EXIT_ZOMBIE processes are not reaped by their |
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* parents before their parents exit, they will be reparented |
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* to pid_ns->child_reaper. Thus pidns->child_reaper needs to |
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* stay valid until they all go away. |
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* |
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* The code relies on the pid_ns->child_reaper ignoring |
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* SIGCHILD to cause those EXIT_ZOMBIE processes to be |
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* autoreaped if reparented. |
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* |
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* Semantically it is also desirable to wait for EXIT_ZOMBIE |
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* processes before allowing the child_reaper to be reaped, as |
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* that gives the invariant that when the init process of a |
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* pid namespace is reaped all of the processes in the pid |
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* namespace are gone. |
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* |
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* Once all of the other tasks are gone from the pid_namespace |
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* free_pid() will awaken this task. |
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*/ |
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for (;;) { |
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set_current_state(TASK_INTERRUPTIBLE); |
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if (pid_ns->pid_allocated == init_pids) |
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break; |
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schedule(); |
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} |
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__set_current_state(TASK_RUNNING); |
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if (pid_ns->reboot) |
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current->signal->group_exit_code = pid_ns->reboot; |
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acct_exit_ns(pid_ns); |
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return; |
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} |
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#ifdef CONFIG_CHECKPOINT_RESTORE |
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static int pid_ns_ctl_handler(struct ctl_table *table, int write, |
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void *buffer, size_t *lenp, loff_t *ppos) |
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{ |
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struct pid_namespace *pid_ns = task_active_pid_ns(current); |
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struct ctl_table tmp = *table; |
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int ret, next; |
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if (write && !checkpoint_restore_ns_capable(pid_ns->user_ns)) |
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return -EPERM; |
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/* |
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* Writing directly to ns' last_pid field is OK, since this field |
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* is volatile in a living namespace anyway and a code writing to |
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* it should synchronize its usage with external means. |
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*/ |
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next = idr_get_cursor(&pid_ns->idr) - 1; |
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tmp.data = &next; |
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ret = proc_dointvec_minmax(&tmp, write, buffer, lenp, ppos); |
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if (!ret && write) |
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idr_set_cursor(&pid_ns->idr, next + 1); |
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return ret; |
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} |
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extern int pid_max; |
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static struct ctl_table pid_ns_ctl_table[] = { |
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{ |
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.procname = "ns_last_pid", |
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.maxlen = sizeof(int), |
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.mode = 0666, /* permissions are checked in the handler */ |
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.proc_handler = pid_ns_ctl_handler, |
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.extra1 = SYSCTL_ZERO, |
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.extra2 = &pid_max, |
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}, |
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{ } |
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}; |
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static struct ctl_path kern_path[] = { { .procname = "kernel", }, { } }; |
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#endif /* CONFIG_CHECKPOINT_RESTORE */ |
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int reboot_pid_ns(struct pid_namespace *pid_ns, int cmd) |
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{ |
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if (pid_ns == &init_pid_ns) |
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return 0; |
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switch (cmd) { |
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case LINUX_REBOOT_CMD_RESTART2: |
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case LINUX_REBOOT_CMD_RESTART: |
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pid_ns->reboot = SIGHUP; |
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break; |
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case LINUX_REBOOT_CMD_POWER_OFF: |
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case LINUX_REBOOT_CMD_HALT: |
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pid_ns->reboot = SIGINT; |
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break; |
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default: |
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return -EINVAL; |
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} |
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read_lock(&tasklist_lock); |
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send_sig(SIGKILL, pid_ns->child_reaper, 1); |
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read_unlock(&tasklist_lock); |
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do_exit(0); |
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/* Not reached */ |
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return 0; |
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} |
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static inline struct pid_namespace *to_pid_ns(struct ns_common *ns) |
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{ |
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return container_of(ns, struct pid_namespace, ns); |
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} |
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static struct ns_common *pidns_get(struct task_struct *task) |
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{ |
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struct pid_namespace *ns; |
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rcu_read_lock(); |
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ns = task_active_pid_ns(task); |
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if (ns) |
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get_pid_ns(ns); |
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rcu_read_unlock(); |
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return ns ? &ns->ns : NULL; |
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} |
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static struct ns_common *pidns_for_children_get(struct task_struct *task) |
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{ |
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struct pid_namespace *ns = NULL; |
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task_lock(task); |
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if (task->nsproxy) { |
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ns = task->nsproxy->pid_ns_for_children; |
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get_pid_ns(ns); |
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} |
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task_unlock(task); |
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if (ns) { |
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read_lock(&tasklist_lock); |
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if (!ns->child_reaper) { |
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put_pid_ns(ns); |
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ns = NULL; |
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} |
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read_unlock(&tasklist_lock); |
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} |
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return ns ? &ns->ns : NULL; |
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} |
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static void pidns_put(struct ns_common *ns) |
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{ |
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put_pid_ns(to_pid_ns(ns)); |
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} |
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static int pidns_install(struct nsset *nsset, struct ns_common *ns) |
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{ |
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struct nsproxy *nsproxy = nsset->nsproxy; |
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struct pid_namespace *active = task_active_pid_ns(current); |
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struct pid_namespace *ancestor, *new = to_pid_ns(ns); |
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if (!ns_capable(new->user_ns, CAP_SYS_ADMIN) || |
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!ns_capable(nsset->cred->user_ns, CAP_SYS_ADMIN)) |
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return -EPERM; |
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/* |
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* Only allow entering the current active pid namespace |
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* or a child of the current active pid namespace. |
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* |
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* This is required for fork to return a usable pid value and |
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* this maintains the property that processes and their |
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* children can not escape their current pid namespace. |
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*/ |
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if (new->level < active->level) |
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return -EINVAL; |
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ancestor = new; |
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while (ancestor->level > active->level) |
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ancestor = ancestor->parent; |
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if (ancestor != active) |
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return -EINVAL; |
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put_pid_ns(nsproxy->pid_ns_for_children); |
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nsproxy->pid_ns_for_children = get_pid_ns(new); |
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return 0; |
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} |
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static struct ns_common *pidns_get_parent(struct ns_common *ns) |
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{ |
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struct pid_namespace *active = task_active_pid_ns(current); |
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struct pid_namespace *pid_ns, *p; |
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/* See if the parent is in the current namespace */ |
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pid_ns = p = to_pid_ns(ns)->parent; |
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for (;;) { |
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if (!p) |
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return ERR_PTR(-EPERM); |
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if (p == active) |
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break; |
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p = p->parent; |
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} |
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return &get_pid_ns(pid_ns)->ns; |
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} |
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static struct user_namespace *pidns_owner(struct ns_common *ns) |
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{ |
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return to_pid_ns(ns)->user_ns; |
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} |
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const struct proc_ns_operations pidns_operations = { |
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.name = "pid", |
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.type = CLONE_NEWPID, |
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.get = pidns_get, |
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.put = pidns_put, |
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.install = pidns_install, |
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.owner = pidns_owner, |
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.get_parent = pidns_get_parent, |
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}; |
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const struct proc_ns_operations pidns_for_children_operations = { |
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.name = "pid_for_children", |
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.real_ns_name = "pid", |
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.type = CLONE_NEWPID, |
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.get = pidns_for_children_get, |
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.put = pidns_put, |
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.install = pidns_install, |
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.owner = pidns_owner, |
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.get_parent = pidns_get_parent, |
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}; |
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static __init int pid_namespaces_init(void) |
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{ |
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pid_ns_cachep = KMEM_CACHE(pid_namespace, SLAB_PANIC | SLAB_ACCOUNT); |
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#ifdef CONFIG_CHECKPOINT_RESTORE |
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register_sysctl_paths(kern_path, pid_ns_ctl_table); |
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#endif |
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return 0; |
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} |
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__initcall(pid_namespaces_init);
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