1 // SPDX-License-Identifier: GPL-2.0-only
6 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
7 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
8 * Many thanks to Oleg Nesterov for comments and help
12 #include <linux/pid.h>
13 #include <linux/pid_namespace.h>
14 #include <linux/user_namespace.h>
15 #include <linux/syscalls.h>
16 #include <linux/cred.h>
17 #include <linux/err.h>
18 #include <linux/acct.h>
19 #include <linux/slab.h>
20 #include <linux/proc_ns.h>
21 #include <linux/reboot.h>
22 #include <linux/export.h>
23 #include <linux/sched/task.h>
24 #include <linux/sched/signal.h>
25 #include <linux/idr.h>
26 #include "pid_sysctl.h"
28 static DEFINE_MUTEX(pid_caches_mutex
);
29 static struct kmem_cache
*pid_ns_cachep
;
30 /* Write once array, filled from the beginning. */
31 static struct kmem_cache
*pid_cache
[MAX_PID_NS_LEVEL
];
34 * creates the kmem cache to allocate pids from.
35 * @level: pid namespace level
38 static struct kmem_cache
*create_pid_cachep(unsigned int level
)
40 /* Level 0 is init_pid_ns.pid_cachep */
41 struct kmem_cache
**pkc
= &pid_cache
[level
- 1];
42 struct kmem_cache
*kc
;
43 char name
[4 + 10 + 1];
50 snprintf(name
, sizeof(name
), "pid_%u", level
+ 1);
51 len
= struct_size_t(struct pid
, numbers
, level
+ 1);
52 mutex_lock(&pid_caches_mutex
);
53 /* Name collision forces to do allocation under mutex. */
55 *pkc
= kmem_cache_create(name
, len
, 0,
56 SLAB_HWCACHE_ALIGN
| SLAB_ACCOUNT
, NULL
);
57 mutex_unlock(&pid_caches_mutex
);
58 /* current can fail, but someone else can succeed. */
59 return READ_ONCE(*pkc
);
62 static struct ucounts
*inc_pid_namespaces(struct user_namespace
*ns
)
64 return inc_ucount(ns
, current_euid(), UCOUNT_PID_NAMESPACES
);
67 static void dec_pid_namespaces(struct ucounts
*ucounts
)
69 dec_ucount(ucounts
, UCOUNT_PID_NAMESPACES
);
72 static struct pid_namespace
*create_pid_namespace(struct user_namespace
*user_ns
,
73 struct pid_namespace
*parent_pid_ns
)
75 struct pid_namespace
*ns
;
76 unsigned int level
= parent_pid_ns
->level
+ 1;
77 struct ucounts
*ucounts
;
81 if (!in_userns(parent_pid_ns
->user_ns
, user_ns
))
85 if (level
> MAX_PID_NS_LEVEL
)
87 ucounts
= inc_pid_namespaces(user_ns
);
92 ns
= kmem_cache_zalloc(pid_ns_cachep
, GFP_KERNEL
);
98 ns
->pid_cachep
= create_pid_cachep(level
);
99 if (ns
->pid_cachep
== NULL
)
102 err
= ns_alloc_inum(&ns
->ns
);
105 ns
->ns
.ops
= &pidns_operations
;
107 refcount_set(&ns
->ns
.count
, 1);
109 ns
->parent
= get_pid_ns(parent_pid_ns
);
110 ns
->user_ns
= get_user_ns(user_ns
);
111 ns
->ucounts
= ucounts
;
112 ns
->pid_allocated
= PIDNS_ADDING
;
113 #if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
114 ns
->memfd_noexec_scope
= pidns_memfd_noexec_scope(parent_pid_ns
);
119 idr_destroy(&ns
->idr
);
120 kmem_cache_free(pid_ns_cachep
, ns
);
122 dec_pid_namespaces(ucounts
);
127 static void delayed_free_pidns(struct rcu_head
*p
)
129 struct pid_namespace
*ns
= container_of(p
, struct pid_namespace
, rcu
);
131 dec_pid_namespaces(ns
->ucounts
);
132 put_user_ns(ns
->user_ns
);
134 kmem_cache_free(pid_ns_cachep
, ns
);
137 static void destroy_pid_namespace(struct pid_namespace
*ns
)
139 ns_free_inum(&ns
->ns
);
141 idr_destroy(&ns
->idr
);
142 call_rcu(&ns
->rcu
, delayed_free_pidns
);
145 struct pid_namespace
*copy_pid_ns(unsigned long flags
,
146 struct user_namespace
*user_ns
, struct pid_namespace
*old_ns
)
148 if (!(flags
& CLONE_NEWPID
))
149 return get_pid_ns(old_ns
);
150 if (task_active_pid_ns(current
) != old_ns
)
151 return ERR_PTR(-EINVAL
);
152 return create_pid_namespace(user_ns
, old_ns
);
155 void put_pid_ns(struct pid_namespace
*ns
)
157 struct pid_namespace
*parent
;
159 while (ns
!= &init_pid_ns
) {
161 if (!refcount_dec_and_test(&ns
->ns
.count
))
163 destroy_pid_namespace(ns
);
167 EXPORT_SYMBOL_GPL(put_pid_ns
);
169 void zap_pid_ns_processes(struct pid_namespace
*pid_ns
)
173 struct task_struct
*task
, *me
= current
;
174 int init_pids
= thread_group_leader(me
) ? 1 : 2;
177 /* Don't allow any more processes into the pid namespace */
178 disable_pid_allocation(pid_ns
);
181 * Ignore SIGCHLD causing any terminated children to autoreap.
182 * This speeds up the namespace shutdown, plus see the comment
185 spin_lock_irq(&me
->sighand
->siglock
);
186 me
->sighand
->action
[SIGCHLD
- 1].sa
.sa_handler
= SIG_IGN
;
187 spin_unlock_irq(&me
->sighand
->siglock
);
190 * The last thread in the cgroup-init thread group is terminating.
191 * Find remaining pid_ts in the namespace, signal and wait for them
194 * Note: This signals each threads in the namespace - even those that
195 * belong to the same thread group, To avoid this, we would have
196 * to walk the entire tasklist looking a processes in this
197 * namespace, but that could be unnecessarily expensive if the
198 * pid namespace has just a few processes. Or we need to
199 * maintain a tasklist for each pid namespace.
203 read_lock(&tasklist_lock
);
205 idr_for_each_entry_continue(&pid_ns
->idr
, pid
, nr
) {
206 task
= pid_task(pid
, PIDTYPE_PID
);
207 if (task
&& !__fatal_signal_pending(task
))
208 group_send_sig_info(SIGKILL
, SEND_SIG_PRIV
, task
, PIDTYPE_MAX
);
210 read_unlock(&tasklist_lock
);
214 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
215 * kernel_wait4() will also block until our children traced from the
216 * parent namespace are detached and become EXIT_DEAD.
219 clear_thread_flag(TIF_SIGPENDING
);
220 rc
= kernel_wait4(-1, NULL
, __WALL
, NULL
);
221 } while (rc
!= -ECHILD
);
224 * kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
225 * process whose parents processes are outside of the pid
226 * namespace. Such processes are created with setns()+fork().
228 * If those EXIT_ZOMBIE processes are not reaped by their
229 * parents before their parents exit, they will be reparented
230 * to pid_ns->child_reaper. Thus pidns->child_reaper needs to
231 * stay valid until they all go away.
233 * The code relies on the pid_ns->child_reaper ignoring
234 * SIGCHILD to cause those EXIT_ZOMBIE processes to be
235 * autoreaped if reparented.
237 * Semantically it is also desirable to wait for EXIT_ZOMBIE
238 * processes before allowing the child_reaper to be reaped, as
239 * that gives the invariant that when the init process of a
240 * pid namespace is reaped all of the processes in the pid
241 * namespace are gone.
243 * Once all of the other tasks are gone from the pid_namespace
244 * free_pid() will awaken this task.
247 set_current_state(TASK_INTERRUPTIBLE
);
248 if (pid_ns
->pid_allocated
== init_pids
)
251 * Release tasks_rcu_exit_srcu to avoid following deadlock:
253 * 1) TASK A unshare(CLONE_NEWPID)
254 * 2) TASK A fork() twice -> TASK B (child reaper for new ns)
256 * 3) TASK B exits, kills TASK C, waits for TASK A to reap it
257 * 4) TASK A calls synchronize_rcu_tasks()
258 * -> synchronize_srcu(tasks_rcu_exit_srcu)
261 * It is considered safe to release tasks_rcu_exit_srcu here
262 * because we assume the current task can not be concurrently
263 * reaped at this point.
265 exit_tasks_rcu_stop();
267 exit_tasks_rcu_start();
269 __set_current_state(TASK_RUNNING
);
272 current
->signal
->group_exit_code
= pid_ns
->reboot
;
274 acct_exit_ns(pid_ns
);
278 #ifdef CONFIG_CHECKPOINT_RESTORE
279 static int pid_ns_ctl_handler(struct ctl_table
*table
, int write
,
280 void *buffer
, size_t *lenp
, loff_t
*ppos
)
282 struct pid_namespace
*pid_ns
= task_active_pid_ns(current
);
283 struct ctl_table tmp
= *table
;
286 if (write
&& !checkpoint_restore_ns_capable(pid_ns
->user_ns
))
289 next
= idr_get_cursor(&pid_ns
->idr
) - 1;
292 ret
= proc_dointvec_minmax(&tmp
, write
, buffer
, lenp
, ppos
);
294 idr_set_cursor(&pid_ns
->idr
, next
+ 1);
300 static struct ctl_table pid_ns_ctl_table
[] = {
302 .procname
= "ns_last_pid",
303 .maxlen
= sizeof(int),
304 .mode
= 0666, /* permissions are checked in the handler */
305 .proc_handler
= pid_ns_ctl_handler
,
306 .extra1
= SYSCTL_ZERO
,
311 #endif /* CONFIG_CHECKPOINT_RESTORE */
313 int reboot_pid_ns(struct pid_namespace
*pid_ns
, int cmd
)
315 if (pid_ns
== &init_pid_ns
)
319 case LINUX_REBOOT_CMD_RESTART2
:
320 case LINUX_REBOOT_CMD_RESTART
:
321 pid_ns
->reboot
= SIGHUP
;
324 case LINUX_REBOOT_CMD_POWER_OFF
:
325 case LINUX_REBOOT_CMD_HALT
:
326 pid_ns
->reboot
= SIGINT
;
332 read_lock(&tasklist_lock
);
333 send_sig(SIGKILL
, pid_ns
->child_reaper
, 1);
334 read_unlock(&tasklist_lock
);
342 static inline struct pid_namespace
*to_pid_ns(struct ns_common
*ns
)
344 return container_of(ns
, struct pid_namespace
, ns
);
347 static struct ns_common
*pidns_get(struct task_struct
*task
)
349 struct pid_namespace
*ns
;
352 ns
= task_active_pid_ns(task
);
357 return ns
? &ns
->ns
: NULL
;
360 static struct ns_common
*pidns_for_children_get(struct task_struct
*task
)
362 struct pid_namespace
*ns
= NULL
;
366 ns
= task
->nsproxy
->pid_ns_for_children
;
372 read_lock(&tasklist_lock
);
373 if (!ns
->child_reaper
) {
377 read_unlock(&tasklist_lock
);
380 return ns
? &ns
->ns
: NULL
;
383 static void pidns_put(struct ns_common
*ns
)
385 put_pid_ns(to_pid_ns(ns
));
388 static int pidns_install(struct nsset
*nsset
, struct ns_common
*ns
)
390 struct nsproxy
*nsproxy
= nsset
->nsproxy
;
391 struct pid_namespace
*active
= task_active_pid_ns(current
);
392 struct pid_namespace
*ancestor
, *new = to_pid_ns(ns
);
394 if (!ns_capable(new->user_ns
, CAP_SYS_ADMIN
) ||
395 !ns_capable(nsset
->cred
->user_ns
, CAP_SYS_ADMIN
))
399 * Only allow entering the current active pid namespace
400 * or a child of the current active pid namespace.
402 * This is required for fork to return a usable pid value and
403 * this maintains the property that processes and their
404 * children can not escape their current pid namespace.
406 if (new->level
< active
->level
)
410 while (ancestor
->level
> active
->level
)
411 ancestor
= ancestor
->parent
;
412 if (ancestor
!= active
)
415 put_pid_ns(nsproxy
->pid_ns_for_children
);
416 nsproxy
->pid_ns_for_children
= get_pid_ns(new);
420 static struct ns_common
*pidns_get_parent(struct ns_common
*ns
)
422 struct pid_namespace
*active
= task_active_pid_ns(current
);
423 struct pid_namespace
*pid_ns
, *p
;
425 /* See if the parent is in the current namespace */
426 pid_ns
= p
= to_pid_ns(ns
)->parent
;
429 return ERR_PTR(-EPERM
);
435 return &get_pid_ns(pid_ns
)->ns
;
438 static struct user_namespace
*pidns_owner(struct ns_common
*ns
)
440 return to_pid_ns(ns
)->user_ns
;
443 const struct proc_ns_operations pidns_operations
= {
445 .type
= CLONE_NEWPID
,
448 .install
= pidns_install
,
449 .owner
= pidns_owner
,
450 .get_parent
= pidns_get_parent
,
453 const struct proc_ns_operations pidns_for_children_operations
= {
454 .name
= "pid_for_children",
455 .real_ns_name
= "pid",
456 .type
= CLONE_NEWPID
,
457 .get
= pidns_for_children_get
,
459 .install
= pidns_install
,
460 .owner
= pidns_owner
,
461 .get_parent
= pidns_get_parent
,
464 static __init
int pid_namespaces_init(void)
466 pid_ns_cachep
= KMEM_CACHE(pid_namespace
, SLAB_PANIC
| SLAB_ACCOUNT
);
468 #ifdef CONFIG_CHECKPOINT_RESTORE
469 register_sysctl_init("kernel", pid_ns_ctl_table
);
472 register_pid_ns_sysctl_table_vm();
476 __initcall(pid_namespaces_init
);