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>
27 static DEFINE_MUTEX(pid_caches_mutex
);
28 static struct kmem_cache
*pid_ns_cachep
;
29 /* Write once array, filled from the beginning. */
30 static struct kmem_cache
*pid_cache
[MAX_PID_NS_LEVEL
];
33 * creates the kmem cache to allocate pids from.
34 * @level: pid namespace level
37 static struct kmem_cache
*create_pid_cachep(unsigned int level
)
39 /* Level 0 is init_pid_ns.pid_cachep */
40 struct kmem_cache
**pkc
= &pid_cache
[level
- 1];
41 struct kmem_cache
*kc
;
42 char name
[4 + 10 + 1];
49 snprintf(name
, sizeof(name
), "pid_%u", level
+ 1);
50 len
= sizeof(struct pid
) + level
* sizeof(struct upid
);
51 mutex_lock(&pid_caches_mutex
);
52 /* Name collision forces to do allocation under mutex. */
54 *pkc
= kmem_cache_create(name
, len
, 0,
55 SLAB_HWCACHE_ALIGN
| SLAB_ACCOUNT
, 0);
56 mutex_unlock(&pid_caches_mutex
);
57 /* current can fail, but someone else can succeed. */
58 return READ_ONCE(*pkc
);
61 static struct ucounts
*inc_pid_namespaces(struct user_namespace
*ns
)
63 return inc_ucount(ns
, current_euid(), UCOUNT_PID_NAMESPACES
);
66 static void dec_pid_namespaces(struct ucounts
*ucounts
)
68 dec_ucount(ucounts
, UCOUNT_PID_NAMESPACES
);
71 static struct pid_namespace
*create_pid_namespace(struct user_namespace
*user_ns
,
72 struct pid_namespace
*parent_pid_ns
)
74 struct pid_namespace
*ns
;
75 unsigned int level
= parent_pid_ns
->level
+ 1;
76 struct ucounts
*ucounts
;
80 if (!in_userns(parent_pid_ns
->user_ns
, user_ns
))
84 if (level
> MAX_PID_NS_LEVEL
)
86 ucounts
= inc_pid_namespaces(user_ns
);
91 ns
= kmem_cache_zalloc(pid_ns_cachep
, GFP_KERNEL
);
97 ns
->pid_cachep
= create_pid_cachep(level
);
98 if (ns
->pid_cachep
== NULL
)
101 err
= ns_alloc_inum(&ns
->ns
);
104 ns
->ns
.ops
= &pidns_operations
;
106 refcount_set(&ns
->ns
.count
, 1);
108 ns
->parent
= get_pid_ns(parent_pid_ns
);
109 ns
->user_ns
= get_user_ns(user_ns
);
110 ns
->ucounts
= ucounts
;
111 ns
->pid_allocated
= PIDNS_ADDING
;
116 idr_destroy(&ns
->idr
);
117 kmem_cache_free(pid_ns_cachep
, ns
);
119 dec_pid_namespaces(ucounts
);
124 static void delayed_free_pidns(struct rcu_head
*p
)
126 struct pid_namespace
*ns
= container_of(p
, struct pid_namespace
, rcu
);
128 dec_pid_namespaces(ns
->ucounts
);
129 put_user_ns(ns
->user_ns
);
131 kmem_cache_free(pid_ns_cachep
, ns
);
134 static void destroy_pid_namespace(struct pid_namespace
*ns
)
136 ns_free_inum(&ns
->ns
);
138 idr_destroy(&ns
->idr
);
139 call_rcu(&ns
->rcu
, delayed_free_pidns
);
142 struct pid_namespace
*copy_pid_ns(unsigned long flags
,
143 struct user_namespace
*user_ns
, struct pid_namespace
*old_ns
)
145 if (!(flags
& CLONE_NEWPID
))
146 return get_pid_ns(old_ns
);
147 if (task_active_pid_ns(current
) != old_ns
)
148 return ERR_PTR(-EINVAL
);
149 return create_pid_namespace(user_ns
, old_ns
);
152 void put_pid_ns(struct pid_namespace
*ns
)
154 struct pid_namespace
*parent
;
156 while (ns
!= &init_pid_ns
) {
158 if (!refcount_dec_and_test(&ns
->ns
.count
))
160 destroy_pid_namespace(ns
);
164 EXPORT_SYMBOL_GPL(put_pid_ns
);
166 void zap_pid_ns_processes(struct pid_namespace
*pid_ns
)
170 struct task_struct
*task
, *me
= current
;
171 int init_pids
= thread_group_leader(me
) ? 1 : 2;
174 /* Don't allow any more processes into the pid namespace */
175 disable_pid_allocation(pid_ns
);
178 * Ignore SIGCHLD causing any terminated children to autoreap.
179 * This speeds up the namespace shutdown, plus see the comment
182 spin_lock_irq(&me
->sighand
->siglock
);
183 me
->sighand
->action
[SIGCHLD
- 1].sa
.sa_handler
= SIG_IGN
;
184 spin_unlock_irq(&me
->sighand
->siglock
);
187 * The last thread in the cgroup-init thread group is terminating.
188 * Find remaining pid_ts in the namespace, signal and wait for them
191 * Note: This signals each threads in the namespace - even those that
192 * belong to the same thread group, To avoid this, we would have
193 * to walk the entire tasklist looking a processes in this
194 * namespace, but that could be unnecessarily expensive if the
195 * pid namespace has just a few processes. Or we need to
196 * maintain a tasklist for each pid namespace.
200 read_lock(&tasklist_lock
);
202 idr_for_each_entry_continue(&pid_ns
->idr
, pid
, nr
) {
203 task
= pid_task(pid
, PIDTYPE_PID
);
204 if (task
&& !__fatal_signal_pending(task
))
205 group_send_sig_info(SIGKILL
, SEND_SIG_PRIV
, task
, PIDTYPE_MAX
);
207 read_unlock(&tasklist_lock
);
211 * Reap the EXIT_ZOMBIE children we had before we ignored SIGCHLD.
212 * kernel_wait4() will also block until our children traced from the
213 * parent namespace are detached and become EXIT_DEAD.
216 clear_thread_flag(TIF_SIGPENDING
);
217 rc
= kernel_wait4(-1, NULL
, __WALL
, NULL
);
218 } while (rc
!= -ECHILD
);
221 * kernel_wait4() misses EXIT_DEAD children, and EXIT_ZOMBIE
222 * process whose parents processes are outside of the pid
223 * namespace. Such processes are created with setns()+fork().
225 * If those EXIT_ZOMBIE processes are not reaped by their
226 * parents before their parents exit, they will be reparented
227 * to pid_ns->child_reaper. Thus pidns->child_reaper needs to
228 * stay valid until they all go away.
230 * The code relies on the pid_ns->child_reaper ignoring
231 * SIGCHILD to cause those EXIT_ZOMBIE processes to be
232 * autoreaped if reparented.
234 * Semantically it is also desirable to wait for EXIT_ZOMBIE
235 * processes before allowing the child_reaper to be reaped, as
236 * that gives the invariant that when the init process of a
237 * pid namespace is reaped all of the processes in the pid
238 * namespace are gone.
240 * Once all of the other tasks are gone from the pid_namespace
241 * free_pid() will awaken this task.
244 set_current_state(TASK_INTERRUPTIBLE
);
245 if (pid_ns
->pid_allocated
== init_pids
)
249 __set_current_state(TASK_RUNNING
);
252 current
->signal
->group_exit_code
= pid_ns
->reboot
;
254 acct_exit_ns(pid_ns
);
258 #ifdef CONFIG_CHECKPOINT_RESTORE
259 static int pid_ns_ctl_handler(struct ctl_table
*table
, int write
,
260 void *buffer
, size_t *lenp
, loff_t
*ppos
)
262 struct pid_namespace
*pid_ns
= task_active_pid_ns(current
);
263 struct ctl_table tmp
= *table
;
266 if (write
&& !checkpoint_restore_ns_capable(pid_ns
->user_ns
))
270 * Writing directly to ns' last_pid field is OK, since this field
271 * is volatile in a living namespace anyway and a code writing to
272 * it should synchronize its usage with external means.
275 next
= idr_get_cursor(&pid_ns
->idr
) - 1;
278 ret
= proc_dointvec_minmax(&tmp
, write
, buffer
, lenp
, ppos
);
280 idr_set_cursor(&pid_ns
->idr
, next
+ 1);
286 static struct ctl_table pid_ns_ctl_table
[] = {
288 .procname
= "ns_last_pid",
289 .maxlen
= sizeof(int),
290 .mode
= 0666, /* permissions are checked in the handler */
291 .proc_handler
= pid_ns_ctl_handler
,
292 .extra1
= SYSCTL_ZERO
,
297 static struct ctl_path kern_path
[] = { { .procname
= "kernel", }, { } };
298 #endif /* CONFIG_CHECKPOINT_RESTORE */
300 int reboot_pid_ns(struct pid_namespace
*pid_ns
, int cmd
)
302 if (pid_ns
== &init_pid_ns
)
306 case LINUX_REBOOT_CMD_RESTART2
:
307 case LINUX_REBOOT_CMD_RESTART
:
308 pid_ns
->reboot
= SIGHUP
;
311 case LINUX_REBOOT_CMD_POWER_OFF
:
312 case LINUX_REBOOT_CMD_HALT
:
313 pid_ns
->reboot
= SIGINT
;
319 read_lock(&tasklist_lock
);
320 send_sig(SIGKILL
, pid_ns
->child_reaper
, 1);
321 read_unlock(&tasklist_lock
);
329 static inline struct pid_namespace
*to_pid_ns(struct ns_common
*ns
)
331 return container_of(ns
, struct pid_namespace
, ns
);
334 static struct ns_common
*pidns_get(struct task_struct
*task
)
336 struct pid_namespace
*ns
;
339 ns
= task_active_pid_ns(task
);
344 return ns
? &ns
->ns
: NULL
;
347 static struct ns_common
*pidns_for_children_get(struct task_struct
*task
)
349 struct pid_namespace
*ns
= NULL
;
353 ns
= task
->nsproxy
->pid_ns_for_children
;
359 read_lock(&tasklist_lock
);
360 if (!ns
->child_reaper
) {
364 read_unlock(&tasklist_lock
);
367 return ns
? &ns
->ns
: NULL
;
370 static void pidns_put(struct ns_common
*ns
)
372 put_pid_ns(to_pid_ns(ns
));
375 static int pidns_install(struct nsset
*nsset
, struct ns_common
*ns
)
377 struct nsproxy
*nsproxy
= nsset
->nsproxy
;
378 struct pid_namespace
*active
= task_active_pid_ns(current
);
379 struct pid_namespace
*ancestor
, *new = to_pid_ns(ns
);
381 if (!ns_capable(new->user_ns
, CAP_SYS_ADMIN
) ||
382 !ns_capable(nsset
->cred
->user_ns
, CAP_SYS_ADMIN
))
386 * Only allow entering the current active pid namespace
387 * or a child of the current active pid namespace.
389 * This is required for fork to return a usable pid value and
390 * this maintains the property that processes and their
391 * children can not escape their current pid namespace.
393 if (new->level
< active
->level
)
397 while (ancestor
->level
> active
->level
)
398 ancestor
= ancestor
->parent
;
399 if (ancestor
!= active
)
402 put_pid_ns(nsproxy
->pid_ns_for_children
);
403 nsproxy
->pid_ns_for_children
= get_pid_ns(new);
407 static struct ns_common
*pidns_get_parent(struct ns_common
*ns
)
409 struct pid_namespace
*active
= task_active_pid_ns(current
);
410 struct pid_namespace
*pid_ns
, *p
;
412 /* See if the parent is in the current namespace */
413 pid_ns
= p
= to_pid_ns(ns
)->parent
;
416 return ERR_PTR(-EPERM
);
422 return &get_pid_ns(pid_ns
)->ns
;
425 static struct user_namespace
*pidns_owner(struct ns_common
*ns
)
427 return to_pid_ns(ns
)->user_ns
;
430 const struct proc_ns_operations pidns_operations
= {
432 .type
= CLONE_NEWPID
,
435 .install
= pidns_install
,
436 .owner
= pidns_owner
,
437 .get_parent
= pidns_get_parent
,
440 const struct proc_ns_operations pidns_for_children_operations
= {
441 .name
= "pid_for_children",
442 .real_ns_name
= "pid",
443 .type
= CLONE_NEWPID
,
444 .get
= pidns_for_children_get
,
446 .install
= pidns_install
,
447 .owner
= pidns_owner
,
448 .get_parent
= pidns_get_parent
,
451 static __init
int pid_namespaces_init(void)
453 pid_ns_cachep
= KMEM_CACHE(pid_namespace
, SLAB_PANIC
| SLAB_ACCOUNT
);
455 #ifdef CONFIG_CHECKPOINT_RESTORE
456 register_sysctl_paths(kern_path
, pid_ns_ctl_table
);
461 __initcall(pid_namespaces_init
);