1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Generic pidhash and scalable, time-bounded PID allocator
4 *
5 * (C) 2002-2003 Nadia Yvette Chambers, IBM
6 * (C) 2004 Nadia Yvette Chambers, Oracle
7 * (C) 2002-2004 Ingo Molnar, Red Hat
8 *
9 * pid-structures are backing objects for tasks sharing a given ID to chain
10 * against. There is very little to them aside from hashing them and
11 * parking tasks using given ID's on a list.
12 *
13 * The hash is always changed with the tasklist_lock write-acquired,
14 * and the hash is only accessed with the tasklist_lock at least
15 * read-acquired, so there's no additional SMP locking needed here.
16 *
17 * We have a list of bitmap pages, which bitmaps represent the PID space.
18 * Allocating and freeing PIDs is completely lockless. The worst-case
19 * allocation scenario when all but one out of 1 million PIDs possible are
20 * allocated already: the scanning of 32 list entries and at most PAGE_SIZE
21 * bytes. The typical fastpath is a single successful setbit. Freeing is O(1).
22 *
23 * Pid namespaces:
24 * (C) 2007 Pavel Emelyanov <xemul@openvz.org>, OpenVZ, SWsoft Inc.
25 * (C) 2007 Sukadev Bhattiprolu <sukadev@us.ibm.com>, IBM
26 * Many thanks to Oleg Nesterov for comments and help
27 *
28 */
29
30#include <linux/mm.h>
31#include <linux/export.h>
32#include <linux/slab.h>
33#include <linux/init.h>
34#include <linux/rculist.h>
35#include <linux/memblock.h>
36#include <linux/pid_namespace.h>
37#include <linux/init_task.h>
38#include <linux/syscalls.h>
39#include <linux/proc_ns.h>
40#include <linux/refcount.h>
41#include <linux/anon_inodes.h>
42#include <linux/sched/signal.h>
43#include <linux/sched/task.h>
44#include <linux/idr.h>
45#include <linux/pidfs.h>
46#include <linux/seqlock.h>
47#include <net/sock.h>
48#include <uapi/linux/pidfd.h>
49
50struct pid init_struct_pid = {
51 .count = REFCOUNT_INIT(1),
52 .tasks = {
53 { .first = NULL },
54 { .first = NULL },
55 { .first = NULL },
56 },
57 .level = 0,
58 .numbers = { {
59 .nr = 0,
60 .ns = &init_pid_ns,
61 }, }
62};
63
64static int pid_max_min = RESERVED_PIDS + 1;
65static int pid_max_max = PID_MAX_LIMIT;
66
67/*
68 * PID-map pages start out as NULL, they get allocated upon
69 * first use and are never deallocated. This way a low pid_max
70 * value does not cause lots of bitmaps to be allocated, but
71 * the scheme scales to up to 4 million PIDs, runtime.
72 */
73struct pid_namespace init_pid_ns = {
74 .ns.__ns_ref = REFCOUNT_INIT(2),
75 .idr = IDR_INIT(init_pid_ns.idr),
76 .pid_allocated = PIDNS_ADDING,
77 .level = 0,
78 .child_reaper = &init_task,
79 .user_ns = &init_user_ns,
80 .ns.inum = ns_init_inum(&init_pid_ns),
81#ifdef CONFIG_PID_NS
82 .ns.ops = &pidns_operations,
83#endif
84 .pid_max = PID_MAX_DEFAULT,
85#if defined(CONFIG_SYSCTL) && defined(CONFIG_MEMFD_CREATE)
86 .memfd_noexec_scope = MEMFD_NOEXEC_SCOPE_EXEC,
87#endif
88 .ns.ns_type = ns_common_type(&init_pid_ns),
89};
90EXPORT_SYMBOL_GPL(init_pid_ns);
91
92static __cacheline_aligned_in_smp DEFINE_SPINLOCK(pidmap_lock);
93seqcount_spinlock_t pidmap_lock_seq = SEQCNT_SPINLOCK_ZERO(pidmap_lock_seq, &pidmap_lock);
94
95void put_pid(struct pid *pid)
96{
97 struct pid_namespace *ns;
98
99 if (!pid)
100 return;
101
102 ns = pid->numbers[pid->level].ns;
103 if (refcount_dec_and_test(r: &pid->count)) {
104 pidfs_free_pid(pid);
105 kmem_cache_free(s: ns->pid_cachep, objp: pid);
106 put_pid_ns(ns);
107 }
108}
109EXPORT_SYMBOL_GPL(put_pid);
110
111static void delayed_put_pid(struct rcu_head *rhp)
112{
113 struct pid *pid = container_of(rhp, struct pid, rcu);
114 put_pid(pid);
115}
116
117void free_pid(struct pid *pid)
118{
119 int i;
120
121 lockdep_assert_not_held(&tasklist_lock);
122
123 spin_lock(lock: &pidmap_lock);
124 for (i = 0; i <= pid->level; i++) {
125 struct upid *upid = pid->numbers + i;
126 struct pid_namespace *ns = upid->ns;
127 switch (--ns->pid_allocated) {
128 case 2:
129 case 1:
130 /* When all that is left in the pid namespace
131 * is the reaper wake up the reaper. The reaper
132 * may be sleeping in zap_pid_ns_processes().
133 */
134 wake_up_process(tsk: ns->child_reaper);
135 break;
136 case PIDNS_ADDING:
137 /* Handle a fork failure of the first process */
138 WARN_ON(ns->child_reaper);
139 ns->pid_allocated = 0;
140 break;
141 }
142
143 idr_remove(&ns->idr, id: upid->nr);
144 }
145 pidfs_remove_pid(pid);
146 spin_unlock(lock: &pidmap_lock);
147
148 call_rcu(head: &pid->rcu, func: delayed_put_pid);
149}
150
151void free_pids(struct pid **pids)
152{
153 int tmp;
154
155 /*
156 * This can batch pidmap_lock.
157 */
158 for (tmp = PIDTYPE_MAX; --tmp >= 0; )
159 if (pids[tmp])
160 free_pid(pid: pids[tmp]);
161}
162
163struct pid *alloc_pid(struct pid_namespace *ns, pid_t *set_tid,
164 size_t set_tid_size)
165{
166 struct pid *pid;
167 enum pid_type type;
168 int i, nr;
169 struct pid_namespace *tmp;
170 struct upid *upid;
171 int retval = -ENOMEM;
172
173 /*
174 * set_tid_size contains the size of the set_tid array. Starting at
175 * the most nested currently active PID namespace it tells alloc_pid()
176 * which PID to set for a process in that most nested PID namespace
177 * up to set_tid_size PID namespaces. It does not have to set the PID
178 * for a process in all nested PID namespaces but set_tid_size must
179 * never be greater than the current ns->level + 1.
180 */
181 if (set_tid_size > ns->level + 1)
182 return ERR_PTR(error: -EINVAL);
183
184 pid = kmem_cache_alloc(ns->pid_cachep, GFP_KERNEL);
185 if (!pid)
186 return ERR_PTR(error: retval);
187
188 tmp = ns;
189 pid->level = ns->level;
190
191 for (i = ns->level; i >= 0; i--) {
192 int tid = 0;
193 int pid_max = READ_ONCE(tmp->pid_max);
194
195 if (set_tid_size) {
196 tid = set_tid[ns->level - i];
197
198 retval = -EINVAL;
199 if (tid < 1 || tid >= pid_max)
200 goto out_free;
201 /*
202 * Also fail if a PID != 1 is requested and
203 * no PID 1 exists.
204 */
205 if (tid != 1 && !tmp->child_reaper)
206 goto out_free;
207 retval = -EPERM;
208 if (!checkpoint_restore_ns_capable(ns: tmp->user_ns))
209 goto out_free;
210 set_tid_size--;
211 }
212
213 idr_preload(GFP_KERNEL);
214 spin_lock(lock: &pidmap_lock);
215
216 if (tid) {
217 nr = idr_alloc(&tmp->idr, NULL, start: tid,
218 end: tid + 1, GFP_ATOMIC);
219 /*
220 * If ENOSPC is returned it means that the PID is
221 * alreay in use. Return EEXIST in that case.
222 */
223 if (nr == -ENOSPC)
224 nr = -EEXIST;
225 } else {
226 int pid_min = 1;
227 /*
228 * init really needs pid 1, but after reaching the
229 * maximum wrap back to RESERVED_PIDS
230 */
231 if (idr_get_cursor(idr: &tmp->idr) > RESERVED_PIDS)
232 pid_min = RESERVED_PIDS;
233
234 /*
235 * Store a null pointer so find_pid_ns does not find
236 * a partially initialized PID (see below).
237 */
238 nr = idr_alloc_cyclic(&tmp->idr, NULL, start: pid_min,
239 end: pid_max, GFP_ATOMIC);
240 }
241 spin_unlock(lock: &pidmap_lock);
242 idr_preload_end();
243
244 if (nr < 0) {
245 retval = (nr == -ENOSPC) ? -EAGAIN : nr;
246 goto out_free;
247 }
248
249 pid->numbers[i].nr = nr;
250 pid->numbers[i].ns = tmp;
251 tmp = tmp->parent;
252 }
253
254 /*
255 * ENOMEM is not the most obvious choice especially for the case
256 * where the child subreaper has already exited and the pid
257 * namespace denies the creation of any new processes. But ENOMEM
258 * is what we have exposed to userspace for a long time and it is
259 * documented behavior for pid namespaces. So we can't easily
260 * change it even if there were an error code better suited.
261 */
262 retval = -ENOMEM;
263
264 get_pid_ns(ns);
265 refcount_set(r: &pid->count, n: 1);
266 spin_lock_init(&pid->lock);
267 for (type = 0; type < PIDTYPE_MAX; ++type)
268 INIT_HLIST_HEAD(&pid->tasks[type]);
269
270 init_waitqueue_head(&pid->wait_pidfd);
271 INIT_HLIST_HEAD(&pid->inodes);
272
273 upid = pid->numbers + ns->level;
274 idr_preload(GFP_KERNEL);
275 spin_lock(lock: &pidmap_lock);
276 if (!(ns->pid_allocated & PIDNS_ADDING))
277 goto out_unlock;
278 pidfs_add_pid(pid);
279 for ( ; upid >= pid->numbers; --upid) {
280 /* Make the PID visible to find_pid_ns. */
281 idr_replace(&upid->ns->idr, pid, id: upid->nr);
282 upid->ns->pid_allocated++;
283 }
284 spin_unlock(lock: &pidmap_lock);
285 idr_preload_end();
286
287 return pid;
288
289out_unlock:
290 spin_unlock(lock: &pidmap_lock);
291 idr_preload_end();
292 put_pid_ns(ns);
293
294out_free:
295 spin_lock(lock: &pidmap_lock);
296 while (++i <= ns->level) {
297 upid = pid->numbers + i;
298 idr_remove(&upid->ns->idr, id: upid->nr);
299 }
300
301 /* On failure to allocate the first pid, reset the state */
302 if (ns->pid_allocated == PIDNS_ADDING)
303 idr_set_cursor(idr: &ns->idr, val: 0);
304
305 spin_unlock(lock: &pidmap_lock);
306
307 kmem_cache_free(s: ns->pid_cachep, objp: pid);
308 return ERR_PTR(error: retval);
309}
310
311void disable_pid_allocation(struct pid_namespace *ns)
312{
313 spin_lock(lock: &pidmap_lock);
314 ns->pid_allocated &= ~PIDNS_ADDING;
315 spin_unlock(lock: &pidmap_lock);
316}
317
318struct pid *find_pid_ns(int nr, struct pid_namespace *ns)
319{
320 return idr_find(&ns->idr, id: nr);
321}
322EXPORT_SYMBOL_GPL(find_pid_ns);
323
324struct pid *find_vpid(int nr)
325{
326 return find_pid_ns(nr, task_active_pid_ns(current));
327}
328EXPORT_SYMBOL_GPL(find_vpid);
329
330static struct pid **task_pid_ptr(struct task_struct *task, enum pid_type type)
331{
332 return (type == PIDTYPE_PID) ?
333 &task->thread_pid :
334 &task->signal->pids[type];
335}
336
337/*
338 * attach_pid() must be called with the tasklist_lock write-held.
339 */
340void attach_pid(struct task_struct *task, enum pid_type type)
341{
342 struct pid *pid;
343
344 lockdep_assert_held_write(&tasklist_lock);
345
346 pid = *task_pid_ptr(task, type);
347 hlist_add_head_rcu(n: &task->pid_links[type], h: &pid->tasks[type]);
348}
349
350static void __change_pid(struct pid **pids, struct task_struct *task,
351 enum pid_type type, struct pid *new)
352{
353 struct pid **pid_ptr, *pid;
354 int tmp;
355
356 lockdep_assert_held_write(&tasklist_lock);
357
358 pid_ptr = task_pid_ptr(task, type);
359 pid = *pid_ptr;
360
361 hlist_del_rcu(n: &task->pid_links[type]);
362 *pid_ptr = new;
363
364 for (tmp = PIDTYPE_MAX; --tmp >= 0; )
365 if (pid_has_task(pid, type: tmp))
366 return;
367
368 WARN_ON(pids[type]);
369 pids[type] = pid;
370}
371
372void detach_pid(struct pid **pids, struct task_struct *task, enum pid_type type)
373{
374 __change_pid(pids, task, type, NULL);
375}
376
377void change_pid(struct pid **pids, struct task_struct *task, enum pid_type type,
378 struct pid *pid)
379{
380 __change_pid(pids, task, type, new: pid);
381 attach_pid(task, type);
382}
383
384void exchange_tids(struct task_struct *left, struct task_struct *right)
385{
386 struct pid *pid1 = left->thread_pid;
387 struct pid *pid2 = right->thread_pid;
388 struct hlist_head *head1 = &pid1->tasks[PIDTYPE_PID];
389 struct hlist_head *head2 = &pid2->tasks[PIDTYPE_PID];
390
391 lockdep_assert_held_write(&tasklist_lock);
392
393 /* Swap the single entry tid lists */
394 hlists_swap_heads_rcu(left: head1, right: head2);
395
396 /* Swap the per task_struct pid */
397 rcu_assign_pointer(left->thread_pid, pid2);
398 rcu_assign_pointer(right->thread_pid, pid1);
399
400 /* Swap the cached value */
401 WRITE_ONCE(left->pid, pid_nr(pid2));
402 WRITE_ONCE(right->pid, pid_nr(pid1));
403}
404
405/* transfer_pid is an optimization of attach_pid(new), detach_pid(old) */
406void transfer_pid(struct task_struct *old, struct task_struct *new,
407 enum pid_type type)
408{
409 WARN_ON_ONCE(type == PIDTYPE_PID);
410 lockdep_assert_held_write(&tasklist_lock);
411 hlist_replace_rcu(old: &old->pid_links[type], new: &new->pid_links[type]);
412}
413
414struct task_struct *pid_task(struct pid *pid, enum pid_type type)
415{
416 struct task_struct *result = NULL;
417 if (pid) {
418 struct hlist_node *first;
419 first = rcu_dereference_check(hlist_first_rcu(&pid->tasks[type]),
420 lockdep_tasklist_lock_is_held());
421 if (first)
422 result = hlist_entry(first, struct task_struct, pid_links[(type)]);
423 }
424 return result;
425}
426EXPORT_SYMBOL(pid_task);
427
428/*
429 * Must be called under rcu_read_lock().
430 */
431struct task_struct *find_task_by_pid_ns(pid_t nr, struct pid_namespace *ns)
432{
433 RCU_LOCKDEP_WARN(!rcu_read_lock_held(),
434 "find_task_by_pid_ns() needs rcu_read_lock() protection");
435 return pid_task(find_pid_ns(nr, ns), PIDTYPE_PID);
436}
437
438struct task_struct *find_task_by_vpid(pid_t vnr)
439{
440 return find_task_by_pid_ns(nr: vnr, ns: task_active_pid_ns(current));
441}
442
443struct task_struct *find_get_task_by_vpid(pid_t nr)
444{
445 struct task_struct *task;
446
447 rcu_read_lock();
448 task = find_task_by_vpid(vnr: nr);
449 if (task)
450 get_task_struct(t: task);
451 rcu_read_unlock();
452
453 return task;
454}
455
456struct pid *get_task_pid(struct task_struct *task, enum pid_type type)
457{
458 struct pid *pid;
459 rcu_read_lock();
460 pid = get_pid(rcu_dereference(*task_pid_ptr(task, type)));
461 rcu_read_unlock();
462 return pid;
463}
464EXPORT_SYMBOL_GPL(get_task_pid);
465
466struct task_struct *get_pid_task(struct pid *pid, enum pid_type type)
467{
468 struct task_struct *result;
469 rcu_read_lock();
470 result = pid_task(pid, type);
471 if (result)
472 get_task_struct(t: result);
473 rcu_read_unlock();
474 return result;
475}
476EXPORT_SYMBOL_GPL(get_pid_task);
477
478struct pid *find_get_pid(pid_t nr)
479{
480 struct pid *pid;
481
482 rcu_read_lock();
483 pid = get_pid(pid: find_vpid(nr));
484 rcu_read_unlock();
485
486 return pid;
487}
488EXPORT_SYMBOL_GPL(find_get_pid);
489
490pid_t pid_nr_ns(struct pid *pid, struct pid_namespace *ns)
491{
492 struct upid *upid;
493 pid_t nr = 0;
494
495 if (pid && ns && ns->level <= pid->level) {
496 upid = &pid->numbers[ns->level];
497 if (upid->ns == ns)
498 nr = upid->nr;
499 }
500 return nr;
501}
502EXPORT_SYMBOL_GPL(pid_nr_ns);
503
504pid_t pid_vnr(struct pid *pid)
505{
506 return pid_nr_ns(pid, task_active_pid_ns(current));
507}
508EXPORT_SYMBOL_GPL(pid_vnr);
509
510pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type,
511 struct pid_namespace *ns)
512{
513 pid_t nr = 0;
514
515 rcu_read_lock();
516 if (!ns)
517 ns = task_active_pid_ns(current);
518 if (ns)
519 nr = pid_nr_ns(rcu_dereference(*task_pid_ptr(task, type)), ns);
520 rcu_read_unlock();
521
522 return nr;
523}
524EXPORT_SYMBOL(__task_pid_nr_ns);
525
526struct pid_namespace *task_active_pid_ns(struct task_struct *tsk)
527{
528 return ns_of_pid(pid: task_pid(task: tsk));
529}
530EXPORT_SYMBOL_GPL(task_active_pid_ns);
531
532/*
533 * Used by proc to find the first pid that is greater than or equal to nr.
534 *
535 * If there is a pid at nr this function is exactly the same as find_pid_ns.
536 */
537struct pid *find_ge_pid(int nr, struct pid_namespace *ns)
538{
539 return idr_get_next(&ns->idr, nextid: &nr);
540}
541EXPORT_SYMBOL_GPL(find_ge_pid);
542
543struct pid *pidfd_get_pid(unsigned int fd, unsigned int *flags)
544{
545 CLASS(fd, f)(fd);
546 struct pid *pid;
547
548 if (fd_empty(f))
549 return ERR_PTR(error: -EBADF);
550
551 pid = pidfd_pid(fd_file(f));
552 if (!IS_ERR(ptr: pid)) {
553 get_pid(pid);
554 *flags = fd_file(f)->f_flags;
555 }
556 return pid;
557}
558
559/**
560 * pidfd_get_task() - Get the task associated with a pidfd
561 *
562 * @pidfd: pidfd for which to get the task
563 * @flags: flags associated with this pidfd
564 *
565 * Return the task associated with @pidfd. The function takes a reference on
566 * the returned task. The caller is responsible for releasing that reference.
567 *
568 * Return: On success, the task_struct associated with the pidfd.
569 * On error, a negative errno number will be returned.
570 */
571struct task_struct *pidfd_get_task(int pidfd, unsigned int *flags)
572{
573 unsigned int f_flags = 0;
574 struct pid *pid;
575 struct task_struct *task;
576 enum pid_type type;
577
578 switch (pidfd) {
579 case PIDFD_SELF_THREAD:
580 type = PIDTYPE_PID;
581 pid = get_task_pid(current, type);
582 break;
583 case PIDFD_SELF_THREAD_GROUP:
584 type = PIDTYPE_TGID;
585 pid = get_task_pid(current, type);
586 break;
587 default:
588 pid = pidfd_get_pid(fd: pidfd, flags: &f_flags);
589 if (IS_ERR(ptr: pid))
590 return ERR_CAST(ptr: pid);
591 type = PIDTYPE_TGID;
592 break;
593 }
594
595 task = get_pid_task(pid, type);
596 put_pid(pid);
597 if (!task)
598 return ERR_PTR(error: -ESRCH);
599
600 *flags = f_flags;
601 return task;
602}
603
604/**
605 * pidfd_create() - Create a new pid file descriptor.
606 *
607 * @pid: struct pid that the pidfd will reference
608 * @flags: flags to pass
609 *
610 * This creates a new pid file descriptor with the O_CLOEXEC flag set.
611 *
612 * Note, that this function can only be called after the fd table has
613 * been unshared to avoid leaking the pidfd to the new process.
614 *
615 * This symbol should not be explicitly exported to loadable modules.
616 *
617 * Return: On success, a cloexec pidfd is returned.
618 * On error, a negative errno number will be returned.
619 */
620static int pidfd_create(struct pid *pid, unsigned int flags)
621{
622 int pidfd;
623 struct file *pidfd_file;
624
625 pidfd = pidfd_prepare(pid, flags, ret_file: &pidfd_file);
626 if (pidfd < 0)
627 return pidfd;
628
629 fd_install(fd: pidfd, file: pidfd_file);
630 return pidfd;
631}
632
633/**
634 * sys_pidfd_open() - Open new pid file descriptor.
635 *
636 * @pid: pid for which to retrieve a pidfd
637 * @flags: flags to pass
638 *
639 * This creates a new pid file descriptor with the O_CLOEXEC flag set for
640 * the task identified by @pid. Without PIDFD_THREAD flag the target task
641 * must be a thread-group leader.
642 *
643 * Return: On success, a cloexec pidfd is returned.
644 * On error, a negative errno number will be returned.
645 */
646SYSCALL_DEFINE2(pidfd_open, pid_t, pid, unsigned int, flags)
647{
648 int fd;
649 struct pid *p;
650
651 if (flags & ~(PIDFD_NONBLOCK | PIDFD_THREAD))
652 return -EINVAL;
653
654 if (pid <= 0)
655 return -EINVAL;
656
657 p = find_get_pid(pid);
658 if (!p)
659 return -ESRCH;
660
661 fd = pidfd_create(pid: p, flags);
662
663 put_pid(p);
664 return fd;
665}
666
667#ifdef CONFIG_SYSCTL
668static struct ctl_table_set *pid_table_root_lookup(struct ctl_table_root *root)
669{
670 return &task_active_pid_ns(current)->set;
671}
672
673static int set_is_seen(struct ctl_table_set *set)
674{
675 return &task_active_pid_ns(current)->set == set;
676}
677
678static int pid_table_root_permissions(struct ctl_table_header *head,
679 const struct ctl_table *table)
680{
681 struct pid_namespace *pidns =
682 container_of(head->set, struct pid_namespace, set);
683 int mode = table->mode;
684
685 if (ns_capable_noaudit(ns: pidns->user_ns, CAP_SYS_ADMIN) ||
686 uid_eq(current_euid(), right: make_kuid(from: pidns->user_ns, uid: 0)))
687 mode = (mode & S_IRWXU) >> 6;
688 else if (in_egroup_p(make_kgid(from: pidns->user_ns, gid: 0)))
689 mode = (mode & S_IRWXG) >> 3;
690 else
691 mode = mode & S_IROTH;
692 return (mode << 6) | (mode << 3) | mode;
693}
694
695static void pid_table_root_set_ownership(struct ctl_table_header *head,
696 kuid_t *uid, kgid_t *gid)
697{
698 struct pid_namespace *pidns =
699 container_of(head->set, struct pid_namespace, set);
700 kuid_t ns_root_uid;
701 kgid_t ns_root_gid;
702
703 ns_root_uid = make_kuid(from: pidns->user_ns, uid: 0);
704 if (uid_valid(uid: ns_root_uid))
705 *uid = ns_root_uid;
706
707 ns_root_gid = make_kgid(from: pidns->user_ns, gid: 0);
708 if (gid_valid(gid: ns_root_gid))
709 *gid = ns_root_gid;
710}
711
712static struct ctl_table_root pid_table_root = {
713 .lookup = pid_table_root_lookup,
714 .permissions = pid_table_root_permissions,
715 .set_ownership = pid_table_root_set_ownership,
716};
717
718static int proc_do_cad_pid(const struct ctl_table *table, int write, void *buffer,
719 size_t *lenp, loff_t *ppos)
720{
721 struct pid *new_pid;
722 pid_t tmp_pid;
723 int r;
724 struct ctl_table tmp_table = *table;
725
726 tmp_pid = pid_vnr(cad_pid);
727 tmp_table.data = &tmp_pid;
728
729 r = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
730 if (r || !write)
731 return r;
732
733 new_pid = find_get_pid(tmp_pid);
734 if (!new_pid)
735 return -ESRCH;
736
737 put_pid(xchg(&cad_pid, new_pid));
738 return 0;
739}
740
741static const struct ctl_table pid_table[] = {
742 {
743 .procname = "pid_max",
744 .data = &init_pid_ns.pid_max,
745 .maxlen = sizeof(int),
746 .mode = 0644,
747 .proc_handler = proc_dointvec_minmax,
748 .extra1 = &pid_max_min,
749 .extra2 = &pid_max_max,
750 },
751#ifdef CONFIG_PROC_SYSCTL
752 {
753 .procname = "cad_pid",
754 .maxlen = sizeof(int),
755 .mode = 0600,
756 .proc_handler = proc_do_cad_pid,
757 },
758#endif
759};
760#endif
761
762int register_pidns_sysctls(struct pid_namespace *pidns)
763{
764#ifdef CONFIG_SYSCTL
765 struct ctl_table *tbl;
766
767 setup_sysctl_set(p: &pidns->set, root: &pid_table_root, is_seen: set_is_seen);
768
769 tbl = kmemdup(pid_table, sizeof(pid_table), GFP_KERNEL);
770 if (!tbl)
771 return -ENOMEM;
772 tbl->data = &pidns->pid_max;
773 pidns->pid_max = min(pid_max_max, max_t(int, pidns->pid_max,
774 PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
775
776 pidns->sysctls = __register_sysctl_table(set: &pidns->set, path: "kernel", table: tbl,
777 ARRAY_SIZE(pid_table));
778 if (!pidns->sysctls) {
779 kfree(objp: tbl);
780 retire_sysctl_set(set: &pidns->set);
781 return -ENOMEM;
782 }
783#endif
784 return 0;
785}
786
787void unregister_pidns_sysctls(struct pid_namespace *pidns)
788{
789#ifdef CONFIG_SYSCTL
790 const struct ctl_table *tbl;
791
792 tbl = pidns->sysctls->ctl_table_arg;
793 unregister_sysctl_table(table: pidns->sysctls);
794 retire_sysctl_set(set: &pidns->set);
795 kfree(objp: tbl);
796#endif
797}
798
799void __init pid_idr_init(void)
800{
801 /* Verify no one has done anything silly: */
802 BUILD_BUG_ON(PID_MAX_LIMIT >= PIDNS_ADDING);
803
804 /* bump default and minimum pid_max based on number of cpus */
805 init_pid_ns.pid_max = min(pid_max_max, max_t(int, init_pid_ns.pid_max,
806 PIDS_PER_CPU_DEFAULT * num_possible_cpus()));
807 pid_max_min = max_t(int, pid_max_min,
808 PIDS_PER_CPU_MIN * num_possible_cpus());
809 pr_info("pid_max: default: %u minimum: %u\n", init_pid_ns.pid_max, pid_max_min);
810
811 idr_init(idr: &init_pid_ns.idr);
812
813 init_pid_ns.pid_cachep = kmem_cache_create("pid",
814 struct_size_t(struct pid, numbers, 1),
815 __alignof__(struct pid),
816 SLAB_HWCACHE_ALIGN | SLAB_PANIC | SLAB_ACCOUNT,
817 NULL);
818}
819
820static __init int pid_namespace_sysctl_init(void)
821{
822#ifdef CONFIG_SYSCTL
823 /* "kernel" directory will have already been initialized. */
824 BUG_ON(register_pidns_sysctls(&init_pid_ns));
825#endif
826 return 0;
827}
828subsys_initcall(pid_namespace_sysctl_init);
829
830static struct file *__pidfd_fget(struct task_struct *task, int fd)
831{
832 struct file *file;
833 int ret;
834
835 ret = down_read_killable(sem: &task->signal->exec_update_lock);
836 if (ret)
837 return ERR_PTR(error: ret);
838
839 if (ptrace_may_access(task, PTRACE_MODE_ATTACH_REALCREDS))
840 file = fget_task(task, fd);
841 else
842 file = ERR_PTR(error: -EPERM);
843
844 up_read(sem: &task->signal->exec_update_lock);
845
846 if (!file) {
847 /*
848 * It is possible that the target thread is exiting; it can be
849 * either:
850 * 1. before exit_signals(), which gives a real fd
851 * 2. before exit_files() takes the task_lock() gives a real fd
852 * 3. after exit_files() releases task_lock(), ->files is NULL;
853 * this has PF_EXITING, since it was set in exit_signals(),
854 * __pidfd_fget() returns EBADF.
855 * In case 3 we get EBADF, but that really means ESRCH, since
856 * the task is currently exiting and has freed its files
857 * struct, so we fix it up.
858 */
859 if (task->flags & PF_EXITING)
860 file = ERR_PTR(error: -ESRCH);
861 else
862 file = ERR_PTR(error: -EBADF);
863 }
864
865 return file;
866}
867
868static int pidfd_getfd(struct pid *pid, int fd)
869{
870 struct task_struct *task;
871 struct file *file;
872 int ret;
873
874 task = get_pid_task(pid, PIDTYPE_PID);
875 if (!task)
876 return -ESRCH;
877
878 file = __pidfd_fget(task, fd);
879 put_task_struct(t: task);
880 if (IS_ERR(ptr: file))
881 return PTR_ERR(ptr: file);
882
883 ret = receive_fd(file, NULL, O_CLOEXEC);
884 fput(file);
885
886 return ret;
887}
888
889/**
890 * sys_pidfd_getfd() - Get a file descriptor from another process
891 *
892 * @pidfd: the pidfd file descriptor of the process
893 * @fd: the file descriptor number to get
894 * @flags: flags on how to get the fd (reserved)
895 *
896 * This syscall gets a copy of a file descriptor from another process
897 * based on the pidfd, and file descriptor number. It requires that
898 * the calling process has the ability to ptrace the process represented
899 * by the pidfd. The process which is having its file descriptor copied
900 * is otherwise unaffected.
901 *
902 * Return: On success, a cloexec file descriptor is returned.
903 * On error, a negative errno number will be returned.
904 */
905SYSCALL_DEFINE3(pidfd_getfd, int, pidfd, int, fd,
906 unsigned int, flags)
907{
908 struct pid *pid;
909
910 /* flags is currently unused - make sure it's unset */
911 if (flags)
912 return -EINVAL;
913
914 CLASS(fd, f)(fd: pidfd);
915 if (fd_empty(f))
916 return -EBADF;
917
918 pid = pidfd_pid(fd_file(f));
919 if (IS_ERR(ptr: pid))
920 return PTR_ERR(ptr: pid);
921
922 return pidfd_getfd(pid, fd);
923}
924