1 // SPDX-License-Identifier: GPL-2.0-only
2 #include "cgroup-internal.h"
3 
4 #include <linux/ctype.h>
5 #include <linux/kmod.h>
6 #include <linux/sort.h>
7 #include <linux/delay.h>
8 #include <linux/mm.h>
9 #include <linux/sched/signal.h>
10 #include <linux/sched/task.h>
11 #include <linux/magic.h>
12 #include <linux/slab.h>
13 #include <linux/vmalloc.h>
14 #include <linux/delayacct.h>
15 #include <linux/pid_namespace.h>
16 #include <linux/cgroupstats.h>
17 #include <linux/fs_parser.h>
18 
19 #include <trace/events/cgroup.h>
20 
21 /*
22  * pidlists linger the following amount before being destroyed.  The goal
23  * is avoiding frequent destruction in the middle of consecutive read calls
24  * Expiring in the middle is a performance problem not a correctness one.
25  * 1 sec should be enough.
26  */
27 #define CGROUP_PIDLIST_DESTROY_DELAY	HZ
28 
29 /* Controllers blocked by the commandline in v1 */
30 static u16 cgroup_no_v1_mask;
31 
32 /* disable named v1 mounts */
33 static bool cgroup_no_v1_named;
34 
35 /*
36  * pidlist destructions need to be flushed on cgroup destruction.  Use a
37  * separate workqueue as flush domain.
38  */
39 static struct workqueue_struct *cgroup_pidlist_destroy_wq;
40 
41 /* protects cgroup_subsys->release_agent_path */
42 static DEFINE_SPINLOCK(release_agent_path_lock);
43 
cgroup1_ssid_disabled(int ssid)44 bool cgroup1_ssid_disabled(int ssid)
45 {
46 	return cgroup_no_v1_mask & (1 << ssid);
47 }
48 
49 /**
50  * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
51  * @from: attach to all cgroups of a given task
52  * @tsk: the task to be attached
53  *
54  * Return: %0 on success or a negative errno code on failure
55  */
cgroup_attach_task_all(struct task_struct * from,struct task_struct * tsk)56 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
57 {
58 	struct cgroup_root *root;
59 	int retval = 0;
60 
61 	cgroup_lock();
62 	cgroup_attach_lock(true);
63 	for_each_root(root) {
64 		struct cgroup *from_cgrp;
65 
66 		spin_lock_irq(&css_set_lock);
67 		from_cgrp = task_cgroup_from_root(from, root);
68 		spin_unlock_irq(&css_set_lock);
69 
70 		retval = cgroup_attach_task(from_cgrp, tsk, false);
71 		if (retval)
72 			break;
73 	}
74 	cgroup_attach_unlock(true);
75 	cgroup_unlock();
76 
77 	return retval;
78 }
79 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
80 
81 /**
82  * cgroup_transfer_tasks - move tasks from one cgroup to another
83  * @to: cgroup to which the tasks will be moved
84  * @from: cgroup in which the tasks currently reside
85  *
86  * Locking rules between cgroup_post_fork() and the migration path
87  * guarantee that, if a task is forking while being migrated, the new child
88  * is guaranteed to be either visible in the source cgroup after the
89  * parent's migration is complete or put into the target cgroup.  No task
90  * can slip out of migration through forking.
91  *
92  * Return: %0 on success or a negative errno code on failure
93  */
cgroup_transfer_tasks(struct cgroup * to,struct cgroup * from)94 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
95 {
96 	DEFINE_CGROUP_MGCTX(mgctx);
97 	struct cgrp_cset_link *link;
98 	struct css_task_iter it;
99 	struct task_struct *task;
100 	int ret;
101 
102 	if (cgroup_on_dfl(to))
103 		return -EINVAL;
104 
105 	ret = cgroup_migrate_vet_dst(to);
106 	if (ret)
107 		return ret;
108 
109 	cgroup_lock();
110 
111 	cgroup_attach_lock(true);
112 
113 	/* all tasks in @from are being moved, all csets are source */
114 	spin_lock_irq(&css_set_lock);
115 	list_for_each_entry(link, &from->cset_links, cset_link)
116 		cgroup_migrate_add_src(link->cset, to, &mgctx);
117 	spin_unlock_irq(&css_set_lock);
118 
119 	ret = cgroup_migrate_prepare_dst(&mgctx);
120 	if (ret)
121 		goto out_err;
122 
123 	/*
124 	 * Migrate tasks one-by-one until @from is empty.  This fails iff
125 	 * ->can_attach() fails.
126 	 */
127 	do {
128 		css_task_iter_start(&from->self, 0, &it);
129 
130 		do {
131 			task = css_task_iter_next(&it);
132 		} while (task && (task->flags & PF_EXITING));
133 
134 		if (task)
135 			get_task_struct(task);
136 		css_task_iter_end(&it);
137 
138 		if (task) {
139 			ret = cgroup_migrate(task, false, &mgctx);
140 			if (!ret)
141 				TRACE_CGROUP_PATH(transfer_tasks, to, task, false);
142 			put_task_struct(task);
143 		}
144 	} while (task && !ret);
145 out_err:
146 	cgroup_migrate_finish(&mgctx);
147 	cgroup_attach_unlock(true);
148 	cgroup_unlock();
149 	return ret;
150 }
151 
152 /*
153  * Stuff for reading the 'tasks'/'procs' files.
154  *
155  * Reading this file can return large amounts of data if a cgroup has
156  * *lots* of attached tasks. So it may need several calls to read(),
157  * but we cannot guarantee that the information we produce is correct
158  * unless we produce it entirely atomically.
159  *
160  */
161 
162 /* which pidlist file are we talking about? */
163 enum cgroup_filetype {
164 	CGROUP_FILE_PROCS,
165 	CGROUP_FILE_TASKS,
166 };
167 
168 /*
169  * A pidlist is a list of pids that virtually represents the contents of one
170  * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
171  * a pair (one each for procs, tasks) for each pid namespace that's relevant
172  * to the cgroup.
173  */
174 struct cgroup_pidlist {
175 	/*
176 	 * used to find which pidlist is wanted. doesn't change as long as
177 	 * this particular list stays in the list.
178 	*/
179 	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
180 	/* array of xids */
181 	pid_t *list;
182 	/* how many elements the above list has */
183 	int length;
184 	/* each of these stored in a list by its cgroup */
185 	struct list_head links;
186 	/* pointer to the cgroup we belong to, for list removal purposes */
187 	struct cgroup *owner;
188 	/* for delayed destruction */
189 	struct delayed_work destroy_dwork;
190 };
191 
192 /*
193  * Used to destroy all pidlists lingering waiting for destroy timer.  None
194  * should be left afterwards.
195  */
cgroup1_pidlist_destroy_all(struct cgroup * cgrp)196 void cgroup1_pidlist_destroy_all(struct cgroup *cgrp)
197 {
198 	struct cgroup_pidlist *l, *tmp_l;
199 
200 	mutex_lock(&cgrp->pidlist_mutex);
201 	list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
202 		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
203 	mutex_unlock(&cgrp->pidlist_mutex);
204 
205 	flush_workqueue(cgroup_pidlist_destroy_wq);
206 	BUG_ON(!list_empty(&cgrp->pidlists));
207 }
208 
cgroup_pidlist_destroy_work_fn(struct work_struct * work)209 static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
210 {
211 	struct delayed_work *dwork = to_delayed_work(work);
212 	struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
213 						destroy_dwork);
214 	struct cgroup_pidlist *tofree = NULL;
215 
216 	mutex_lock(&l->owner->pidlist_mutex);
217 
218 	/*
219 	 * Destroy iff we didn't get queued again.  The state won't change
220 	 * as destroy_dwork can only be queued while locked.
221 	 */
222 	if (!delayed_work_pending(dwork)) {
223 		list_del(&l->links);
224 		kvfree(l->list);
225 		put_pid_ns(l->key.ns);
226 		tofree = l;
227 	}
228 
229 	mutex_unlock(&l->owner->pidlist_mutex);
230 	kfree(tofree);
231 }
232 
233 /*
234  * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
235  * Returns the number of unique elements.
236  */
pidlist_uniq(pid_t * list,int length)237 static int pidlist_uniq(pid_t *list, int length)
238 {
239 	int src, dest = 1;
240 
241 	/*
242 	 * we presume the 0th element is unique, so i starts at 1. trivial
243 	 * edge cases first; no work needs to be done for either
244 	 */
245 	if (length == 0 || length == 1)
246 		return length;
247 	/* src and dest walk down the list; dest counts unique elements */
248 	for (src = 1; src < length; src++) {
249 		/* find next unique element */
250 		while (list[src] == list[src-1]) {
251 			src++;
252 			if (src == length)
253 				goto after;
254 		}
255 		/* dest always points to where the next unique element goes */
256 		list[dest] = list[src];
257 		dest++;
258 	}
259 after:
260 	return dest;
261 }
262 
263 /*
264  * The two pid files - task and cgroup.procs - guaranteed that the result
265  * is sorted, which forced this whole pidlist fiasco.  As pid order is
266  * different per namespace, each namespace needs differently sorted list,
267  * making it impossible to use, for example, single rbtree of member tasks
268  * sorted by task pointer.  As pidlists can be fairly large, allocating one
269  * per open file is dangerous, so cgroup had to implement shared pool of
270  * pidlists keyed by cgroup and namespace.
271  */
cmppid(const void * a,const void * b)272 static int cmppid(const void *a, const void *b)
273 {
274 	return *(pid_t *)a - *(pid_t *)b;
275 }
276 
cgroup_pidlist_find(struct cgroup * cgrp,enum cgroup_filetype type)277 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
278 						  enum cgroup_filetype type)
279 {
280 	struct cgroup_pidlist *l;
281 	/* don't need task_nsproxy() if we're looking at ourself */
282 	struct pid_namespace *ns = task_active_pid_ns(current);
283 
284 	lockdep_assert_held(&cgrp->pidlist_mutex);
285 
286 	list_for_each_entry(l, &cgrp->pidlists, links)
287 		if (l->key.type == type && l->key.ns == ns)
288 			return l;
289 	return NULL;
290 }
291 
292 /*
293  * find the appropriate pidlist for our purpose (given procs vs tasks)
294  * returns with the lock on that pidlist already held, and takes care
295  * of the use count, or returns NULL with no locks held if we're out of
296  * memory.
297  */
cgroup_pidlist_find_create(struct cgroup * cgrp,enum cgroup_filetype type)298 static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
299 						enum cgroup_filetype type)
300 {
301 	struct cgroup_pidlist *l;
302 
303 	lockdep_assert_held(&cgrp->pidlist_mutex);
304 
305 	l = cgroup_pidlist_find(cgrp, type);
306 	if (l)
307 		return l;
308 
309 	/* entry not found; create a new one */
310 	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
311 	if (!l)
312 		return l;
313 
314 	INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
315 	l->key.type = type;
316 	/* don't need task_nsproxy() if we're looking at ourself */
317 	l->key.ns = get_pid_ns(task_active_pid_ns(current));
318 	l->owner = cgrp;
319 	list_add(&l->links, &cgrp->pidlists);
320 	return l;
321 }
322 
323 /*
324  * Load a cgroup's pidarray with either procs' tgids or tasks' pids
325  */
pidlist_array_load(struct cgroup * cgrp,enum cgroup_filetype type,struct cgroup_pidlist ** lp)326 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
327 			      struct cgroup_pidlist **lp)
328 {
329 	pid_t *array;
330 	int length;
331 	int pid, n = 0; /* used for populating the array */
332 	struct css_task_iter it;
333 	struct task_struct *tsk;
334 	struct cgroup_pidlist *l;
335 
336 	lockdep_assert_held(&cgrp->pidlist_mutex);
337 
338 	/*
339 	 * If cgroup gets more users after we read count, we won't have
340 	 * enough space - tough.  This race is indistinguishable to the
341 	 * caller from the case that the additional cgroup users didn't
342 	 * show up until sometime later on.
343 	 */
344 	length = cgroup_task_count(cgrp);
345 	array = kvmalloc_array(length, sizeof(pid_t), GFP_KERNEL);
346 	if (!array)
347 		return -ENOMEM;
348 	/* now, populate the array */
349 	css_task_iter_start(&cgrp->self, 0, &it);
350 	while ((tsk = css_task_iter_next(&it))) {
351 		if (unlikely(n == length))
352 			break;
353 		/* get tgid or pid for procs or tasks file respectively */
354 		if (type == CGROUP_FILE_PROCS)
355 			pid = task_tgid_vnr(tsk);
356 		else
357 			pid = task_pid_vnr(tsk);
358 		if (pid > 0) /* make sure to only use valid results */
359 			array[n++] = pid;
360 	}
361 	css_task_iter_end(&it);
362 	length = n;
363 	/* now sort & strip out duplicates (tgids or recycled thread PIDs) */
364 	sort(array, length, sizeof(pid_t), cmppid, NULL);
365 	length = pidlist_uniq(array, length);
366 
367 	l = cgroup_pidlist_find_create(cgrp, type);
368 	if (!l) {
369 		kvfree(array);
370 		return -ENOMEM;
371 	}
372 
373 	/* store array, freeing old if necessary */
374 	kvfree(l->list);
375 	l->list = array;
376 	l->length = length;
377 	*lp = l;
378 	return 0;
379 }
380 
381 /*
382  * seq_file methods for the tasks/procs files. The seq_file position is the
383  * next pid to display; the seq_file iterator is a pointer to the pid
384  * in the cgroup->l->list array.
385  */
386 
cgroup_pidlist_start(struct seq_file * s,loff_t * pos)387 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
388 {
389 	/*
390 	 * Initially we receive a position value that corresponds to
391 	 * one more than the last pid shown (or 0 on the first call or
392 	 * after a seek to the start). Use a binary-search to find the
393 	 * next pid to display, if any
394 	 */
395 	struct kernfs_open_file *of = s->private;
396 	struct cgroup_file_ctx *ctx = of->priv;
397 	struct cgroup *cgrp = seq_css(s)->cgroup;
398 	struct cgroup_pidlist *l;
399 	enum cgroup_filetype type = seq_cft(s)->private;
400 	int index = 0, pid = *pos;
401 	int *iter, ret;
402 
403 	mutex_lock(&cgrp->pidlist_mutex);
404 
405 	/*
406 	 * !NULL @ctx->procs1.pidlist indicates that this isn't the first
407 	 * start() after open. If the matching pidlist is around, we can use
408 	 * that. Look for it. Note that @ctx->procs1.pidlist can't be used
409 	 * directly. It could already have been destroyed.
410 	 */
411 	if (ctx->procs1.pidlist)
412 		ctx->procs1.pidlist = cgroup_pidlist_find(cgrp, type);
413 
414 	/*
415 	 * Either this is the first start() after open or the matching
416 	 * pidlist has been destroyed inbetween.  Create a new one.
417 	 */
418 	if (!ctx->procs1.pidlist) {
419 		ret = pidlist_array_load(cgrp, type, &ctx->procs1.pidlist);
420 		if (ret)
421 			return ERR_PTR(ret);
422 	}
423 	l = ctx->procs1.pidlist;
424 
425 	if (pid) {
426 		int end = l->length;
427 
428 		while (index < end) {
429 			int mid = (index + end) / 2;
430 			if (l->list[mid] == pid) {
431 				index = mid;
432 				break;
433 			} else if (l->list[mid] < pid)
434 				index = mid + 1;
435 			else
436 				end = mid;
437 		}
438 	}
439 	/* If we're off the end of the array, we're done */
440 	if (index >= l->length)
441 		return NULL;
442 	/* Update the abstract position to be the actual pid that we found */
443 	iter = l->list + index;
444 	*pos = *iter;
445 	return iter;
446 }
447 
cgroup_pidlist_stop(struct seq_file * s,void * v)448 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
449 {
450 	struct kernfs_open_file *of = s->private;
451 	struct cgroup_file_ctx *ctx = of->priv;
452 	struct cgroup_pidlist *l = ctx->procs1.pidlist;
453 
454 	if (l)
455 		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
456 				 CGROUP_PIDLIST_DESTROY_DELAY);
457 	mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
458 }
459 
cgroup_pidlist_next(struct seq_file * s,void * v,loff_t * pos)460 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
461 {
462 	struct kernfs_open_file *of = s->private;
463 	struct cgroup_file_ctx *ctx = of->priv;
464 	struct cgroup_pidlist *l = ctx->procs1.pidlist;
465 	pid_t *p = v;
466 	pid_t *end = l->list + l->length;
467 	/*
468 	 * Advance to the next pid in the array. If this goes off the
469 	 * end, we're done
470 	 */
471 	p++;
472 	if (p >= end) {
473 		(*pos)++;
474 		return NULL;
475 	} else {
476 		*pos = *p;
477 		return p;
478 	}
479 }
480 
cgroup_pidlist_show(struct seq_file * s,void * v)481 static int cgroup_pidlist_show(struct seq_file *s, void *v)
482 {
483 	seq_printf(s, "%d\n", *(int *)v);
484 
485 	return 0;
486 }
487 
__cgroup1_procs_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off,bool threadgroup)488 static ssize_t __cgroup1_procs_write(struct kernfs_open_file *of,
489 				     char *buf, size_t nbytes, loff_t off,
490 				     bool threadgroup)
491 {
492 	struct cgroup *cgrp;
493 	struct task_struct *task;
494 	const struct cred *cred, *tcred;
495 	ssize_t ret;
496 	bool locked;
497 
498 	cgrp = cgroup_kn_lock_live(of->kn, false);
499 	if (!cgrp)
500 		return -ENODEV;
501 
502 	task = cgroup_procs_write_start(buf, threadgroup, &locked);
503 	ret = PTR_ERR_OR_ZERO(task);
504 	if (ret)
505 		goto out_unlock;
506 
507 	/*
508 	 * Even if we're attaching all tasks in the thread group, we only need
509 	 * to check permissions on one of them. Check permissions using the
510 	 * credentials from file open to protect against inherited fd attacks.
511 	 */
512 	cred = of->file->f_cred;
513 	tcred = get_task_cred(task);
514 	if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
515 	    !uid_eq(cred->euid, tcred->uid) &&
516 	    !uid_eq(cred->euid, tcred->suid))
517 		ret = -EACCES;
518 	put_cred(tcred);
519 	if (ret)
520 		goto out_finish;
521 
522 	ret = cgroup_attach_task(cgrp, task, threadgroup);
523 
524 out_finish:
525 	cgroup_procs_write_finish(task, locked);
526 out_unlock:
527 	cgroup_kn_unlock(of->kn);
528 
529 	return ret ?: nbytes;
530 }
531 
cgroup1_procs_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)532 static ssize_t cgroup1_procs_write(struct kernfs_open_file *of,
533 				   char *buf, size_t nbytes, loff_t off)
534 {
535 	return __cgroup1_procs_write(of, buf, nbytes, off, true);
536 }
537 
cgroup1_tasks_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)538 static ssize_t cgroup1_tasks_write(struct kernfs_open_file *of,
539 				   char *buf, size_t nbytes, loff_t off)
540 {
541 	return __cgroup1_procs_write(of, buf, nbytes, off, false);
542 }
543 
cgroup_release_agent_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)544 static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
545 					  char *buf, size_t nbytes, loff_t off)
546 {
547 	struct cgroup *cgrp;
548 	struct cgroup_file_ctx *ctx;
549 
550 	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
551 
552 	/*
553 	 * Release agent gets called with all capabilities,
554 	 * require capabilities to set release agent.
555 	 */
556 	ctx = of->priv;
557 	if ((ctx->ns->user_ns != &init_user_ns) ||
558 	    !file_ns_capable(of->file, &init_user_ns, CAP_SYS_ADMIN))
559 		return -EPERM;
560 
561 	cgrp = cgroup_kn_lock_live(of->kn, false);
562 	if (!cgrp)
563 		return -ENODEV;
564 	spin_lock(&release_agent_path_lock);
565 	strscpy(cgrp->root->release_agent_path, strstrip(buf),
566 		sizeof(cgrp->root->release_agent_path));
567 	spin_unlock(&release_agent_path_lock);
568 	cgroup_kn_unlock(of->kn);
569 	return nbytes;
570 }
571 
cgroup_release_agent_show(struct seq_file * seq,void * v)572 static int cgroup_release_agent_show(struct seq_file *seq, void *v)
573 {
574 	struct cgroup *cgrp = seq_css(seq)->cgroup;
575 
576 	spin_lock(&release_agent_path_lock);
577 	seq_puts(seq, cgrp->root->release_agent_path);
578 	spin_unlock(&release_agent_path_lock);
579 	seq_putc(seq, '\n');
580 	return 0;
581 }
582 
cgroup_sane_behavior_show(struct seq_file * seq,void * v)583 static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
584 {
585 	seq_puts(seq, "0\n");
586 	return 0;
587 }
588 
cgroup_read_notify_on_release(struct cgroup_subsys_state * css,struct cftype * cft)589 static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
590 					 struct cftype *cft)
591 {
592 	return notify_on_release(css->cgroup);
593 }
594 
cgroup_write_notify_on_release(struct cgroup_subsys_state * css,struct cftype * cft,u64 val)595 static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
596 					  struct cftype *cft, u64 val)
597 {
598 	if (val)
599 		set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
600 	else
601 		clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
602 	return 0;
603 }
604 
cgroup_clone_children_read(struct cgroup_subsys_state * css,struct cftype * cft)605 static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
606 				      struct cftype *cft)
607 {
608 	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
609 }
610 
cgroup_clone_children_write(struct cgroup_subsys_state * css,struct cftype * cft,u64 val)611 static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
612 				       struct cftype *cft, u64 val)
613 {
614 	if (val)
615 		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
616 	else
617 		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
618 	return 0;
619 }
620 
621 /* cgroup core interface files for the legacy hierarchies */
622 struct cftype cgroup1_base_files[] = {
623 	{
624 		.name = "cgroup.procs",
625 		.seq_start = cgroup_pidlist_start,
626 		.seq_next = cgroup_pidlist_next,
627 		.seq_stop = cgroup_pidlist_stop,
628 		.seq_show = cgroup_pidlist_show,
629 		.private = CGROUP_FILE_PROCS,
630 		.write = cgroup1_procs_write,
631 	},
632 	{
633 		.name = "cgroup.clone_children",
634 		.read_u64 = cgroup_clone_children_read,
635 		.write_u64 = cgroup_clone_children_write,
636 	},
637 	{
638 		.name = "cgroup.sane_behavior",
639 		.flags = CFTYPE_ONLY_ON_ROOT,
640 		.seq_show = cgroup_sane_behavior_show,
641 	},
642 	{
643 		.name = "tasks",
644 		.seq_start = cgroup_pidlist_start,
645 		.seq_next = cgroup_pidlist_next,
646 		.seq_stop = cgroup_pidlist_stop,
647 		.seq_show = cgroup_pidlist_show,
648 		.private = CGROUP_FILE_TASKS,
649 		.write = cgroup1_tasks_write,
650 	},
651 	{
652 		.name = "notify_on_release",
653 		.read_u64 = cgroup_read_notify_on_release,
654 		.write_u64 = cgroup_write_notify_on_release,
655 	},
656 	{
657 		.name = "release_agent",
658 		.flags = CFTYPE_ONLY_ON_ROOT,
659 		.seq_show = cgroup_release_agent_show,
660 		.write = cgroup_release_agent_write,
661 		.max_write_len = PATH_MAX - 1,
662 	},
663 	{ }	/* terminate */
664 };
665 
666 /* Display information about each subsystem and each hierarchy */
proc_cgroupstats_show(struct seq_file * m,void * v)667 int proc_cgroupstats_show(struct seq_file *m, void *v)
668 {
669 	struct cgroup_subsys *ss;
670 	int i;
671 
672 	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
673 	/*
674 	 * Grab the subsystems state racily. No need to add avenue to
675 	 * cgroup_mutex contention.
676 	 */
677 
678 	for_each_subsys(ss, i)
679 		seq_printf(m, "%s\t%d\t%d\t%d\n",
680 			   ss->legacy_name, ss->root->hierarchy_id,
681 			   atomic_read(&ss->root->nr_cgrps),
682 			   cgroup_ssid_enabled(i));
683 
684 	return 0;
685 }
686 
687 /**
688  * cgroupstats_build - build and fill cgroupstats
689  * @stats: cgroupstats to fill information into
690  * @dentry: A dentry entry belonging to the cgroup for which stats have
691  * been requested.
692  *
693  * Build and fill cgroupstats so that taskstats can export it to user
694  * space.
695  *
696  * Return: %0 on success or a negative errno code on failure
697  */
cgroupstats_build(struct cgroupstats * stats,struct dentry * dentry)698 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
699 {
700 	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
701 	struct cgroup *cgrp;
702 	struct css_task_iter it;
703 	struct task_struct *tsk;
704 
705 	/* it should be kernfs_node belonging to cgroupfs and is a directory */
706 	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
707 	    kernfs_type(kn) != KERNFS_DIR)
708 		return -EINVAL;
709 
710 	/*
711 	 * We aren't being called from kernfs and there's no guarantee on
712 	 * @kn->priv's validity.  For this and css_tryget_online_from_dir(),
713 	 * @kn->priv is RCU safe.  Let's do the RCU dancing.
714 	 */
715 	rcu_read_lock();
716 	cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
717 	if (!cgrp || !cgroup_tryget(cgrp)) {
718 		rcu_read_unlock();
719 		return -ENOENT;
720 	}
721 	rcu_read_unlock();
722 
723 	css_task_iter_start(&cgrp->self, 0, &it);
724 	while ((tsk = css_task_iter_next(&it))) {
725 		switch (READ_ONCE(tsk->__state)) {
726 		case TASK_RUNNING:
727 			stats->nr_running++;
728 			break;
729 		case TASK_INTERRUPTIBLE:
730 			stats->nr_sleeping++;
731 			break;
732 		case TASK_UNINTERRUPTIBLE:
733 			stats->nr_uninterruptible++;
734 			break;
735 		case TASK_STOPPED:
736 			stats->nr_stopped++;
737 			break;
738 		default:
739 			if (tsk->in_iowait)
740 				stats->nr_io_wait++;
741 			break;
742 		}
743 	}
744 	css_task_iter_end(&it);
745 
746 	cgroup_put(cgrp);
747 	return 0;
748 }
749 
cgroup1_check_for_release(struct cgroup * cgrp)750 void cgroup1_check_for_release(struct cgroup *cgrp)
751 {
752 	if (notify_on_release(cgrp) && !cgroup_is_populated(cgrp) &&
753 	    !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
754 		schedule_work(&cgrp->release_agent_work);
755 }
756 
757 /*
758  * Notify userspace when a cgroup is released, by running the
759  * configured release agent with the name of the cgroup (path
760  * relative to the root of cgroup file system) as the argument.
761  *
762  * Most likely, this user command will try to rmdir this cgroup.
763  *
764  * This races with the possibility that some other task will be
765  * attached to this cgroup before it is removed, or that some other
766  * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
767  * The presumed 'rmdir' will fail quietly if this cgroup is no longer
768  * unused, and this cgroup will be reprieved from its death sentence,
769  * to continue to serve a useful existence.  Next time it's released,
770  * we will get notified again, if it still has 'notify_on_release' set.
771  *
772  * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
773  * means only wait until the task is successfully execve()'d.  The
774  * separate release agent task is forked by call_usermodehelper(),
775  * then control in this thread returns here, without waiting for the
776  * release agent task.  We don't bother to wait because the caller of
777  * this routine has no use for the exit status of the release agent
778  * task, so no sense holding our caller up for that.
779  */
cgroup1_release_agent(struct work_struct * work)780 void cgroup1_release_agent(struct work_struct *work)
781 {
782 	struct cgroup *cgrp =
783 		container_of(work, struct cgroup, release_agent_work);
784 	char *pathbuf, *agentbuf;
785 	char *argv[3], *envp[3];
786 	int ret;
787 
788 	/* snoop agent path and exit early if empty */
789 	if (!cgrp->root->release_agent_path[0])
790 		return;
791 
792 	/* prepare argument buffers */
793 	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
794 	agentbuf = kmalloc(PATH_MAX, GFP_KERNEL);
795 	if (!pathbuf || !agentbuf)
796 		goto out_free;
797 
798 	spin_lock(&release_agent_path_lock);
799 	strscpy(agentbuf, cgrp->root->release_agent_path, PATH_MAX);
800 	spin_unlock(&release_agent_path_lock);
801 	if (!agentbuf[0])
802 		goto out_free;
803 
804 	ret = cgroup_path_ns(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
805 	if (ret < 0 || ret >= PATH_MAX)
806 		goto out_free;
807 
808 	argv[0] = agentbuf;
809 	argv[1] = pathbuf;
810 	argv[2] = NULL;
811 
812 	/* minimal command environment */
813 	envp[0] = "HOME=/";
814 	envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
815 	envp[2] = NULL;
816 
817 	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
818 out_free:
819 	kfree(agentbuf);
820 	kfree(pathbuf);
821 }
822 
823 /*
824  * cgroup_rename - Only allow simple rename of directories in place.
825  */
cgroup1_rename(struct kernfs_node * kn,struct kernfs_node * new_parent,const char * new_name_str)826 static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
827 			  const char *new_name_str)
828 {
829 	struct cgroup *cgrp = kn->priv;
830 	int ret;
831 
832 	/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
833 	if (strchr(new_name_str, '\n'))
834 		return -EINVAL;
835 
836 	if (kernfs_type(kn) != KERNFS_DIR)
837 		return -ENOTDIR;
838 	if (kn->parent != new_parent)
839 		return -EIO;
840 
841 	/*
842 	 * We're gonna grab cgroup_mutex which nests outside kernfs
843 	 * active_ref.  kernfs_rename() doesn't require active_ref
844 	 * protection.  Break them before grabbing cgroup_mutex.
845 	 */
846 	kernfs_break_active_protection(new_parent);
847 	kernfs_break_active_protection(kn);
848 
849 	cgroup_lock();
850 
851 	ret = kernfs_rename(kn, new_parent, new_name_str);
852 	if (!ret)
853 		TRACE_CGROUP_PATH(rename, cgrp);
854 
855 	cgroup_unlock();
856 
857 	kernfs_unbreak_active_protection(kn);
858 	kernfs_unbreak_active_protection(new_parent);
859 	return ret;
860 }
861 
cgroup1_show_options(struct seq_file * seq,struct kernfs_root * kf_root)862 static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
863 {
864 	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
865 	struct cgroup_subsys *ss;
866 	int ssid;
867 
868 	for_each_subsys(ss, ssid)
869 		if (root->subsys_mask & (1 << ssid))
870 			seq_show_option(seq, ss->legacy_name, NULL);
871 	if (root->flags & CGRP_ROOT_NOPREFIX)
872 		seq_puts(seq, ",noprefix");
873 	if (root->flags & CGRP_ROOT_XATTR)
874 		seq_puts(seq, ",xattr");
875 	if (root->flags & CGRP_ROOT_CPUSET_V2_MODE)
876 		seq_puts(seq, ",cpuset_v2_mode");
877 	if (root->flags & CGRP_ROOT_FAVOR_DYNMODS)
878 		seq_puts(seq, ",favordynmods");
879 
880 	spin_lock(&release_agent_path_lock);
881 	if (strlen(root->release_agent_path))
882 		seq_show_option(seq, "release_agent",
883 				root->release_agent_path);
884 	spin_unlock(&release_agent_path_lock);
885 
886 	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
887 		seq_puts(seq, ",clone_children");
888 	if (strlen(root->name))
889 		seq_show_option(seq, "name", root->name);
890 	return 0;
891 }
892 
893 enum cgroup1_param {
894 	Opt_all,
895 	Opt_clone_children,
896 	Opt_cpuset_v2_mode,
897 	Opt_name,
898 	Opt_none,
899 	Opt_noprefix,
900 	Opt_release_agent,
901 	Opt_xattr,
902 	Opt_favordynmods,
903 	Opt_nofavordynmods,
904 };
905 
906 const struct fs_parameter_spec cgroup1_fs_parameters[] = {
907 	fsparam_flag  ("all",		Opt_all),
908 	fsparam_flag  ("clone_children", Opt_clone_children),
909 	fsparam_flag  ("cpuset_v2_mode", Opt_cpuset_v2_mode),
910 	fsparam_string("name",		Opt_name),
911 	fsparam_flag  ("none",		Opt_none),
912 	fsparam_flag  ("noprefix",	Opt_noprefix),
913 	fsparam_string("release_agent",	Opt_release_agent),
914 	fsparam_flag  ("xattr",		Opt_xattr),
915 	fsparam_flag  ("favordynmods",	Opt_favordynmods),
916 	fsparam_flag  ("nofavordynmods", Opt_nofavordynmods),
917 	{}
918 };
919 
cgroup1_parse_param(struct fs_context * fc,struct fs_parameter * param)920 int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param)
921 {
922 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
923 	struct cgroup_subsys *ss;
924 	struct fs_parse_result result;
925 	int opt, i;
926 
927 	opt = fs_parse(fc, cgroup1_fs_parameters, param, &result);
928 	if (opt == -ENOPARAM) {
929 		int ret;
930 
931 		ret = vfs_parse_fs_param_source(fc, param);
932 		if (ret != -ENOPARAM)
933 			return ret;
934 		for_each_subsys(ss, i) {
935 			if (strcmp(param->key, ss->legacy_name))
936 				continue;
937 			if (!cgroup_ssid_enabled(i) || cgroup1_ssid_disabled(i))
938 				return invalfc(fc, "Disabled controller '%s'",
939 					       param->key);
940 			ctx->subsys_mask |= (1 << i);
941 			return 0;
942 		}
943 		return invalfc(fc, "Unknown subsys name '%s'", param->key);
944 	}
945 	if (opt < 0)
946 		return opt;
947 
948 	switch (opt) {
949 	case Opt_none:
950 		/* Explicitly have no subsystems */
951 		ctx->none = true;
952 		break;
953 	case Opt_all:
954 		ctx->all_ss = true;
955 		break;
956 	case Opt_noprefix:
957 		ctx->flags |= CGRP_ROOT_NOPREFIX;
958 		break;
959 	case Opt_clone_children:
960 		ctx->cpuset_clone_children = true;
961 		break;
962 	case Opt_cpuset_v2_mode:
963 		ctx->flags |= CGRP_ROOT_CPUSET_V2_MODE;
964 		break;
965 	case Opt_xattr:
966 		ctx->flags |= CGRP_ROOT_XATTR;
967 		break;
968 	case Opt_favordynmods:
969 		ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
970 		break;
971 	case Opt_nofavordynmods:
972 		ctx->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
973 		break;
974 	case Opt_release_agent:
975 		/* Specifying two release agents is forbidden */
976 		if (ctx->release_agent)
977 			return invalfc(fc, "release_agent respecified");
978 		/*
979 		 * Release agent gets called with all capabilities,
980 		 * require capabilities to set release agent.
981 		 */
982 		if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))
983 			return invalfc(fc, "Setting release_agent not allowed");
984 		ctx->release_agent = param->string;
985 		param->string = NULL;
986 		break;
987 	case Opt_name:
988 		/* blocked by boot param? */
989 		if (cgroup_no_v1_named)
990 			return -ENOENT;
991 		/* Can't specify an empty name */
992 		if (!param->size)
993 			return invalfc(fc, "Empty name");
994 		if (param->size > MAX_CGROUP_ROOT_NAMELEN - 1)
995 			return invalfc(fc, "Name too long");
996 		/* Must match [\w.-]+ */
997 		for (i = 0; i < param->size; i++) {
998 			char c = param->string[i];
999 			if (isalnum(c))
1000 				continue;
1001 			if ((c == '.') || (c == '-') || (c == '_'))
1002 				continue;
1003 			return invalfc(fc, "Invalid name");
1004 		}
1005 		/* Specifying two names is forbidden */
1006 		if (ctx->name)
1007 			return invalfc(fc, "name respecified");
1008 		ctx->name = param->string;
1009 		param->string = NULL;
1010 		break;
1011 	}
1012 	return 0;
1013 }
1014 
check_cgroupfs_options(struct fs_context * fc)1015 static int check_cgroupfs_options(struct fs_context *fc)
1016 {
1017 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1018 	u16 mask = U16_MAX;
1019 	u16 enabled = 0;
1020 	struct cgroup_subsys *ss;
1021 	int i;
1022 
1023 #ifdef CONFIG_CPUSETS
1024 	mask = ~((u16)1 << cpuset_cgrp_id);
1025 #endif
1026 	for_each_subsys(ss, i)
1027 		if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i))
1028 			enabled |= 1 << i;
1029 
1030 	ctx->subsys_mask &= enabled;
1031 
1032 	/*
1033 	 * In absence of 'none', 'name=' and subsystem name options,
1034 	 * let's default to 'all'.
1035 	 */
1036 	if (!ctx->subsys_mask && !ctx->none && !ctx->name)
1037 		ctx->all_ss = true;
1038 
1039 	if (ctx->all_ss) {
1040 		/* Mutually exclusive option 'all' + subsystem name */
1041 		if (ctx->subsys_mask)
1042 			return invalfc(fc, "subsys name conflicts with all");
1043 		/* 'all' => select all the subsystems */
1044 		ctx->subsys_mask = enabled;
1045 	}
1046 
1047 	/*
1048 	 * We either have to specify by name or by subsystems. (So all
1049 	 * empty hierarchies must have a name).
1050 	 */
1051 	if (!ctx->subsys_mask && !ctx->name)
1052 		return invalfc(fc, "Need name or subsystem set");
1053 
1054 	/*
1055 	 * Option noprefix was introduced just for backward compatibility
1056 	 * with the old cpuset, so we allow noprefix only if mounting just
1057 	 * the cpuset subsystem.
1058 	 */
1059 	if ((ctx->flags & CGRP_ROOT_NOPREFIX) && (ctx->subsys_mask & mask))
1060 		return invalfc(fc, "noprefix used incorrectly");
1061 
1062 	/* Can't specify "none" and some subsystems */
1063 	if (ctx->subsys_mask && ctx->none)
1064 		return invalfc(fc, "none used incorrectly");
1065 
1066 	return 0;
1067 }
1068 
cgroup1_reconfigure(struct fs_context * fc)1069 int cgroup1_reconfigure(struct fs_context *fc)
1070 {
1071 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1072 	struct kernfs_root *kf_root = kernfs_root_from_sb(fc->root->d_sb);
1073 	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1074 	int ret = 0;
1075 	u16 added_mask, removed_mask;
1076 
1077 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1078 
1079 	/* See what subsystems are wanted */
1080 	ret = check_cgroupfs_options(fc);
1081 	if (ret)
1082 		goto out_unlock;
1083 
1084 	if (ctx->subsys_mask != root->subsys_mask || ctx->release_agent)
1085 		pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1086 			task_tgid_nr(current), current->comm);
1087 
1088 	added_mask = ctx->subsys_mask & ~root->subsys_mask;
1089 	removed_mask = root->subsys_mask & ~ctx->subsys_mask;
1090 
1091 	/* Don't allow flags or name to change at remount */
1092 	if ((ctx->flags ^ root->flags) ||
1093 	    (ctx->name && strcmp(ctx->name, root->name))) {
1094 		errorfc(fc, "option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"",
1095 		       ctx->flags, ctx->name ?: "", root->flags, root->name);
1096 		ret = -EINVAL;
1097 		goto out_unlock;
1098 	}
1099 
1100 	/* remounting is not allowed for populated hierarchies */
1101 	if (!list_empty(&root->cgrp.self.children)) {
1102 		ret = -EBUSY;
1103 		goto out_unlock;
1104 	}
1105 
1106 	ret = rebind_subsystems(root, added_mask);
1107 	if (ret)
1108 		goto out_unlock;
1109 
1110 	WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));
1111 
1112 	if (ctx->release_agent) {
1113 		spin_lock(&release_agent_path_lock);
1114 		strcpy(root->release_agent_path, ctx->release_agent);
1115 		spin_unlock(&release_agent_path_lock);
1116 	}
1117 
1118 	trace_cgroup_remount(root);
1119 
1120  out_unlock:
1121 	cgroup_unlock();
1122 	return ret;
1123 }
1124 
1125 struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
1126 	.rename			= cgroup1_rename,
1127 	.show_options		= cgroup1_show_options,
1128 	.mkdir			= cgroup_mkdir,
1129 	.rmdir			= cgroup_rmdir,
1130 	.show_path		= cgroup_show_path,
1131 };
1132 
1133 /*
1134  * The guts of cgroup1 mount - find or create cgroup_root to use.
1135  * Called with cgroup_mutex held; returns 0 on success, -E... on
1136  * error and positive - in case when the candidate is busy dying.
1137  * On success it stashes a reference to cgroup_root into given
1138  * cgroup_fs_context; that reference is *NOT* counting towards the
1139  * cgroup_root refcount.
1140  */
cgroup1_root_to_use(struct fs_context * fc)1141 static int cgroup1_root_to_use(struct fs_context *fc)
1142 {
1143 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1144 	struct cgroup_root *root;
1145 	struct cgroup_subsys *ss;
1146 	int i, ret;
1147 
1148 	/* First find the desired set of subsystems */
1149 	ret = check_cgroupfs_options(fc);
1150 	if (ret)
1151 		return ret;
1152 
1153 	/*
1154 	 * Destruction of cgroup root is asynchronous, so subsystems may
1155 	 * still be dying after the previous unmount.  Let's drain the
1156 	 * dying subsystems.  We just need to ensure that the ones
1157 	 * unmounted previously finish dying and don't care about new ones
1158 	 * starting.  Testing ref liveliness is good enough.
1159 	 */
1160 	for_each_subsys(ss, i) {
1161 		if (!(ctx->subsys_mask & (1 << i)) ||
1162 		    ss->root == &cgrp_dfl_root)
1163 			continue;
1164 
1165 		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt))
1166 			return 1;	/* restart */
1167 		cgroup_put(&ss->root->cgrp);
1168 	}
1169 
1170 	for_each_root(root) {
1171 		bool name_match = false;
1172 
1173 		if (root == &cgrp_dfl_root)
1174 			continue;
1175 
1176 		/*
1177 		 * If we asked for a name then it must match.  Also, if
1178 		 * name matches but sybsys_mask doesn't, we should fail.
1179 		 * Remember whether name matched.
1180 		 */
1181 		if (ctx->name) {
1182 			if (strcmp(ctx->name, root->name))
1183 				continue;
1184 			name_match = true;
1185 		}
1186 
1187 		/*
1188 		 * If we asked for subsystems (or explicitly for no
1189 		 * subsystems) then they must match.
1190 		 */
1191 		if ((ctx->subsys_mask || ctx->none) &&
1192 		    (ctx->subsys_mask != root->subsys_mask)) {
1193 			if (!name_match)
1194 				continue;
1195 			return -EBUSY;
1196 		}
1197 
1198 		if (root->flags ^ ctx->flags)
1199 			pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1200 
1201 		ctx->root = root;
1202 		return 0;
1203 	}
1204 
1205 	/*
1206 	 * No such thing, create a new one.  name= matching without subsys
1207 	 * specification is allowed for already existing hierarchies but we
1208 	 * can't create new one without subsys specification.
1209 	 */
1210 	if (!ctx->subsys_mask && !ctx->none)
1211 		return invalfc(fc, "No subsys list or none specified");
1212 
1213 	/* Hierarchies may only be created in the initial cgroup namespace. */
1214 	if (ctx->ns != &init_cgroup_ns)
1215 		return -EPERM;
1216 
1217 	root = kzalloc(sizeof(*root), GFP_KERNEL);
1218 	if (!root)
1219 		return -ENOMEM;
1220 
1221 	ctx->root = root;
1222 	init_cgroup_root(ctx);
1223 
1224 	ret = cgroup_setup_root(root, ctx->subsys_mask);
1225 	if (!ret)
1226 		cgroup_favor_dynmods(root, ctx->flags & CGRP_ROOT_FAVOR_DYNMODS);
1227 	else
1228 		cgroup_free_root(root);
1229 
1230 	return ret;
1231 }
1232 
cgroup1_get_tree(struct fs_context * fc)1233 int cgroup1_get_tree(struct fs_context *fc)
1234 {
1235 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1236 	int ret;
1237 
1238 	/* Check if the caller has permission to mount. */
1239 	if (!ns_capable(ctx->ns->user_ns, CAP_SYS_ADMIN))
1240 		return -EPERM;
1241 
1242 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1243 
1244 	ret = cgroup1_root_to_use(fc);
1245 	if (!ret && !percpu_ref_tryget_live(&ctx->root->cgrp.self.refcnt))
1246 		ret = 1;	/* restart */
1247 
1248 	cgroup_unlock();
1249 
1250 	if (!ret)
1251 		ret = cgroup_do_get_tree(fc);
1252 
1253 	if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) {
1254 		fc_drop_locked(fc);
1255 		ret = 1;
1256 	}
1257 
1258 	if (unlikely(ret > 0)) {
1259 		msleep(10);
1260 		return restart_syscall();
1261 	}
1262 	return ret;
1263 }
1264 
cgroup1_wq_init(void)1265 static int __init cgroup1_wq_init(void)
1266 {
1267 	/*
1268 	 * Used to destroy pidlists and separate to serve as flush domain.
1269 	 * Cap @max_active to 1 too.
1270 	 */
1271 	cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
1272 						    0, 1);
1273 	BUG_ON(!cgroup_pidlist_destroy_wq);
1274 	return 0;
1275 }
1276 core_initcall(cgroup1_wq_init);
1277 
cgroup_no_v1(char * str)1278 static int __init cgroup_no_v1(char *str)
1279 {
1280 	struct cgroup_subsys *ss;
1281 	char *token;
1282 	int i;
1283 
1284 	while ((token = strsep(&str, ",")) != NULL) {
1285 		if (!*token)
1286 			continue;
1287 
1288 		if (!strcmp(token, "all")) {
1289 			cgroup_no_v1_mask = U16_MAX;
1290 			continue;
1291 		}
1292 
1293 		if (!strcmp(token, "named")) {
1294 			cgroup_no_v1_named = true;
1295 			continue;
1296 		}
1297 
1298 		for_each_subsys(ss, i) {
1299 			if (strcmp(token, ss->name) &&
1300 			    strcmp(token, ss->legacy_name))
1301 				continue;
1302 
1303 			cgroup_no_v1_mask |= 1 << i;
1304 		}
1305 	}
1306 	return 1;
1307 }
1308 __setup("cgroup_no_v1=", cgroup_no_v1);
1309