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 
cgroup1_subsys_absent(struct cgroup_subsys * ss)49 static bool cgroup1_subsys_absent(struct cgroup_subsys *ss)
50 {
51 	/* Check also dfl_cftypes for file-less controllers, i.e. perf_event */
52 	return ss->legacy_cftypes == NULL && ss->dfl_cftypes;
53 }
54 
55 /**
56  * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'
57  * @from: attach to all cgroups of a given task
58  * @tsk: the task to be attached
59  *
60  * Return: %0 on success or a negative errno code on failure
61  */
cgroup_attach_task_all(struct task_struct * from,struct task_struct * tsk)62 int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)
63 {
64 	struct cgroup_root *root;
65 	int retval = 0;
66 
67 	cgroup_lock();
68 	cgroup_attach_lock(true);
69 	for_each_root(root) {
70 		struct cgroup *from_cgrp;
71 
72 		spin_lock_irq(&css_set_lock);
73 		from_cgrp = task_cgroup_from_root(from, root);
74 		spin_unlock_irq(&css_set_lock);
75 
76 		retval = cgroup_attach_task(from_cgrp, tsk, false);
77 		if (retval)
78 			break;
79 	}
80 	cgroup_attach_unlock(true);
81 	cgroup_unlock();
82 
83 	return retval;
84 }
85 EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
86 
87 /**
88  * cgroup_transfer_tasks - move tasks from one cgroup to another
89  * @to: cgroup to which the tasks will be moved
90  * @from: cgroup in which the tasks currently reside
91  *
92  * Locking rules between cgroup_post_fork() and the migration path
93  * guarantee that, if a task is forking while being migrated, the new child
94  * is guaranteed to be either visible in the source cgroup after the
95  * parent's migration is complete or put into the target cgroup.  No task
96  * can slip out of migration through forking.
97  *
98  * Return: %0 on success or a negative errno code on failure
99  */
cgroup_transfer_tasks(struct cgroup * to,struct cgroup * from)100 int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
101 {
102 	DEFINE_CGROUP_MGCTX(mgctx);
103 	struct cgrp_cset_link *link;
104 	struct css_task_iter it;
105 	struct task_struct *task;
106 	int ret;
107 
108 	if (cgroup_on_dfl(to))
109 		return -EINVAL;
110 
111 	ret = cgroup_migrate_vet_dst(to);
112 	if (ret)
113 		return ret;
114 
115 	cgroup_lock();
116 
117 	cgroup_attach_lock(true);
118 
119 	/* all tasks in @from are being moved, all csets are source */
120 	spin_lock_irq(&css_set_lock);
121 	list_for_each_entry(link, &from->cset_links, cset_link)
122 		cgroup_migrate_add_src(link->cset, to, &mgctx);
123 	spin_unlock_irq(&css_set_lock);
124 
125 	ret = cgroup_migrate_prepare_dst(&mgctx);
126 	if (ret)
127 		goto out_err;
128 
129 	/*
130 	 * Migrate tasks one-by-one until @from is empty.  This fails iff
131 	 * ->can_attach() fails.
132 	 */
133 	do {
134 		css_task_iter_start(&from->self, 0, &it);
135 
136 		do {
137 			task = css_task_iter_next(&it);
138 		} while (task && (task->flags & PF_EXITING));
139 
140 		if (task)
141 			get_task_struct(task);
142 		css_task_iter_end(&it);
143 
144 		if (task) {
145 			ret = cgroup_migrate(task, false, &mgctx);
146 			if (!ret)
147 				TRACE_CGROUP_PATH(transfer_tasks, to, task, false);
148 			put_task_struct(task);
149 		}
150 	} while (task && !ret);
151 out_err:
152 	cgroup_migrate_finish(&mgctx);
153 	cgroup_attach_unlock(true);
154 	cgroup_unlock();
155 	return ret;
156 }
157 
158 /*
159  * Stuff for reading the 'tasks'/'procs' files.
160  *
161  * Reading this file can return large amounts of data if a cgroup has
162  * *lots* of attached tasks. So it may need several calls to read(),
163  * but we cannot guarantee that the information we produce is correct
164  * unless we produce it entirely atomically.
165  *
166  */
167 
168 /* which pidlist file are we talking about? */
169 enum cgroup_filetype {
170 	CGROUP_FILE_PROCS,
171 	CGROUP_FILE_TASKS,
172 };
173 
174 /*
175  * A pidlist is a list of pids that virtually represents the contents of one
176  * of the cgroup files ("procs" or "tasks"). We keep a list of such pidlists,
177  * a pair (one each for procs, tasks) for each pid namespace that's relevant
178  * to the cgroup.
179  */
180 struct cgroup_pidlist {
181 	/*
182 	 * used to find which pidlist is wanted. doesn't change as long as
183 	 * this particular list stays in the list.
184 	*/
185 	struct { enum cgroup_filetype type; struct pid_namespace *ns; } key;
186 	/* array of xids */
187 	pid_t *list;
188 	/* how many elements the above list has */
189 	int length;
190 	/* each of these stored in a list by its cgroup */
191 	struct list_head links;
192 	/* pointer to the cgroup we belong to, for list removal purposes */
193 	struct cgroup *owner;
194 	/* for delayed destruction */
195 	struct delayed_work destroy_dwork;
196 };
197 
198 /*
199  * Used to destroy all pidlists lingering waiting for destroy timer.  None
200  * should be left afterwards.
201  */
cgroup1_pidlist_destroy_all(struct cgroup * cgrp)202 void cgroup1_pidlist_destroy_all(struct cgroup *cgrp)
203 {
204 	struct cgroup_pidlist *l, *tmp_l;
205 
206 	mutex_lock(&cgrp->pidlist_mutex);
207 	list_for_each_entry_safe(l, tmp_l, &cgrp->pidlists, links)
208 		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork, 0);
209 	mutex_unlock(&cgrp->pidlist_mutex);
210 
211 	flush_workqueue(cgroup_pidlist_destroy_wq);
212 	BUG_ON(!list_empty(&cgrp->pidlists));
213 }
214 
cgroup_pidlist_destroy_work_fn(struct work_struct * work)215 static void cgroup_pidlist_destroy_work_fn(struct work_struct *work)
216 {
217 	struct delayed_work *dwork = to_delayed_work(work);
218 	struct cgroup_pidlist *l = container_of(dwork, struct cgroup_pidlist,
219 						destroy_dwork);
220 	struct cgroup_pidlist *tofree = NULL;
221 
222 	mutex_lock(&l->owner->pidlist_mutex);
223 
224 	/*
225 	 * Destroy iff we didn't get queued again.  The state won't change
226 	 * as destroy_dwork can only be queued while locked.
227 	 */
228 	if (!delayed_work_pending(dwork)) {
229 		list_del(&l->links);
230 		kvfree(l->list);
231 		put_pid_ns(l->key.ns);
232 		tofree = l;
233 	}
234 
235 	mutex_unlock(&l->owner->pidlist_mutex);
236 	kfree(tofree);
237 }
238 
239 /*
240  * pidlist_uniq - given a kmalloc()ed list, strip out all duplicate entries
241  * Returns the number of unique elements.
242  */
pidlist_uniq(pid_t * list,int length)243 static int pidlist_uniq(pid_t *list, int length)
244 {
245 	int src, dest = 1;
246 
247 	/*
248 	 * we presume the 0th element is unique, so i starts at 1. trivial
249 	 * edge cases first; no work needs to be done for either
250 	 */
251 	if (length == 0 || length == 1)
252 		return length;
253 	/* src and dest walk down the list; dest counts unique elements */
254 	for (src = 1; src < length; src++) {
255 		/* find next unique element */
256 		while (list[src] == list[src-1]) {
257 			src++;
258 			if (src == length)
259 				goto after;
260 		}
261 		/* dest always points to where the next unique element goes */
262 		list[dest] = list[src];
263 		dest++;
264 	}
265 after:
266 	return dest;
267 }
268 
269 /*
270  * The two pid files - task and cgroup.procs - guaranteed that the result
271  * is sorted, which forced this whole pidlist fiasco.  As pid order is
272  * different per namespace, each namespace needs differently sorted list,
273  * making it impossible to use, for example, single rbtree of member tasks
274  * sorted by task pointer.  As pidlists can be fairly large, allocating one
275  * per open file is dangerous, so cgroup had to implement shared pool of
276  * pidlists keyed by cgroup and namespace.
277  */
cmppid(const void * a,const void * b)278 static int cmppid(const void *a, const void *b)
279 {
280 	return *(pid_t *)a - *(pid_t *)b;
281 }
282 
cgroup_pidlist_find(struct cgroup * cgrp,enum cgroup_filetype type)283 static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
284 						  enum cgroup_filetype type)
285 {
286 	struct cgroup_pidlist *l;
287 	/* don't need task_nsproxy() if we're looking at ourself */
288 	struct pid_namespace *ns = task_active_pid_ns(current);
289 
290 	lockdep_assert_held(&cgrp->pidlist_mutex);
291 
292 	list_for_each_entry(l, &cgrp->pidlists, links)
293 		if (l->key.type == type && l->key.ns == ns)
294 			return l;
295 	return NULL;
296 }
297 
298 /*
299  * find the appropriate pidlist for our purpose (given procs vs tasks)
300  * returns with the lock on that pidlist already held, and takes care
301  * of the use count, or returns NULL with no locks held if we're out of
302  * memory.
303  */
cgroup_pidlist_find_create(struct cgroup * cgrp,enum cgroup_filetype type)304 static struct cgroup_pidlist *cgroup_pidlist_find_create(struct cgroup *cgrp,
305 						enum cgroup_filetype type)
306 {
307 	struct cgroup_pidlist *l;
308 
309 	lockdep_assert_held(&cgrp->pidlist_mutex);
310 
311 	l = cgroup_pidlist_find(cgrp, type);
312 	if (l)
313 		return l;
314 
315 	/* entry not found; create a new one */
316 	l = kzalloc(sizeof(struct cgroup_pidlist), GFP_KERNEL);
317 	if (!l)
318 		return l;
319 
320 	INIT_DELAYED_WORK(&l->destroy_dwork, cgroup_pidlist_destroy_work_fn);
321 	l->key.type = type;
322 	/* don't need task_nsproxy() if we're looking at ourself */
323 	l->key.ns = get_pid_ns(task_active_pid_ns(current));
324 	l->owner = cgrp;
325 	list_add(&l->links, &cgrp->pidlists);
326 	return l;
327 }
328 
329 /*
330  * Load a cgroup's pidarray with either procs' tgids or tasks' pids
331  */
pidlist_array_load(struct cgroup * cgrp,enum cgroup_filetype type,struct cgroup_pidlist ** lp)332 static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
333 			      struct cgroup_pidlist **lp)
334 {
335 	pid_t *array;
336 	int length;
337 	int pid, n = 0; /* used for populating the array */
338 	struct css_task_iter it;
339 	struct task_struct *tsk;
340 	struct cgroup_pidlist *l;
341 
342 	lockdep_assert_held(&cgrp->pidlist_mutex);
343 
344 	/*
345 	 * If cgroup gets more users after we read count, we won't have
346 	 * enough space - tough.  This race is indistinguishable to the
347 	 * caller from the case that the additional cgroup users didn't
348 	 * show up until sometime later on.
349 	 */
350 	length = cgroup_task_count(cgrp);
351 	array = kvmalloc_array(length, sizeof(pid_t), GFP_KERNEL);
352 	if (!array)
353 		return -ENOMEM;
354 	/* now, populate the array */
355 	css_task_iter_start(&cgrp->self, 0, &it);
356 	while ((tsk = css_task_iter_next(&it))) {
357 		if (unlikely(n == length))
358 			break;
359 		/* get tgid or pid for procs or tasks file respectively */
360 		if (type == CGROUP_FILE_PROCS)
361 			pid = task_tgid_vnr(tsk);
362 		else
363 			pid = task_pid_vnr(tsk);
364 		if (pid > 0) /* make sure to only use valid results */
365 			array[n++] = pid;
366 	}
367 	css_task_iter_end(&it);
368 	length = n;
369 	/* now sort & strip out duplicates (tgids or recycled thread PIDs) */
370 	sort(array, length, sizeof(pid_t), cmppid, NULL);
371 	length = pidlist_uniq(array, length);
372 
373 	l = cgroup_pidlist_find_create(cgrp, type);
374 	if (!l) {
375 		kvfree(array);
376 		return -ENOMEM;
377 	}
378 
379 	/* store array, freeing old if necessary */
380 	kvfree(l->list);
381 	l->list = array;
382 	l->length = length;
383 	*lp = l;
384 	return 0;
385 }
386 
387 /*
388  * seq_file methods for the tasks/procs files. The seq_file position is the
389  * next pid to display; the seq_file iterator is a pointer to the pid
390  * in the cgroup->l->list array.
391  */
392 
cgroup_pidlist_start(struct seq_file * s,loff_t * pos)393 static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
394 {
395 	/*
396 	 * Initially we receive a position value that corresponds to
397 	 * one more than the last pid shown (or 0 on the first call or
398 	 * after a seek to the start). Use a binary-search to find the
399 	 * next pid to display, if any
400 	 */
401 	struct kernfs_open_file *of = s->private;
402 	struct cgroup_file_ctx *ctx = of->priv;
403 	struct cgroup *cgrp = seq_css(s)->cgroup;
404 	struct cgroup_pidlist *l;
405 	enum cgroup_filetype type = seq_cft(s)->private;
406 	int index = 0, pid = *pos;
407 	int *iter, ret;
408 
409 	mutex_lock(&cgrp->pidlist_mutex);
410 
411 	/*
412 	 * !NULL @ctx->procs1.pidlist indicates that this isn't the first
413 	 * start() after open. If the matching pidlist is around, we can use
414 	 * that. Look for it. Note that @ctx->procs1.pidlist can't be used
415 	 * directly. It could already have been destroyed.
416 	 */
417 	if (ctx->procs1.pidlist)
418 		ctx->procs1.pidlist = cgroup_pidlist_find(cgrp, type);
419 
420 	/*
421 	 * Either this is the first start() after open or the matching
422 	 * pidlist has been destroyed inbetween.  Create a new one.
423 	 */
424 	if (!ctx->procs1.pidlist) {
425 		ret = pidlist_array_load(cgrp, type, &ctx->procs1.pidlist);
426 		if (ret)
427 			return ERR_PTR(ret);
428 	}
429 	l = ctx->procs1.pidlist;
430 
431 	if (pid) {
432 		int end = l->length;
433 
434 		while (index < end) {
435 			int mid = (index + end) / 2;
436 			if (l->list[mid] == pid) {
437 				index = mid;
438 				break;
439 			} else if (l->list[mid] < pid)
440 				index = mid + 1;
441 			else
442 				end = mid;
443 		}
444 	}
445 	/* If we're off the end of the array, we're done */
446 	if (index >= l->length)
447 		return NULL;
448 	/* Update the abstract position to be the actual pid that we found */
449 	iter = l->list + index;
450 	*pos = *iter;
451 	return iter;
452 }
453 
cgroup_pidlist_stop(struct seq_file * s,void * v)454 static void cgroup_pidlist_stop(struct seq_file *s, void *v)
455 {
456 	struct kernfs_open_file *of = s->private;
457 	struct cgroup_file_ctx *ctx = of->priv;
458 	struct cgroup_pidlist *l = ctx->procs1.pidlist;
459 
460 	if (l)
461 		mod_delayed_work(cgroup_pidlist_destroy_wq, &l->destroy_dwork,
462 				 CGROUP_PIDLIST_DESTROY_DELAY);
463 	mutex_unlock(&seq_css(s)->cgroup->pidlist_mutex);
464 }
465 
cgroup_pidlist_next(struct seq_file * s,void * v,loff_t * pos)466 static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
467 {
468 	struct kernfs_open_file *of = s->private;
469 	struct cgroup_file_ctx *ctx = of->priv;
470 	struct cgroup_pidlist *l = ctx->procs1.pidlist;
471 	pid_t *p = v;
472 	pid_t *end = l->list + l->length;
473 	/*
474 	 * Advance to the next pid in the array. If this goes off the
475 	 * end, we're done
476 	 */
477 	p++;
478 	if (p >= end) {
479 		(*pos)++;
480 		return NULL;
481 	} else {
482 		*pos = *p;
483 		return p;
484 	}
485 }
486 
cgroup_pidlist_show(struct seq_file * s,void * v)487 static int cgroup_pidlist_show(struct seq_file *s, void *v)
488 {
489 	seq_printf(s, "%d\n", *(int *)v);
490 
491 	return 0;
492 }
493 
__cgroup1_procs_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off,bool threadgroup)494 static ssize_t __cgroup1_procs_write(struct kernfs_open_file *of,
495 				     char *buf, size_t nbytes, loff_t off,
496 				     bool threadgroup)
497 {
498 	struct cgroup *cgrp;
499 	struct task_struct *task;
500 	const struct cred *cred, *tcred;
501 	ssize_t ret;
502 	bool locked;
503 
504 	cgrp = cgroup_kn_lock_live(of->kn, false);
505 	if (!cgrp)
506 		return -ENODEV;
507 
508 	task = cgroup_procs_write_start(buf, threadgroup, &locked);
509 	ret = PTR_ERR_OR_ZERO(task);
510 	if (ret)
511 		goto out_unlock;
512 
513 	/*
514 	 * Even if we're attaching all tasks in the thread group, we only need
515 	 * to check permissions on one of them. Check permissions using the
516 	 * credentials from file open to protect against inherited fd attacks.
517 	 */
518 	cred = of->file->f_cred;
519 	tcred = get_task_cred(task);
520 	if (!uid_eq(cred->euid, GLOBAL_ROOT_UID) &&
521 	    !uid_eq(cred->euid, tcred->uid) &&
522 	    !uid_eq(cred->euid, tcred->suid))
523 		ret = -EACCES;
524 	put_cred(tcred);
525 	if (ret)
526 		goto out_finish;
527 
528 	ret = cgroup_attach_task(cgrp, task, threadgroup);
529 
530 out_finish:
531 	cgroup_procs_write_finish(task, locked);
532 out_unlock:
533 	cgroup_kn_unlock(of->kn);
534 
535 	return ret ?: nbytes;
536 }
537 
cgroup1_procs_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)538 static ssize_t cgroup1_procs_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, true);
542 }
543 
cgroup1_tasks_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)544 static ssize_t cgroup1_tasks_write(struct kernfs_open_file *of,
545 				   char *buf, size_t nbytes, loff_t off)
546 {
547 	return __cgroup1_procs_write(of, buf, nbytes, off, false);
548 }
549 
cgroup_release_agent_write(struct kernfs_open_file * of,char * buf,size_t nbytes,loff_t off)550 static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
551 					  char *buf, size_t nbytes, loff_t off)
552 {
553 	struct cgroup *cgrp;
554 	struct cgroup_file_ctx *ctx;
555 
556 	BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX);
557 
558 	/*
559 	 * Release agent gets called with all capabilities,
560 	 * require capabilities to set release agent.
561 	 */
562 	ctx = of->priv;
563 	if ((ctx->ns->user_ns != &init_user_ns) ||
564 	    !file_ns_capable(of->file, &init_user_ns, CAP_SYS_ADMIN))
565 		return -EPERM;
566 
567 	cgrp = cgroup_kn_lock_live(of->kn, false);
568 	if (!cgrp)
569 		return -ENODEV;
570 	spin_lock(&release_agent_path_lock);
571 	strscpy(cgrp->root->release_agent_path, strstrip(buf),
572 		sizeof(cgrp->root->release_agent_path));
573 	spin_unlock(&release_agent_path_lock);
574 	cgroup_kn_unlock(of->kn);
575 	return nbytes;
576 }
577 
cgroup_release_agent_show(struct seq_file * seq,void * v)578 static int cgroup_release_agent_show(struct seq_file *seq, void *v)
579 {
580 	struct cgroup *cgrp = seq_css(seq)->cgroup;
581 
582 	spin_lock(&release_agent_path_lock);
583 	seq_puts(seq, cgrp->root->release_agent_path);
584 	spin_unlock(&release_agent_path_lock);
585 	seq_putc(seq, '\n');
586 	return 0;
587 }
588 
cgroup_sane_behavior_show(struct seq_file * seq,void * v)589 static int cgroup_sane_behavior_show(struct seq_file *seq, void *v)
590 {
591 	seq_puts(seq, "0\n");
592 	return 0;
593 }
594 
cgroup_read_notify_on_release(struct cgroup_subsys_state * css,struct cftype * cft)595 static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
596 					 struct cftype *cft)
597 {
598 	return notify_on_release(css->cgroup);
599 }
600 
cgroup_write_notify_on_release(struct cgroup_subsys_state * css,struct cftype * cft,u64 val)601 static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
602 					  struct cftype *cft, u64 val)
603 {
604 	if (val)
605 		set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
606 	else
607 		clear_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
608 	return 0;
609 }
610 
cgroup_clone_children_read(struct cgroup_subsys_state * css,struct cftype * cft)611 static u64 cgroup_clone_children_read(struct cgroup_subsys_state *css,
612 				      struct cftype *cft)
613 {
614 	return test_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
615 }
616 
cgroup_clone_children_write(struct cgroup_subsys_state * css,struct cftype * cft,u64 val)617 static int cgroup_clone_children_write(struct cgroup_subsys_state *css,
618 				       struct cftype *cft, u64 val)
619 {
620 	if (val)
621 		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
622 	else
623 		clear_bit(CGRP_CPUSET_CLONE_CHILDREN, &css->cgroup->flags);
624 	return 0;
625 }
626 
627 /* cgroup core interface files for the legacy hierarchies */
628 struct cftype cgroup1_base_files[] = {
629 	{
630 		.name = "cgroup.procs",
631 		.seq_start = cgroup_pidlist_start,
632 		.seq_next = cgroup_pidlist_next,
633 		.seq_stop = cgroup_pidlist_stop,
634 		.seq_show = cgroup_pidlist_show,
635 		.private = CGROUP_FILE_PROCS,
636 		.write = cgroup1_procs_write,
637 	},
638 	{
639 		.name = "cgroup.clone_children",
640 		.read_u64 = cgroup_clone_children_read,
641 		.write_u64 = cgroup_clone_children_write,
642 	},
643 	{
644 		.name = "cgroup.sane_behavior",
645 		.flags = CFTYPE_ONLY_ON_ROOT,
646 		.seq_show = cgroup_sane_behavior_show,
647 	},
648 	{
649 		.name = "tasks",
650 		.seq_start = cgroup_pidlist_start,
651 		.seq_next = cgroup_pidlist_next,
652 		.seq_stop = cgroup_pidlist_stop,
653 		.seq_show = cgroup_pidlist_show,
654 		.private = CGROUP_FILE_TASKS,
655 		.write = cgroup1_tasks_write,
656 	},
657 	{
658 		.name = "notify_on_release",
659 		.read_u64 = cgroup_read_notify_on_release,
660 		.write_u64 = cgroup_write_notify_on_release,
661 	},
662 	{
663 		.name = "release_agent",
664 		.flags = CFTYPE_ONLY_ON_ROOT,
665 		.seq_show = cgroup_release_agent_show,
666 		.write = cgroup_release_agent_write,
667 		.max_write_len = PATH_MAX - 1,
668 	},
669 	{ }	/* terminate */
670 };
671 
672 /* Display information about each subsystem and each hierarchy */
proc_cgroupstats_show(struct seq_file * m,void * v)673 int proc_cgroupstats_show(struct seq_file *m, void *v)
674 {
675 	struct cgroup_subsys *ss;
676 	bool cgrp_v1_visible = false;
677 	int i;
678 
679 	seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
680 	/*
681 	 * Grab the subsystems state racily. No need to add avenue to
682 	 * cgroup_mutex contention.
683 	 */
684 
685 	for_each_subsys(ss, i) {
686 		if (cgroup1_subsys_absent(ss))
687 			continue;
688 		cgrp_v1_visible |= ss->root != &cgrp_dfl_root;
689 
690 		seq_printf(m, "%s\t%d\t%d\t%d\n",
691 			   ss->legacy_name, ss->root->hierarchy_id,
692 			   atomic_read(&ss->root->nr_cgrps),
693 			   cgroup_ssid_enabled(i));
694 	}
695 
696 	if (cgrp_dfl_visible && !cgrp_v1_visible)
697 		pr_info_once("/proc/cgroups lists only v1 controllers, use cgroup.controllers of root cgroup for v2 info\n");
698 
699 
700 	return 0;
701 }
702 
703 /**
704  * cgroupstats_build - build and fill cgroupstats
705  * @stats: cgroupstats to fill information into
706  * @dentry: A dentry entry belonging to the cgroup for which stats have
707  * been requested.
708  *
709  * Build and fill cgroupstats so that taskstats can export it to user
710  * space.
711  *
712  * Return: %0 on success or a negative errno code on failure
713  */
cgroupstats_build(struct cgroupstats * stats,struct dentry * dentry)714 int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
715 {
716 	struct kernfs_node *kn = kernfs_node_from_dentry(dentry);
717 	struct cgroup *cgrp;
718 	struct css_task_iter it;
719 	struct task_struct *tsk;
720 
721 	/* it should be kernfs_node belonging to cgroupfs and is a directory */
722 	if (dentry->d_sb->s_type != &cgroup_fs_type || !kn ||
723 	    kernfs_type(kn) != KERNFS_DIR)
724 		return -EINVAL;
725 
726 	/*
727 	 * We aren't being called from kernfs and there's no guarantee on
728 	 * @kn->priv's validity.  For this and css_tryget_online_from_dir(),
729 	 * @kn->priv is RCU safe.  Let's do the RCU dancing.
730 	 */
731 	rcu_read_lock();
732 	cgrp = rcu_dereference(*(void __rcu __force **)&kn->priv);
733 	if (!cgrp || !cgroup_tryget(cgrp)) {
734 		rcu_read_unlock();
735 		return -ENOENT;
736 	}
737 	rcu_read_unlock();
738 
739 	css_task_iter_start(&cgrp->self, 0, &it);
740 	while ((tsk = css_task_iter_next(&it))) {
741 		switch (READ_ONCE(tsk->__state)) {
742 		case TASK_RUNNING:
743 			stats->nr_running++;
744 			break;
745 		case TASK_INTERRUPTIBLE:
746 			stats->nr_sleeping++;
747 			break;
748 		case TASK_UNINTERRUPTIBLE:
749 			stats->nr_uninterruptible++;
750 			break;
751 		case TASK_STOPPED:
752 			stats->nr_stopped++;
753 			break;
754 		default:
755 			if (tsk->in_iowait)
756 				stats->nr_io_wait++;
757 			break;
758 		}
759 	}
760 	css_task_iter_end(&it);
761 
762 	cgroup_put(cgrp);
763 	return 0;
764 }
765 
cgroup1_check_for_release(struct cgroup * cgrp)766 void cgroup1_check_for_release(struct cgroup *cgrp)
767 {
768 	if (notify_on_release(cgrp) && !cgroup_is_populated(cgrp) &&
769 	    !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
770 		schedule_work(&cgrp->release_agent_work);
771 }
772 
773 /*
774  * Notify userspace when a cgroup is released, by running the
775  * configured release agent with the name of the cgroup (path
776  * relative to the root of cgroup file system) as the argument.
777  *
778  * Most likely, this user command will try to rmdir this cgroup.
779  *
780  * This races with the possibility that some other task will be
781  * attached to this cgroup before it is removed, or that some other
782  * user task will 'mkdir' a child cgroup of this cgroup.  That's ok.
783  * The presumed 'rmdir' will fail quietly if this cgroup is no longer
784  * unused, and this cgroup will be reprieved from its death sentence,
785  * to continue to serve a useful existence.  Next time it's released,
786  * we will get notified again, if it still has 'notify_on_release' set.
787  *
788  * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which
789  * means only wait until the task is successfully execve()'d.  The
790  * separate release agent task is forked by call_usermodehelper(),
791  * then control in this thread returns here, without waiting for the
792  * release agent task.  We don't bother to wait because the caller of
793  * this routine has no use for the exit status of the release agent
794  * task, so no sense holding our caller up for that.
795  */
cgroup1_release_agent(struct work_struct * work)796 void cgroup1_release_agent(struct work_struct *work)
797 {
798 	struct cgroup *cgrp =
799 		container_of(work, struct cgroup, release_agent_work);
800 	char *pathbuf, *agentbuf;
801 	char *argv[3], *envp[3];
802 	int ret;
803 
804 	/* snoop agent path and exit early if empty */
805 	if (!cgrp->root->release_agent_path[0])
806 		return;
807 
808 	/* prepare argument buffers */
809 	pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
810 	agentbuf = kmalloc(PATH_MAX, GFP_KERNEL);
811 	if (!pathbuf || !agentbuf)
812 		goto out_free;
813 
814 	spin_lock(&release_agent_path_lock);
815 	strscpy(agentbuf, cgrp->root->release_agent_path, PATH_MAX);
816 	spin_unlock(&release_agent_path_lock);
817 	if (!agentbuf[0])
818 		goto out_free;
819 
820 	ret = cgroup_path_ns(cgrp, pathbuf, PATH_MAX, &init_cgroup_ns);
821 	if (ret < 0)
822 		goto out_free;
823 
824 	argv[0] = agentbuf;
825 	argv[1] = pathbuf;
826 	argv[2] = NULL;
827 
828 	/* minimal command environment */
829 	envp[0] = "HOME=/";
830 	envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
831 	envp[2] = NULL;
832 
833 	call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
834 out_free:
835 	kfree(agentbuf);
836 	kfree(pathbuf);
837 }
838 
839 /*
840  * cgroup_rename - Only allow simple rename of directories in place.
841  */
cgroup1_rename(struct kernfs_node * kn,struct kernfs_node * new_parent,const char * new_name_str)842 static int cgroup1_rename(struct kernfs_node *kn, struct kernfs_node *new_parent,
843 			  const char *new_name_str)
844 {
845 	struct cgroup *cgrp = kn->priv;
846 	int ret;
847 
848 	/* do not accept '\n' to prevent making /proc/<pid>/cgroup unparsable */
849 	if (strchr(new_name_str, '\n'))
850 		return -EINVAL;
851 
852 	if (kernfs_type(kn) != KERNFS_DIR)
853 		return -ENOTDIR;
854 	if (rcu_access_pointer(kn->__parent) != new_parent)
855 		return -EIO;
856 
857 	/*
858 	 * We're gonna grab cgroup_mutex which nests outside kernfs
859 	 * active_ref.  kernfs_rename() doesn't require active_ref
860 	 * protection.  Break them before grabbing cgroup_mutex.
861 	 */
862 	kernfs_break_active_protection(new_parent);
863 	kernfs_break_active_protection(kn);
864 
865 	cgroup_lock();
866 
867 	ret = kernfs_rename(kn, new_parent, new_name_str);
868 	if (!ret)
869 		TRACE_CGROUP_PATH(rename, cgrp);
870 
871 	cgroup_unlock();
872 
873 	kernfs_unbreak_active_protection(kn);
874 	kernfs_unbreak_active_protection(new_parent);
875 	return ret;
876 }
877 
cgroup1_show_options(struct seq_file * seq,struct kernfs_root * kf_root)878 static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_root)
879 {
880 	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
881 	struct cgroup_subsys *ss;
882 	int ssid;
883 
884 	for_each_subsys(ss, ssid)
885 		if (root->subsys_mask & (1 << ssid))
886 			seq_show_option(seq, ss->legacy_name, NULL);
887 	if (root->flags & CGRP_ROOT_NOPREFIX)
888 		seq_puts(seq, ",noprefix");
889 	if (root->flags & CGRP_ROOT_XATTR)
890 		seq_puts(seq, ",xattr");
891 	if (root->flags & CGRP_ROOT_CPUSET_V2_MODE)
892 		seq_puts(seq, ",cpuset_v2_mode");
893 	if (root->flags & CGRP_ROOT_FAVOR_DYNMODS)
894 		seq_puts(seq, ",favordynmods");
895 
896 	spin_lock(&release_agent_path_lock);
897 	if (strlen(root->release_agent_path))
898 		seq_show_option(seq, "release_agent",
899 				root->release_agent_path);
900 	spin_unlock(&release_agent_path_lock);
901 
902 	if (test_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags))
903 		seq_puts(seq, ",clone_children");
904 	if (strlen(root->name))
905 		seq_show_option(seq, "name", root->name);
906 	return 0;
907 }
908 
909 enum cgroup1_param {
910 	Opt_all,
911 	Opt_clone_children,
912 	Opt_cpuset_v2_mode,
913 	Opt_name,
914 	Opt_none,
915 	Opt_noprefix,
916 	Opt_release_agent,
917 	Opt_xattr,
918 	Opt_favordynmods,
919 	Opt_nofavordynmods,
920 };
921 
922 const struct fs_parameter_spec cgroup1_fs_parameters[] = {
923 	fsparam_flag  ("all",		Opt_all),
924 	fsparam_flag  ("clone_children", Opt_clone_children),
925 	fsparam_flag  ("cpuset_v2_mode", Opt_cpuset_v2_mode),
926 	fsparam_string("name",		Opt_name),
927 	fsparam_flag  ("none",		Opt_none),
928 	fsparam_flag  ("noprefix",	Opt_noprefix),
929 	fsparam_string("release_agent",	Opt_release_agent),
930 	fsparam_flag  ("xattr",		Opt_xattr),
931 	fsparam_flag  ("favordynmods",	Opt_favordynmods),
932 	fsparam_flag  ("nofavordynmods", Opt_nofavordynmods),
933 	{}
934 };
935 
cgroup1_parse_param(struct fs_context * fc,struct fs_parameter * param)936 int cgroup1_parse_param(struct fs_context *fc, struct fs_parameter *param)
937 {
938 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
939 	struct cgroup_subsys *ss;
940 	struct fs_parse_result result;
941 	int opt, i;
942 
943 	opt = fs_parse(fc, cgroup1_fs_parameters, param, &result);
944 	if (opt == -ENOPARAM) {
945 		int ret;
946 
947 		ret = vfs_parse_fs_param_source(fc, param);
948 		if (ret != -ENOPARAM)
949 			return ret;
950 		for_each_subsys(ss, i) {
951 			if (strcmp(param->key, ss->legacy_name) ||
952 			    cgroup1_subsys_absent(ss))
953 				continue;
954 			if (!cgroup_ssid_enabled(i) || cgroup1_ssid_disabled(i))
955 				return invalfc(fc, "Disabled controller '%s'",
956 					       param->key);
957 			ctx->subsys_mask |= (1 << i);
958 			return 0;
959 		}
960 		return invalfc(fc, "Unknown subsys name '%s'", param->key);
961 	}
962 	if (opt < 0)
963 		return opt;
964 
965 	switch (opt) {
966 	case Opt_none:
967 		/* Explicitly have no subsystems */
968 		ctx->none = true;
969 		break;
970 	case Opt_all:
971 		ctx->all_ss = true;
972 		break;
973 	case Opt_noprefix:
974 		ctx->flags |= CGRP_ROOT_NOPREFIX;
975 		break;
976 	case Opt_clone_children:
977 		ctx->cpuset_clone_children = true;
978 		break;
979 	case Opt_cpuset_v2_mode:
980 		ctx->flags |= CGRP_ROOT_CPUSET_V2_MODE;
981 		break;
982 	case Opt_xattr:
983 		ctx->flags |= CGRP_ROOT_XATTR;
984 		break;
985 	case Opt_favordynmods:
986 		ctx->flags |= CGRP_ROOT_FAVOR_DYNMODS;
987 		break;
988 	case Opt_nofavordynmods:
989 		ctx->flags &= ~CGRP_ROOT_FAVOR_DYNMODS;
990 		break;
991 	case Opt_release_agent:
992 		/* Specifying two release agents is forbidden */
993 		if (ctx->release_agent)
994 			return invalfc(fc, "release_agent respecified");
995 		/*
996 		 * Release agent gets called with all capabilities,
997 		 * require capabilities to set release agent.
998 		 */
999 		if ((fc->user_ns != &init_user_ns) || !capable(CAP_SYS_ADMIN))
1000 			return invalfc(fc, "Setting release_agent not allowed");
1001 		ctx->release_agent = param->string;
1002 		param->string = NULL;
1003 		break;
1004 	case Opt_name:
1005 		/* blocked by boot param? */
1006 		if (cgroup_no_v1_named)
1007 			return -ENOENT;
1008 		/* Can't specify an empty name */
1009 		if (!param->size)
1010 			return invalfc(fc, "Empty name");
1011 		if (param->size > MAX_CGROUP_ROOT_NAMELEN - 1)
1012 			return invalfc(fc, "Name too long");
1013 		/* Must match [\w.-]+ */
1014 		for (i = 0; i < param->size; i++) {
1015 			char c = param->string[i];
1016 			if (isalnum(c))
1017 				continue;
1018 			if ((c == '.') || (c == '-') || (c == '_'))
1019 				continue;
1020 			return invalfc(fc, "Invalid name");
1021 		}
1022 		/* Specifying two names is forbidden */
1023 		if (ctx->name)
1024 			return invalfc(fc, "name respecified");
1025 		ctx->name = param->string;
1026 		param->string = NULL;
1027 		break;
1028 	}
1029 	return 0;
1030 }
1031 
check_cgroupfs_options(struct fs_context * fc)1032 static int check_cgroupfs_options(struct fs_context *fc)
1033 {
1034 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1035 	u16 mask = U16_MAX;
1036 	u16 enabled = 0;
1037 	struct cgroup_subsys *ss;
1038 	int i;
1039 
1040 #ifdef CONFIG_CPUSETS
1041 	mask = ~((u16)1 << cpuset_cgrp_id);
1042 #endif
1043 	for_each_subsys(ss, i)
1044 		if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i) &&
1045 		    !cgroup1_subsys_absent(ss))
1046 			enabled |= 1 << i;
1047 
1048 	ctx->subsys_mask &= enabled;
1049 
1050 	/*
1051 	 * In absence of 'none', 'name=' and subsystem name options,
1052 	 * let's default to 'all'.
1053 	 */
1054 	if (!ctx->subsys_mask && !ctx->none && !ctx->name)
1055 		ctx->all_ss = true;
1056 
1057 	if (ctx->all_ss) {
1058 		/* Mutually exclusive option 'all' + subsystem name */
1059 		if (ctx->subsys_mask)
1060 			return invalfc(fc, "subsys name conflicts with all");
1061 		/* 'all' => select all the subsystems */
1062 		ctx->subsys_mask = enabled;
1063 	}
1064 
1065 	/*
1066 	 * We either have to specify by name or by subsystems. (So all
1067 	 * empty hierarchies must have a name).
1068 	 */
1069 	if (!ctx->subsys_mask && !ctx->name)
1070 		return invalfc(fc, "Need name or subsystem set");
1071 
1072 	/*
1073 	 * Option noprefix was introduced just for backward compatibility
1074 	 * with the old cpuset, so we allow noprefix only if mounting just
1075 	 * the cpuset subsystem.
1076 	 */
1077 	if ((ctx->flags & CGRP_ROOT_NOPREFIX) && (ctx->subsys_mask & mask))
1078 		return invalfc(fc, "noprefix used incorrectly");
1079 
1080 	/* Can't specify "none" and some subsystems */
1081 	if (ctx->subsys_mask && ctx->none)
1082 		return invalfc(fc, "none used incorrectly");
1083 
1084 	return 0;
1085 }
1086 
cgroup1_reconfigure(struct fs_context * fc)1087 int cgroup1_reconfigure(struct fs_context *fc)
1088 {
1089 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1090 	struct kernfs_root *kf_root = kernfs_root_from_sb(fc->root->d_sb);
1091 	struct cgroup_root *root = cgroup_root_from_kf(kf_root);
1092 	int ret = 0;
1093 	u16 added_mask, removed_mask;
1094 
1095 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1096 
1097 	/* See what subsystems are wanted */
1098 	ret = check_cgroupfs_options(fc);
1099 	if (ret)
1100 		goto out_unlock;
1101 
1102 	if (ctx->subsys_mask != root->subsys_mask || ctx->release_agent)
1103 		pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
1104 			task_tgid_nr(current), current->comm);
1105 
1106 	added_mask = ctx->subsys_mask & ~root->subsys_mask;
1107 	removed_mask = root->subsys_mask & ~ctx->subsys_mask;
1108 
1109 	/* Don't allow flags or name to change at remount */
1110 	if ((ctx->flags ^ root->flags) ||
1111 	    (ctx->name && strcmp(ctx->name, root->name))) {
1112 		errorfc(fc, "option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"",
1113 		       ctx->flags, ctx->name ?: "", root->flags, root->name);
1114 		ret = -EINVAL;
1115 		goto out_unlock;
1116 	}
1117 
1118 	/* remounting is not allowed for populated hierarchies */
1119 	if (!list_empty(&root->cgrp.self.children)) {
1120 		ret = -EBUSY;
1121 		goto out_unlock;
1122 	}
1123 
1124 	ret = rebind_subsystems(root, added_mask);
1125 	if (ret)
1126 		goto out_unlock;
1127 
1128 	WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));
1129 
1130 	if (ctx->release_agent) {
1131 		spin_lock(&release_agent_path_lock);
1132 		strcpy(root->release_agent_path, ctx->release_agent);
1133 		spin_unlock(&release_agent_path_lock);
1134 	}
1135 
1136 	trace_cgroup_remount(root);
1137 
1138  out_unlock:
1139 	cgroup_unlock();
1140 	return ret;
1141 }
1142 
1143 struct kernfs_syscall_ops cgroup1_kf_syscall_ops = {
1144 	.rename			= cgroup1_rename,
1145 	.show_options		= cgroup1_show_options,
1146 	.mkdir			= cgroup_mkdir,
1147 	.rmdir			= cgroup_rmdir,
1148 	.show_path		= cgroup_show_path,
1149 };
1150 
1151 /*
1152  * The guts of cgroup1 mount - find or create cgroup_root to use.
1153  * Called with cgroup_mutex held; returns 0 on success, -E... on
1154  * error and positive - in case when the candidate is busy dying.
1155  * On success it stashes a reference to cgroup_root into given
1156  * cgroup_fs_context; that reference is *NOT* counting towards the
1157  * cgroup_root refcount.
1158  */
cgroup1_root_to_use(struct fs_context * fc)1159 static int cgroup1_root_to_use(struct fs_context *fc)
1160 {
1161 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1162 	struct cgroup_root *root;
1163 	struct cgroup_subsys *ss;
1164 	int i, ret;
1165 
1166 	/* First find the desired set of subsystems */
1167 	ret = check_cgroupfs_options(fc);
1168 	if (ret)
1169 		return ret;
1170 
1171 	/*
1172 	 * Destruction of cgroup root is asynchronous, so subsystems may
1173 	 * still be dying after the previous unmount.  Let's drain the
1174 	 * dying subsystems.  We just need to ensure that the ones
1175 	 * unmounted previously finish dying and don't care about new ones
1176 	 * starting.  Testing ref liveliness is good enough.
1177 	 */
1178 	for_each_subsys(ss, i) {
1179 		if (!(ctx->subsys_mask & (1 << i)) ||
1180 		    ss->root == &cgrp_dfl_root)
1181 			continue;
1182 
1183 		if (!percpu_ref_tryget_live(&ss->root->cgrp.self.refcnt))
1184 			return 1;	/* restart */
1185 		cgroup_put(&ss->root->cgrp);
1186 	}
1187 
1188 	for_each_root(root) {
1189 		bool name_match = false;
1190 
1191 		if (root == &cgrp_dfl_root)
1192 			continue;
1193 
1194 		/*
1195 		 * If we asked for a name then it must match.  Also, if
1196 		 * name matches but sybsys_mask doesn't, we should fail.
1197 		 * Remember whether name matched.
1198 		 */
1199 		if (ctx->name) {
1200 			if (strcmp(ctx->name, root->name))
1201 				continue;
1202 			name_match = true;
1203 		}
1204 
1205 		/*
1206 		 * If we asked for subsystems (or explicitly for no
1207 		 * subsystems) then they must match.
1208 		 */
1209 		if ((ctx->subsys_mask || ctx->none) &&
1210 		    (ctx->subsys_mask != root->subsys_mask)) {
1211 			if (!name_match)
1212 				continue;
1213 			return -EBUSY;
1214 		}
1215 
1216 		if (root->flags ^ ctx->flags)
1217 			pr_warn("new mount options do not match the existing superblock, will be ignored\n");
1218 
1219 		ctx->root = root;
1220 		return 0;
1221 	}
1222 
1223 	/*
1224 	 * No such thing, create a new one.  name= matching without subsys
1225 	 * specification is allowed for already existing hierarchies but we
1226 	 * can't create new one without subsys specification.
1227 	 */
1228 	if (!ctx->subsys_mask && !ctx->none)
1229 		return invalfc(fc, "No subsys list or none specified");
1230 
1231 	/* Hierarchies may only be created in the initial cgroup namespace. */
1232 	if (ctx->ns != &init_cgroup_ns)
1233 		return -EPERM;
1234 
1235 	root = kzalloc(sizeof(*root), GFP_KERNEL);
1236 	if (!root)
1237 		return -ENOMEM;
1238 
1239 	ctx->root = root;
1240 	init_cgroup_root(ctx);
1241 
1242 	ret = cgroup_setup_root(root, ctx->subsys_mask);
1243 	if (!ret)
1244 		cgroup_favor_dynmods(root, ctx->flags & CGRP_ROOT_FAVOR_DYNMODS);
1245 	else
1246 		cgroup_free_root(root);
1247 
1248 	return ret;
1249 }
1250 
cgroup1_get_tree(struct fs_context * fc)1251 int cgroup1_get_tree(struct fs_context *fc)
1252 {
1253 	struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
1254 	int ret;
1255 
1256 	/* Check if the caller has permission to mount. */
1257 	if (!ns_capable(ctx->ns->user_ns, CAP_SYS_ADMIN))
1258 		return -EPERM;
1259 
1260 	cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
1261 
1262 	ret = cgroup1_root_to_use(fc);
1263 	if (!ret && !percpu_ref_tryget_live(&ctx->root->cgrp.self.refcnt))
1264 		ret = 1;	/* restart */
1265 
1266 	cgroup_unlock();
1267 
1268 	if (!ret)
1269 		ret = cgroup_do_get_tree(fc);
1270 
1271 	if (!ret && percpu_ref_is_dying(&ctx->root->cgrp.self.refcnt)) {
1272 		fc_drop_locked(fc);
1273 		ret = 1;
1274 	}
1275 
1276 	if (unlikely(ret > 0)) {
1277 		msleep(10);
1278 		return restart_syscall();
1279 	}
1280 	return ret;
1281 }
1282 
1283 /**
1284  * task_get_cgroup1 - Acquires the associated cgroup of a task within a
1285  * specific cgroup1 hierarchy. The cgroup1 hierarchy is identified by its
1286  * hierarchy ID.
1287  * @tsk: The target task
1288  * @hierarchy_id: The ID of a cgroup1 hierarchy
1289  *
1290  * On success, the cgroup is returned. On failure, ERR_PTR is returned.
1291  * We limit it to cgroup1 only.
1292  */
task_get_cgroup1(struct task_struct * tsk,int hierarchy_id)1293 struct cgroup *task_get_cgroup1(struct task_struct *tsk, int hierarchy_id)
1294 {
1295 	struct cgroup *cgrp = ERR_PTR(-ENOENT);
1296 	struct cgroup_root *root;
1297 	unsigned long flags;
1298 
1299 	rcu_read_lock();
1300 	for_each_root(root) {
1301 		/* cgroup1 only*/
1302 		if (root == &cgrp_dfl_root)
1303 			continue;
1304 		if (root->hierarchy_id != hierarchy_id)
1305 			continue;
1306 		spin_lock_irqsave(&css_set_lock, flags);
1307 		cgrp = task_cgroup_from_root(tsk, root);
1308 		if (!cgrp || !cgroup_tryget(cgrp))
1309 			cgrp = ERR_PTR(-ENOENT);
1310 		spin_unlock_irqrestore(&css_set_lock, flags);
1311 		break;
1312 	}
1313 	rcu_read_unlock();
1314 	return cgrp;
1315 }
1316 
cgroup1_wq_init(void)1317 static int __init cgroup1_wq_init(void)
1318 {
1319 	/*
1320 	 * Used to destroy pidlists and separate to serve as flush domain.
1321 	 * Cap @max_active to 1 too.
1322 	 */
1323 	cgroup_pidlist_destroy_wq = alloc_workqueue("cgroup_pidlist_destroy",
1324 						    0, 1);
1325 	BUG_ON(!cgroup_pidlist_destroy_wq);
1326 	return 0;
1327 }
1328 core_initcall(cgroup1_wq_init);
1329 
cgroup_no_v1(char * str)1330 static int __init cgroup_no_v1(char *str)
1331 {
1332 	struct cgroup_subsys *ss;
1333 	char *token;
1334 	int i;
1335 
1336 	while ((token = strsep(&str, ",")) != NULL) {
1337 		if (!*token)
1338 			continue;
1339 
1340 		if (!strcmp(token, "all")) {
1341 			cgroup_no_v1_mask = U16_MAX;
1342 			continue;
1343 		}
1344 
1345 		if (!strcmp(token, "named")) {
1346 			cgroup_no_v1_named = true;
1347 			continue;
1348 		}
1349 
1350 		for_each_subsys(ss, i) {
1351 			if (strcmp(token, ss->name) &&
1352 			    strcmp(token, ss->legacy_name))
1353 				continue;
1354 
1355 			cgroup_no_v1_mask |= 1 << i;
1356 			break;
1357 		}
1358 	}
1359 	return 1;
1360 }
1361 __setup("cgroup_no_v1=", cgroup_no_v1);
1362