1// SPDX-License-Identifier: GPL-2.0-only
 
 
 
 
 
   2
   3#include <linux/export.h>
   4#include <linux/nsproxy.h>
   5#include <linux/slab.h>
   6#include <linux/sched/signal.h>
   7#include <linux/user_namespace.h>
   8#include <linux/proc_ns.h>
   9#include <linux/highuid.h>
  10#include <linux/cred.h>
  11#include <linux/securebits.h>
  12#include <linux/security.h>
  13#include <linux/keyctl.h>
  14#include <linux/key-type.h>
  15#include <keys/user-type.h>
  16#include <linux/seq_file.h>
  17#include <linux/fs.h>
  18#include <linux/uaccess.h>
  19#include <linux/ctype.h>
  20#include <linux/projid.h>
  21#include <linux/fs_struct.h>
  22#include <linux/bsearch.h>
  23#include <linux/sort.h>
  24
  25static struct kmem_cache *user_ns_cachep __ro_after_init;
  26static DEFINE_MUTEX(userns_state_mutex);
  27
  28static bool new_idmap_permitted(const struct file *file,
  29				struct user_namespace *ns, int cap_setid,
  30				struct uid_gid_map *map);
  31static void free_user_ns(struct work_struct *work);
  32
  33static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
  34{
  35	return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
  36}
  37
  38static void dec_user_namespaces(struct ucounts *ucounts)
  39{
  40	return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
  41}
  42
  43static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
  44{
  45	/* Start with the same capabilities as init but useless for doing
  46	 * anything as the capabilities are bound to the new user namespace.
  47	 */
  48	cred->securebits = SECUREBITS_DEFAULT;
  49	cred->cap_inheritable = CAP_EMPTY_SET;
  50	cred->cap_permitted = CAP_FULL_SET;
  51	cred->cap_effective = CAP_FULL_SET;
  52	cred->cap_ambient = CAP_EMPTY_SET;
  53	cred->cap_bset = CAP_FULL_SET;
  54#ifdef CONFIG_KEYS
  55	key_put(cred->request_key_auth);
  56	cred->request_key_auth = NULL;
  57#endif
  58	/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
  59	cred->user_ns = user_ns;
  60}
  61
  62static unsigned long enforced_nproc_rlimit(void)
  63{
  64	unsigned long limit = RLIM_INFINITY;
  65
  66	/* Is RLIMIT_NPROC currently enforced? */
  67	if (!uid_eq(current_uid(), GLOBAL_ROOT_UID) ||
  68	    (current_user_ns() != &init_user_ns))
  69		limit = rlimit(RLIMIT_NPROC);
  70
  71	return limit;
  72}
  73
  74/*
  75 * Create a new user namespace, deriving the creator from the user in the
  76 * passed credentials, and replacing that user with the new root user for the
  77 * new namespace.
  78 *
  79 * This is called by copy_creds(), which will finish setting the target task's
  80 * credentials.
  81 */
  82int create_user_ns(struct cred *new)
  83{
  84	struct user_namespace *ns, *parent_ns = new->user_ns;
  85	kuid_t owner = new->euid;
  86	kgid_t group = new->egid;
  87	struct ucounts *ucounts;
  88	int ret, i;
  89
  90	ret = -ENOSPC;
  91	if (parent_ns->level > 32)
  92		goto fail;
  93
  94	ucounts = inc_user_namespaces(parent_ns, owner);
  95	if (!ucounts)
  96		goto fail;
  97
  98	/*
  99	 * Verify that we can not violate the policy of which files
 100	 * may be accessed that is specified by the root directory,
 101	 * by verifying that the root directory is at the root of the
 102	 * mount namespace which allows all files to be accessed.
 103	 */
 104	ret = -EPERM;
 105	if (current_chrooted())
 106		goto fail_dec;
 107
 108	/* The creator needs a mapping in the parent user namespace
 109	 * or else we won't be able to reasonably tell userspace who
 110	 * created a user_namespace.
 111	 */
 112	ret = -EPERM;
 113	if (!kuid_has_mapping(parent_ns, owner) ||
 114	    !kgid_has_mapping(parent_ns, group))
 115		goto fail_dec;
 116
 117	ret = security_create_user_ns(new);
 118	if (ret < 0)
 119		goto fail_dec;
 120
 121	ret = -ENOMEM;
 122	ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
 123	if (!ns)
 124		goto fail_dec;
 125
 126	ns->parent_could_setfcap = cap_raised(new->cap_effective, CAP_SETFCAP);
 127	ret = ns_alloc_inum(&ns->ns);
 128	if (ret)
 129		goto fail_free;
 130	ns->ns.ops = &userns_operations;
 131
 132	refcount_set(&ns->ns.count, 1);
 133	/* Leave the new->user_ns reference with the new user namespace. */
 134	ns->parent = parent_ns;
 135	ns->level = parent_ns->level + 1;
 136	ns->owner = owner;
 137	ns->group = group;
 138	INIT_WORK(&ns->work, free_user_ns);
 139	for (i = 0; i < UCOUNT_COUNTS; i++) {
 140		ns->ucount_max[i] = INT_MAX;
 141	}
 142	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_NPROC, enforced_nproc_rlimit());
 143	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MSGQUEUE, rlimit(RLIMIT_MSGQUEUE));
 144	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_SIGPENDING, rlimit(RLIMIT_SIGPENDING));
 145	set_userns_rlimit_max(ns, UCOUNT_RLIMIT_MEMLOCK, rlimit(RLIMIT_MEMLOCK));
 146	ns->ucounts = ucounts;
 147
 148	/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
 149	mutex_lock(&userns_state_mutex);
 150	ns->flags = parent_ns->flags;
 151	mutex_unlock(&userns_state_mutex);
 152
 
 
 
 
 
 
 
 
 153#ifdef CONFIG_KEYS
 154	INIT_LIST_HEAD(&ns->keyring_name_list);
 155	init_rwsem(&ns->keyring_sem);
 156#endif
 157	ret = -ENOMEM;
 158	if (!setup_userns_sysctls(ns))
 159		goto fail_keyring;
 160
 161	set_cred_user_ns(new, ns);
 162	return 0;
 163fail_keyring:
 164#ifdef CONFIG_PERSISTENT_KEYRINGS
 165	key_put(ns->persistent_keyring_register);
 166#endif
 167	ns_free_inum(&ns->ns);
 168fail_free:
 169	kmem_cache_free(user_ns_cachep, ns);
 170fail_dec:
 171	dec_user_namespaces(ucounts);
 172fail:
 173	return ret;
 174}
 175
 176int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
 177{
 178	struct cred *cred;
 179	int err = -ENOMEM;
 180
 181	if (!(unshare_flags & CLONE_NEWUSER))
 182		return 0;
 183
 184	cred = prepare_creds();
 185	if (cred) {
 186		err = create_user_ns(cred);
 187		if (err)
 188			put_cred(cred);
 189		else
 190			*new_cred = cred;
 191	}
 192
 193	return err;
 194}
 195
 196static void free_user_ns(struct work_struct *work)
 197{
 198	struct user_namespace *parent, *ns =
 199		container_of(work, struct user_namespace, work);
 200
 201	do {
 202		struct ucounts *ucounts = ns->ucounts;
 203		parent = ns->parent;
 204		if (ns->gid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
 205			kfree(ns->gid_map.forward);
 206			kfree(ns->gid_map.reverse);
 207		}
 208		if (ns->uid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
 209			kfree(ns->uid_map.forward);
 210			kfree(ns->uid_map.reverse);
 211		}
 212		if (ns->projid_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
 213			kfree(ns->projid_map.forward);
 214			kfree(ns->projid_map.reverse);
 215		}
 216#if IS_ENABLED(CONFIG_BINFMT_MISC)
 217		kfree(ns->binfmt_misc);
 218#endif
 219		retire_userns_sysctls(ns);
 220		key_free_user_ns(ns);
 221		ns_free_inum(&ns->ns);
 222		kmem_cache_free(user_ns_cachep, ns);
 223		dec_user_namespaces(ucounts);
 224		ns = parent;
 225	} while (refcount_dec_and_test(&parent->ns.count));
 226}
 227
 228void __put_user_ns(struct user_namespace *ns)
 229{
 230	schedule_work(&ns->work);
 231}
 232EXPORT_SYMBOL(__put_user_ns);
 233
 234/*
 235 * struct idmap_key - holds the information necessary to find an idmapping in a
 236 * sorted idmap array. It is passed to cmp_map_id() as first argument.
 237 */
 238struct idmap_key {
 239	bool map_up; /* true  -> id from kid; false -> kid from id */
 240	u32 id; /* id to find */
 241	u32 count; /* == 0 unless used with map_id_range_down() */
 242};
 243
 244/*
 245 * cmp_map_id - Function to be passed to bsearch() to find the requested
 246 * idmapping. Expects struct idmap_key to be passed via @k.
 247 */
 248static int cmp_map_id(const void *k, const void *e)
 249{
 250	u32 first, last, id2;
 251	const struct idmap_key *key = k;
 252	const struct uid_gid_extent *el = e;
 253
 254	id2 = key->id + key->count - 1;
 255
 256	/* handle map_id_{down,up}() */
 257	if (key->map_up)
 258		first = el->lower_first;
 259	else
 260		first = el->first;
 261
 262	last = first + el->count - 1;
 263
 264	if (key->id >= first && key->id <= last &&
 265	    (id2 >= first && id2 <= last))
 266		return 0;
 267
 268	if (key->id < first || id2 < first)
 269		return -1;
 270
 271	return 1;
 272}
 273
 274/*
 275 * map_id_range_down_max - Find idmap via binary search in ordered idmap array.
 276 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 277 */
 278static struct uid_gid_extent *
 279map_id_range_down_max(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
 280{
 281	struct idmap_key key;
 282
 283	key.map_up = false;
 284	key.count = count;
 285	key.id = id;
 286
 287	return bsearch(&key, map->forward, extents,
 288		       sizeof(struct uid_gid_extent), cmp_map_id);
 289}
 
 290
 291/*
 292 * map_id_range_down_base - Find idmap via binary search in static extent array.
 293 * Can only be called if number of mappings is equal or less than
 294 * UID_GID_MAP_MAX_BASE_EXTENTS.
 295 */
 296static struct uid_gid_extent *
 297map_id_range_down_base(unsigned extents, struct uid_gid_map *map, u32 id, u32 count)
 298{
 299	unsigned idx;
 300	u32 first, last, id2;
 301
 302	id2 = id + count - 1;
 303
 304	/* Find the matching extent */
 
 
 305	for (idx = 0; idx < extents; idx++) {
 306		first = map->extent[idx].first;
 307		last = first + map->extent[idx].count - 1;
 308		if (id >= first && id <= last &&
 309		    (id2 >= first && id2 <= last))
 310			return &map->extent[idx];
 311	}
 312	return NULL;
 313}
 314
 315static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
 316{
 317	struct uid_gid_extent *extent;
 318	unsigned extents = map->nr_extents;
 319	smp_rmb();
 320
 321	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 322		extent = map_id_range_down_base(extents, map, id, count);
 323	else
 324		extent = map_id_range_down_max(extents, map, id, count);
 325
 326	/* Map the id or note failure */
 327	if (extent)
 328		id = (id - extent->first) + extent->lower_first;
 329	else
 330		id = (u32) -1;
 331
 332	return id;
 333}
 334
 335u32 map_id_down(struct uid_gid_map *map, u32 id)
 336{
 337	return map_id_range_down(map, id, 1);
 338}
 339
 340/*
 341 * map_id_up_base - Find idmap via binary search in static extent array.
 342 * Can only be called if number of mappings is equal or less than
 343 * UID_GID_MAP_MAX_BASE_EXTENTS.
 344 */
 345static struct uid_gid_extent *
 346map_id_up_base(unsigned extents, struct uid_gid_map *map, u32 id)
 347{
 348	unsigned idx;
 349	u32 first, last;
 350
 351	/* Find the matching extent */
 
 
 352	for (idx = 0; idx < extents; idx++) {
 353		first = map->extent[idx].lower_first;
 354		last = first + map->extent[idx].count - 1;
 355		if (id >= first && id <= last)
 356			return &map->extent[idx];
 357	}
 358	return NULL;
 359}
 360
 361/*
 362 * map_id_up_max - Find idmap via binary search in ordered idmap array.
 363 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 364 */
 365static struct uid_gid_extent *
 366map_id_up_max(unsigned extents, struct uid_gid_map *map, u32 id)
 367{
 368	struct idmap_key key;
 369
 370	key.map_up = true;
 371	key.count = 1;
 372	key.id = id;
 373
 374	return bsearch(&key, map->reverse, extents,
 375		       sizeof(struct uid_gid_extent), cmp_map_id);
 376}
 377
 378u32 map_id_up(struct uid_gid_map *map, u32 id)
 379{
 380	struct uid_gid_extent *extent;
 381	unsigned extents = map->nr_extents;
 382	smp_rmb();
 383
 384	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 385		extent = map_id_up_base(extents, map, id);
 386	else
 387		extent = map_id_up_max(extents, map, id);
 388
 
 
 
 
 
 
 
 
 
 389	/* Map the id or note failure */
 390	if (extent)
 391		id = (id - extent->lower_first) + extent->first;
 392	else
 393		id = (u32) -1;
 394
 395	return id;
 396}
 397
 398/**
 399 *	make_kuid - Map a user-namespace uid pair into a kuid.
 400 *	@ns:  User namespace that the uid is in
 401 *	@uid: User identifier
 402 *
 403 *	Maps a user-namespace uid pair into a kernel internal kuid,
 404 *	and returns that kuid.
 405 *
 406 *	When there is no mapping defined for the user-namespace uid
 407 *	pair INVALID_UID is returned.  Callers are expected to test
 408 *	for and handle INVALID_UID being returned.  INVALID_UID
 409 *	may be tested for using uid_valid().
 410 */
 411kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
 412{
 413	/* Map the uid to a global kernel uid */
 414	return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
 415}
 416EXPORT_SYMBOL(make_kuid);
 417
 418/**
 419 *	from_kuid - Create a uid from a kuid user-namespace pair.
 420 *	@targ: The user namespace we want a uid in.
 421 *	@kuid: The kernel internal uid to start with.
 422 *
 423 *	Map @kuid into the user-namespace specified by @targ and
 424 *	return the resulting uid.
 425 *
 426 *	There is always a mapping into the initial user_namespace.
 427 *
 428 *	If @kuid has no mapping in @targ (uid_t)-1 is returned.
 429 */
 430uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
 431{
 432	/* Map the uid from a global kernel uid */
 433	return map_id_up(&targ->uid_map, __kuid_val(kuid));
 434}
 435EXPORT_SYMBOL(from_kuid);
 436
 437/**
 438 *	from_kuid_munged - Create a uid from a kuid user-namespace pair.
 439 *	@targ: The user namespace we want a uid in.
 440 *	@kuid: The kernel internal uid to start with.
 441 *
 442 *	Map @kuid into the user-namespace specified by @targ and
 443 *	return the resulting uid.
 444 *
 445 *	There is always a mapping into the initial user_namespace.
 446 *
 447 *	Unlike from_kuid from_kuid_munged never fails and always
 448 *	returns a valid uid.  This makes from_kuid_munged appropriate
 449 *	for use in syscalls like stat and getuid where failing the
 450 *	system call and failing to provide a valid uid are not an
 451 *	options.
 452 *
 453 *	If @kuid has no mapping in @targ overflowuid is returned.
 454 */
 455uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
 456{
 457	uid_t uid;
 458	uid = from_kuid(targ, kuid);
 459
 460	if (uid == (uid_t) -1)
 461		uid = overflowuid;
 462	return uid;
 463}
 464EXPORT_SYMBOL(from_kuid_munged);
 465
 466/**
 467 *	make_kgid - Map a user-namespace gid pair into a kgid.
 468 *	@ns:  User namespace that the gid is in
 469 *	@gid: group identifier
 470 *
 471 *	Maps a user-namespace gid pair into a kernel internal kgid,
 472 *	and returns that kgid.
 473 *
 474 *	When there is no mapping defined for the user-namespace gid
 475 *	pair INVALID_GID is returned.  Callers are expected to test
 476 *	for and handle INVALID_GID being returned.  INVALID_GID may be
 477 *	tested for using gid_valid().
 478 */
 479kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
 480{
 481	/* Map the gid to a global kernel gid */
 482	return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
 483}
 484EXPORT_SYMBOL(make_kgid);
 485
 486/**
 487 *	from_kgid - Create a gid from a kgid user-namespace pair.
 488 *	@targ: The user namespace we want a gid in.
 489 *	@kgid: The kernel internal gid to start with.
 490 *
 491 *	Map @kgid into the user-namespace specified by @targ and
 492 *	return the resulting gid.
 493 *
 494 *	There is always a mapping into the initial user_namespace.
 495 *
 496 *	If @kgid has no mapping in @targ (gid_t)-1 is returned.
 497 */
 498gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
 499{
 500	/* Map the gid from a global kernel gid */
 501	return map_id_up(&targ->gid_map, __kgid_val(kgid));
 502}
 503EXPORT_SYMBOL(from_kgid);
 504
 505/**
 506 *	from_kgid_munged - Create a gid from a kgid user-namespace pair.
 507 *	@targ: The user namespace we want a gid in.
 508 *	@kgid: The kernel internal gid to start with.
 509 *
 510 *	Map @kgid into the user-namespace specified by @targ and
 511 *	return the resulting gid.
 512 *
 513 *	There is always a mapping into the initial user_namespace.
 514 *
 515 *	Unlike from_kgid from_kgid_munged never fails and always
 516 *	returns a valid gid.  This makes from_kgid_munged appropriate
 517 *	for use in syscalls like stat and getgid where failing the
 518 *	system call and failing to provide a valid gid are not options.
 519 *
 520 *	If @kgid has no mapping in @targ overflowgid is returned.
 521 */
 522gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
 523{
 524	gid_t gid;
 525	gid = from_kgid(targ, kgid);
 526
 527	if (gid == (gid_t) -1)
 528		gid = overflowgid;
 529	return gid;
 530}
 531EXPORT_SYMBOL(from_kgid_munged);
 532
 533/**
 534 *	make_kprojid - Map a user-namespace projid pair into a kprojid.
 535 *	@ns:  User namespace that the projid is in
 536 *	@projid: Project identifier
 537 *
 538 *	Maps a user-namespace uid pair into a kernel internal kuid,
 539 *	and returns that kuid.
 540 *
 541 *	When there is no mapping defined for the user-namespace projid
 542 *	pair INVALID_PROJID is returned.  Callers are expected to test
 543 *	for and handle INVALID_PROJID being returned.  INVALID_PROJID
 544 *	may be tested for using projid_valid().
 545 */
 546kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
 547{
 548	/* Map the uid to a global kernel uid */
 549	return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
 550}
 551EXPORT_SYMBOL(make_kprojid);
 552
 553/**
 554 *	from_kprojid - Create a projid from a kprojid user-namespace pair.
 555 *	@targ: The user namespace we want a projid in.
 556 *	@kprojid: The kernel internal project identifier to start with.
 557 *
 558 *	Map @kprojid into the user-namespace specified by @targ and
 559 *	return the resulting projid.
 560 *
 561 *	There is always a mapping into the initial user_namespace.
 562 *
 563 *	If @kprojid has no mapping in @targ (projid_t)-1 is returned.
 564 */
 565projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
 566{
 567	/* Map the uid from a global kernel uid */
 568	return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
 569}
 570EXPORT_SYMBOL(from_kprojid);
 571
 572/**
 573 *	from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
 574 *	@targ: The user namespace we want a projid in.
 575 *	@kprojid: The kernel internal projid to start with.
 576 *
 577 *	Map @kprojid into the user-namespace specified by @targ and
 578 *	return the resulting projid.
 579 *
 580 *	There is always a mapping into the initial user_namespace.
 581 *
 582 *	Unlike from_kprojid from_kprojid_munged never fails and always
 583 *	returns a valid projid.  This makes from_kprojid_munged
 584 *	appropriate for use in syscalls like stat and where
 585 *	failing the system call and failing to provide a valid projid are
 586 *	not an options.
 587 *
 588 *	If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
 589 */
 590projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
 591{
 592	projid_t projid;
 593	projid = from_kprojid(targ, kprojid);
 594
 595	if (projid == (projid_t) -1)
 596		projid = OVERFLOW_PROJID;
 597	return projid;
 598}
 599EXPORT_SYMBOL(from_kprojid_munged);
 600
 601
 602static int uid_m_show(struct seq_file *seq, void *v)
 603{
 604	struct user_namespace *ns = seq->private;
 605	struct uid_gid_extent *extent = v;
 606	struct user_namespace *lower_ns;
 607	uid_t lower;
 608
 609	lower_ns = seq_user_ns(seq);
 610	if ((lower_ns == ns) && lower_ns->parent)
 611		lower_ns = lower_ns->parent;
 612
 613	lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));
 614
 615	seq_printf(seq, "%10u %10u %10u\n",
 616		extent->first,
 617		lower,
 618		extent->count);
 619
 620	return 0;
 621}
 622
 623static int gid_m_show(struct seq_file *seq, void *v)
 624{
 625	struct user_namespace *ns = seq->private;
 626	struct uid_gid_extent *extent = v;
 627	struct user_namespace *lower_ns;
 628	gid_t lower;
 629
 630	lower_ns = seq_user_ns(seq);
 631	if ((lower_ns == ns) && lower_ns->parent)
 632		lower_ns = lower_ns->parent;
 633
 634	lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));
 635
 636	seq_printf(seq, "%10u %10u %10u\n",
 637		extent->first,
 638		lower,
 639		extent->count);
 640
 641	return 0;
 642}
 643
 644static int projid_m_show(struct seq_file *seq, void *v)
 645{
 646	struct user_namespace *ns = seq->private;
 647	struct uid_gid_extent *extent = v;
 648	struct user_namespace *lower_ns;
 649	projid_t lower;
 650
 651	lower_ns = seq_user_ns(seq);
 652	if ((lower_ns == ns) && lower_ns->parent)
 653		lower_ns = lower_ns->parent;
 654
 655	lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));
 656
 657	seq_printf(seq, "%10u %10u %10u\n",
 658		extent->first,
 659		lower,
 660		extent->count);
 661
 662	return 0;
 663}
 664
 665static void *m_start(struct seq_file *seq, loff_t *ppos,
 666		     struct uid_gid_map *map)
 667{
 
 668	loff_t pos = *ppos;
 669	unsigned extents = map->nr_extents;
 670	smp_rmb();
 671
 672	if (pos >= extents)
 673		return NULL;
 674
 675	if (extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 676		return &map->extent[pos];
 677
 678	return &map->forward[pos];
 679}
 680
 681static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
 682{
 683	struct user_namespace *ns = seq->private;
 684
 685	return m_start(seq, ppos, &ns->uid_map);
 686}
 687
 688static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
 689{
 690	struct user_namespace *ns = seq->private;
 691
 692	return m_start(seq, ppos, &ns->gid_map);
 693}
 694
 695static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
 696{
 697	struct user_namespace *ns = seq->private;
 698
 699	return m_start(seq, ppos, &ns->projid_map);
 700}
 701
 702static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
 703{
 704	(*pos)++;
 705	return seq->op->start(seq, pos);
 706}
 707
 708static void m_stop(struct seq_file *seq, void *v)
 709{
 710	return;
 711}
 712
 713const struct seq_operations proc_uid_seq_operations = {
 714	.start = uid_m_start,
 715	.stop = m_stop,
 716	.next = m_next,
 717	.show = uid_m_show,
 718};
 719
 720const struct seq_operations proc_gid_seq_operations = {
 721	.start = gid_m_start,
 722	.stop = m_stop,
 723	.next = m_next,
 724	.show = gid_m_show,
 725};
 726
 727const struct seq_operations proc_projid_seq_operations = {
 728	.start = projid_m_start,
 729	.stop = m_stop,
 730	.next = m_next,
 731	.show = projid_m_show,
 732};
 733
 734static bool mappings_overlap(struct uid_gid_map *new_map,
 735			     struct uid_gid_extent *extent)
 736{
 737	u32 upper_first, lower_first, upper_last, lower_last;
 738	unsigned idx;
 739
 740	upper_first = extent->first;
 741	lower_first = extent->lower_first;
 742	upper_last = upper_first + extent->count - 1;
 743	lower_last = lower_first + extent->count - 1;
 744
 745	for (idx = 0; idx < new_map->nr_extents; idx++) {
 746		u32 prev_upper_first, prev_lower_first;
 747		u32 prev_upper_last, prev_lower_last;
 748		struct uid_gid_extent *prev;
 749
 750		if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 751			prev = &new_map->extent[idx];
 752		else
 753			prev = &new_map->forward[idx];
 754
 755		prev_upper_first = prev->first;
 756		prev_lower_first = prev->lower_first;
 757		prev_upper_last = prev_upper_first + prev->count - 1;
 758		prev_lower_last = prev_lower_first + prev->count - 1;
 759
 760		/* Does the upper range intersect a previous extent? */
 761		if ((prev_upper_first <= upper_last) &&
 762		    (prev_upper_last >= upper_first))
 763			return true;
 764
 765		/* Does the lower range intersect a previous extent? */
 766		if ((prev_lower_first <= lower_last) &&
 767		    (prev_lower_last >= lower_first))
 768			return true;
 769	}
 770	return false;
 771}
 772
 773/*
 774 * insert_extent - Safely insert a new idmap extent into struct uid_gid_map.
 775 * Takes care to allocate a 4K block of memory if the number of mappings exceeds
 776 * UID_GID_MAP_MAX_BASE_EXTENTS.
 777 */
 778static int insert_extent(struct uid_gid_map *map, struct uid_gid_extent *extent)
 779{
 780	struct uid_gid_extent *dest;
 781
 782	if (map->nr_extents == UID_GID_MAP_MAX_BASE_EXTENTS) {
 783		struct uid_gid_extent *forward;
 784
 785		/* Allocate memory for 340 mappings. */
 786		forward = kmalloc_array(UID_GID_MAP_MAX_EXTENTS,
 787					sizeof(struct uid_gid_extent),
 788					GFP_KERNEL);
 789		if (!forward)
 790			return -ENOMEM;
 791
 792		/* Copy over memory. Only set up memory for the forward pointer.
 793		 * Defer the memory setup for the reverse pointer.
 794		 */
 795		memcpy(forward, map->extent,
 796		       map->nr_extents * sizeof(map->extent[0]));
 797
 798		map->forward = forward;
 799		map->reverse = NULL;
 800	}
 801
 802	if (map->nr_extents < UID_GID_MAP_MAX_BASE_EXTENTS)
 803		dest = &map->extent[map->nr_extents];
 804	else
 805		dest = &map->forward[map->nr_extents];
 806
 807	*dest = *extent;
 808	map->nr_extents++;
 809	return 0;
 810}
 811
 812/* cmp function to sort() forward mappings */
 813static int cmp_extents_forward(const void *a, const void *b)
 814{
 815	const struct uid_gid_extent *e1 = a;
 816	const struct uid_gid_extent *e2 = b;
 817
 818	if (e1->first < e2->first)
 819		return -1;
 820
 821	if (e1->first > e2->first)
 822		return 1;
 823
 824	return 0;
 825}
 826
 827/* cmp function to sort() reverse mappings */
 828static int cmp_extents_reverse(const void *a, const void *b)
 829{
 830	const struct uid_gid_extent *e1 = a;
 831	const struct uid_gid_extent *e2 = b;
 832
 833	if (e1->lower_first < e2->lower_first)
 834		return -1;
 835
 836	if (e1->lower_first > e2->lower_first)
 837		return 1;
 838
 839	return 0;
 840}
 841
 842/*
 843 * sort_idmaps - Sorts an array of idmap entries.
 844 * Can only be called if number of mappings exceeds UID_GID_MAP_MAX_BASE_EXTENTS.
 845 */
 846static int sort_idmaps(struct uid_gid_map *map)
 847{
 848	if (map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 849		return 0;
 850
 851	/* Sort forward array. */
 852	sort(map->forward, map->nr_extents, sizeof(struct uid_gid_extent),
 853	     cmp_extents_forward, NULL);
 854
 855	/* Only copy the memory from forward we actually need. */
 856	map->reverse = kmemdup_array(map->forward, map->nr_extents,
 857				     sizeof(struct uid_gid_extent), GFP_KERNEL);
 858	if (!map->reverse)
 859		return -ENOMEM;
 860
 861	/* Sort reverse array. */
 862	sort(map->reverse, map->nr_extents, sizeof(struct uid_gid_extent),
 863	     cmp_extents_reverse, NULL);
 864
 865	return 0;
 866}
 867
 868/**
 869 * verify_root_map() - check the uid 0 mapping
 870 * @file: idmapping file
 871 * @map_ns: user namespace of the target process
 872 * @new_map: requested idmap
 873 *
 874 * If a process requests mapping parent uid 0 into the new ns, verify that the
 875 * process writing the map had the CAP_SETFCAP capability as the target process
 876 * will be able to write fscaps that are valid in ancestor user namespaces.
 877 *
 878 * Return: true if the mapping is allowed, false if not.
 879 */
 880static bool verify_root_map(const struct file *file,
 881			    struct user_namespace *map_ns,
 882			    struct uid_gid_map *new_map)
 883{
 884	int idx;
 885	const struct user_namespace *file_ns = file->f_cred->user_ns;
 886	struct uid_gid_extent *extent0 = NULL;
 887
 888	for (idx = 0; idx < new_map->nr_extents; idx++) {
 889		if (new_map->nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
 890			extent0 = &new_map->extent[idx];
 891		else
 892			extent0 = &new_map->forward[idx];
 893		if (extent0->lower_first == 0)
 894			break;
 895
 896		extent0 = NULL;
 897	}
 898
 899	if (!extent0)
 900		return true;
 901
 902	if (map_ns == file_ns) {
 903		/* The process unshared its ns and is writing to its own
 904		 * /proc/self/uid_map.  User already has full capabilites in
 905		 * the new namespace.  Verify that the parent had CAP_SETFCAP
 906		 * when it unshared.
 907		 * */
 908		if (!file_ns->parent_could_setfcap)
 909			return false;
 910	} else {
 911		/* Process p1 is writing to uid_map of p2, who is in a child
 912		 * user namespace to p1's.  Verify that the opener of the map
 913		 * file has CAP_SETFCAP against the parent of the new map
 914		 * namespace */
 915		if (!file_ns_capable(file, map_ns->parent, CAP_SETFCAP))
 916			return false;
 917	}
 918
 919	return true;
 920}
 921
 922static ssize_t map_write(struct file *file, const char __user *buf,
 923			 size_t count, loff_t *ppos,
 924			 int cap_setid,
 925			 struct uid_gid_map *map,
 926			 struct uid_gid_map *parent_map)
 927{
 928	struct seq_file *seq = file->private_data;
 929	struct user_namespace *map_ns = seq->private;
 930	struct uid_gid_map new_map;
 931	unsigned idx;
 932	struct uid_gid_extent extent;
 
 933	char *kbuf, *pos, *next_line;
 934	ssize_t ret;
 935
 936	/* Only allow < page size writes at the beginning of the file */
 937	if ((*ppos != 0) || (count >= PAGE_SIZE))
 938		return -EINVAL;
 939
 940	/* Slurp in the user data */
 941	kbuf = memdup_user_nul(buf, count);
 942	if (IS_ERR(kbuf))
 943		return PTR_ERR(kbuf);
 944
 945	/*
 946	 * The userns_state_mutex serializes all writes to any given map.
 947	 *
 948	 * Any map is only ever written once.
 949	 *
 950	 * An id map fits within 1 cache line on most architectures.
 951	 *
 952	 * On read nothing needs to be done unless you are on an
 953	 * architecture with a crazy cache coherency model like alpha.
 954	 *
 955	 * There is a one time data dependency between reading the
 956	 * count of the extents and the values of the extents.  The
 957	 * desired behavior is to see the values of the extents that
 958	 * were written before the count of the extents.
 959	 *
 960	 * To achieve this smp_wmb() is used on guarantee the write
 961	 * order and smp_rmb() is guaranteed that we don't have crazy
 962	 * architectures returning stale data.
 
 963	 */
 964	mutex_lock(&userns_state_mutex);
 965
 966	memset(&new_map, 0, sizeof(struct uid_gid_map));
 967
 968	ret = -EPERM;
 969	/* Only allow one successful write to the map */
 970	if (map->nr_extents != 0)
 971		goto out;
 972
 973	/*
 974	 * Adjusting namespace settings requires capabilities on the target.
 975	 */
 976	if (cap_valid(cap_setid) && !file_ns_capable(file, map_ns, CAP_SYS_ADMIN))
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 977		goto out;
 
 978
 979	/* Parse the user data */
 980	ret = -EINVAL;
 981	pos = kbuf;
 982	for (; pos; pos = next_line) {
 
 
 983
 984		/* Find the end of line and ensure I don't look past it */
 985		next_line = strchr(pos, '\n');
 986		if (next_line) {
 987			*next_line = '\0';
 988			next_line++;
 989			if (*next_line == '\0')
 990				next_line = NULL;
 991		}
 992
 993		pos = skip_spaces(pos);
 994		extent.first = simple_strtoul(pos, &pos, 10);
 995		if (!isspace(*pos))
 996			goto out;
 997
 998		pos = skip_spaces(pos);
 999		extent.lower_first = simple_strtoul(pos, &pos, 10);
1000		if (!isspace(*pos))
1001			goto out;
1002
1003		pos = skip_spaces(pos);
1004		extent.count = simple_strtoul(pos, &pos, 10);
1005		if (*pos && !isspace(*pos))
1006			goto out;
1007
1008		/* Verify there is not trailing junk on the line */
1009		pos = skip_spaces(pos);
1010		if (*pos != '\0')
1011			goto out;
1012
1013		/* Verify we have been given valid starting values */
1014		if ((extent.first == (u32) -1) ||
1015		    (extent.lower_first == (u32) -1))
1016			goto out;
1017
1018		/* Verify count is not zero and does not cause the
1019		 * extent to wrap
1020		 */
1021		if ((extent.first + extent.count) <= extent.first)
1022			goto out;
1023		if ((extent.lower_first + extent.count) <=
1024		     extent.lower_first)
1025			goto out;
1026
1027		/* Do the ranges in extent overlap any previous extents? */
1028		if (mappings_overlap(&new_map, &extent))
 
 
1029			goto out;
1030
1031		if ((new_map.nr_extents + 1) == UID_GID_MAP_MAX_EXTENTS &&
1032		    (next_line != NULL))
1033			goto out;
1034
1035		ret = insert_extent(&new_map, &extent);
1036		if (ret < 0)
 
1037			goto out;
1038		ret = -EINVAL;
1039	}
1040	/* Be very certain the new map actually exists */
1041	if (new_map.nr_extents == 0)
1042		goto out;
1043
1044	ret = -EPERM;
1045	/* Validate the user is allowed to use user id's mapped to. */
1046	if (!new_idmap_permitted(file, map_ns, cap_setid, &new_map))
1047		goto out;
1048
1049	ret = -EPERM;
1050	/* Map the lower ids from the parent user namespace to the
1051	 * kernel global id space.
1052	 */
1053	for (idx = 0; idx < new_map.nr_extents; idx++) {
1054		struct uid_gid_extent *e;
1055		u32 lower_first;
1056
1057		if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS)
1058			e = &new_map.extent[idx];
1059		else
1060			e = &new_map.forward[idx];
1061
1062		lower_first = map_id_range_down(parent_map,
1063						e->lower_first,
1064						e->count);
1065
1066		/* Fail if we can not map the specified extent to
1067		 * the kernel global id space.
1068		 */
1069		if (lower_first == (u32) -1)
1070			goto out;
1071
1072		e->lower_first = lower_first;
1073	}
1074
1075	/*
1076	 * If we want to use binary search for lookup, this clones the extent
1077	 * array and sorts both copies.
1078	 */
1079	ret = sort_idmaps(&new_map);
1080	if (ret < 0)
1081		goto out;
1082
1083	/* Install the map */
1084	if (new_map.nr_extents <= UID_GID_MAP_MAX_BASE_EXTENTS) {
1085		memcpy(map->extent, new_map.extent,
1086		       new_map.nr_extents * sizeof(new_map.extent[0]));
1087	} else {
1088		map->forward = new_map.forward;
1089		map->reverse = new_map.reverse;
1090	}
1091	smp_wmb();
1092	map->nr_extents = new_map.nr_extents;
1093
1094	*ppos = count;
1095	ret = count;
1096out:
1097	if (ret < 0 && new_map.nr_extents > UID_GID_MAP_MAX_BASE_EXTENTS) {
1098		kfree(new_map.forward);
1099		kfree(new_map.reverse);
1100		map->forward = NULL;
1101		map->reverse = NULL;
1102		map->nr_extents = 0;
1103	}
1104
1105	mutex_unlock(&userns_state_mutex);
1106	kfree(kbuf);
1107	return ret;
1108}
1109
1110ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
1111			   size_t size, loff_t *ppos)
1112{
1113	struct seq_file *seq = file->private_data;
1114	struct user_namespace *ns = seq->private;
1115	struct user_namespace *seq_ns = seq_user_ns(seq);
1116
1117	if (!ns->parent)
1118		return -EPERM;
1119
1120	if ((seq_ns != ns) && (seq_ns != ns->parent))
1121		return -EPERM;
1122
1123	return map_write(file, buf, size, ppos, CAP_SETUID,
1124			 &ns->uid_map, &ns->parent->uid_map);
1125}
1126
1127ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
1128			   size_t size, loff_t *ppos)
1129{
1130	struct seq_file *seq = file->private_data;
1131	struct user_namespace *ns = seq->private;
1132	struct user_namespace *seq_ns = seq_user_ns(seq);
1133
1134	if (!ns->parent)
1135		return -EPERM;
1136
1137	if ((seq_ns != ns) && (seq_ns != ns->parent))
1138		return -EPERM;
1139
1140	return map_write(file, buf, size, ppos, CAP_SETGID,
1141			 &ns->gid_map, &ns->parent->gid_map);
1142}
1143
1144ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
1145			      size_t size, loff_t *ppos)
1146{
1147	struct seq_file *seq = file->private_data;
1148	struct user_namespace *ns = seq->private;
1149	struct user_namespace *seq_ns = seq_user_ns(seq);
1150
1151	if (!ns->parent)
1152		return -EPERM;
1153
1154	if ((seq_ns != ns) && (seq_ns != ns->parent))
1155		return -EPERM;
1156
1157	/* Anyone can set any valid project id no capability needed */
1158	return map_write(file, buf, size, ppos, -1,
1159			 &ns->projid_map, &ns->parent->projid_map);
1160}
1161
1162static bool new_idmap_permitted(const struct file *file,
1163				struct user_namespace *ns, int cap_setid,
1164				struct uid_gid_map *new_map)
1165{
1166	const struct cred *cred = file->f_cred;
1167
1168	if (cap_setid == CAP_SETUID && !verify_root_map(file, ns, new_map))
1169		return false;
1170
1171	/* Don't allow mappings that would allow anything that wouldn't
1172	 * be allowed without the establishment of unprivileged mappings.
1173	 */
1174	if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
1175	    uid_eq(ns->owner, cred->euid)) {
1176		u32 id = new_map->extent[0].lower_first;
1177		if (cap_setid == CAP_SETUID) {
1178			kuid_t uid = make_kuid(ns->parent, id);
1179			if (uid_eq(uid, cred->euid))
1180				return true;
1181		} else if (cap_setid == CAP_SETGID) {
1182			kgid_t gid = make_kgid(ns->parent, id);
1183			if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
1184			    gid_eq(gid, cred->egid))
1185				return true;
1186		}
1187	}
1188
1189	/* Allow anyone to set a mapping that doesn't require privilege */
1190	if (!cap_valid(cap_setid))
1191		return true;
1192
1193	/* Allow the specified ids if we have the appropriate capability
1194	 * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
1195	 * And the opener of the id file also has the appropriate capability.
1196	 */
1197	if (ns_capable(ns->parent, cap_setid) &&
1198	    file_ns_capable(file, ns->parent, cap_setid))
1199		return true;
1200
1201	return false;
1202}
1203
1204int proc_setgroups_show(struct seq_file *seq, void *v)
1205{
1206	struct user_namespace *ns = seq->private;
1207	unsigned long userns_flags = READ_ONCE(ns->flags);
1208
1209	seq_printf(seq, "%s\n",
1210		   (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
1211		   "allow" : "deny");
1212	return 0;
1213}
1214
1215ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
1216			     size_t count, loff_t *ppos)
1217{
1218	struct seq_file *seq = file->private_data;
1219	struct user_namespace *ns = seq->private;
1220	char kbuf[8], *pos;
1221	bool setgroups_allowed;
1222	ssize_t ret;
1223
1224	/* Only allow a very narrow range of strings to be written */
1225	ret = -EINVAL;
1226	if ((*ppos != 0) || (count >= sizeof(kbuf)))
1227		goto out;
1228
1229	/* What was written? */
1230	ret = -EFAULT;
1231	if (copy_from_user(kbuf, buf, count))
1232		goto out;
1233	kbuf[count] = '\0';
1234	pos = kbuf;
1235
1236	/* What is being requested? */
1237	ret = -EINVAL;
1238	if (strncmp(pos, "allow", 5) == 0) {
1239		pos += 5;
1240		setgroups_allowed = true;
1241	}
1242	else if (strncmp(pos, "deny", 4) == 0) {
1243		pos += 4;
1244		setgroups_allowed = false;
1245	}
1246	else
1247		goto out;
1248
1249	/* Verify there is not trailing junk on the line */
1250	pos = skip_spaces(pos);
1251	if (*pos != '\0')
1252		goto out;
1253
1254	ret = -EPERM;
1255	mutex_lock(&userns_state_mutex);
1256	if (setgroups_allowed) {
1257		/* Enabling setgroups after setgroups has been disabled
1258		 * is not allowed.
1259		 */
1260		if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
1261			goto out_unlock;
1262	} else {
1263		/* Permanently disabling setgroups after setgroups has
1264		 * been enabled by writing the gid_map is not allowed.
1265		 */
1266		if (ns->gid_map.nr_extents != 0)
1267			goto out_unlock;
1268		ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
1269	}
1270	mutex_unlock(&userns_state_mutex);
1271
1272	/* Report a successful write */
1273	*ppos = count;
1274	ret = count;
1275out:
1276	return ret;
1277out_unlock:
1278	mutex_unlock(&userns_state_mutex);
1279	goto out;
1280}
1281
1282bool userns_may_setgroups(const struct user_namespace *ns)
1283{
1284	bool allowed;
1285
1286	mutex_lock(&userns_state_mutex);
1287	/* It is not safe to use setgroups until a gid mapping in
1288	 * the user namespace has been established.
1289	 */
1290	allowed = ns->gid_map.nr_extents != 0;
1291	/* Is setgroups allowed? */
1292	allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
1293	mutex_unlock(&userns_state_mutex);
1294
1295	return allowed;
1296}
1297
1298/*
1299 * Returns true if @child is the same namespace or a descendant of
1300 * @ancestor.
1301 */
1302bool in_userns(const struct user_namespace *ancestor,
1303	       const struct user_namespace *child)
1304{
1305	const struct user_namespace *ns;
1306	for (ns = child; ns->level > ancestor->level; ns = ns->parent)
1307		;
1308	return (ns == ancestor);
1309}
1310
1311bool current_in_userns(const struct user_namespace *target_ns)
1312{
1313	return in_userns(target_ns, current_user_ns());
1314}
1315EXPORT_SYMBOL(current_in_userns);
1316
1317static inline struct user_namespace *to_user_ns(struct ns_common *ns)
1318{
1319	return container_of(ns, struct user_namespace, ns);
1320}
1321
1322static struct ns_common *userns_get(struct task_struct *task)
1323{
1324	struct user_namespace *user_ns;
1325
1326	rcu_read_lock();
1327	user_ns = get_user_ns(__task_cred(task)->user_ns);
1328	rcu_read_unlock();
1329
1330	return user_ns ? &user_ns->ns : NULL;
1331}
1332
1333static void userns_put(struct ns_common *ns)
1334{
1335	put_user_ns(to_user_ns(ns));
1336}
1337
1338static int userns_install(struct nsset *nsset, struct ns_common *ns)
1339{
1340	struct user_namespace *user_ns = to_user_ns(ns);
1341	struct cred *cred;
1342
1343	/* Don't allow gaining capabilities by reentering
1344	 * the same user namespace.
1345	 */
1346	if (user_ns == current_user_ns())
1347		return -EINVAL;
1348
1349	/* Tasks that share a thread group must share a user namespace */
1350	if (!thread_group_empty(current))
1351		return -EINVAL;
1352
1353	if (current->fs->users != 1)
1354		return -EINVAL;
1355
1356	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
1357		return -EPERM;
1358
1359	cred = nsset_cred(nsset);
1360	if (!cred)
1361		return -EINVAL;
1362
1363	put_user_ns(cred->user_ns);
1364	set_cred_user_ns(cred, get_user_ns(user_ns));
1365
1366	if (set_cred_ucounts(cred) < 0)
1367		return -EINVAL;
1368
1369	return 0;
1370}
1371
1372struct ns_common *ns_get_owner(struct ns_common *ns)
1373{
1374	struct user_namespace *my_user_ns = current_user_ns();
1375	struct user_namespace *owner, *p;
1376
1377	/* See if the owner is in the current user namespace */
1378	owner = p = ns->ops->owner(ns);
1379	for (;;) {
1380		if (!p)
1381			return ERR_PTR(-EPERM);
1382		if (p == my_user_ns)
1383			break;
1384		p = p->parent;
1385	}
1386
1387	return &get_user_ns(owner)->ns;
1388}
1389
1390static struct user_namespace *userns_owner(struct ns_common *ns)
1391{
1392	return to_user_ns(ns)->parent;
1393}
1394
1395const struct proc_ns_operations userns_operations = {
1396	.name		= "user",
1397	.type		= CLONE_NEWUSER,
1398	.get		= userns_get,
1399	.put		= userns_put,
1400	.install	= userns_install,
1401	.owner		= userns_owner,
1402	.get_parent	= ns_get_owner,
1403};
1404
1405static __init int user_namespaces_init(void)
1406{
1407	user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC | SLAB_ACCOUNT);
1408	return 0;
1409}
1410subsys_initcall(user_namespaces_init);