Training courses

Kernel and Embedded Linux

Bootlin training courses

Embedded Linux, kernel,
Yocto Project, Buildroot, real-time,
graphics, boot time, debugging...

Bootlin logo

Elixir Cross Referencer

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 110
 111
 112
 113
 114
 115
 116
 117
 118
 119
 120
 121
 122
 123
 124
 125
 126
 127
 128
 129
 130
 131
 132
 133
 134
 135
 136
 137
 138
 139
 140
 141
 142
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 153
 154
 155
 156
 157
 158
 159
 160
 161
 162
 163
 164
 165
 166
 167
 168
 169
 170
 171
 172
 173
 174
 175
 176
 177
 178
 179
 180
 181
 182
 183
 184
 185
 186
 187
 188
 189
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 223
 224
 225
 226
 227
 228
 229
 230
 231
 232
 233
 234
 235
 236
 237
 238
 239
 240
 241
 242
 243
 244
 245
 246
 247
 248
 249
 250
 251
 252
 253
 254
 255
 256
 257
 258
 259
 260
 261
 262
 263
 264
 265
 266
 267
 268
 269
 270
 271
 272
 273
 274
 275
 276
 277
 278
 279
 280
 281
 282
 283
 284
 285
 286
 287
 288
 289
 290
 291
 292
 293
 294
 295
 296
 297
 298
 299
 300
 301
 302
 303
 304
 305
 306
 307
 308
 309
 310
 311
 312
 313
 314
 315
 316
 317
 318
 319
 320
 321
 322
 323
 324
 325
 326
 327
 328
 329
 330
 331
 332
 333
 334
 335
 336
 337
 338
 339
 340
 341
 342
 343
 344
 345
 346
 347
 348
 349
 350
 351
 352
 353
 354
 355
 356
 357
 358
 359
 360
 361
 362
 363
 364
 365
 366
 367
 368
 369
 370
 371
 372
 373
 374
 375
 376
 377
 378
 379
 380
 381
 382
 383
 384
 385
 386
 387
 388
 389
 390
 391
 392
 393
 394
 395
 396
 397
 398
 399
 400
 401
 402
 403
 404
 405
 406
 407
 408
 409
 410
 411
 412
 413
 414
 415
 416
 417
 418
 419
 420
 421
 422
 423
 424
 425
 426
 427
 428
 429
 430
 431
 432
 433
 434
 435
 436
 437
 438
 439
 440
 441
 442
 443
 444
 445
 446
 447
 448
 449
 450
 451
 452
 453
 454
 455
 456
 457
 458
 459
 460
 461
 462
 463
 464
 465
 466
 467
 468
 469
 470
 471
 472
 473
 474
 475
 476
 477
 478
 479
 480
 481
 482
 483
 484
 485
 486
 487
 488
 489
 490
 491
 492
 493
 494
 495
 496
 497
 498
 499
 500
 501
 502
 503
 504
 505
 506
 507
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
/*
 *  This program is free software; you can redistribute it and/or
 *  modify it under the terms of the GNU General Public License as
 *  published by the Free Software Foundation, version 2 of the
 *  License.
 */

#include <linux/export.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
#include <linux/user_namespace.h>
#include <linux/proc_ns.h>
#include <linux/highuid.h>
#include <linux/cred.h>
#include <linux/securebits.h>
#include <linux/keyctl.h>
#include <linux/key-type.h>
#include <keys/user-type.h>
#include <linux/seq_file.h>
#include <linux/fs.h>
#include <linux/uaccess.h>
#include <linux/ctype.h>
#include <linux/projid.h>
#include <linux/fs_struct.h>

static struct kmem_cache *user_ns_cachep __read_mostly;
static DEFINE_MUTEX(userns_state_mutex);

static bool new_idmap_permitted(const struct file *file,
				struct user_namespace *ns, int cap_setid,
				struct uid_gid_map *map);
static void free_user_ns(struct work_struct *work);

static struct ucounts *inc_user_namespaces(struct user_namespace *ns, kuid_t uid)
{
	return inc_ucount(ns, uid, UCOUNT_USER_NAMESPACES);
}

static void dec_user_namespaces(struct ucounts *ucounts)
{
	return dec_ucount(ucounts, UCOUNT_USER_NAMESPACES);
}

static void set_cred_user_ns(struct cred *cred, struct user_namespace *user_ns)
{
	/* Start with the same capabilities as init but useless for doing
	 * anything as the capabilities are bound to the new user namespace.
	 */
	cred->securebits = SECUREBITS_DEFAULT;
	cred->cap_inheritable = CAP_EMPTY_SET;
	cred->cap_permitted = CAP_FULL_SET;
	cred->cap_effective = CAP_FULL_SET;
	cred->cap_ambient = CAP_EMPTY_SET;
	cred->cap_bset = CAP_FULL_SET;
#ifdef CONFIG_KEYS
	key_put(cred->request_key_auth);
	cred->request_key_auth = NULL;
#endif
	/* tgcred will be cleared in our caller bc CLONE_THREAD won't be set */
	cred->user_ns = user_ns;
}

/*
 * Create a new user namespace, deriving the creator from the user in the
 * passed credentials, and replacing that user with the new root user for the
 * new namespace.
 *
 * This is called by copy_creds(), which will finish setting the target task's
 * credentials.
 */
int create_user_ns(struct cred *new)
{
	struct user_namespace *ns, *parent_ns = new->user_ns;
	kuid_t owner = new->euid;
	kgid_t group = new->egid;
	struct ucounts *ucounts;
	int ret, i;

	ret = -ENOSPC;
	if (parent_ns->level > 32)
		goto fail;

	ucounts = inc_user_namespaces(parent_ns, owner);
	if (!ucounts)
		goto fail;

	/*
	 * Verify that we can not violate the policy of which files
	 * may be accessed that is specified by the root directory,
	 * by verifing that the root directory is at the root of the
	 * mount namespace which allows all files to be accessed.
	 */
	ret = -EPERM;
	if (current_chrooted())
		goto fail_dec;

	/* The creator needs a mapping in the parent user namespace
	 * or else we won't be able to reasonably tell userspace who
	 * created a user_namespace.
	 */
	ret = -EPERM;
	if (!kuid_has_mapping(parent_ns, owner) ||
	    !kgid_has_mapping(parent_ns, group))
		goto fail_dec;

	ret = -ENOMEM;
	ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL);
	if (!ns)
		goto fail_dec;

	ret = ns_alloc_inum(&ns->ns);
	if (ret)
		goto fail_free;
	ns->ns.ops = &userns_operations;

	atomic_set(&ns->count, 1);
	/* Leave the new->user_ns reference with the new user namespace. */
	ns->parent = parent_ns;
	ns->level = parent_ns->level + 1;
	ns->owner = owner;
	ns->group = group;
	INIT_WORK(&ns->work, free_user_ns);
	for (i = 0; i < UCOUNT_COUNTS; i++) {
		ns->ucount_max[i] = INT_MAX;
	}
	ns->ucounts = ucounts;

	/* Inherit USERNS_SETGROUPS_ALLOWED from our parent */
	mutex_lock(&userns_state_mutex);
	ns->flags = parent_ns->flags;
	mutex_unlock(&userns_state_mutex);

#ifdef CONFIG_PERSISTENT_KEYRINGS
	init_rwsem(&ns->persistent_keyring_register_sem);
#endif
	ret = -ENOMEM;
	if (!setup_userns_sysctls(ns))
		goto fail_keyring;

	set_cred_user_ns(new, ns);
	return 0;
fail_keyring:
#ifdef CONFIG_PERSISTENT_KEYRINGS
	key_put(ns->persistent_keyring_register);
#endif
	ns_free_inum(&ns->ns);
fail_free:
	kmem_cache_free(user_ns_cachep, ns);
fail_dec:
	dec_user_namespaces(ucounts);
fail:
	return ret;
}

int unshare_userns(unsigned long unshare_flags, struct cred **new_cred)
{
	struct cred *cred;
	int err = -ENOMEM;

	if (!(unshare_flags & CLONE_NEWUSER))
		return 0;

	cred = prepare_creds();
	if (cred) {
		err = create_user_ns(cred);
		if (err)
			put_cred(cred);
		else
			*new_cred = cred;
	}

	return err;
}

static void free_user_ns(struct work_struct *work)
{
	struct user_namespace *parent, *ns =
		container_of(work, struct user_namespace, work);

	do {
		struct ucounts *ucounts = ns->ucounts;
		parent = ns->parent;
		retire_userns_sysctls(ns);
#ifdef CONFIG_PERSISTENT_KEYRINGS
		key_put(ns->persistent_keyring_register);
#endif
		ns_free_inum(&ns->ns);
		kmem_cache_free(user_ns_cachep, ns);
		dec_user_namespaces(ucounts);
		ns = parent;
	} while (atomic_dec_and_test(&parent->count));
}

void __put_user_ns(struct user_namespace *ns)
{
	schedule_work(&ns->work);
}
EXPORT_SYMBOL(__put_user_ns);

static u32 map_id_range_down(struct uid_gid_map *map, u32 id, u32 count)
{
	unsigned idx, extents;
	u32 first, last, id2;

	id2 = id + count - 1;

	/* Find the matching extent */
	extents = map->nr_extents;
	smp_rmb();
	for (idx = 0; idx < extents; idx++) {
		first = map->extent[idx].first;
		last = first + map->extent[idx].count - 1;
		if (id >= first && id <= last &&
		    (id2 >= first && id2 <= last))
			break;
	}
	/* Map the id or note failure */
	if (idx < extents)
		id = (id - first) + map->extent[idx].lower_first;
	else
		id = (u32) -1;

	return id;
}

static u32 map_id_down(struct uid_gid_map *map, u32 id)
{
	unsigned idx, extents;
	u32 first, last;

	/* Find the matching extent */
	extents = map->nr_extents;
	smp_rmb();
	for (idx = 0; idx < extents; idx++) {
		first = map->extent[idx].first;
		last = first + map->extent[idx].count - 1;
		if (id >= first && id <= last)
			break;
	}
	/* Map the id or note failure */
	if (idx < extents)
		id = (id - first) + map->extent[idx].lower_first;
	else
		id = (u32) -1;

	return id;
}

static u32 map_id_up(struct uid_gid_map *map, u32 id)
{
	unsigned idx, extents;
	u32 first, last;

	/* Find the matching extent */
	extents = map->nr_extents;
	smp_rmb();
	for (idx = 0; idx < extents; idx++) {
		first = map->extent[idx].lower_first;
		last = first + map->extent[idx].count - 1;
		if (id >= first && id <= last)
			break;
	}
	/* Map the id or note failure */
	if (idx < extents)
		id = (id - first) + map->extent[idx].first;
	else
		id = (u32) -1;

	return id;
}

/**
 *	make_kuid - Map a user-namespace uid pair into a kuid.
 *	@ns:  User namespace that the uid is in
 *	@uid: User identifier
 *
 *	Maps a user-namespace uid pair into a kernel internal kuid,
 *	and returns that kuid.
 *
 *	When there is no mapping defined for the user-namespace uid
 *	pair INVALID_UID is returned.  Callers are expected to test
 *	for and handle INVALID_UID being returned.  INVALID_UID
 *	may be tested for using uid_valid().
 */
kuid_t make_kuid(struct user_namespace *ns, uid_t uid)
{
	/* Map the uid to a global kernel uid */
	return KUIDT_INIT(map_id_down(&ns->uid_map, uid));
}
EXPORT_SYMBOL(make_kuid);

/**
 *	from_kuid - Create a uid from a kuid user-namespace pair.
 *	@targ: The user namespace we want a uid in.
 *	@kuid: The kernel internal uid to start with.
 *
 *	Map @kuid into the user-namespace specified by @targ and
 *	return the resulting uid.
 *
 *	There is always a mapping into the initial user_namespace.
 *
 *	If @kuid has no mapping in @targ (uid_t)-1 is returned.
 */
uid_t from_kuid(struct user_namespace *targ, kuid_t kuid)
{
	/* Map the uid from a global kernel uid */
	return map_id_up(&targ->uid_map, __kuid_val(kuid));
}
EXPORT_SYMBOL(from_kuid);

/**
 *	from_kuid_munged - Create a uid from a kuid user-namespace pair.
 *	@targ: The user namespace we want a uid in.
 *	@kuid: The kernel internal uid to start with.
 *
 *	Map @kuid into the user-namespace specified by @targ and
 *	return the resulting uid.
 *
 *	There is always a mapping into the initial user_namespace.
 *
 *	Unlike from_kuid from_kuid_munged never fails and always
 *	returns a valid uid.  This makes from_kuid_munged appropriate
 *	for use in syscalls like stat and getuid where failing the
 *	system call and failing to provide a valid uid are not an
 *	options.
 *
 *	If @kuid has no mapping in @targ overflowuid is returned.
 */
uid_t from_kuid_munged(struct user_namespace *targ, kuid_t kuid)
{
	uid_t uid;
	uid = from_kuid(targ, kuid);

	if (uid == (uid_t) -1)
		uid = overflowuid;
	return uid;
}
EXPORT_SYMBOL(from_kuid_munged);

/**
 *	make_kgid - Map a user-namespace gid pair into a kgid.
 *	@ns:  User namespace that the gid is in
 *	@gid: group identifier
 *
 *	Maps a user-namespace gid pair into a kernel internal kgid,
 *	and returns that kgid.
 *
 *	When there is no mapping defined for the user-namespace gid
 *	pair INVALID_GID is returned.  Callers are expected to test
 *	for and handle INVALID_GID being returned.  INVALID_GID may be
 *	tested for using gid_valid().
 */
kgid_t make_kgid(struct user_namespace *ns, gid_t gid)
{
	/* Map the gid to a global kernel gid */
	return KGIDT_INIT(map_id_down(&ns->gid_map, gid));
}
EXPORT_SYMBOL(make_kgid);

/**
 *	from_kgid - Create a gid from a kgid user-namespace pair.
 *	@targ: The user namespace we want a gid in.
 *	@kgid: The kernel internal gid to start with.
 *
 *	Map @kgid into the user-namespace specified by @targ and
 *	return the resulting gid.
 *
 *	There is always a mapping into the initial user_namespace.
 *
 *	If @kgid has no mapping in @targ (gid_t)-1 is returned.
 */
gid_t from_kgid(struct user_namespace *targ, kgid_t kgid)
{
	/* Map the gid from a global kernel gid */
	return map_id_up(&targ->gid_map, __kgid_val(kgid));
}
EXPORT_SYMBOL(from_kgid);

/**
 *	from_kgid_munged - Create a gid from a kgid user-namespace pair.
 *	@targ: The user namespace we want a gid in.
 *	@kgid: The kernel internal gid to start with.
 *
 *	Map @kgid into the user-namespace specified by @targ and
 *	return the resulting gid.
 *
 *	There is always a mapping into the initial user_namespace.
 *
 *	Unlike from_kgid from_kgid_munged never fails and always
 *	returns a valid gid.  This makes from_kgid_munged appropriate
 *	for use in syscalls like stat and getgid where failing the
 *	system call and failing to provide a valid gid are not options.
 *
 *	If @kgid has no mapping in @targ overflowgid is returned.
 */
gid_t from_kgid_munged(struct user_namespace *targ, kgid_t kgid)
{
	gid_t gid;
	gid = from_kgid(targ, kgid);

	if (gid == (gid_t) -1)
		gid = overflowgid;
	return gid;
}
EXPORT_SYMBOL(from_kgid_munged);

/**
 *	make_kprojid - Map a user-namespace projid pair into a kprojid.
 *	@ns:  User namespace that the projid is in
 *	@projid: Project identifier
 *
 *	Maps a user-namespace uid pair into a kernel internal kuid,
 *	and returns that kuid.
 *
 *	When there is no mapping defined for the user-namespace projid
 *	pair INVALID_PROJID is returned.  Callers are expected to test
 *	for and handle handle INVALID_PROJID being returned.  INVALID_PROJID
 *	may be tested for using projid_valid().
 */
kprojid_t make_kprojid(struct user_namespace *ns, projid_t projid)
{
	/* Map the uid to a global kernel uid */
	return KPROJIDT_INIT(map_id_down(&ns->projid_map, projid));
}
EXPORT_SYMBOL(make_kprojid);

/**
 *	from_kprojid - Create a projid from a kprojid user-namespace pair.
 *	@targ: The user namespace we want a projid in.
 *	@kprojid: The kernel internal project identifier to start with.
 *
 *	Map @kprojid into the user-namespace specified by @targ and
 *	return the resulting projid.
 *
 *	There is always a mapping into the initial user_namespace.
 *
 *	If @kprojid has no mapping in @targ (projid_t)-1 is returned.
 */
projid_t from_kprojid(struct user_namespace *targ, kprojid_t kprojid)
{
	/* Map the uid from a global kernel uid */
	return map_id_up(&targ->projid_map, __kprojid_val(kprojid));
}
EXPORT_SYMBOL(from_kprojid);

/**
 *	from_kprojid_munged - Create a projiid from a kprojid user-namespace pair.
 *	@targ: The user namespace we want a projid in.
 *	@kprojid: The kernel internal projid to start with.
 *
 *	Map @kprojid into the user-namespace specified by @targ and
 *	return the resulting projid.
 *
 *	There is always a mapping into the initial user_namespace.
 *
 *	Unlike from_kprojid from_kprojid_munged never fails and always
 *	returns a valid projid.  This makes from_kprojid_munged
 *	appropriate for use in syscalls like stat and where
 *	failing the system call and failing to provide a valid projid are
 *	not an options.
 *
 *	If @kprojid has no mapping in @targ OVERFLOW_PROJID is returned.
 */
projid_t from_kprojid_munged(struct user_namespace *targ, kprojid_t kprojid)
{
	projid_t projid;
	projid = from_kprojid(targ, kprojid);

	if (projid == (projid_t) -1)
		projid = OVERFLOW_PROJID;
	return projid;
}
EXPORT_SYMBOL(from_kprojid_munged);


static int uid_m_show(struct seq_file *seq, void *v)
{
	struct user_namespace *ns = seq->private;
	struct uid_gid_extent *extent = v;
	struct user_namespace *lower_ns;
	uid_t lower;

	lower_ns = seq_user_ns(seq);
	if ((lower_ns == ns) && lower_ns->parent)
		lower_ns = lower_ns->parent;

	lower = from_kuid(lower_ns, KUIDT_INIT(extent->lower_first));

	seq_printf(seq, "%10u %10u %10u\n",
		extent->first,
		lower,
		extent->count);

	return 0;
}

static int gid_m_show(struct seq_file *seq, void *v)
{
	struct user_namespace *ns = seq->private;
	struct uid_gid_extent *extent = v;
	struct user_namespace *lower_ns;
	gid_t lower;

	lower_ns = seq_user_ns(seq);
	if ((lower_ns == ns) && lower_ns->parent)
		lower_ns = lower_ns->parent;

	lower = from_kgid(lower_ns, KGIDT_INIT(extent->lower_first));

	seq_printf(seq, "%10u %10u %10u\n",
		extent->first,
		lower,
		extent->count);

	return 0;
}

static int projid_m_show(struct seq_file *seq, void *v)
{
	struct user_namespace *ns = seq->private;
	struct uid_gid_extent *extent = v;
	struct user_namespace *lower_ns;
	projid_t lower;

	lower_ns = seq_user_ns(seq);
	if ((lower_ns == ns) && lower_ns->parent)
		lower_ns = lower_ns->parent;

	lower = from_kprojid(lower_ns, KPROJIDT_INIT(extent->lower_first));

	seq_printf(seq, "%10u %10u %10u\n",
		extent->first,
		lower,
		extent->count);

	return 0;
}

static void *m_start(struct seq_file *seq, loff_t *ppos,
		     struct uid_gid_map *map)
{
	struct uid_gid_extent *extent = NULL;
	loff_t pos = *ppos;

	if (pos < map->nr_extents)
		extent = &map->extent[pos];

	return extent;
}

static void *uid_m_start(struct seq_file *seq, loff_t *ppos)
{
	struct user_namespace *ns = seq->private;

	return m_start(seq, ppos, &ns->uid_map);
}

static void *gid_m_start(struct seq_file *seq, loff_t *ppos)
{
	struct user_namespace *ns = seq->private;

	return m_start(seq, ppos, &ns->gid_map);
}

static void *projid_m_start(struct seq_file *seq, loff_t *ppos)
{
	struct user_namespace *ns = seq->private;

	return m_start(seq, ppos, &ns->projid_map);
}

static void *m_next(struct seq_file *seq, void *v, loff_t *pos)
{
	(*pos)++;
	return seq->op->start(seq, pos);
}

static void m_stop(struct seq_file *seq, void *v)
{
	return;
}

const struct seq_operations proc_uid_seq_operations = {
	.start = uid_m_start,
	.stop = m_stop,
	.next = m_next,
	.show = uid_m_show,
};

const struct seq_operations proc_gid_seq_operations = {
	.start = gid_m_start,
	.stop = m_stop,
	.next = m_next,
	.show = gid_m_show,
};

const struct seq_operations proc_projid_seq_operations = {
	.start = projid_m_start,
	.stop = m_stop,
	.next = m_next,
	.show = projid_m_show,
};

static bool mappings_overlap(struct uid_gid_map *new_map,
			     struct uid_gid_extent *extent)
{
	u32 upper_first, lower_first, upper_last, lower_last;
	unsigned idx;

	upper_first = extent->first;
	lower_first = extent->lower_first;
	upper_last = upper_first + extent->count - 1;
	lower_last = lower_first + extent->count - 1;

	for (idx = 0; idx < new_map->nr_extents; idx++) {
		u32 prev_upper_first, prev_lower_first;
		u32 prev_upper_last, prev_lower_last;
		struct uid_gid_extent *prev;

		prev = &new_map->extent[idx];

		prev_upper_first = prev->first;
		prev_lower_first = prev->lower_first;
		prev_upper_last = prev_upper_first + prev->count - 1;
		prev_lower_last = prev_lower_first + prev->count - 1;

		/* Does the upper range intersect a previous extent? */
		if ((prev_upper_first <= upper_last) &&
		    (prev_upper_last >= upper_first))
			return true;

		/* Does the lower range intersect a previous extent? */
		if ((prev_lower_first <= lower_last) &&
		    (prev_lower_last >= lower_first))
			return true;
	}
	return false;
}

static ssize_t map_write(struct file *file, const char __user *buf,
			 size_t count, loff_t *ppos,
			 int cap_setid,
			 struct uid_gid_map *map,
			 struct uid_gid_map *parent_map)
{
	struct seq_file *seq = file->private_data;
	struct user_namespace *ns = seq->private;
	struct uid_gid_map new_map;
	unsigned idx;
	struct uid_gid_extent *extent = NULL;
	char *kbuf = NULL, *pos, *next_line;
	ssize_t ret = -EINVAL;

	/*
	 * The userns_state_mutex serializes all writes to any given map.
	 *
	 * Any map is only ever written once.
	 *
	 * An id map fits within 1 cache line on most architectures.
	 *
	 * On read nothing needs to be done unless you are on an
	 * architecture with a crazy cache coherency model like alpha.
	 *
	 * There is a one time data dependency between reading the
	 * count of the extents and the values of the extents.  The
	 * desired behavior is to see the values of the extents that
	 * were written before the count of the extents.
	 *
	 * To achieve this smp_wmb() is used on guarantee the write
	 * order and smp_rmb() is guaranteed that we don't have crazy
	 * architectures returning stale data.
	 */
	mutex_lock(&userns_state_mutex);

	ret = -EPERM;
	/* Only allow one successful write to the map */
	if (map->nr_extents != 0)
		goto out;

	/*
	 * Adjusting namespace settings requires capabilities on the target.
	 */
	if (cap_valid(cap_setid) && !file_ns_capable(file, ns, CAP_SYS_ADMIN))
		goto out;

	/* Only allow < page size writes at the beginning of the file */
	ret = -EINVAL;
	if ((*ppos != 0) || (count >= PAGE_SIZE))
		goto out;

	/* Slurp in the user data */
	kbuf = memdup_user_nul(buf, count);
	if (IS_ERR(kbuf)) {
		ret = PTR_ERR(kbuf);
		kbuf = NULL;
		goto out;
	}

	/* Parse the user data */
	ret = -EINVAL;
	pos = kbuf;
	new_map.nr_extents = 0;
	for (; pos; pos = next_line) {
		extent = &new_map.extent[new_map.nr_extents];

		/* Find the end of line and ensure I don't look past it */
		next_line = strchr(pos, '\n');
		if (next_line) {
			*next_line = '\0';
			next_line++;
			if (*next_line == '\0')
				next_line = NULL;
		}

		pos = skip_spaces(pos);
		extent->first = simple_strtoul(pos, &pos, 10);
		if (!isspace(*pos))
			goto out;

		pos = skip_spaces(pos);
		extent->lower_first = simple_strtoul(pos, &pos, 10);
		if (!isspace(*pos))
			goto out;

		pos = skip_spaces(pos);
		extent->count = simple_strtoul(pos, &pos, 10);
		if (*pos && !isspace(*pos))
			goto out;

		/* Verify there is not trailing junk on the line */
		pos = skip_spaces(pos);
		if (*pos != '\0')
			goto out;

		/* Verify we have been given valid starting values */
		if ((extent->first == (u32) -1) ||
		    (extent->lower_first == (u32) -1))
			goto out;

		/* Verify count is not zero and does not cause the
		 * extent to wrap
		 */
		if ((extent->first + extent->count) <= extent->first)
			goto out;
		if ((extent->lower_first + extent->count) <=
		     extent->lower_first)
			goto out;

		/* Do the ranges in extent overlap any previous extents? */
		if (mappings_overlap(&new_map, extent))
			goto out;

		new_map.nr_extents++;

		/* Fail if the file contains too many extents */
		if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) &&
		    (next_line != NULL))
			goto out;
	}
	/* Be very certaint the new map actually exists */
	if (new_map.nr_extents == 0)
		goto out;

	ret = -EPERM;
	/* Validate the user is allowed to use user id's mapped to. */
	if (!new_idmap_permitted(file, ns, cap_setid, &new_map))
		goto out;

	/* Map the lower ids from the parent user namespace to the
	 * kernel global id space.
	 */
	for (idx = 0; idx < new_map.nr_extents; idx++) {
		u32 lower_first;
		extent = &new_map.extent[idx];

		lower_first = map_id_range_down(parent_map,
						extent->lower_first,
						extent->count);

		/* Fail if we can not map the specified extent to
		 * the kernel global id space.
		 */
		if (lower_first == (u32) -1)
			goto out;

		extent->lower_first = lower_first;
	}

	/* Install the map */
	memcpy(map->extent, new_map.extent,
		new_map.nr_extents*sizeof(new_map.extent[0]));
	smp_wmb();
	map->nr_extents = new_map.nr_extents;

	*ppos = count;
	ret = count;
out:
	mutex_unlock(&userns_state_mutex);
	kfree(kbuf);
	return ret;
}

ssize_t proc_uid_map_write(struct file *file, const char __user *buf,
			   size_t size, loff_t *ppos)
{
	struct seq_file *seq = file->private_data;
	struct user_namespace *ns = seq->private;
	struct user_namespace *seq_ns = seq_user_ns(seq);

	if (!ns->parent)
		return -EPERM;

	if ((seq_ns != ns) && (seq_ns != ns->parent))
		return -EPERM;

	return map_write(file, buf, size, ppos, CAP_SETUID,
			 &ns->uid_map, &ns->parent->uid_map);
}

ssize_t proc_gid_map_write(struct file *file, const char __user *buf,
			   size_t size, loff_t *ppos)
{
	struct seq_file *seq = file->private_data;
	struct user_namespace *ns = seq->private;
	struct user_namespace *seq_ns = seq_user_ns(seq);

	if (!ns->parent)
		return -EPERM;

	if ((seq_ns != ns) && (seq_ns != ns->parent))
		return -EPERM;

	return map_write(file, buf, size, ppos, CAP_SETGID,
			 &ns->gid_map, &ns->parent->gid_map);
}

ssize_t proc_projid_map_write(struct file *file, const char __user *buf,
			      size_t size, loff_t *ppos)
{
	struct seq_file *seq = file->private_data;
	struct user_namespace *ns = seq->private;
	struct user_namespace *seq_ns = seq_user_ns(seq);

	if (!ns->parent)
		return -EPERM;

	if ((seq_ns != ns) && (seq_ns != ns->parent))
		return -EPERM;

	/* Anyone can set any valid project id no capability needed */
	return map_write(file, buf, size, ppos, -1,
			 &ns->projid_map, &ns->parent->projid_map);
}

static bool new_idmap_permitted(const struct file *file,
				struct user_namespace *ns, int cap_setid,
				struct uid_gid_map *new_map)
{
	const struct cred *cred = file->f_cred;
	/* Don't allow mappings that would allow anything that wouldn't
	 * be allowed without the establishment of unprivileged mappings.
	 */
	if ((new_map->nr_extents == 1) && (new_map->extent[0].count == 1) &&
	    uid_eq(ns->owner, cred->euid)) {
		u32 id = new_map->extent[0].lower_first;
		if (cap_setid == CAP_SETUID) {
			kuid_t uid = make_kuid(ns->parent, id);
			if (uid_eq(uid, cred->euid))
				return true;
		} else if (cap_setid == CAP_SETGID) {
			kgid_t gid = make_kgid(ns->parent, id);
			if (!(ns->flags & USERNS_SETGROUPS_ALLOWED) &&
			    gid_eq(gid, cred->egid))
				return true;
		}
	}

	/* Allow anyone to set a mapping that doesn't require privilege */
	if (!cap_valid(cap_setid))
		return true;

	/* Allow the specified ids if we have the appropriate capability
	 * (CAP_SETUID or CAP_SETGID) over the parent user namespace.
	 * And the opener of the id file also had the approprpiate capability.
	 */
	if (ns_capable(ns->parent, cap_setid) &&
	    file_ns_capable(file, ns->parent, cap_setid))
		return true;

	return false;
}

int proc_setgroups_show(struct seq_file *seq, void *v)
{
	struct user_namespace *ns = seq->private;
	unsigned long userns_flags = ACCESS_ONCE(ns->flags);

	seq_printf(seq, "%s\n",
		   (userns_flags & USERNS_SETGROUPS_ALLOWED) ?
		   "allow" : "deny");
	return 0;
}

ssize_t proc_setgroups_write(struct file *file, const char __user *buf,
			     size_t count, loff_t *ppos)
{
	struct seq_file *seq = file->private_data;
	struct user_namespace *ns = seq->private;
	char kbuf[8], *pos;
	bool setgroups_allowed;
	ssize_t ret;

	/* Only allow a very narrow range of strings to be written */
	ret = -EINVAL;
	if ((*ppos != 0) || (count >= sizeof(kbuf)))
		goto out;

	/* What was written? */
	ret = -EFAULT;
	if (copy_from_user(kbuf, buf, count))
		goto out;
	kbuf[count] = '\0';
	pos = kbuf;

	/* What is being requested? */
	ret = -EINVAL;
	if (strncmp(pos, "allow", 5) == 0) {
		pos += 5;
		setgroups_allowed = true;
	}
	else if (strncmp(pos, "deny", 4) == 0) {
		pos += 4;
		setgroups_allowed = false;
	}
	else
		goto out;

	/* Verify there is not trailing junk on the line */
	pos = skip_spaces(pos);
	if (*pos != '\0')
		goto out;

	ret = -EPERM;
	mutex_lock(&userns_state_mutex);
	if (setgroups_allowed) {
		/* Enabling setgroups after setgroups has been disabled
		 * is not allowed.
		 */
		if (!(ns->flags & USERNS_SETGROUPS_ALLOWED))
			goto out_unlock;
	} else {
		/* Permanently disabling setgroups after setgroups has
		 * been enabled by writing the gid_map is not allowed.
		 */
		if (ns->gid_map.nr_extents != 0)
			goto out_unlock;
		ns->flags &= ~USERNS_SETGROUPS_ALLOWED;
	}
	mutex_unlock(&userns_state_mutex);

	/* Report a successful write */
	*ppos = count;
	ret = count;
out:
	return ret;
out_unlock:
	mutex_unlock(&userns_state_mutex);
	goto out;
}

bool userns_may_setgroups(const struct user_namespace *ns)
{
	bool allowed;

	mutex_lock(&userns_state_mutex);
	/* It is not safe to use setgroups until a gid mapping in
	 * the user namespace has been established.
	 */
	allowed = ns->gid_map.nr_extents != 0;
	/* Is setgroups allowed? */
	allowed = allowed && (ns->flags & USERNS_SETGROUPS_ALLOWED);
	mutex_unlock(&userns_state_mutex);

	return allowed;
}

/*
 * Returns true if @ns is the same namespace as or a descendant of
 * @target_ns.
 */
bool current_in_userns(const struct user_namespace *target_ns)
{
	struct user_namespace *ns;
	for (ns = current_user_ns(); ns; ns = ns->parent) {
		if (ns == target_ns)
			return true;
	}
	return false;
}

static inline struct user_namespace *to_user_ns(struct ns_common *ns)
{
	return container_of(ns, struct user_namespace, ns);
}

static struct ns_common *userns_get(struct task_struct *task)
{
	struct user_namespace *user_ns;

	rcu_read_lock();
	user_ns = get_user_ns(__task_cred(task)->user_ns);
	rcu_read_unlock();

	return user_ns ? &user_ns->ns : NULL;
}

static void userns_put(struct ns_common *ns)
{
	put_user_ns(to_user_ns(ns));
}

static int userns_install(struct nsproxy *nsproxy, struct ns_common *ns)
{
	struct user_namespace *user_ns = to_user_ns(ns);
	struct cred *cred;

	/* Don't allow gaining capabilities by reentering
	 * the same user namespace.
	 */
	if (user_ns == current_user_ns())
		return -EINVAL;

	/* Tasks that share a thread group must share a user namespace */
	if (!thread_group_empty(current))
		return -EINVAL;

	if (current->fs->users != 1)
		return -EINVAL;

	if (!ns_capable(user_ns, CAP_SYS_ADMIN))
		return -EPERM;

	cred = prepare_creds();
	if (!cred)
		return -ENOMEM;

	put_user_ns(cred->user_ns);
	set_cred_user_ns(cred, get_user_ns(user_ns));

	return commit_creds(cred);
}

struct ns_common *ns_get_owner(struct ns_common *ns)
{
	struct user_namespace *my_user_ns = current_user_ns();
	struct user_namespace *owner, *p;

	/* See if the owner is in the current user namespace */
	owner = p = ns->ops->owner(ns);
	for (;;) {
		if (!p)
			return ERR_PTR(-EPERM);
		if (p == my_user_ns)
			break;
		p = p->parent;
	}

	return &get_user_ns(owner)->ns;
}

static struct user_namespace *userns_owner(struct ns_common *ns)
{
	return to_user_ns(ns)->parent;
}

const struct proc_ns_operations userns_operations = {
	.name		= "user",
	.type		= CLONE_NEWUSER,
	.get		= userns_get,
	.put		= userns_put,
	.install	= userns_install,
	.owner		= userns_owner,
	.get_parent	= ns_get_owner,
};

static __init int user_namespaces_init(void)
{
	user_ns_cachep = KMEM_CACHE(user_namespace, SLAB_PANIC);
	return 0;
}
subsys_initcall(user_namespaces_init);