summaryrefslogtreecommitdiff
path: root/security/keys/keyring.c
blob: 3663e516858393c8c764ccc931c944787307ae11 (plain)
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
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
1409
1410
1411
1412
1413
1414
1415
1416
1417
1418
1419
1420
1421
1422
1423
1424
1425
1426
1427
1428
1429
1430
1431
1432
1433
1434
1435
1436
1437
1438
1439
1440
1441
1442
1443
1444
1445
1446
1447
1448
1449
1450
1451
1452
1453
1454
1455
1456
1457
1458
1459
1460
1461
1462
1463
1464
1465
1466
1467
1468
1469
1470
1471
1472
1473
1474
1475
1476
1477
1478
1479
1480
1481
1482
1483
1484
1485
1486
1487
1488
1489
1490
1491
1492
1493
1494
1495
1496
1497
1498
1499
1500
1501
1502
1503
1504
1505
1506
1507
1508
1509
1510
1511
1512
1513
1514
1515
1516
1517
1518
1519
1520
1521
1522
1523
1524
1525
1526
1527
1528
1529
1530
1531
1532
1533
1534
1535
1536
1537
1538
1539
1540
1541
1542
1543
1544
1545
1546
1547
1548
1549
1550
1551
1552
1553
1554
1555
1556
1557
1558
1559
1560
1561
1562
1563
1564
1565
1566
1567
1568
1569
1570
1571
1572
1573
1574
1575
1576
1577
1578
1579
1580
1581
1582
1583
1584
1585
1586
1587
1588
1589
1590
1591
1592
1593
1594
1595
1596
1597
1598
1599
1600
1601
1602
1603
1604
1605
1606
1607
1608
1609
1610
1611
1612
1613
1614
1615
1616
1617
1618
1619
1620
1621
1622
1623
1624
1625
1626
1627
1628
1629
1630
1631
1632
1633
1634
1635
1636
1637
1638
1639
1640
1641
1642
1643
1644
1645
1646
1647
1648
1649
1650
1651
1652
1653
1654
1655
1656
1657
1658
1659
1660
1661
1662
1663
1664
1665
1666
1667
1668
1669
1670
1671
1672
1673
1674
1675
1676
1677
1678
1679
1680
1681
1682
1683
1684
1685
1686
1687
1688
1689
1690
1691
1692
1693
1694
1695
1696
1697
1698
1699
1700
1701
1702
1703
1704
1705
1706
1707
1708
1709
1710
1711
1712
1713
1714
1715
1716
1717
1718
1719
1720
1721
1722
1723
1724
1725
1726
1727
1728
1729
1730
1731
1732
1733
1734
1735
1736
1737
1738
1739
1740
1741
/* Keyring handling
 *
 * Copyright (C) 2004-2005, 2008, 2013 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 *
 * 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; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/export.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/security.h>
#include <linux/seq_file.h>
#include <linux/err.h>
#include <linux/user_namespace.h>
#include <keys/keyring-type.h>
#include <keys/user-type.h>
#include <linux/assoc_array_priv.h>
#include <linux/uaccess.h>
#include "internal.h"

/*
 * When plumbing the depths of the key tree, this sets a hard limit
 * set on how deep we're willing to go.
 */
#define KEYRING_SEARCH_MAX_DEPTH 6

/*
 * We mark pointers we pass to the associative array with bit 1 set if
 * they're keyrings and clear otherwise.
 */
#define KEYRING_PTR_SUBTYPE	0x2UL

static inline bool keyring_ptr_is_keyring(const struct assoc_array_ptr *x)
{
	return (unsigned long)x & KEYRING_PTR_SUBTYPE;
}
static inline struct key *keyring_ptr_to_key(const struct assoc_array_ptr *x)
{
	void *object = assoc_array_ptr_to_leaf(x);
	return (struct key *)((unsigned long)object & ~KEYRING_PTR_SUBTYPE);
}
static inline void *keyring_key_to_ptr(struct key *key)
{
	if (key->type == &key_type_keyring)
		return (void *)((unsigned long)key | KEYRING_PTR_SUBTYPE);
	return key;
}

static DEFINE_RWLOCK(keyring_name_lock);

/*
 * Clean up the bits of user_namespace that belong to us.
 */
void key_free_user_ns(struct user_namespace *ns)
{
	write_lock(&keyring_name_lock);
	list_del_init(&ns->keyring_name_list);
	write_unlock(&keyring_name_lock);

	key_put(ns->user_keyring_register);
#ifdef CONFIG_PERSISTENT_KEYRINGS
	key_put(ns->persistent_keyring_register);
#endif
}

/*
 * The keyring key type definition.  Keyrings are simply keys of this type and
 * can be treated as ordinary keys in addition to having their own special
 * operations.
 */
static int keyring_preparse(struct key_preparsed_payload *prep);
static void keyring_free_preparse(struct key_preparsed_payload *prep);
static int keyring_instantiate(struct key *keyring,
			       struct key_preparsed_payload *prep);
static void keyring_revoke(struct key *keyring);
static void keyring_destroy(struct key *keyring);
static void keyring_describe(const struct key *keyring, struct seq_file *m);
static long keyring_read(const struct key *keyring,
			 char __user *buffer, size_t buflen);

struct key_type key_type_keyring = {
	.name		= "keyring",
	.def_datalen	= 0,
	.preparse	= keyring_preparse,
	.free_preparse	= keyring_free_preparse,
	.instantiate	= keyring_instantiate,
	.revoke		= keyring_revoke,
	.destroy	= keyring_destroy,
	.describe	= keyring_describe,
	.read		= keyring_read,
};
EXPORT_SYMBOL(key_type_keyring);

/*
 * Semaphore to serialise link/link calls to prevent two link calls in parallel
 * introducing a cycle.
 */
static DEFINE_MUTEX(keyring_serialise_link_lock);

/*
 * Publish the name of a keyring so that it can be found by name (if it has
 * one and it doesn't begin with a dot).
 */
static void keyring_publish_name(struct key *keyring)
{
	struct user_namespace *ns = current_user_ns();

	if (keyring->description &&
	    keyring->description[0] &&
	    keyring->description[0] != '.') {
		write_lock(&keyring_name_lock);
		list_add_tail(&keyring->name_link, &ns->keyring_name_list);
		write_unlock(&keyring_name_lock);
	}
}

/*
 * Preparse a keyring payload
 */
static int keyring_preparse(struct key_preparsed_payload *prep)
{
	return prep->datalen != 0 ? -EINVAL : 0;
}

/*
 * Free a preparse of a user defined key payload
 */
static void keyring_free_preparse(struct key_preparsed_payload *prep)
{
}

/*
 * Initialise a keyring.
 *
 * Returns 0 on success, -EINVAL if given any data.
 */
static int keyring_instantiate(struct key *keyring,
			       struct key_preparsed_payload *prep)
{
	assoc_array_init(&keyring->keys);
	/* make the keyring available by name if it has one */
	keyring_publish_name(keyring);
	return 0;
}

/*
 * Multiply 64-bits by 32-bits to 96-bits and fold back to 64-bit.  Ideally we'd
 * fold the carry back too, but that requires inline asm.
 */
static u64 mult_64x32_and_fold(u64 x, u32 y)
{
	u64 hi = (u64)(u32)(x >> 32) * y;
	u64 lo = (u64)(u32)(x) * y;
	return lo + ((u64)(u32)hi << 32) + (u32)(hi >> 32);
}

/*
 * Hash a key type and description.
 */
static void hash_key_type_and_desc(struct keyring_index_key *index_key)
{
	const unsigned level_shift = ASSOC_ARRAY_LEVEL_STEP;
	const unsigned long fan_mask = ASSOC_ARRAY_FAN_MASK;
	const char *description = index_key->description;
	unsigned long hash, type;
	u32 piece;
	u64 acc;
	int n, desc_len = index_key->desc_len;

	type = (unsigned long)index_key->type;
	acc = mult_64x32_and_fold(type, desc_len + 13);
	acc = mult_64x32_and_fold(acc, 9207);

	for (;;) {
		n = desc_len;
		if (n <= 0)
			break;
		if (n > 4)
			n = 4;
		piece = 0;
		memcpy(&piece, description, n);
		description += n;
		desc_len -= n;
		acc = mult_64x32_and_fold(acc, piece);
		acc = mult_64x32_and_fold(acc, 9207);
	}

	/* Fold the hash down to 32 bits if need be. */
	hash = acc;
	if (ASSOC_ARRAY_KEY_CHUNK_SIZE == 32)
		hash ^= acc >> 32;

	/* Squidge all the keyrings into a separate part of the tree to
	 * ordinary keys by making sure the lowest level segment in the hash is
	 * zero for keyrings and non-zero otherwise.
	 */
	if (index_key->type != &key_type_keyring && (hash & fan_mask) == 0)
		hash |= (hash >> (ASSOC_ARRAY_KEY_CHUNK_SIZE - level_shift)) | 1;
	else if (index_key->type == &key_type_keyring && (hash & fan_mask) != 0)
		hash = (hash + (hash << level_shift)) & ~fan_mask;
	index_key->hash = hash;
}

/*
 * Finalise an index key to include a part of the description actually in the
 * index key and to add in the hash too.
 */
void key_set_index_key(struct keyring_index_key *index_key)
{
	size_t n = min_t(size_t, index_key->desc_len, sizeof(index_key->desc));
	memcpy(index_key->desc, index_key->description, n);

	hash_key_type_and_desc(index_key);
}

/*
 * Build the next index key chunk.
 *
 * We return it one word-sized chunk at a time.
 */
static unsigned long keyring_get_key_chunk(const void *data, int level)
{
	const struct keyring_index_key *index_key = data;
	unsigned long chunk = 0;
	const u8 *d;
	int desc_len = index_key->desc_len, n = sizeof(chunk);

	level /= ASSOC_ARRAY_KEY_CHUNK_SIZE;
	switch (level) {
	case 0:
		return index_key->hash;
	case 1:
		return index_key->x;
	case 2:
		return (unsigned long)index_key->type;
	default:
		level -= 3;
		if (desc_len <= sizeof(index_key->desc))
			return 0;

		d = index_key->description + sizeof(index_key->desc);
		d += level * sizeof(long);
		desc_len -= sizeof(index_key->desc);
		if (desc_len > n)
			desc_len = n;
		do {
			chunk <<= 8;
			chunk |= *d++;
		} while (--desc_len > 0);
		return chunk;
	}
}

static unsigned long keyring_get_object_key_chunk(const void *object, int level)
{
	const struct key *key = keyring_ptr_to_key(object);
	return keyring_get_key_chunk(&key->index_key, level);
}

static bool keyring_compare_object(const void *object, const void *data)
{
	const struct keyring_index_key *index_key = data;
	const struct key *key = keyring_ptr_to_key(object);

	return key->index_key.type == index_key->type &&
		key->index_key.desc_len == index_key->desc_len &&
		memcmp(key->index_key.description, index_key->description,
		       index_key->desc_len) == 0;
}

/*
 * Compare the index keys of a pair of objects and determine the bit position
 * at which they differ - if they differ.
 */
static int keyring_diff_objects(const void *object, const void *data)
{
	const struct key *key_a = keyring_ptr_to_key(object);
	const struct keyring_index_key *a = &key_a->index_key;
	const struct keyring_index_key *b = data;
	unsigned long seg_a, seg_b;
	int level, i;

	level = 0;
	seg_a = a->hash;
	seg_b = b->hash;
	if ((seg_a ^ seg_b) != 0)
		goto differ;
	level += ASSOC_ARRAY_KEY_CHUNK_SIZE / 8;

	/* The number of bits contributed by the hash is controlled by a
	 * constant in the assoc_array headers.  Everything else thereafter we
	 * can deal with as being machine word-size dependent.
	 */
	seg_a = a->x;
	seg_b = b->x;
	if ((seg_a ^ seg_b) != 0)
		goto differ;
	level += sizeof(unsigned long);

	/* The next bit may not work on big endian */
	seg_a = (unsigned long)a->type;
	seg_b = (unsigned long)b->type;
	if ((seg_a ^ seg_b) != 0)
		goto differ;
	level += sizeof(unsigned long);

	i = sizeof(a->desc);
	if (a->desc_len <= i)
		goto same;

	for (; i < a->desc_len; i++) {
		seg_a = *(unsigned char *)(a->description + i);
		seg_b = *(unsigned char *)(b->description + i);
		if ((seg_a ^ seg_b) != 0)
			goto differ_plus_i;
	}

same:
	return -1;

differ_plus_i:
	level += i;
differ:
	i = level * 8 + __ffs(seg_a ^ seg_b);
	return i;
}

/*
 * Free an object after stripping the keyring flag off of the pointer.
 */
static void keyring_free_object(void *object)
{
	key_put(keyring_ptr_to_key(object));
}

/*
 * Operations for keyring management by the index-tree routines.
 */
static const struct assoc_array_ops keyring_assoc_array_ops = {
	.get_key_chunk		= keyring_get_key_chunk,
	.get_object_key_chunk	= keyring_get_object_key_chunk,
	.compare_object		= keyring_compare_object,
	.diff_objects		= keyring_diff_objects,
	.free_object		= keyring_free_object,
};

/*
 * Clean up a keyring when it is destroyed.  Unpublish its name if it had one
 * and dispose of its data.
 *
 * The garbage collector detects the final key_put(), removes the keyring from
 * the serial number tree and then does RCU synchronisation before coming here,
 * so we shouldn't need to worry about code poking around here with the RCU
 * readlock held by this time.
 */
static void keyring_destroy(struct key *keyring)
{
	if (keyring->description) {
		write_lock(&keyring_name_lock);

		if (keyring->name_link.next != NULL &&
		    !list_empty(&keyring->name_link))
			list_del(&keyring->name_link);

		write_unlock(&keyring_name_lock);
	}

	if (keyring->restrict_link) {
		struct key_restriction *keyres = keyring->restrict_link;

		key_put(keyres->key);
		kfree(keyres);
	}

	assoc_array_destroy(&keyring->keys, &keyring_assoc_array_ops);
}

/*
 * Describe a keyring for /proc.
 */
static void keyring_describe(const struct key *keyring, struct seq_file *m)
{
	if (keyring->description)
		seq_puts(m, keyring->description);
	else
		seq_puts(m, "[anon]");

	if (key_is_positive(keyring)) {
		if (keyring->keys.nr_leaves_on_tree != 0)
			seq_printf(m, ": %lu", keyring->keys.nr_leaves_on_tree);
		else
			seq_puts(m, ": empty");
	}
}

struct keyring_read_iterator_context {
	size_t			buflen;
	size_t			count;
	key_serial_t __user	*buffer;
};

static int keyring_read_iterator(const void *object, void *data)
{
	struct keyring_read_iterator_context *ctx = data;
	const struct key *key = keyring_ptr_to_key(object);
	int ret;

	kenter("{%s,%d},,{%zu/%zu}",
	       key->type->name, key->serial, ctx->count, ctx->buflen);

	if (ctx->count >= ctx->buflen)
		return 1;

	ret = put_user(key->serial, ctx->buffer);
	if (ret < 0)
		return ret;
	ctx->buffer++;
	ctx->count += sizeof(key->serial);
	return 0;
}

/*
 * Read a list of key IDs from the keyring's contents in binary form
 *
 * The keyring's semaphore is read-locked by the caller.  This prevents someone
 * from modifying it under us - which could cause us to read key IDs multiple
 * times.
 */
static long keyring_read(const struct key *keyring,
			 char __user *buffer, size_t buflen)
{
	struct keyring_read_iterator_context ctx;
	long ret;

	kenter("{%d},,%zu", key_serial(keyring), buflen);

	if (buflen & (sizeof(key_serial_t) - 1))
		return -EINVAL;

	/* Copy as many key IDs as fit into the buffer */
	if (buffer && buflen) {
		ctx.buffer = (key_serial_t __user *)buffer;
		ctx.buflen = buflen;
		ctx.count = 0;
		ret = assoc_array_iterate(&keyring->keys,
					  keyring_read_iterator, &ctx);
		if (ret < 0) {
			kleave(" = %ld [iterate]", ret);
			return ret;
		}
	}

	/* Return the size of the buffer needed */
	ret = keyring->keys.nr_leaves_on_tree * sizeof(key_serial_t);
	if (ret <= buflen)
		kleave("= %ld [ok]", ret);
	else
		kleave("= %ld [buffer too small]", ret);
	return ret;
}

/*
 * Allocate a keyring and link into the destination keyring.
 */
struct key *keyring_alloc(const char *description, kuid_t uid, kgid_t gid,
			  const struct cred *cred, key_perm_t perm,
			  unsigned long flags,
			  struct key_restriction *restrict_link,
			  struct key *dest)
{
	struct key *keyring;
	int ret;

	keyring = key_alloc(&key_type_keyring, description,
			    uid, gid, cred, perm, flags, restrict_link);
	if (!IS_ERR(keyring)) {
		ret = key_instantiate_and_link(keyring, NULL, 0, dest, NULL);
		if (ret < 0) {
			key_put(keyring);
			keyring = ERR_PTR(ret);
		}
	}

	return keyring;
}
EXPORT_SYMBOL(keyring_alloc);

/**
 * restrict_link_reject - Give -EPERM to restrict link
 * @keyring: The keyring being added to.
 * @type: The type of key being added.
 * @payload: The payload of the key intended to be added.
 * @restriction_key: Keys providing additional data for evaluating restriction.
 *
 * Reject the addition of any links to a keyring.  It can be overridden by
 * passing KEY_ALLOC_BYPASS_RESTRICTION to key_instantiate_and_link() when
 * adding a key to a keyring.
 *
 * This is meant to be stored in a key_restriction structure which is passed
 * in the restrict_link parameter to keyring_alloc().
 */
int restrict_link_reject(struct key *keyring,
			 const struct key_type *type,
			 const union key_payload *payload,
			 struct key *restriction_key)
{
	return -EPERM;
}

/*
 * By default, we keys found by getting an exact match on their descriptions.
 */
bool key_default_cmp(const struct key *key,
		     const struct key_match_data *match_data)
{
	return strcmp(key->description, match_data->raw_data) == 0;
}

/*
 * Iteration function to consider each key found.
 */
static int keyring_search_iterator(const void *object, void *iterator_data)
{
	struct keyring_search_context *ctx = iterator_data;
	const struct key *key = keyring_ptr_to_key(object);
	unsigned long kflags = READ_ONCE(key->flags);
	short state = READ_ONCE(key->state);

	kenter("{%d}", key->serial);

	/* ignore keys not of this type */
	if (key->type != ctx->index_key.type) {
		kleave(" = 0 [!type]");
		return 0;
	}

	/* skip invalidated, revoked and expired keys */
	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
		time64_t expiry = READ_ONCE(key->expiry);

		if (kflags & ((1 << KEY_FLAG_INVALIDATED) |
			      (1 << KEY_FLAG_REVOKED))) {
			ctx->result = ERR_PTR(-EKEYREVOKED);
			kleave(" = %d [invrev]", ctx->skipped_ret);
			goto skipped;
		}

		if (expiry && ctx->now >= expiry) {
			if (!(ctx->flags & KEYRING_SEARCH_SKIP_EXPIRED))
				ctx->result = ERR_PTR(-EKEYEXPIRED);
			kleave(" = %d [expire]", ctx->skipped_ret);
			goto skipped;
		}
	}

	/* keys that don't match */
	if (!ctx->match_data.cmp(key, &ctx->match_data)) {
		kleave(" = 0 [!match]");
		return 0;
	}

	/* key must have search permissions */
	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
	    key_task_permission(make_key_ref(key, ctx->possessed),
				ctx->cred, KEY_NEED_SEARCH) < 0) {
		ctx->result = ERR_PTR(-EACCES);
		kleave(" = %d [!perm]", ctx->skipped_ret);
		goto skipped;
	}

	if (ctx->flags & KEYRING_SEARCH_DO_STATE_CHECK) {
		/* we set a different error code if we pass a negative key */
		if (state < 0) {
			ctx->result = ERR_PTR(state);
			kleave(" = %d [neg]", ctx->skipped_ret);
			goto skipped;
		}
	}

	/* Found */
	ctx->result = make_key_ref(key, ctx->possessed);
	kleave(" = 1 [found]");
	return 1;

skipped:
	return ctx->skipped_ret;
}

/*
 * Search inside a keyring for a key.  We can search by walking to it
 * directly based on its index-key or we can iterate over the entire
 * tree looking for it, based on the match function.
 */
static int search_keyring(struct key *keyring, struct keyring_search_context *ctx)
{
	if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_DIRECT) {
		const void *object;

		object = assoc_array_find(&keyring->keys,
					  &keyring_assoc_array_ops,
					  &ctx->index_key);
		return object ? ctx->iterator(object, ctx) : 0;
	}
	return assoc_array_iterate(&keyring->keys, ctx->iterator, ctx);
}

/*
 * Search a tree of keyrings that point to other keyrings up to the maximum
 * depth.
 */
static bool search_nested_keyrings(struct key *keyring,
				   struct keyring_search_context *ctx)
{
	struct {
		struct key *keyring;
		struct assoc_array_node *node;
		int slot;
	} stack[KEYRING_SEARCH_MAX_DEPTH];

	struct assoc_array_shortcut *shortcut;
	struct assoc_array_node *node;
	struct assoc_array_ptr *ptr;
	struct key *key;
	int sp = 0, slot;

	kenter("{%d},{%s,%s}",
	       keyring->serial,
	       ctx->index_key.type->name,
	       ctx->index_key.description);

#define STATE_CHECKS (KEYRING_SEARCH_NO_STATE_CHECK | KEYRING_SEARCH_DO_STATE_CHECK)
	BUG_ON((ctx->flags & STATE_CHECKS) == 0 ||
	       (ctx->flags & STATE_CHECKS) == STATE_CHECKS);

	if (ctx->index_key.description)
		key_set_index_key(&ctx->index_key);

	/* Check to see if this top-level keyring is what we are looking for
	 * and whether it is valid or not.
	 */
	if (ctx->match_data.lookup_type == KEYRING_SEARCH_LOOKUP_ITERATE ||
	    keyring_compare_object(keyring, &ctx->index_key)) {
		ctx->skipped_ret = 2;
		switch (ctx->iterator(keyring_key_to_ptr(keyring), ctx)) {
		case 1:
			goto found;
		case 2:
			return false;
		default:
			break;
		}
	}

	ctx->skipped_ret = 0;

	/* Start processing a new keyring */
descend_to_keyring:
	kdebug("descend to %d", keyring->serial);
	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
			      (1 << KEY_FLAG_REVOKED)))
		goto not_this_keyring;

	/* Search through the keys in this keyring before its searching its
	 * subtrees.
	 */
	if (search_keyring(keyring, ctx))
		goto found;

	/* Then manually iterate through the keyrings nested in this one.
	 *
	 * Start from the root node of the index tree.  Because of the way the
	 * hash function has been set up, keyrings cluster on the leftmost
	 * branch of the root node (root slot 0) or in the root node itself.
	 * Non-keyrings avoid the leftmost branch of the root entirely (root
	 * slots 1-15).
	 */
	if (!(ctx->flags & KEYRING_SEARCH_RECURSE))
		goto not_this_keyring;

	ptr = READ_ONCE(keyring->keys.root);
	if (!ptr)
		goto not_this_keyring;

	if (assoc_array_ptr_is_shortcut(ptr)) {
		/* If the root is a shortcut, either the keyring only contains
		 * keyring pointers (everything clusters behind root slot 0) or
		 * doesn't contain any keyring pointers.
		 */
		shortcut = assoc_array_ptr_to_shortcut(ptr);
		if ((shortcut->index_key[0] & ASSOC_ARRAY_FAN_MASK) != 0)
			goto not_this_keyring;

		ptr = READ_ONCE(shortcut->next_node);
		node = assoc_array_ptr_to_node(ptr);
		goto begin_node;
	}

	node = assoc_array_ptr_to_node(ptr);
	ptr = node->slots[0];
	if (!assoc_array_ptr_is_meta(ptr))
		goto begin_node;

descend_to_node:
	/* Descend to a more distal node in this keyring's content tree and go
	 * through that.
	 */
	kdebug("descend");
	if (assoc_array_ptr_is_shortcut(ptr)) {
		shortcut = assoc_array_ptr_to_shortcut(ptr);
		ptr = READ_ONCE(shortcut->next_node);
		BUG_ON(!assoc_array_ptr_is_node(ptr));
	}
	node = assoc_array_ptr_to_node(ptr);

begin_node:
	kdebug("begin_node");
	slot = 0;
ascend_to_node:
	/* Go through the slots in a node */
	for (; slot < ASSOC_ARRAY_FAN_OUT; slot++) {
		ptr = READ_ONCE(node->slots[slot]);

		if (assoc_array_ptr_is_meta(ptr) && node->back_pointer)
			goto descend_to_node;

		if (!keyring_ptr_is_keyring(ptr))
			continue;

		key = keyring_ptr_to_key(ptr);

		if (sp >= KEYRING_SEARCH_MAX_DEPTH) {
			if (ctx->flags & KEYRING_SEARCH_DETECT_TOO_DEEP) {
				ctx->result = ERR_PTR(-ELOOP);
				return false;
			}
			goto not_this_keyring;
		}

		/* Search a nested keyring */
		if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM) &&
		    key_task_permission(make_key_ref(key, ctx->possessed),
					ctx->cred, KEY_NEED_SEARCH) < 0)
			continue;

		/* stack the current position */
		stack[sp].keyring = keyring;
		stack[sp].node = node;
		stack[sp].slot = slot;
		sp++;

		/* begin again with the new keyring */
		keyring = key;
		goto descend_to_keyring;
	}

	/* We've dealt with all the slots in the current node, so now we need
	 * to ascend to the parent and continue processing there.
	 */
	ptr = READ_ONCE(node->back_pointer);
	slot = node->parent_slot;

	if (ptr && assoc_array_ptr_is_shortcut(ptr)) {
		shortcut = assoc_array_ptr_to_shortcut(ptr);
		ptr = READ_ONCE(shortcut->back_pointer);
		slot = shortcut->parent_slot;
	}
	if (!ptr)
		goto not_this_keyring;
	node = assoc_array_ptr_to_node(ptr);
	slot++;

	/* If we've ascended to the root (zero backpointer), we must have just
	 * finished processing the leftmost branch rather than the root slots -
	 * so there can't be any more keyrings for us to find.
	 */
	if (node->back_pointer) {
		kdebug("ascend %d", slot);
		goto ascend_to_node;
	}

	/* The keyring we're looking at was disqualified or didn't contain a
	 * matching key.
	 */
not_this_keyring:
	kdebug("not_this_keyring %d", sp);
	if (sp <= 0) {
		kleave(" = false");
		return false;
	}

	/* Resume the processing of a keyring higher up in the tree */
	sp--;
	keyring = stack[sp].keyring;
	node = stack[sp].node;
	slot = stack[sp].slot + 1;
	kdebug("ascend to %d [%d]", keyring->serial, slot);
	goto ascend_to_node;

	/* We found a viable match */
found:
	key = key_ref_to_ptr(ctx->result);
	key_check(key);
	if (!(ctx->flags & KEYRING_SEARCH_NO_UPDATE_TIME)) {
		key->last_used_at = ctx->now;
		keyring->last_used_at = ctx->now;
		while (sp > 0)
			stack[--sp].keyring->last_used_at = ctx->now;
	}
	kleave(" = true");
	return true;
}

/**
 * keyring_search_rcu - Search a keyring tree for a matching key under RCU
 * @keyring_ref: A pointer to the keyring with possession indicator.
 * @ctx: The keyring search context.
 *
 * Search the supplied keyring tree for a key that matches the criteria given.
 * The root keyring and any linked keyrings must grant Search permission to the
 * caller to be searchable and keys can only be found if they too grant Search
 * to the caller. The possession flag on the root keyring pointer controls use
 * of the possessor bits in permissions checking of the entire tree.  In
 * addition, the LSM gets to forbid keyring searches and key matches.
 *
 * The search is performed as a breadth-then-depth search up to the prescribed
 * limit (KEYRING_SEARCH_MAX_DEPTH).  The caller must hold the RCU read lock to
 * prevent keyrings from being destroyed or rearranged whilst they are being
 * searched.
 *
 * Keys are matched to the type provided and are then filtered by the match
 * function, which is given the description to use in any way it sees fit.  The
 * match function may use any attributes of a key that it wishes to to
 * determine the match.  Normally the match function from the key type would be
 * used.
 *
 * RCU can be used to prevent the keyring key lists from disappearing without
 * the need to take lots of locks.
 *
 * Returns a pointer to the found key and increments the key usage count if
 * successful; -EAGAIN if no matching keys were found, or if expired or revoked
 * keys were found; -ENOKEY if only negative keys were found; -ENOTDIR if the
 * specified keyring wasn't a keyring.
 *
 * In the case of a successful return, the possession attribute from
 * @keyring_ref is propagated to the returned key reference.
 */
key_ref_t keyring_search_rcu(key_ref_t keyring_ref,
			     struct keyring_search_context *ctx)
{
	struct key *keyring;
	long err;

	ctx->iterator = keyring_search_iterator;
	ctx->possessed = is_key_possessed(keyring_ref);
	ctx->result = ERR_PTR(-EAGAIN);

	keyring = key_ref_to_ptr(keyring_ref);
	key_check(keyring);

	if (keyring->type != &key_type_keyring)
		return ERR_PTR(-ENOTDIR);

	if (!(ctx->flags & KEYRING_SEARCH_NO_CHECK_PERM)) {
		err = key_task_permission(keyring_ref, ctx->cred, KEY_NEED_SEARCH);
		if (err < 0)
			return ERR_PTR(err);
	}

	ctx->now = ktime_get_real_seconds();
	if (search_nested_keyrings(keyring, ctx))
		__key_get(key_ref_to_ptr(ctx->result));
	return ctx->result;
}

/**
 * keyring_search - Search the supplied keyring tree for a matching key
 * @keyring: The root of the keyring tree to be searched.
 * @type: The type of keyring we want to find.
 * @description: The name of the keyring we want to find.
 * @recurse: True to search the children of @keyring also
 *
 * As keyring_search_rcu() above, but using the current task's credentials and
 * type's default matching function and preferred search method.
 */
key_ref_t keyring_search(key_ref_t keyring,
			 struct key_type *type,
			 const char *description,
			 bool recurse)
{
	struct keyring_search_context ctx = {
		.index_key.type		= type,
		.index_key.description	= description,
		.index_key.desc_len	= strlen(description),
		.cred			= current_cred(),
		.match_data.cmp		= key_default_cmp,
		.match_data.raw_data	= description,
		.match_data.lookup_type	= KEYRING_SEARCH_LOOKUP_DIRECT,
		.flags			= KEYRING_SEARCH_DO_STATE_CHECK,
	};
	key_ref_t key;
	int ret;

	if (recurse)
		ctx.flags |= KEYRING_SEARCH_RECURSE;
	if (type->match_preparse) {
		ret = type->match_preparse(&ctx.match_data);
		if (ret < 0)
			return ERR_PTR(ret);
	}

	rcu_read_lock();
	key = keyring_search_rcu(keyring, &ctx);
	rcu_read_unlock();

	if (type->match_free)
		type->match_free(&ctx.match_data);
	return key;
}
EXPORT_SYMBOL(keyring_search);

static struct key_restriction *keyring_restriction_alloc(
	key_restrict_link_func_t check)
{
	struct key_restriction *keyres =
		kzalloc(sizeof(struct key_restriction), GFP_KERNEL);

	if (!keyres)
		return ERR_PTR(-ENOMEM);

	keyres->check = check;

	return keyres;
}

/*
 * Semaphore to serialise restriction setup to prevent reference count
 * cycles through restriction key pointers.
 */
static DECLARE_RWSEM(keyring_serialise_restrict_sem);

/*
 * Check for restriction cycles that would prevent keyring garbage collection.
 * keyring_serialise_restrict_sem must be held.
 */
static bool keyring_detect_restriction_cycle(const struct key *dest_keyring,
					     struct key_restriction *keyres)
{
	while (keyres && keyres->key &&
	       keyres->key->type == &key_type_keyring) {
		if (keyres->key == dest_keyring)
			return true;

		keyres = keyres->key->restrict_link;
	}

	return false;
}

/**
 * keyring_restrict - Look up and apply a restriction to a keyring
 * @keyring_ref: The keyring to be restricted
 * @type: The key type that will provide the restriction checker.
 * @restriction: The restriction options to apply to the keyring
 *
 * Look up a keyring and apply a restriction to it.  The restriction is managed
 * by the specific key type, but can be configured by the options specified in
 * the restriction string.
 */
int keyring_restrict(key_ref_t keyring_ref, const char *type,
		     const char *restriction)
{
	struct key *keyring;
	struct key_type *restrict_type = NULL;
	struct key_restriction *restrict_link;
	int ret = 0;

	keyring = key_ref_to_ptr(keyring_ref);
	key_check(keyring);

	if (keyring->type != &key_type_keyring)
		return -ENOTDIR;

	if (!type) {
		restrict_link = keyring_restriction_alloc(restrict_link_reject);
	} else {
		restrict_type = key_type_lookup(type);

		if (IS_ERR(restrict_type))
			return PTR_ERR(restrict_type);

		if (!restrict_type->lookup_restriction) {
			ret = -ENOENT;
			goto error;
		}

		restrict_link = restrict_type->lookup_restriction(restriction);
	}

	if (IS_ERR(restrict_link)) {
		ret = PTR_ERR(restrict_link);
		goto error;
	}

	down_write(&keyring->sem);
	down_write(&keyring_serialise_restrict_sem);

	if (keyring->restrict_link)
		ret = -EEXIST;
	else if (keyring_detect_restriction_cycle(keyring, restrict_link))
		ret = -EDEADLK;
	else
		keyring->restrict_link = restrict_link;

	up_write(&keyring_serialise_restrict_sem);
	up_write(&keyring->sem);

	if (ret < 0) {
		key_put(restrict_link->key);
		kfree(restrict_link);
	}

error:
	if (restrict_type)
		key_type_put(restrict_type);

	return ret;
}
EXPORT_SYMBOL(keyring_restrict);

/*
 * Search the given keyring for a key that might be updated.
 *
 * The caller must guarantee that the keyring is a keyring and that the
 * permission is granted to modify the keyring as no check is made here.  The
 * caller must also hold a lock on the keyring semaphore.
 *
 * Returns a pointer to the found key with usage count incremented if
 * successful and returns NULL if not found.  Revoked and invalidated keys are
 * skipped over.
 *
 * If successful, the possession indicator is propagated from the keyring ref
 * to the returned key reference.
 */
key_ref_t find_key_to_update(key_ref_t keyring_ref,
			     const struct keyring_index_key *index_key)
{
	struct key *keyring, *key;
	const void *object;

	keyring = key_ref_to_ptr(keyring_ref);

	kenter("{%d},{%s,%s}",
	       keyring->serial, index_key->type->name, index_key->description);

	object = assoc_array_find(&keyring->keys, &keyring_assoc_array_ops,
				  index_key);

	if (object)
		goto found;

	kleave(" = NULL");
	return NULL;

found:
	key = keyring_ptr_to_key(object);
	if (key->flags & ((1 << KEY_FLAG_INVALIDATED) |
			  (1 << KEY_FLAG_REVOKED))) {
		kleave(" = NULL [x]");
		return NULL;
	}
	__key_get(key);
	kleave(" = {%d}", key->serial);
	return make_key_ref(key, is_key_possessed(keyring_ref));
}

/*
 * Find a keyring with the specified name.
 *
 * Only keyrings that have nonzero refcount, are not revoked, and are owned by a
 * user in the current user namespace are considered.  If @uid_keyring is %true,
 * the keyring additionally must have been allocated as a user or user session
 * keyring; otherwise, it must grant Search permission directly to the caller.
 *
 * Returns a pointer to the keyring with the keyring's refcount having being
 * incremented on success.  -ENOKEY is returned if a key could not be found.
 */
struct key *find_keyring_by_name(const char *name, bool uid_keyring)
{
	struct user_namespace *ns = current_user_ns();
	struct key *keyring;

	if (!name)
		return ERR_PTR(-EINVAL);

	read_lock(&keyring_name_lock);

	/* Search this hash bucket for a keyring with a matching name that
	 * grants Search permission and that hasn't been revoked
	 */
	list_for_each_entry(keyring, &ns->keyring_name_list, name_link) {
		if (!kuid_has_mapping(ns, keyring->user->uid))
			continue;

		if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
			continue;

		if (strcmp(keyring->description, name) != 0)
			continue;

		if (uid_keyring) {
			if (!test_bit(KEY_FLAG_UID_KEYRING,
				      &keyring->flags))
				continue;
		} else {
			if (key_permission(make_key_ref(keyring, 0),
					   KEY_NEED_SEARCH) < 0)
				continue;
		}

		/* we've got a match but we might end up racing with
		 * key_cleanup() if the keyring is currently 'dead'
		 * (ie. it has a zero usage count) */
		if (!refcount_inc_not_zero(&keyring->usage))
			continue;
		keyring->last_used_at = ktime_get_real_seconds();
		goto out;
	}

	keyring = ERR_PTR(-ENOKEY);
out:
	read_unlock(&keyring_name_lock);
	return keyring;
}

static int keyring_detect_cycle_iterator(const void *object,
					 void *iterator_data)
{
	struct keyring_search_context *ctx = iterator_data;
	const struct key *key = keyring_ptr_to_key(object);

	kenter("{%d}", key->serial);

	/* We might get a keyring with matching index-key that is nonetheless a
	 * different keyring. */
	if (key != ctx->match_data.raw_data)
		return 0;

	ctx->result = ERR_PTR(-EDEADLK);
	return 1;
}

/*
 * See if a cycle will will be created by inserting acyclic tree B in acyclic
 * tree A at the topmost level (ie: as a direct child of A).
 *
 * Since we are adding B to A at the top level, checking for cycles should just
 * be a matter of seeing if node A is somewhere in tree B.
 */
static int keyring_detect_cycle(struct key *A, struct key *B)
{
	struct keyring_search_context ctx = {
		.index_key		= A->index_key,
		.match_data.raw_data	= A,
		.match_data.lookup_type = KEYRING_SEARCH_LOOKUP_DIRECT,
		.iterator		= keyring_detect_cycle_iterator,
		.flags			= (KEYRING_SEARCH_NO_STATE_CHECK |
					   KEYRING_SEARCH_NO_UPDATE_TIME |
					   KEYRING_SEARCH_NO_CHECK_PERM |
					   KEYRING_SEARCH_DETECT_TOO_DEEP |
					   KEYRING_SEARCH_RECURSE),
	};

	rcu_read_lock();
	search_nested_keyrings(B, &ctx);
	rcu_read_unlock();
	return PTR_ERR(ctx.result) == -EAGAIN ? 0 : PTR_ERR(ctx.result);
}

/*
 * Lock keyring for link.
 */
int __key_link_lock(struct key *keyring,
		    const struct keyring_index_key *index_key)
	__acquires(&keyring->sem)
	__acquires(&keyring_serialise_link_lock)
{
	if (keyring->type != &key_type_keyring)
		return -ENOTDIR;

	down_write(&keyring->sem);

	/* Serialise link/link calls to prevent parallel calls causing a cycle
	 * when linking two keyring in opposite orders.
	 */
	if (index_key->type == &key_type_keyring)
		mutex_lock(&keyring_serialise_link_lock);

	return 0;
}

/*
 * Lock keyrings for move (link/unlink combination).
 */
int __key_move_lock(struct key *l_keyring, struct key *u_keyring,
		    const struct keyring_index_key *index_key)
	__acquires(&l_keyring->sem)
	__acquires(&u_keyring->sem)
	__acquires(&keyring_serialise_link_lock)
{
	if (l_keyring->type != &key_type_keyring ||
	    u_keyring->type != &key_type_keyring)
		return -ENOTDIR;

	/* We have to be very careful here to take the keyring locks in the
	 * right order, lest we open ourselves to deadlocking against another
	 * move operation.
	 */
	if (l_keyring < u_keyring) {
		down_write(&l_keyring->sem);
		down_write_nested(&u_keyring->sem, 1);
	} else {
		down_write(&u_keyring->sem);
		down_write_nested(&l_keyring->sem, 1);
	}

	/* Serialise link/link calls to prevent parallel calls causing a cycle
	 * when linking two keyring in opposite orders.
	 */
	if (index_key->type == &key_type_keyring)
		mutex_lock(&keyring_serialise_link_lock);

	return 0;
}

/*
 * Preallocate memory so that a key can be linked into to a keyring.
 */
int __key_link_begin(struct key *keyring,
		     const struct keyring_index_key *index_key,
		     struct assoc_array_edit **_edit)
{
	struct assoc_array_edit *edit;
	int ret;

	kenter("%d,%s,%s,",
	       keyring->serial, index_key->type->name, index_key->description);

	BUG_ON(index_key->desc_len == 0);
	BUG_ON(*_edit != NULL);

	*_edit = NULL;

	ret = -EKEYREVOKED;
	if (test_bit(KEY_FLAG_REVOKED, &keyring->flags))
		goto error;

	/* Create an edit script that will insert/replace the key in the
	 * keyring tree.
	 */
	edit = assoc_array_insert(&keyring->keys,
				  &keyring_assoc_array_ops,
				  index_key,
				  NULL);
	if (IS_ERR(edit)) {
		ret = PTR_ERR(edit);
		goto error;
	}

	/* If we're not replacing a link in-place then we're going to need some
	 * extra quota.
	 */
	if (!edit->dead_leaf) {
		ret = key_payload_reserve(keyring,
					  keyring->datalen + KEYQUOTA_LINK_BYTES);
		if (ret < 0)
			goto error_cancel;
	}

	*_edit = edit;
	kleave(" = 0");
	return 0;

error_cancel:
	assoc_array_cancel_edit(edit);
error:
	kleave(" = %d", ret);
	return ret;
}

/*
 * Check already instantiated keys aren't going to be a problem.
 *
 * The caller must have called __key_link_begin(). Don't need to call this for
 * keys that were created since __key_link_begin() was called.
 */
int __key_link_check_live_key(struct key *keyring, struct key *key)
{
	if (key->type == &key_type_keyring)
		/* check that we aren't going to create a cycle by linking one
		 * keyring to another */
		return keyring_detect_cycle(keyring, key);
	return 0;
}

/*
 * Link a key into to a keyring.
 *
 * Must be called with __key_link_begin() having being called.  Discards any
 * already extant link to matching key if there is one, so that each keyring
 * holds at most one link to any given key of a particular type+description
 * combination.
 */
void __key_link(struct key *key, struct assoc_array_edit **_edit)
{
	__key_get(key);
	assoc_array_insert_set_object(*_edit, keyring_key_to_ptr(key));
	assoc_array_apply_edit(*_edit);
	*_edit = NULL;
}

/*
 * Finish linking a key into to a keyring.
 *
 * Must be called with __key_link_begin() having being called.
 */
void __key_link_end(struct key *keyring,
		    const struct keyring_index_key *index_key,
		    struct assoc_array_edit *edit)
	__releases(&keyring->sem)
	__releases(&keyring_serialise_link_lock)
{
	BUG_ON(index_key->type == NULL);
	kenter("%d,%s,", keyring->serial, index_key->type->name);

	if (edit) {
		if (!edit->dead_leaf) {
			key_payload_reserve(keyring,
				keyring->datalen - KEYQUOTA_LINK_BYTES);
		}
		assoc_array_cancel_edit(edit);
	}
	up_write(&keyring->sem);

	if (index_key->type == &key_type_keyring)
		mutex_unlock(&keyring_serialise_link_lock);
}

/*
 * Check addition of keys to restricted keyrings.
 */
static int __key_link_check_restriction(struct key *keyring, struct key *key)
{
	if (!keyring->restrict_link || !keyring->restrict_link->check)
		return 0;
	return keyring->restrict_link->check(keyring, key->type, &key->payload,
					     keyring->restrict_link->key);
}

/**
 * key_link - Link a key to a keyring
 * @keyring: The keyring to make the link in.
 * @key: The key to link to.
 *
 * Make a link in a keyring to a key, such that the keyring holds a reference
 * on that key and the key can potentially be found by searching that keyring.
 *
 * This function will write-lock the keyring's semaphore and will consume some
 * of the user's key data quota to hold the link.
 *
 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring,
 * -EKEYREVOKED if the keyring has been revoked, -ENFILE if the keyring is
 * full, -EDQUOT if there is insufficient key data quota remaining to add
 * another link or -ENOMEM if there's insufficient memory.
 *
 * It is assumed that the caller has checked that it is permitted for a link to
 * be made (the keyring should have Write permission and the key Link
 * permission).
 */
int key_link(struct key *keyring, struct key *key)
{
	struct assoc_array_edit *edit = NULL;
	int ret;

	kenter("{%d,%d}", keyring->serial, refcount_read(&keyring->usage));

	key_check(keyring);
	key_check(key);

	ret = __key_link_lock(keyring, &key->index_key);
	if (ret < 0)
		goto error;

	ret = __key_link_begin(keyring, &key->index_key, &edit);
	if (ret < 0)
		goto error_end;

	kdebug("begun {%d,%d}", keyring->serial, refcount_read(&keyring->usage));
	ret = __key_link_check_restriction(keyring, key);
	if (ret == 0)
		ret = __key_link_check_live_key(keyring, key);
	if (ret == 0)
		__key_link(key, &edit);

error_end:
	__key_link_end(keyring, &key->index_key, edit);
error:
	kleave(" = %d {%d,%d}", ret, keyring->serial, refcount_read(&keyring->usage));
	return ret;
}
EXPORT_SYMBOL(key_link);

/*
 * Lock a keyring for unlink.
 */
static int __key_unlink_lock(struct key *keyring)
	__acquires(&keyring->sem)
{
	if (keyring->type != &key_type_keyring)
		return -ENOTDIR;

	down_write(&keyring->sem);
	return 0;
}

/*
 * Begin the process of unlinking a key from a keyring.
 */
static int __key_unlink_begin(struct key *keyring, struct key *key,
			      struct assoc_array_edit **_edit)
{
	struct assoc_array_edit *edit;

	BUG_ON(*_edit != NULL);
	
	edit = assoc_array_delete(&keyring->keys, &keyring_assoc_array_ops,
				  &key->index_key);
	if (IS_ERR(edit))
		return PTR_ERR(edit);

	if (!edit)
		return -ENOENT;

	*_edit = edit;
	return 0;
}

/*
 * Apply an unlink change.
 */
static void __key_unlink(struct key *keyring, struct key *key,
			 struct assoc_array_edit **_edit)
{
	assoc_array_apply_edit(*_edit);
	*_edit = NULL;
	key_payload_reserve(keyring, keyring->datalen - KEYQUOTA_LINK_BYTES);
}

/*
 * Finish unlinking a key from to a keyring.
 */
static void __key_unlink_end(struct key *keyring,
			     struct key *key,
			     struct assoc_array_edit *edit)
	__releases(&keyring->sem)
{
	if (edit)
		assoc_array_cancel_edit(edit);
	up_write(&keyring->sem);
}

/**
 * key_unlink - Unlink the first link to a key from a keyring.
 * @keyring: The keyring to remove the link from.
 * @key: The key the link is to.
 *
 * Remove a link from a keyring to a key.
 *
 * This function will write-lock the keyring's semaphore.
 *
 * Returns 0 if successful, -ENOTDIR if the keyring isn't a keyring, -ENOENT if
 * the key isn't linked to by the keyring or -ENOMEM if there's insufficient
 * memory.
 *
 * It is assumed that the caller has checked that it is permitted for a link to
 * be removed (the keyring should have Write permission; no permissions are
 * required on the key).
 */
int key_unlink(struct key *keyring, struct key *key)
{
	struct assoc_array_edit *edit = NULL;
	int ret;

	key_check(keyring);
	key_check(key);

	ret = __key_unlink_lock(keyring);
	if (ret < 0)
		return ret;

	ret = __key_unlink_begin(keyring, key, &edit);
	if (ret == 0)
		__key_unlink(keyring, key, &edit);
	__key_unlink_end(keyring, key, edit);
	return ret;
}
EXPORT_SYMBOL(key_unlink);

/**
 * key_move - Move a key from one keyring to another
 * @key: The key to move
 * @from_keyring: The keyring to remove the link from.
 * @to_keyring: The keyring to make the link in.
 * @flags: Qualifying flags, such as KEYCTL_MOVE_EXCL.
 *
 * Make a link in @to_keyring to a key, such that the keyring holds a reference
 * on that key and the key can potentially be found by searching that keyring
 * whilst simultaneously removing a link to the key from @from_keyring.
 *
 * This function will write-lock both keyring's semaphores and will consume
 * some of the user's key data quota to hold the link on @to_keyring.
 *
 * Returns 0 if successful, -ENOTDIR if either keyring isn't a keyring,
 * -EKEYREVOKED if either keyring has been revoked, -ENFILE if the second
 * keyring is full, -EDQUOT if there is insufficient key data quota remaining
 * to add another link or -ENOMEM if there's insufficient memory.  If
 * KEYCTL_MOVE_EXCL is set, then -EEXIST will be returned if there's already a
 * matching key in @to_keyring.
 *
 * It is assumed that the caller has checked that it is permitted for a link to
 * be made (the keyring should have Write permission and the key Link
 * permission).
 */
int key_move(struct key *key,
	     struct key *from_keyring,
	     struct key *to_keyring,
	     unsigned int flags)
{
	struct assoc_array_edit *from_edit = NULL, *to_edit = NULL;
	int ret;

	kenter("%d,%d,%d", key->serial, from_keyring->serial, to_keyring->serial);

	if (from_keyring == to_keyring)
		return 0;

	key_check(key);
	key_check(from_keyring);
	key_check(to_keyring);

	ret = __key_move_lock(from_keyring, to_keyring, &key->index_key);
	if (ret < 0)
		goto out;
	ret = __key_unlink_begin(from_keyring, key, &from_edit);
	if (ret < 0)
		goto error;
	ret = __key_link_begin(to_keyring, &key->index_key, &to_edit);
	if (ret < 0)
		goto error;

	ret = -EEXIST;
	if (to_edit->dead_leaf && (flags & KEYCTL_MOVE_EXCL))
		goto error;

	ret = __key_link_check_restriction(to_keyring, key);
	if (ret < 0)
		goto error;
	ret = __key_link_check_live_key(to_keyring, key);
	if (ret < 0)
		goto error;

	__key_unlink(from_keyring, key, &from_edit);
	__key_link(key, &to_edit);
error:
	__key_link_end(to_keyring, &key->index_key, to_edit);
	__key_unlink_end(from_keyring, key, from_edit);
out:
	kleave(" = %d", ret);
	return ret;
}
EXPORT_SYMBOL(key_move);

/**
 * keyring_clear - Clear a keyring
 * @keyring: The keyring to clear.
 *
 * Clear the contents of the specified keyring.
 *
 * Returns 0 if successful or -ENOTDIR if the keyring isn't a keyring.
 */
int keyring_clear(struct key *keyring)
{
	struct assoc_array_edit *edit;
	int ret;

	if (keyring->type != &key_type_keyring)
		return -ENOTDIR;

	down_write(&keyring->sem);

	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
	if (IS_ERR(edit)) {
		ret = PTR_ERR(edit);
	} else {
		if (edit)
			assoc_array_apply_edit(edit);
		key_payload_reserve(keyring, 0);
		ret = 0;
	}

	up_write(&keyring->sem);
	return ret;
}
EXPORT_SYMBOL(keyring_clear);

/*
 * Dispose of the links from a revoked keyring.
 *
 * This is called with the key sem write-locked.
 */
static void keyring_revoke(struct key *keyring)
{
	struct assoc_array_edit *edit;

	edit = assoc_array_clear(&keyring->keys, &keyring_assoc_array_ops);
	if (!IS_ERR(edit)) {
		if (edit)
			assoc_array_apply_edit(edit);
		key_payload_reserve(keyring, 0);
	}
}

static bool keyring_gc_select_iterator(void *object, void *iterator_data)
{
	struct key *key = keyring_ptr_to_key(object);
	time64_t *limit = iterator_data;

	if (key_is_dead(key, *limit))
		return false;
	key_get(key);
	return true;
}

static int keyring_gc_check_iterator(const void *object, void *iterator_data)
{
	const struct key *key = keyring_ptr_to_key(object);
	time64_t *limit = iterator_data;

	key_check(key);
	return key_is_dead(key, *limit);
}

/*
 * Garbage collect pointers from a keyring.
 *
 * Not called with any locks held.  The keyring's key struct will not be
 * deallocated under us as only our caller may deallocate it.
 */
void keyring_gc(struct key *keyring, time64_t limit)
{
	int result;

	kenter("%x{%s}", keyring->serial, keyring->description ?: "");

	if (keyring->flags & ((1 << KEY_FLAG_INVALIDATED) |
			      (1 << KEY_FLAG_REVOKED)))
		goto dont_gc;

	/* scan the keyring looking for dead keys */
	rcu_read_lock();
	result = assoc_array_iterate(&keyring->keys,
				     keyring_gc_check_iterator, &limit);
	rcu_read_unlock();
	if (result == true)
		goto do_gc;

dont_gc:
	kleave(" [no gc]");
	return;

do_gc:
	down_write(&keyring->sem);
	assoc_array_gc(&keyring->keys, &keyring_assoc_array_ops,
		       keyring_gc_select_iterator, &limit);
	up_write(&keyring->sem);
	kleave(" [gc]");
}

/*
 * Garbage collect restriction pointers from a keyring.
 *
 * Keyring restrictions are associated with a key type, and must be cleaned
 * up if the key type is unregistered. The restriction is altered to always
 * reject additional keys so a keyring cannot be opened up by unregistering
 * a key type.
 *
 * Not called with any keyring locks held. The keyring's key struct will not
 * be deallocated under us as only our caller may deallocate it.
 *
 * The caller is required to hold key_types_sem and dead_type->sem. This is
 * fulfilled by key_gc_keytype() holding the locks on behalf of
 * key_garbage_collector(), which it invokes on a workqueue.
 */
void keyring_restriction_gc(struct key *keyring, struct key_type *dead_type)
{
	struct key_restriction *keyres;

	kenter("%x{%s}", keyring->serial, keyring->description ?: "");

	/*
	 * keyring->restrict_link is only assigned at key allocation time
	 * or with the key type locked, so the only values that could be
	 * concurrently assigned to keyring->restrict_link are for key
	 * types other than dead_type. Given this, it's ok to check
	 * the key type before acquiring keyring->sem.
	 */
	if (!dead_type || !keyring->restrict_link ||
	    keyring->restrict_link->keytype != dead_type) {
		kleave(" [no restriction gc]");
		return;
	}

	/* Lock the keyring to ensure that a link is not in progress */
	down_write(&keyring->sem);

	keyres = keyring->restrict_link;

	keyres->check = restrict_link_reject;

	key_put(keyres->key);
	keyres->key = NULL;
	keyres->keytype = NULL;

	up_write(&keyring->sem);

	kleave(" [restriction gc]");
}