aboutsummaryrefslogtreecommitdiff
path: root/security/keys/keyctl.c
blob: 070a53eab80f92df725142fc3aa51e44a33e73aa (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
/* keyctl.c: userspace keyctl operations
 *
 * Copyright (C) 2004-5 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/module.h>
#include <linux/init.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/syscalls.h>
#include <linux/keyctl.h>
#include <linux/fs.h>
#include <linux/capability.h>
#include <linux/string.h>
#include <linux/err.h>
#include <linux/vmalloc.h>
#include <linux/security.h>
#include <asm/uaccess.h>
#include "internal.h"

static int key_get_type_from_user(char *type,
				  const char __user *_type,
				  unsigned len)
{
	int ret;

	ret = strncpy_from_user(type, _type, len);

	if (ret < 0)
		return -EFAULT;

	if (ret == 0 || ret >= len)
		return -EINVAL;

	if (type[0] == '.')
		return -EPERM;

	type[len - 1] = '\0';

	return 0;
}

/*****************************************************************************/
/*
 * extract the description of a new key from userspace and either add it as a
 * new key to the specified keyring or update a matching key in that keyring
 * - the keyring must be writable
 * - returns the new key's serial number
 * - implements add_key()
 */
SYSCALL_DEFINE5(add_key, const char __user *, _type,
		const char __user *, _description,
		const void __user *, _payload,
		size_t, plen,
		key_serial_t, ringid)
{
	key_ref_t keyring_ref, key_ref;
	char type[32], *description;
	void *payload;
	long ret;
	bool vm;

	ret = -EINVAL;
	if (plen > 1024 * 1024 - 1)
		goto error;

	/* draw all the data into kernel space */
	ret = key_get_type_from_user(type, _type, sizeof(type));
	if (ret < 0)
		goto error;

	description = strndup_user(_description, PAGE_SIZE);
	if (IS_ERR(description)) {
		ret = PTR_ERR(description);
		goto error;
	}

	/* pull the payload in if one was supplied */
	payload = NULL;

	vm = false;
	if (_payload) {
		ret = -ENOMEM;
		payload = kmalloc(plen, GFP_KERNEL);
		if (!payload) {
			if (plen <= PAGE_SIZE)
				goto error2;
			vm = true;
			payload = vmalloc(plen);
			if (!payload)
				goto error2;
		}

		ret = -EFAULT;
		if (copy_from_user(payload, _payload, plen) != 0)
			goto error3;
	}

	/* find the target keyring (which must be writable) */
	keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
	if (IS_ERR(keyring_ref)) {
		ret = PTR_ERR(keyring_ref);
		goto error3;
	}

	/* create or update the requested key and add it to the target
	 * keyring */
	key_ref = key_create_or_update(keyring_ref, type, description,
				       payload, plen, KEY_PERM_UNDEF,
				       KEY_ALLOC_IN_QUOTA);
	if (!IS_ERR(key_ref)) {
		ret = key_ref_to_ptr(key_ref)->serial;
		key_ref_put(key_ref);
	}
	else {
		ret = PTR_ERR(key_ref);
	}

	key_ref_put(keyring_ref);
 error3:
	if (!vm)
		kfree(payload);
	else
		vfree(payload);
 error2:
	kfree(description);
 error:
	return ret;

} /* end sys_add_key() */

/*****************************************************************************/
/*
 * search the process keyrings for a matching key
 * - nested keyrings may also be searched if they have Search permission
 * - if a key is found, it will be attached to the destination keyring if
 *   there's one specified
 * - /sbin/request-key will be invoked if _callout_info is non-NULL
 *   - the _callout_info string will be passed to /sbin/request-key
 *   - if the _callout_info string is empty, it will be rendered as "-"
 * - implements request_key()
 */
SYSCALL_DEFINE4(request_key, const char __user *, _type,
		const char __user *, _description,
		const char __user *, _callout_info,
		key_serial_t, destringid)
{
	struct key_type *ktype;
	struct key *key;
	key_ref_t dest_ref;
	size_t callout_len;
	char type[32], *description, *callout_info;
	long ret;

	/* pull the type into kernel space */
	ret = key_get_type_from_user(type, _type, sizeof(type));
	if (ret < 0)
		goto error;

	/* pull the description into kernel space */
	description = strndup_user(_description, PAGE_SIZE);
	if (IS_ERR(description)) {
		ret = PTR_ERR(description);
		goto error;
	}

	/* pull the callout info into kernel space */
	callout_info = NULL;
	callout_len = 0;
	if (_callout_info) {
		callout_info = strndup_user(_callout_info, PAGE_SIZE);
		if (IS_ERR(callout_info)) {
			ret = PTR_ERR(callout_info);
			goto error2;
		}
		callout_len = strlen(callout_info);
	}

	/* get the destination keyring if specified */
	dest_ref = NULL;
	if (destringid) {
		dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
		if (IS_ERR(dest_ref)) {
			ret = PTR_ERR(dest_ref);
			goto error3;
		}
	}

	/* find the key type */
	ktype = key_type_lookup(type);
	if (IS_ERR(ktype)) {
		ret = PTR_ERR(ktype);
		goto error4;
	}

	/* do the search */
	key = request_key_and_link(ktype, description, callout_info,
				   callout_len, NULL, key_ref_to_ptr(dest_ref),
				   KEY_ALLOC_IN_QUOTA);
	if (IS_ERR(key)) {
		ret = PTR_ERR(key);
		goto error5;
	}

	ret = key->serial;

 	key_put(key);
 error5:
	key_type_put(ktype);
 error4:
	key_ref_put(dest_ref);
 error3:
	kfree(callout_info);
 error2:
	kfree(description);
 error:
	return ret;

} /* end sys_request_key() */

/*****************************************************************************/
/*
 * get the ID of the specified process keyring
 * - the keyring must have search permission to be found
 * - implements keyctl(KEYCTL_GET_KEYRING_ID)
 */
long keyctl_get_keyring_ID(key_serial_t id, int create)
{
	key_ref_t key_ref;
	long ret;

	key_ref = lookup_user_key(id, create, 0, KEY_SEARCH);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	ret = key_ref_to_ptr(key_ref)->serial;
	key_ref_put(key_ref);
 error:
	return ret;

} /* end keyctl_get_keyring_ID() */

/*****************************************************************************/
/*
 * join the session keyring
 * - implements keyctl(KEYCTL_JOIN_SESSION_KEYRING)
 */
long keyctl_join_session_keyring(const char __user *_name)
{
	char *name;
	long ret;

	/* fetch the name from userspace */
	name = NULL;
	if (_name) {
		name = strndup_user(_name, PAGE_SIZE);
		if (IS_ERR(name)) {
			ret = PTR_ERR(name);
			goto error;
		}
	}

	/* join the session */
	ret = join_session_keyring(name);

 error:
	return ret;

} /* end keyctl_join_session_keyring() */

/*****************************************************************************/
/*
 * update a key's data payload
 * - the key must be writable
 * - implements keyctl(KEYCTL_UPDATE)
 */
long keyctl_update_key(key_serial_t id,
		       const void __user *_payload,
		       size_t plen)
{
	key_ref_t key_ref;
	void *payload;
	long ret;

	ret = -EINVAL;
	if (plen > PAGE_SIZE)
		goto error;

	/* pull the payload in if one was supplied */
	payload = NULL;
	if (_payload) {
		ret = -ENOMEM;
		payload = kmalloc(plen, GFP_KERNEL);
		if (!payload)
			goto error;

		ret = -EFAULT;
		if (copy_from_user(payload, _payload, plen) != 0)
			goto error2;
	}

	/* find the target key (which must be writable) */
	key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error2;
	}

	/* update the key */
	ret = key_update(key_ref, payload, plen);

	key_ref_put(key_ref);
 error2:
	kfree(payload);
 error:
	return ret;

} /* end keyctl_update_key() */

/*****************************************************************************/
/*
 * revoke a key
 * - the key must be writable
 * - implements keyctl(KEYCTL_REVOKE)
 */
long keyctl_revoke_key(key_serial_t id)
{
	key_ref_t key_ref;
	long ret;

	key_ref = lookup_user_key(id, 0, 0, KEY_WRITE);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	key_revoke(key_ref_to_ptr(key_ref));
	ret = 0;

	key_ref_put(key_ref);
 error:
	return ret;

} /* end keyctl_revoke_key() */

/*****************************************************************************/
/*
 * clear the specified process keyring
 * - the keyring must be writable
 * - implements keyctl(KEYCTL_CLEAR)
 */
long keyctl_keyring_clear(key_serial_t ringid)
{
	key_ref_t keyring_ref;
	long ret;

	keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
	if (IS_ERR(keyring_ref)) {
		ret = PTR_ERR(keyring_ref);
		goto error;
	}

	ret = keyring_clear(key_ref_to_ptr(keyring_ref));

	key_ref_put(keyring_ref);
 error:
	return ret;

} /* end keyctl_keyring_clear() */

/*****************************************************************************/
/*
 * link a key into a keyring
 * - the keyring must be writable
 * - the key must be linkable
 * - implements keyctl(KEYCTL_LINK)
 */
long keyctl_keyring_link(key_serial_t id, key_serial_t ringid)
{
	key_ref_t keyring_ref, key_ref;
	long ret;

	keyring_ref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
	if (IS_ERR(keyring_ref)) {
		ret = PTR_ERR(keyring_ref);
		goto error;
	}

	key_ref = lookup_user_key(id, 1, 0, KEY_LINK);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error2;
	}

	ret = key_link(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

	key_ref_put(key_ref);
 error2:
	key_ref_put(keyring_ref);
 error:
	return ret;

} /* end keyctl_keyring_link() */

/*****************************************************************************/
/*
 * unlink the first attachment of a key from a keyring
 * - the keyring must be writable
 * - we don't need any permissions on the key
 * - implements keyctl(KEYCTL_UNLINK)
 */
long keyctl_keyring_unlink(key_serial_t id, key_serial_t ringid)
{
	key_ref_t keyring_ref, key_ref;
	long ret;

	keyring_ref = lookup_user_key(ringid, 0, 0, KEY_WRITE);
	if (IS_ERR(keyring_ref)) {
		ret = PTR_ERR(keyring_ref);
		goto error;
	}

	key_ref = lookup_user_key(id, 0, 0, 0);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error2;
	}

	ret = key_unlink(key_ref_to_ptr(keyring_ref), key_ref_to_ptr(key_ref));

	key_ref_put(key_ref);
 error2:
	key_ref_put(keyring_ref);
 error:
	return ret;

} /* end keyctl_keyring_unlink() */

/*****************************************************************************/
/*
 * describe a user key
 * - the key must have view permission
 * - if there's a buffer, we place up to buflen bytes of data into it
 * - unless there's an error, we return the amount of description available,
 *   irrespective of how much we may have copied
 * - the description is formatted thus:
 *	type;uid;gid;perm;description<NUL>
 * - implements keyctl(KEYCTL_DESCRIBE)
 */
long keyctl_describe_key(key_serial_t keyid,
			 char __user *buffer,
			 size_t buflen)
{
	struct key *key, *instkey;
	key_ref_t key_ref;
	char *tmpbuf;
	long ret;

	key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
	if (IS_ERR(key_ref)) {
		/* viewing a key under construction is permitted if we have the
		 * authorisation token handy */
		if (PTR_ERR(key_ref) == -EACCES) {
			instkey = key_get_instantiation_authkey(keyid);
			if (!IS_ERR(instkey)) {
				key_put(instkey);
				key_ref = lookup_user_key(keyid,
							  0, 1, 0);
				if (!IS_ERR(key_ref))
					goto okay;
			}
		}

		ret = PTR_ERR(key_ref);
		goto error;
	}

okay:
	/* calculate how much description we're going to return */
	ret = -ENOMEM;
	tmpbuf = kmalloc(PAGE_SIZE, GFP_KERNEL);
	if (!tmpbuf)
		goto error2;

	key = key_ref_to_ptr(key_ref);

	ret = snprintf(tmpbuf, PAGE_SIZE - 1,
		       "%s;%d;%d;%08x;%s",
		       key_ref_to_ptr(key_ref)->type->name,
		       key_ref_to_ptr(key_ref)->uid,
		       key_ref_to_ptr(key_ref)->gid,
		       key_ref_to_ptr(key_ref)->perm,
		       key_ref_to_ptr(key_ref)->description ?
		       key_ref_to_ptr(key_ref)->description : ""
		       );

	/* include a NUL char at the end of the data */
	if (ret > PAGE_SIZE - 1)
		ret = PAGE_SIZE - 1;
	tmpbuf[ret] = 0;
	ret++;

	/* consider returning the data */
	if (buffer && buflen > 0) {
		if (buflen > ret)
			buflen = ret;

		if (copy_to_user(buffer, tmpbuf, buflen) != 0)
			ret = -EFAULT;
	}

	kfree(tmpbuf);
 error2:
	key_ref_put(key_ref);
 error:
	return ret;

} /* end keyctl_describe_key() */

/*****************************************************************************/
/*
 * search the specified keyring for a matching key
 * - the start keyring must be searchable
 * - nested keyrings may also be searched if they are searchable
 * - only keys with search permission may be found
 * - if a key is found, it will be attached to the destination keyring if
 *   there's one specified
 * - implements keyctl(KEYCTL_SEARCH)
 */
long keyctl_keyring_search(key_serial_t ringid,
			   const char __user *_type,
			   const char __user *_description,
			   key_serial_t destringid)
{
	struct key_type *ktype;
	key_ref_t keyring_ref, key_ref, dest_ref;
	char type[32], *description;
	long ret;

	/* pull the type and description into kernel space */
	ret = key_get_type_from_user(type, _type, sizeof(type));
	if (ret < 0)
		goto error;

	description = strndup_user(_description, PAGE_SIZE);
	if (IS_ERR(description)) {
		ret = PTR_ERR(description);
		goto error;
	}

	/* get the keyring at which to begin the search */
	keyring_ref = lookup_user_key(ringid, 0, 0, KEY_SEARCH);
	if (IS_ERR(keyring_ref)) {
		ret = PTR_ERR(keyring_ref);
		goto error2;
	}

	/* get the destination keyring if specified */
	dest_ref = NULL;
	if (destringid) {
		dest_ref = lookup_user_key(destringid, 1, 0, KEY_WRITE);
		if (IS_ERR(dest_ref)) {
			ret = PTR_ERR(dest_ref);
			goto error3;
		}
	}

	/* find the key type */
	ktype = key_type_lookup(type);
	if (IS_ERR(ktype)) {
		ret = PTR_ERR(ktype);
		goto error4;
	}

	/* do the search */
	key_ref = keyring_search(keyring_ref, ktype, description);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);

		/* treat lack or presence of a negative key the same */
		if (ret == -EAGAIN)
			ret = -ENOKEY;
		goto error5;
	}

	/* link the resulting key to the destination keyring if we can */
	if (dest_ref) {
		ret = key_permission(key_ref, KEY_LINK);
		if (ret < 0)
			goto error6;

		ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
		if (ret < 0)
			goto error6;
	}

	ret = key_ref_to_ptr(key_ref)->serial;

 error6:
	key_ref_put(key_ref);
 error5:
	key_type_put(ktype);
 error4:
	key_ref_put(dest_ref);
 error3:
	key_ref_put(keyring_ref);
 error2:
	kfree(description);
 error:
	return ret;

} /* end keyctl_keyring_search() */

/*****************************************************************************/
/*
 * read a user key's payload
 * - the keyring must be readable or the key must be searchable from the
 *   process's keyrings
 * - if there's a buffer, we place up to buflen bytes of data into it
 * - unless there's an error, we return the amount of data in the key,
 *   irrespective of how much we may have copied
 * - implements keyctl(KEYCTL_READ)
 */
long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
{
	struct key *key;
	key_ref_t key_ref;
	long ret;

	/* find the key first */
	key_ref = lookup_user_key(keyid, 0, 0, 0);
	if (IS_ERR(key_ref)) {
		ret = -ENOKEY;
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* see if we can read it directly */
	ret = key_permission(key_ref, KEY_READ);
	if (ret == 0)
		goto can_read_key;
	if (ret != -EACCES)
		goto error;

	/* we can't; see if it's searchable from this process's keyrings
	 * - we automatically take account of the fact that it may be
	 *   dangling off an instantiation key
	 */
	if (!is_key_possessed(key_ref)) {
		ret = -EACCES;
		goto error2;
	}

	/* the key is probably readable - now try to read it */
 can_read_key:
	ret = key_validate(key);
	if (ret == 0) {
		ret = -EOPNOTSUPP;
		if (key->type->read) {
			/* read the data with the semaphore held (since we
			 * might sleep) */
			down_read(&key->sem);
			ret = key->type->read(key, buffer, buflen);
			up_read(&key->sem);
		}
	}

 error2:
	key_put(key);
 error:
	return ret;

} /* end keyctl_read_key() */

/*****************************************************************************/
/*
 * change the ownership of a key
 * - the keyring owned by the changer
 * - if the uid or gid is -1, then that parameter is not changed
 * - implements keyctl(KEYCTL_CHOWN)
 */
long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
{
	struct key_user *newowner, *zapowner = NULL;
	struct key *key;
	key_ref_t key_ref;
	long ret;

	ret = 0;
	if (uid == (uid_t) -1 && gid == (gid_t) -1)
		goto error;

	key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* make the changes with the locks held to prevent chown/chown races */
	ret = -EACCES;
	down_write(&key->sem);

	if (!capable(CAP_SYS_ADMIN)) {
		/* only the sysadmin can chown a key to some other UID */
		if (uid != (uid_t) -1 && key->uid != uid)
			goto error_put;

		/* only the sysadmin can set the key's GID to a group other
		 * than one of those that the current process subscribes to */
		if (gid != (gid_t) -1 && gid != key->gid && !in_group_p(gid))
			goto error_put;
	}

	/* change the UID */
	if (uid != (uid_t) -1 && uid != key->uid) {
		ret = -ENOMEM;
		newowner = key_user_lookup(uid);
		if (!newowner)
			goto error_put;

		/* transfer the quota burden to the new user */
		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
			unsigned maxkeys = (uid == 0) ?
				key_quota_root_maxkeys : key_quota_maxkeys;
			unsigned maxbytes = (uid == 0) ?
				key_quota_root_maxbytes : key_quota_maxbytes;

			spin_lock(&newowner->lock);
			if (newowner->qnkeys + 1 >= maxkeys ||
			    newowner->qnbytes + key->quotalen >= maxbytes ||
			    newowner->qnbytes + key->quotalen <
			    newowner->qnbytes)
				goto quota_overrun;

			newowner->qnkeys++;
			newowner->qnbytes += key->quotalen;
			spin_unlock(&newowner->lock);

			spin_lock(&key->user->lock);
			key->user->qnkeys--;
			key->user->qnbytes -= key->quotalen;
			spin_unlock(&key->user->lock);
		}

		atomic_dec(&key->user->nkeys);
		atomic_inc(&newowner->nkeys);

		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
			atomic_dec(&key->user->nikeys);
			atomic_inc(&newowner->nikeys);
		}

		zapowner = key->user;
		key->user = newowner;
		key->uid = uid;
	}

	/* change the GID */
	if (gid != (gid_t) -1)
		key->gid = gid;

	ret = 0;

error_put:
	up_write(&key->sem);
	key_put(key);
	if (zapowner)
		key_user_put(zapowner);
error:
	return ret;

quota_overrun:
	spin_unlock(&newowner->lock);
	zapowner = newowner;
	ret = -EDQUOT;
	goto error_put;

} /* end keyctl_chown_key() */

/*****************************************************************************/
/*
 * change the permission mask on a key
 * - the keyring owned by the changer
 * - implements keyctl(KEYCTL_SETPERM)
 */
long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
{
	struct key *key;
	key_ref_t key_ref;
	long ret;

	ret = -EINVAL;
	if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
		goto error;

	key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* make the changes with the locks held to prevent chown/chmod races */
	ret = -EACCES;
	down_write(&key->sem);

	/* if we're not the sysadmin, we can only change a key that we own */
	if (capable(CAP_SYS_ADMIN) || key->uid == current_fsuid()) {
		key->perm = perm;
		ret = 0;
	}

	up_write(&key->sem);
	key_put(key);
error:
	return ret;

} /* end keyctl_setperm_key() */

/*
 * get the destination keyring for instantiation
 */
static long get_instantiation_keyring(key_serial_t ringid,
				      struct request_key_auth *rka,
				      struct key **_dest_keyring)
{
	key_ref_t dkref;

	*_dest_keyring = NULL;

	/* just return a NULL pointer if we weren't asked to make a link */
	if (ringid == 0)
		return 0;

	/* if a specific keyring is nominated by ID, then use that */
	if (ringid > 0) {
		dkref = lookup_user_key(ringid, 1, 0, KEY_WRITE);
		if (IS_ERR(dkref))
			return PTR_ERR(dkref);
		*_dest_keyring = key_ref_to_ptr(dkref);
		return 0;
	}

	if (ringid == KEY_SPEC_REQKEY_AUTH_KEY)
		return -EINVAL;

	/* otherwise specify the destination keyring recorded in the
	 * authorisation key (any KEY_SPEC_*_KEYRING) */
	if (ringid >= KEY_SPEC_REQUESTOR_KEYRING) {
		*_dest_keyring = rka->dest_keyring;
		return 0;
	}

	return -ENOKEY;
}

/*
 * change the request_key authorisation key on the current process
 */
static int keyctl_change_reqkey_auth(struct key *key)
{
	struct cred *new;

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

	key_put(new->request_key_auth);
	new->request_key_auth = key_get(key);

	return commit_creds(new);
}

/*****************************************************************************/
/*
 * instantiate the key with the specified payload, and, if one is given, link
 * the key into the keyring
 */
long keyctl_instantiate_key(key_serial_t id,
			    const void __user *_payload,
			    size_t plen,
			    key_serial_t ringid)
{
	const struct cred *cred = current_cred();
	struct request_key_auth *rka;
	struct key *instkey, *dest_keyring;
	void *payload;
	long ret;
	bool vm = false;

	kenter("%d,,%zu,%d", id, plen, ringid);

	ret = -EINVAL;
	if (plen > 1024 * 1024 - 1)
		goto error;

	/* the appropriate instantiation authorisation key must have been
	 * assumed before calling this */
	ret = -EPERM;
	instkey = cred->request_key_auth;
	if (!instkey)
		goto error;

	rka = instkey->payload.data;
	if (rka->target_key->serial != id)
		goto error;

	/* pull the payload in if one was supplied */
	payload = NULL;

	if (_payload) {
		ret = -ENOMEM;
		payload = kmalloc(plen, GFP_KERNEL);
		if (!payload) {
			if (plen <= PAGE_SIZE)
				goto error;
			vm = true;
			payload = vmalloc(plen);
			if (!payload)
				goto error;
		}

		ret = -EFAULT;
		if (copy_from_user(payload, _payload, plen) != 0)
			goto error2;
	}

	/* find the destination keyring amongst those belonging to the
	 * requesting task */
	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
	if (ret < 0)
		goto error2;

	/* instantiate the key and link it into a keyring */
	ret = key_instantiate_and_link(rka->target_key, payload, plen,
				       dest_keyring, instkey);

	key_put(dest_keyring);

	/* discard the assumed authority if it's just been disabled by
	 * instantiation of the key */
	if (ret == 0)
		keyctl_change_reqkey_auth(NULL);

error2:
	if (!vm)
		kfree(payload);
	else
		vfree(payload);
error:
	return ret;

} /* end keyctl_instantiate_key() */

/*****************************************************************************/
/*
 * negatively instantiate the key with the given timeout (in seconds), and, if
 * one is given, link the key into the keyring
 */
long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
{
	const struct cred *cred = current_cred();
	struct request_key_auth *rka;
	struct key *instkey, *dest_keyring;
	long ret;

	kenter("%d,%u,%d", id, timeout, ringid);

	/* the appropriate instantiation authorisation key must have been
	 * assumed before calling this */
	ret = -EPERM;
	instkey = cred->request_key_auth;
	if (!instkey)
		goto error;

	rka = instkey->payload.data;
	if (rka->target_key->serial != id)
		goto error;

	/* find the destination keyring if present (which must also be
	 * writable) */
	ret = get_instantiation_keyring(ringid, rka, &dest_keyring);
	if (ret < 0)
		goto error;

	/* instantiate the key and link it into a keyring */
	ret = key_negate_and_link(rka->target_key, timeout,
				  dest_keyring, instkey);

	key_put(dest_keyring);

	/* discard the assumed authority if it's just been disabled by
	 * instantiation of the key */
	if (ret == 0)
		keyctl_change_reqkey_auth(NULL);

error:
	return ret;

} /* end keyctl_negate_key() */

/*****************************************************************************/
/*
 * set the default keyring in which request_key() will cache keys
 * - return the old setting
 */
long keyctl_set_reqkey_keyring(int reqkey_defl)
{
	struct cred *new;
	int ret, old_setting;

	old_setting = current_cred_xxx(jit_keyring);

	if (reqkey_defl == KEY_REQKEY_DEFL_NO_CHANGE)
		return old_setting;

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

	switch (reqkey_defl) {
	case KEY_REQKEY_DEFL_THREAD_KEYRING:
		ret = install_thread_keyring_to_cred(new);
		if (ret < 0)
			goto error;
		goto set;

	case KEY_REQKEY_DEFL_PROCESS_KEYRING:
		ret = install_process_keyring_to_cred(new);
		if (ret < 0) {
			if (ret != -EEXIST)
				goto error;
			ret = 0;
		}
		goto set;

	case KEY_REQKEY_DEFL_DEFAULT:
	case KEY_REQKEY_DEFL_SESSION_KEYRING:
	case KEY_REQKEY_DEFL_USER_KEYRING:
	case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
	case KEY_REQKEY_DEFL_REQUESTOR_KEYRING:
		goto set;

	case KEY_REQKEY_DEFL_NO_CHANGE:
	case KEY_REQKEY_DEFL_GROUP_KEYRING:
	default:
		ret = -EINVAL;
		goto error;
	}

set:
	new->jit_keyring = reqkey_defl;
	commit_creds(new);
	return old_setting;
error:
	abort_creds(new);
	return -EINVAL;

} /* end keyctl_set_reqkey_keyring() */

/*****************************************************************************/
/*
 * set or clear the timeout for a key
 */
long keyctl_set_timeout(key_serial_t id, unsigned timeout)
{
	struct timespec now;
	struct key *key;
	key_ref_t key_ref;
	time_t expiry;
	long ret;

	key_ref = lookup_user_key(id, 1, 1, KEY_SETATTR);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* make the changes with the locks held to prevent races */
	down_write(&key->sem);

	expiry = 0;
	if (timeout > 0) {
		now = current_kernel_time();
		expiry = now.tv_sec + timeout;
	}

	key->expiry = expiry;

	up_write(&key->sem);
	key_put(key);

	ret = 0;
error:
	return ret;

} /* end keyctl_set_timeout() */

/*****************************************************************************/
/*
 * assume the authority to instantiate the specified key
 */
long keyctl_assume_authority(key_serial_t id)
{
	struct key *authkey;
	long ret;

	/* special key IDs aren't permitted */
	ret = -EINVAL;
	if (id < 0)
		goto error;

	/* we divest ourselves of authority if given an ID of 0 */
	if (id == 0) {
		ret = keyctl_change_reqkey_auth(NULL);
		goto error;
	}

	/* attempt to assume the authority temporarily granted to us whilst we
	 * instantiate the specified key
	 * - the authorisation key must be in the current task's keyrings
	 *   somewhere
	 */
	authkey = key_get_instantiation_authkey(id);
	if (IS_ERR(authkey)) {
		ret = PTR_ERR(authkey);
		goto error;
	}

	ret = keyctl_change_reqkey_auth(authkey);
	if (ret < 0)
		goto error;
	key_put(authkey);

	ret = authkey->serial;
error:
	return ret;

} /* end keyctl_assume_authority() */

/*
 * get the security label of a key
 * - the key must grant us view permission
 * - if there's a buffer, we place up to buflen bytes of data into it
 * - unless there's an error, we return the amount of information available,
 *   irrespective of how much we may have copied (including the terminal NUL)
 * - implements keyctl(KEYCTL_GET_SECURITY)
 */
long keyctl_get_security(key_serial_t keyid,
			 char __user *buffer,
			 size_t buflen)
{
	struct key *key, *instkey;
	key_ref_t key_ref;
	char *context;
	long ret;

	key_ref = lookup_user_key(keyid, 0, 1, KEY_VIEW);
	if (IS_ERR(key_ref)) {
		if (PTR_ERR(key_ref) != -EACCES)
			return PTR_ERR(key_ref);

		/* viewing a key under construction is also permitted if we
		 * have the authorisation token handy */
		instkey = key_get_instantiation_authkey(keyid);
		if (IS_ERR(instkey))
			return PTR_ERR(key_ref);
		key_put(instkey);

		key_ref = lookup_user_key(keyid, 0, 1, 0);
		if (IS_ERR(key_ref))
			return PTR_ERR(key_ref);
	}

	key = key_ref_to_ptr(key_ref);
	ret = security_key_getsecurity(key, &context);
	if (ret == 0) {
		/* if no information was returned, give userspace an empty
		 * string */
		ret = 1;
		if (buffer && buflen > 0 &&
		    copy_to_user(buffer, "", 1) != 0)
			ret = -EFAULT;
	} else if (ret > 0) {
		/* return as much data as there's room for */
		if (buffer && buflen > 0) {
			if (buflen > ret)
				buflen = ret;

			if (copy_to_user(buffer, context, buflen) != 0)
				ret = -EFAULT;
		}

		kfree(context);
	}

	key_ref_put(key_ref);
	return ret;
}

/*****************************************************************************/
/*
 * the key control system call
 */
asmlinkage long sys_keyctl(int option, unsigned long arg2, unsigned long arg3,
			   unsigned long arg4, unsigned long arg5)
{
	switch (option) {
	case KEYCTL_GET_KEYRING_ID:
		return keyctl_get_keyring_ID((key_serial_t) arg2,
					     (int) arg3);

	case KEYCTL_JOIN_SESSION_KEYRING:
		return keyctl_join_session_keyring((const char __user *) arg2);

	case KEYCTL_UPDATE:
		return keyctl_update_key((key_serial_t) arg2,
					 (const void __user *) arg3,
					 (size_t) arg4);

	case KEYCTL_REVOKE:
		return keyctl_revoke_key((key_serial_t) arg2);

	case KEYCTL_DESCRIBE:
		return keyctl_describe_key((key_serial_t) arg2,
					   (char __user *) arg3,
					   (unsigned) arg4);

	case KEYCTL_CLEAR:
		return keyctl_keyring_clear((key_serial_t) arg2);

	case KEYCTL_LINK:
		return keyctl_keyring_link((key_serial_t) arg2,
					   (key_serial_t) arg3);

	case KEYCTL_UNLINK:
		return keyctl_keyring_unlink((key_serial_t) arg2,
					     (key_serial_t) arg3);

	case KEYCTL_SEARCH:
		return keyctl_keyring_search((key_serial_t) arg2,
					     (const char __user *) arg3,
					     (const char __user *) arg4,
					     (key_serial_t) arg5);

	case KEYCTL_READ:
		return keyctl_read_key((key_serial_t) arg2,
				       (char __user *) arg3,
				       (size_t) arg4);

	case KEYCTL_CHOWN:
		return keyctl_chown_key((key_serial_t) arg2,
					(uid_t) arg3,
					(gid_t) arg4);

	case KEYCTL_SETPERM:
		return keyctl_setperm_key((key_serial_t) arg2,
					  (key_perm_t) arg3);

	case KEYCTL_INSTANTIATE:
		return keyctl_instantiate_key((key_serial_t) arg2,
					      (const void __user *) arg3,
					      (size_t) arg4,
					      (key_serial_t) arg5);

	case KEYCTL_NEGATE:
		return keyctl_negate_key((key_serial_t) arg2,
					 (unsigned) arg3,
					 (key_serial_t) arg4);

	case KEYCTL_SET_REQKEY_KEYRING:
		return keyctl_set_reqkey_keyring(arg2);

	case KEYCTL_SET_TIMEOUT:
		return keyctl_set_timeout((key_serial_t) arg2,
					  (unsigned) arg3);

	case KEYCTL_ASSUME_AUTHORITY:
		return keyctl_assume_authority((key_serial_t) arg2);

	case KEYCTL_GET_SECURITY:
		return keyctl_get_security((key_serial_t) arg2,
					   (char __user *) arg3,
					   (size_t) arg4);

	default:
		return -EOPNOTSUPP;
	}

} /* end sys_keyctl() */