summaryrefslogtreecommitdiff
path: root/net/netlink/genetlink.c
blob: 3e16527beb9148b5da97baf7d193f1da9af445a9 (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
// SPDX-License-Identifier: GPL-2.0
/*
 * NETLINK      Generic Netlink Family
 *
 * 		Authors:	Jamal Hadi Salim
 * 				Thomas Graf <tgraf@suug.ch>
 *				Johannes Berg <johannes@sipsolutions.net>
 */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/string.h>
#include <linux/skbuff.h>
#include <linux/mutex.h>
#include <linux/bitmap.h>
#include <linux/rwsem.h>
#include <linux/idr.h>
#include <net/sock.h>
#include <net/genetlink.h>

static DEFINE_MUTEX(genl_mutex); /* serialization of message processing */
static DECLARE_RWSEM(cb_lock);

atomic_t genl_sk_destructing_cnt = ATOMIC_INIT(0);
DECLARE_WAIT_QUEUE_HEAD(genl_sk_destructing_waitq);

void genl_lock(void)
{
	mutex_lock(&genl_mutex);
}
EXPORT_SYMBOL(genl_lock);

void genl_unlock(void)
{
	mutex_unlock(&genl_mutex);
}
EXPORT_SYMBOL(genl_unlock);

static void genl_lock_all(void)
{
	down_write(&cb_lock);
	genl_lock();
}

static void genl_unlock_all(void)
{
	genl_unlock();
	up_write(&cb_lock);
}

static DEFINE_IDR(genl_fam_idr);

/*
 * Bitmap of multicast groups that are currently in use.
 *
 * To avoid an allocation at boot of just one unsigned long,
 * declare it global instead.
 * Bit 0 is marked as already used since group 0 is invalid.
 * Bit 1 is marked as already used since the drop-monitor code
 * abuses the API and thinks it can statically use group 1.
 * That group will typically conflict with other groups that
 * any proper users use.
 * Bit 16 is marked as used since it's used for generic netlink
 * and the code no longer marks pre-reserved IDs as used.
 * Bit 17 is marked as already used since the VFS quota code
 * also abused this API and relied on family == group ID, we
 * cater to that by giving it a static family and group ID.
 * Bit 18 is marked as already used since the PMCRAID driver
 * did the same thing as the VFS quota code (maybe copied?)
 */
static unsigned long mc_group_start = 0x3 | BIT(GENL_ID_CTRL) |
				      BIT(GENL_ID_VFS_DQUOT) |
				      BIT(GENL_ID_PMCRAID);
static unsigned long *mc_groups = &mc_group_start;
static unsigned long mc_groups_longs = 1;

/* We need the last attribute with non-zero ID therefore a 2-entry array */
static struct nla_policy genl_policy_reject_all[] = {
	{ .type = NLA_REJECT },
	{ .type = NLA_REJECT },
};

static int genl_ctrl_event(int event, const struct genl_family *family,
			   const struct genl_multicast_group *grp,
			   int grp_id);

static void
genl_op_fill_in_reject_policy(const struct genl_family *family,
			      struct genl_ops *op)
{
	BUILD_BUG_ON(ARRAY_SIZE(genl_policy_reject_all) - 1 != 1);

	if (op->policy || op->cmd < family->resv_start_op)
		return;

	op->policy = genl_policy_reject_all;
	op->maxattr = 1;
}

static const struct genl_family *genl_family_find_byid(unsigned int id)
{
	return idr_find(&genl_fam_idr, id);
}

static const struct genl_family *genl_family_find_byname(char *name)
{
	const struct genl_family *family;
	unsigned int id;

	idr_for_each_entry(&genl_fam_idr, family, id)
		if (strcmp(family->name, name) == 0)
			return family;

	return NULL;
}

static int genl_get_cmd_cnt(const struct genl_family *family)
{
	return family->n_ops + family->n_small_ops;
}

static void genl_op_from_full(const struct genl_family *family,
			      unsigned int i, struct genl_ops *op)
{
	*op = family->ops[i];

	if (!op->maxattr)
		op->maxattr = family->maxattr;
	if (!op->policy)
		op->policy = family->policy;

	genl_op_fill_in_reject_policy(family, op);
}

static int genl_get_cmd_full(u32 cmd, const struct genl_family *family,
			     struct genl_ops *op)
{
	int i;

	for (i = 0; i < family->n_ops; i++)
		if (family->ops[i].cmd == cmd) {
			genl_op_from_full(family, i, op);
			return 0;
		}

	return -ENOENT;
}

static void genl_op_from_small(const struct genl_family *family,
			       unsigned int i, struct genl_ops *op)
{
	memset(op, 0, sizeof(*op));
	op->doit	= family->small_ops[i].doit;
	op->dumpit	= family->small_ops[i].dumpit;
	op->cmd		= family->small_ops[i].cmd;
	op->internal_flags = family->small_ops[i].internal_flags;
	op->flags	= family->small_ops[i].flags;
	op->validate	= family->small_ops[i].validate;

	op->maxattr = family->maxattr;
	op->policy = family->policy;

	genl_op_fill_in_reject_policy(family, op);
}

static int genl_get_cmd_small(u32 cmd, const struct genl_family *family,
			      struct genl_ops *op)
{
	int i;

	for (i = 0; i < family->n_small_ops; i++)
		if (family->small_ops[i].cmd == cmd) {
			genl_op_from_small(family, i, op);
			return 0;
		}

	return -ENOENT;
}

static int genl_get_cmd(u32 cmd, const struct genl_family *family,
			struct genl_ops *op)
{
	if (!genl_get_cmd_full(cmd, family, op))
		return 0;
	return genl_get_cmd_small(cmd, family, op);
}

static void genl_get_cmd_by_index(unsigned int i,
				  const struct genl_family *family,
				  struct genl_ops *op)
{
	if (i < family->n_ops)
		genl_op_from_full(family, i, op);
	else if (i < family->n_ops + family->n_small_ops)
		genl_op_from_small(family, i - family->n_ops, op);
	else
		WARN_ON_ONCE(1);
}

static int genl_allocate_reserve_groups(int n_groups, int *first_id)
{
	unsigned long *new_groups;
	int start = 0;
	int i;
	int id;
	bool fits;

	do {
		if (start == 0)
			id = find_first_zero_bit(mc_groups,
						 mc_groups_longs *
						 BITS_PER_LONG);
		else
			id = find_next_zero_bit(mc_groups,
						mc_groups_longs * BITS_PER_LONG,
						start);

		fits = true;
		for (i = id;
		     i < min_t(int, id + n_groups,
			       mc_groups_longs * BITS_PER_LONG);
		     i++) {
			if (test_bit(i, mc_groups)) {
				start = i;
				fits = false;
				break;
			}
		}

		if (id + n_groups > mc_groups_longs * BITS_PER_LONG) {
			unsigned long new_longs = mc_groups_longs +
						  BITS_TO_LONGS(n_groups);
			size_t nlen = new_longs * sizeof(unsigned long);

			if (mc_groups == &mc_group_start) {
				new_groups = kzalloc(nlen, GFP_KERNEL);
				if (!new_groups)
					return -ENOMEM;
				mc_groups = new_groups;
				*mc_groups = mc_group_start;
			} else {
				new_groups = krealloc(mc_groups, nlen,
						      GFP_KERNEL);
				if (!new_groups)
					return -ENOMEM;
				mc_groups = new_groups;
				for (i = 0; i < BITS_TO_LONGS(n_groups); i++)
					mc_groups[mc_groups_longs + i] = 0;
			}
			mc_groups_longs = new_longs;
		}
	} while (!fits);

	for (i = id; i < id + n_groups; i++)
		set_bit(i, mc_groups);
	*first_id = id;
	return 0;
}

static struct genl_family genl_ctrl;

static int genl_validate_assign_mc_groups(struct genl_family *family)
{
	int first_id;
	int n_groups = family->n_mcgrps;
	int err = 0, i;
	bool groups_allocated = false;

	if (!n_groups)
		return 0;

	for (i = 0; i < n_groups; i++) {
		const struct genl_multicast_group *grp = &family->mcgrps[i];

		if (WARN_ON(grp->name[0] == '\0'))
			return -EINVAL;
		if (WARN_ON(memchr(grp->name, '\0', GENL_NAMSIZ) == NULL))
			return -EINVAL;
	}

	/* special-case our own group and hacks */
	if (family == &genl_ctrl) {
		first_id = GENL_ID_CTRL;
		BUG_ON(n_groups != 1);
	} else if (strcmp(family->name, "NET_DM") == 0) {
		first_id = 1;
		BUG_ON(n_groups != 1);
	} else if (family->id == GENL_ID_VFS_DQUOT) {
		first_id = GENL_ID_VFS_DQUOT;
		BUG_ON(n_groups != 1);
	} else if (family->id == GENL_ID_PMCRAID) {
		first_id = GENL_ID_PMCRAID;
		BUG_ON(n_groups != 1);
	} else {
		groups_allocated = true;
		err = genl_allocate_reserve_groups(n_groups, &first_id);
		if (err)
			return err;
	}

	family->mcgrp_offset = first_id;

	/* if still initializing, can't and don't need to realloc bitmaps */
	if (!init_net.genl_sock)
		return 0;

	if (family->netnsok) {
		struct net *net;

		netlink_table_grab();
		rcu_read_lock();
		for_each_net_rcu(net) {
			err = __netlink_change_ngroups(net->genl_sock,
					mc_groups_longs * BITS_PER_LONG);
			if (err) {
				/*
				 * No need to roll back, can only fail if
				 * memory allocation fails and then the
				 * number of _possible_ groups has been
				 * increased on some sockets which is ok.
				 */
				break;
			}
		}
		rcu_read_unlock();
		netlink_table_ungrab();
	} else {
		err = netlink_change_ngroups(init_net.genl_sock,
					     mc_groups_longs * BITS_PER_LONG);
	}

	if (groups_allocated && err) {
		for (i = 0; i < family->n_mcgrps; i++)
			clear_bit(family->mcgrp_offset + i, mc_groups);
	}

	return err;
}

static void genl_unregister_mc_groups(const struct genl_family *family)
{
	struct net *net;
	int i;

	netlink_table_grab();
	rcu_read_lock();
	for_each_net_rcu(net) {
		for (i = 0; i < family->n_mcgrps; i++)
			__netlink_clear_multicast_users(
				net->genl_sock, family->mcgrp_offset + i);
	}
	rcu_read_unlock();
	netlink_table_ungrab();

	for (i = 0; i < family->n_mcgrps; i++) {
		int grp_id = family->mcgrp_offset + i;

		if (grp_id != 1)
			clear_bit(grp_id, mc_groups);
		genl_ctrl_event(CTRL_CMD_DELMCAST_GRP, family,
				&family->mcgrps[i], grp_id);
	}
}

static int genl_validate_ops(const struct genl_family *family)
{
	int i, j;

	if (WARN_ON(family->n_ops && !family->ops) ||
	    WARN_ON(family->n_small_ops && !family->small_ops))
		return -EINVAL;

	for (i = 0; i < genl_get_cmd_cnt(family); i++) {
		struct genl_ops op;

		genl_get_cmd_by_index(i, family, &op);
		if (op.dumpit == NULL && op.doit == NULL)
			return -EINVAL;
		if (WARN_ON(op.cmd >= family->resv_start_op && op.validate))
			return -EINVAL;
		for (j = i + 1; j < genl_get_cmd_cnt(family); j++) {
			struct genl_ops op2;

			genl_get_cmd_by_index(j, family, &op2);
			if (op.cmd == op2.cmd)
				return -EINVAL;
		}
	}

	return 0;
}

/**
 * genl_register_family - register a generic netlink family
 * @family: generic netlink family
 *
 * Registers the specified family after validating it first. Only one
 * family may be registered with the same family name or identifier.
 *
 * The family's ops, multicast groups and module pointer must already
 * be assigned.
 *
 * Return 0 on success or a negative error code.
 */
int genl_register_family(struct genl_family *family)
{
	int err, i;
	int start = GENL_START_ALLOC, end = GENL_MAX_ID;

	err = genl_validate_ops(family);
	if (err)
		return err;

	genl_lock_all();

	if (genl_family_find_byname(family->name)) {
		err = -EEXIST;
		goto errout_locked;
	}

	/*
	 * Sadly, a few cases need to be special-cased
	 * due to them having previously abused the API
	 * and having used their family ID also as their
	 * multicast group ID, so we use reserved IDs
	 * for both to be sure we can do that mapping.
	 */
	if (family == &genl_ctrl) {
		/* and this needs to be special for initial family lookups */
		start = end = GENL_ID_CTRL;
	} else if (strcmp(family->name, "pmcraid") == 0) {
		start = end = GENL_ID_PMCRAID;
	} else if (strcmp(family->name, "VFS_DQUOT") == 0) {
		start = end = GENL_ID_VFS_DQUOT;
	}

	family->id = idr_alloc_cyclic(&genl_fam_idr, family,
				      start, end + 1, GFP_KERNEL);
	if (family->id < 0) {
		err = family->id;
		goto errout_locked;
	}

	err = genl_validate_assign_mc_groups(family);
	if (err)
		goto errout_remove;

	genl_unlock_all();

	/* send all events */
	genl_ctrl_event(CTRL_CMD_NEWFAMILY, family, NULL, 0);
	for (i = 0; i < family->n_mcgrps; i++)
		genl_ctrl_event(CTRL_CMD_NEWMCAST_GRP, family,
				&family->mcgrps[i], family->mcgrp_offset + i);

	return 0;

errout_remove:
	idr_remove(&genl_fam_idr, family->id);
errout_locked:
	genl_unlock_all();
	return err;
}
EXPORT_SYMBOL(genl_register_family);

/**
 * genl_unregister_family - unregister generic netlink family
 * @family: generic netlink family
 *
 * Unregisters the specified family.
 *
 * Returns 0 on success or a negative error code.
 */
int genl_unregister_family(const struct genl_family *family)
{
	genl_lock_all();

	if (!genl_family_find_byid(family->id)) {
		genl_unlock_all();
		return -ENOENT;
	}

	genl_unregister_mc_groups(family);

	idr_remove(&genl_fam_idr, family->id);

	up_write(&cb_lock);
	wait_event(genl_sk_destructing_waitq,
		   atomic_read(&genl_sk_destructing_cnt) == 0);
	genl_unlock();

	genl_ctrl_event(CTRL_CMD_DELFAMILY, family, NULL, 0);

	return 0;
}
EXPORT_SYMBOL(genl_unregister_family);

/**
 * genlmsg_put - Add generic netlink header to netlink message
 * @skb: socket buffer holding the message
 * @portid: netlink portid the message is addressed to
 * @seq: sequence number (usually the one of the sender)
 * @family: generic netlink family
 * @flags: netlink message flags
 * @cmd: generic netlink command
 *
 * Returns pointer to user specific header
 */
void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
		  const struct genl_family *family, int flags, u8 cmd)
{
	struct nlmsghdr *nlh;
	struct genlmsghdr *hdr;

	nlh = nlmsg_put(skb, portid, seq, family->id, GENL_HDRLEN +
			family->hdrsize, flags);
	if (nlh == NULL)
		return NULL;

	hdr = nlmsg_data(nlh);
	hdr->cmd = cmd;
	hdr->version = family->version;
	hdr->reserved = 0;

	return (char *) hdr + GENL_HDRLEN;
}
EXPORT_SYMBOL(genlmsg_put);

static struct genl_dumpit_info *genl_dumpit_info_alloc(void)
{
	return kmalloc(sizeof(struct genl_dumpit_info), GFP_KERNEL);
}

static void genl_dumpit_info_free(const struct genl_dumpit_info *info)
{
	kfree(info);
}

static struct nlattr **
genl_family_rcv_msg_attrs_parse(const struct genl_family *family,
				struct nlmsghdr *nlh,
				struct netlink_ext_ack *extack,
				const struct genl_ops *ops,
				int hdrlen,
				enum genl_validate_flags no_strict_flag)
{
	enum netlink_validation validate = ops->validate & no_strict_flag ?
					   NL_VALIDATE_LIBERAL :
					   NL_VALIDATE_STRICT;
	struct nlattr **attrbuf;
	int err;

	if (!ops->maxattr)
		return NULL;

	attrbuf = kmalloc_array(ops->maxattr + 1,
				sizeof(struct nlattr *), GFP_KERNEL);
	if (!attrbuf)
		return ERR_PTR(-ENOMEM);

	err = __nlmsg_parse(nlh, hdrlen, attrbuf, ops->maxattr, ops->policy,
			    validate, extack);
	if (err) {
		kfree(attrbuf);
		return ERR_PTR(err);
	}
	return attrbuf;
}

static void genl_family_rcv_msg_attrs_free(struct nlattr **attrbuf)
{
	kfree(attrbuf);
}

struct genl_start_context {
	const struct genl_family *family;
	struct nlmsghdr *nlh;
	struct netlink_ext_ack *extack;
	const struct genl_ops *ops;
	int hdrlen;
};

static int genl_start(struct netlink_callback *cb)
{
	struct genl_start_context *ctx = cb->data;
	const struct genl_ops *ops = ctx->ops;
	struct genl_dumpit_info *info;
	struct nlattr **attrs = NULL;
	int rc = 0;

	if (ops->validate & GENL_DONT_VALIDATE_DUMP)
		goto no_attrs;

	if (ctx->nlh->nlmsg_len < nlmsg_msg_size(ctx->hdrlen))
		return -EINVAL;

	attrs = genl_family_rcv_msg_attrs_parse(ctx->family, ctx->nlh, ctx->extack,
						ops, ctx->hdrlen,
						GENL_DONT_VALIDATE_DUMP_STRICT);
	if (IS_ERR(attrs))
		return PTR_ERR(attrs);

no_attrs:
	info = genl_dumpit_info_alloc();
	if (!info) {
		genl_family_rcv_msg_attrs_free(attrs);
		return -ENOMEM;
	}
	info->family = ctx->family;
	info->op = *ops;
	info->attrs = attrs;

	cb->data = info;
	if (ops->start) {
		if (!ctx->family->parallel_ops)
			genl_lock();
		rc = ops->start(cb);
		if (!ctx->family->parallel_ops)
			genl_unlock();
	}

	if (rc) {
		genl_family_rcv_msg_attrs_free(info->attrs);
		genl_dumpit_info_free(info);
		cb->data = NULL;
	}
	return rc;
}

static int genl_lock_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
{
	const struct genl_ops *ops = &genl_dumpit_info(cb)->op;
	int rc;

	genl_lock();
	rc = ops->dumpit(skb, cb);
	genl_unlock();
	return rc;
}

static int genl_lock_done(struct netlink_callback *cb)
{
	const struct genl_dumpit_info *info = genl_dumpit_info(cb);
	const struct genl_ops *ops = &info->op;
	int rc = 0;

	if (ops->done) {
		genl_lock();
		rc = ops->done(cb);
		genl_unlock();
	}
	genl_family_rcv_msg_attrs_free(info->attrs);
	genl_dumpit_info_free(info);
	return rc;
}

static int genl_parallel_done(struct netlink_callback *cb)
{
	const struct genl_dumpit_info *info = genl_dumpit_info(cb);
	const struct genl_ops *ops = &info->op;
	int rc = 0;

	if (ops->done)
		rc = ops->done(cb);
	genl_family_rcv_msg_attrs_free(info->attrs);
	genl_dumpit_info_free(info);
	return rc;
}

static int genl_family_rcv_msg_dumpit(const struct genl_family *family,
				      struct sk_buff *skb,
				      struct nlmsghdr *nlh,
				      struct netlink_ext_ack *extack,
				      const struct genl_ops *ops,
				      int hdrlen, struct net *net)
{
	struct genl_start_context ctx;
	int err;

	if (!ops->dumpit)
		return -EOPNOTSUPP;

	ctx.family = family;
	ctx.nlh = nlh;
	ctx.extack = extack;
	ctx.ops = ops;
	ctx.hdrlen = hdrlen;

	if (!family->parallel_ops) {
		struct netlink_dump_control c = {
			.module = family->module,
			.data = &ctx,
			.start = genl_start,
			.dump = genl_lock_dumpit,
			.done = genl_lock_done,
		};

		genl_unlock();
		err = __netlink_dump_start(net->genl_sock, skb, nlh, &c);
		genl_lock();
	} else {
		struct netlink_dump_control c = {
			.module = family->module,
			.data = &ctx,
			.start = genl_start,
			.dump = ops->dumpit,
			.done = genl_parallel_done,
		};

		err = __netlink_dump_start(net->genl_sock, skb, nlh, &c);
	}

	return err;
}

static int genl_family_rcv_msg_doit(const struct genl_family *family,
				    struct sk_buff *skb,
				    struct nlmsghdr *nlh,
				    struct netlink_ext_ack *extack,
				    const struct genl_ops *ops,
				    int hdrlen, struct net *net)
{
	struct nlattr **attrbuf;
	struct genl_info info;
	int err;

	if (!ops->doit)
		return -EOPNOTSUPP;

	attrbuf = genl_family_rcv_msg_attrs_parse(family, nlh, extack,
						  ops, hdrlen,
						  GENL_DONT_VALIDATE_STRICT);
	if (IS_ERR(attrbuf))
		return PTR_ERR(attrbuf);

	info.snd_seq = nlh->nlmsg_seq;
	info.snd_portid = NETLINK_CB(skb).portid;
	info.nlhdr = nlh;
	info.genlhdr = nlmsg_data(nlh);
	info.userhdr = nlmsg_data(nlh) + GENL_HDRLEN;
	info.attrs = attrbuf;
	info.extack = extack;
	genl_info_net_set(&info, net);
	memset(&info.user_ptr, 0, sizeof(info.user_ptr));

	if (family->pre_doit) {
		err = family->pre_doit(ops, skb, &info);
		if (err)
			goto out;
	}

	err = ops->doit(skb, &info);

	if (family->post_doit)
		family->post_doit(ops, skb, &info);

out:
	genl_family_rcv_msg_attrs_free(attrbuf);

	return err;
}

static int genl_header_check(const struct genl_family *family,
			     struct nlmsghdr *nlh, struct genlmsghdr *hdr,
			     struct netlink_ext_ack *extack)
{
	u16 flags;

	/* Only for commands added after we started validating */
	if (hdr->cmd < family->resv_start_op)
		return 0;

	if (hdr->reserved) {
		NL_SET_ERR_MSG(extack, "genlmsghdr.reserved field is not 0");
		return -EINVAL;
	}

	/* Old netlink flags have pretty loose semantics, allow only the flags
	 * consumed by the core where we can enforce the meaning.
	 */
	flags = nlh->nlmsg_flags;
	if ((flags & NLM_F_DUMP) == NLM_F_DUMP) /* DUMP is 2 bits */
		flags &= ~NLM_F_DUMP;
	if (flags & ~(NLM_F_REQUEST | NLM_F_ACK | NLM_F_ECHO)) {
		NL_SET_ERR_MSG(extack,
			       "ambiguous or reserved bits set in nlmsg_flags");
		return -EINVAL;
	}

	return 0;
}

static int genl_family_rcv_msg(const struct genl_family *family,
			       struct sk_buff *skb,
			       struct nlmsghdr *nlh,
			       struct netlink_ext_ack *extack)
{
	struct net *net = sock_net(skb->sk);
	struct genlmsghdr *hdr = nlmsg_data(nlh);
	struct genl_ops op;
	int hdrlen;

	/* this family doesn't exist in this netns */
	if (!family->netnsok && !net_eq(net, &init_net))
		return -ENOENT;

	hdrlen = GENL_HDRLEN + family->hdrsize;
	if (nlh->nlmsg_len < nlmsg_msg_size(hdrlen))
		return -EINVAL;

	if (genl_header_check(family, nlh, hdr, extack))
		return -EINVAL;

	if (genl_get_cmd(hdr->cmd, family, &op))
		return -EOPNOTSUPP;

	if ((op.flags & GENL_ADMIN_PERM) &&
	    !netlink_capable(skb, CAP_NET_ADMIN))
		return -EPERM;

	if ((op.flags & GENL_UNS_ADMIN_PERM) &&
	    !netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
		return -EPERM;

	if ((nlh->nlmsg_flags & NLM_F_DUMP) == NLM_F_DUMP)
		return genl_family_rcv_msg_dumpit(family, skb, nlh, extack,
						  &op, hdrlen, net);
	else
		return genl_family_rcv_msg_doit(family, skb, nlh, extack,
						&op, hdrlen, net);
}

static int genl_rcv_msg(struct sk_buff *skb, struct nlmsghdr *nlh,
			struct netlink_ext_ack *extack)
{
	const struct genl_family *family;
	int err;

	family = genl_family_find_byid(nlh->nlmsg_type);
	if (family == NULL)
		return -ENOENT;

	if (!family->parallel_ops)
		genl_lock();

	err = genl_family_rcv_msg(family, skb, nlh, extack);

	if (!family->parallel_ops)
		genl_unlock();

	return err;
}

static void genl_rcv(struct sk_buff *skb)
{
	down_read(&cb_lock);
	netlink_rcv_skb(skb, &genl_rcv_msg);
	up_read(&cb_lock);
}

/**************************************************************************
 * Controller
 **************************************************************************/

static struct genl_family genl_ctrl;

static int ctrl_fill_info(const struct genl_family *family, u32 portid, u32 seq,
			  u32 flags, struct sk_buff *skb, u8 cmd)
{
	void *hdr;

	hdr = genlmsg_put(skb, portid, seq, &genl_ctrl, flags, cmd);
	if (hdr == NULL)
		return -1;

	if (nla_put_string(skb, CTRL_ATTR_FAMILY_NAME, family->name) ||
	    nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, family->id) ||
	    nla_put_u32(skb, CTRL_ATTR_VERSION, family->version) ||
	    nla_put_u32(skb, CTRL_ATTR_HDRSIZE, family->hdrsize) ||
	    nla_put_u32(skb, CTRL_ATTR_MAXATTR, family->maxattr))
		goto nla_put_failure;

	if (genl_get_cmd_cnt(family)) {
		struct nlattr *nla_ops;
		int i;

		nla_ops = nla_nest_start_noflag(skb, CTRL_ATTR_OPS);
		if (nla_ops == NULL)
			goto nla_put_failure;

		for (i = 0; i < genl_get_cmd_cnt(family); i++) {
			struct nlattr *nest;
			struct genl_ops op;
			u32 op_flags;

			genl_get_cmd_by_index(i, family, &op);
			op_flags = op.flags;
			if (op.dumpit)
				op_flags |= GENL_CMD_CAP_DUMP;
			if (op.doit)
				op_flags |= GENL_CMD_CAP_DO;
			if (op.policy)
				op_flags |= GENL_CMD_CAP_HASPOL;

			nest = nla_nest_start_noflag(skb, i + 1);
			if (nest == NULL)
				goto nla_put_failure;

			if (nla_put_u32(skb, CTRL_ATTR_OP_ID, op.cmd) ||
			    nla_put_u32(skb, CTRL_ATTR_OP_FLAGS, op_flags))
				goto nla_put_failure;

			nla_nest_end(skb, nest);
		}

		nla_nest_end(skb, nla_ops);
	}

	if (family->n_mcgrps) {
		struct nlattr *nla_grps;
		int i;

		nla_grps = nla_nest_start_noflag(skb, CTRL_ATTR_MCAST_GROUPS);
		if (nla_grps == NULL)
			goto nla_put_failure;

		for (i = 0; i < family->n_mcgrps; i++) {
			struct nlattr *nest;
			const struct genl_multicast_group *grp;

			grp = &family->mcgrps[i];

			nest = nla_nest_start_noflag(skb, i + 1);
			if (nest == NULL)
				goto nla_put_failure;

			if (nla_put_u32(skb, CTRL_ATTR_MCAST_GRP_ID,
					family->mcgrp_offset + i) ||
			    nla_put_string(skb, CTRL_ATTR_MCAST_GRP_NAME,
					   grp->name))
				goto nla_put_failure;

			nla_nest_end(skb, nest);
		}
		nla_nest_end(skb, nla_grps);
	}

	genlmsg_end(skb, hdr);
	return 0;

nla_put_failure:
	genlmsg_cancel(skb, hdr);
	return -EMSGSIZE;
}

static int ctrl_fill_mcgrp_info(const struct genl_family *family,
				const struct genl_multicast_group *grp,
				int grp_id, u32 portid, u32 seq, u32 flags,
				struct sk_buff *skb, u8 cmd)
{
	void *hdr;
	struct nlattr *nla_grps;
	struct nlattr *nest;

	hdr = genlmsg_put(skb, portid, seq, &genl_ctrl, flags, cmd);
	if (hdr == NULL)
		return -1;

	if (nla_put_string(skb, CTRL_ATTR_FAMILY_NAME, family->name) ||
	    nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, family->id))
		goto nla_put_failure;

	nla_grps = nla_nest_start_noflag(skb, CTRL_ATTR_MCAST_GROUPS);
	if (nla_grps == NULL)
		goto nla_put_failure;

	nest = nla_nest_start_noflag(skb, 1);
	if (nest == NULL)
		goto nla_put_failure;

	if (nla_put_u32(skb, CTRL_ATTR_MCAST_GRP_ID, grp_id) ||
	    nla_put_string(skb, CTRL_ATTR_MCAST_GRP_NAME,
			   grp->name))
		goto nla_put_failure;

	nla_nest_end(skb, nest);
	nla_nest_end(skb, nla_grps);

	genlmsg_end(skb, hdr);
	return 0;

nla_put_failure:
	genlmsg_cancel(skb, hdr);
	return -EMSGSIZE;
}

static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
{
	int n = 0;
	struct genl_family *rt;
	struct net *net = sock_net(skb->sk);
	int fams_to_skip = cb->args[0];
	unsigned int id;

	idr_for_each_entry(&genl_fam_idr, rt, id) {
		if (!rt->netnsok && !net_eq(net, &init_net))
			continue;

		if (n++ < fams_to_skip)
			continue;

		if (ctrl_fill_info(rt, NETLINK_CB(cb->skb).portid,
				   cb->nlh->nlmsg_seq, NLM_F_MULTI,
				   skb, CTRL_CMD_NEWFAMILY) < 0) {
			n--;
			break;
		}
	}

	cb->args[0] = n;
	return skb->len;
}

static struct sk_buff *ctrl_build_family_msg(const struct genl_family *family,
					     u32 portid, int seq, u8 cmd)
{
	struct sk_buff *skb;
	int err;

	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
	if (skb == NULL)
		return ERR_PTR(-ENOBUFS);

	err = ctrl_fill_info(family, portid, seq, 0, skb, cmd);
	if (err < 0) {
		nlmsg_free(skb);
		return ERR_PTR(err);
	}

	return skb;
}

static struct sk_buff *
ctrl_build_mcgrp_msg(const struct genl_family *family,
		     const struct genl_multicast_group *grp,
		     int grp_id, u32 portid, int seq, u8 cmd)
{
	struct sk_buff *skb;
	int err;

	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
	if (skb == NULL)
		return ERR_PTR(-ENOBUFS);

	err = ctrl_fill_mcgrp_info(family, grp, grp_id, portid,
				   seq, 0, skb, cmd);
	if (err < 0) {
		nlmsg_free(skb);
		return ERR_PTR(err);
	}

	return skb;
}

static const struct nla_policy ctrl_policy_family[] = {
	[CTRL_ATTR_FAMILY_ID]	= { .type = NLA_U16 },
	[CTRL_ATTR_FAMILY_NAME]	= { .type = NLA_NUL_STRING,
				    .len = GENL_NAMSIZ - 1 },
};

static int ctrl_getfamily(struct sk_buff *skb, struct genl_info *info)
{
	struct sk_buff *msg;
	const struct genl_family *res = NULL;
	int err = -EINVAL;

	if (info->attrs[CTRL_ATTR_FAMILY_ID]) {
		u16 id = nla_get_u16(info->attrs[CTRL_ATTR_FAMILY_ID]);
		res = genl_family_find_byid(id);
		err = -ENOENT;
	}

	if (info->attrs[CTRL_ATTR_FAMILY_NAME]) {
		char *name;

		name = nla_data(info->attrs[CTRL_ATTR_FAMILY_NAME]);
		res = genl_family_find_byname(name);
#ifdef CONFIG_MODULES
		if (res == NULL) {
			genl_unlock();
			up_read(&cb_lock);
			request_module("net-pf-%d-proto-%d-family-%s",
				       PF_NETLINK, NETLINK_GENERIC, name);
			down_read(&cb_lock);
			genl_lock();
			res = genl_family_find_byname(name);
		}
#endif
		err = -ENOENT;
	}

	if (res == NULL)
		return err;

	if (!res->netnsok && !net_eq(genl_info_net(info), &init_net)) {
		/* family doesn't exist here */
		return -ENOENT;
	}

	msg = ctrl_build_family_msg(res, info->snd_portid, info->snd_seq,
				    CTRL_CMD_NEWFAMILY);
	if (IS_ERR(msg))
		return PTR_ERR(msg);

	return genlmsg_reply(msg, info);
}

static int genl_ctrl_event(int event, const struct genl_family *family,
			   const struct genl_multicast_group *grp,
			   int grp_id)
{
	struct sk_buff *msg;

	/* genl is still initialising */
	if (!init_net.genl_sock)
		return 0;

	switch (event) {
	case CTRL_CMD_NEWFAMILY:
	case CTRL_CMD_DELFAMILY:
		WARN_ON(grp);
		msg = ctrl_build_family_msg(family, 0, 0, event);
		break;
	case CTRL_CMD_NEWMCAST_GRP:
	case CTRL_CMD_DELMCAST_GRP:
		BUG_ON(!grp);
		msg = ctrl_build_mcgrp_msg(family, grp, grp_id, 0, 0, event);
		break;
	default:
		return -EINVAL;
	}

	if (IS_ERR(msg))
		return PTR_ERR(msg);

	if (!family->netnsok) {
		genlmsg_multicast_netns(&genl_ctrl, &init_net, msg, 0,
					0, GFP_KERNEL);
	} else {
		rcu_read_lock();
		genlmsg_multicast_allns(&genl_ctrl, msg, 0,
					0, GFP_ATOMIC);
		rcu_read_unlock();
	}

	return 0;
}

struct ctrl_dump_policy_ctx {
	struct netlink_policy_dump_state *state;
	const struct genl_family *rt;
	unsigned int opidx;
	u32 op;
	u16 fam_id;
	u8 policies:1,
	   single_op:1;
};

static const struct nla_policy ctrl_policy_policy[] = {
	[CTRL_ATTR_FAMILY_ID]	= { .type = NLA_U16 },
	[CTRL_ATTR_FAMILY_NAME]	= { .type = NLA_NUL_STRING,
				    .len = GENL_NAMSIZ - 1 },
	[CTRL_ATTR_OP]		= { .type = NLA_U32 },
};

static int ctrl_dumppolicy_start(struct netlink_callback *cb)
{
	const struct genl_dumpit_info *info = genl_dumpit_info(cb);
	struct ctrl_dump_policy_ctx *ctx = (void *)cb->ctx;
	struct nlattr **tb = info->attrs;
	const struct genl_family *rt;
	struct genl_ops op;
	int err, i;

	BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));

	if (!tb[CTRL_ATTR_FAMILY_ID] && !tb[CTRL_ATTR_FAMILY_NAME])
		return -EINVAL;

	if (tb[CTRL_ATTR_FAMILY_ID]) {
		ctx->fam_id = nla_get_u16(tb[CTRL_ATTR_FAMILY_ID]);
	} else {
		rt = genl_family_find_byname(
			nla_data(tb[CTRL_ATTR_FAMILY_NAME]));
		if (!rt)
			return -ENOENT;
		ctx->fam_id = rt->id;
	}

	rt = genl_family_find_byid(ctx->fam_id);
	if (!rt)
		return -ENOENT;

	ctx->rt = rt;

	if (tb[CTRL_ATTR_OP]) {
		ctx->single_op = true;
		ctx->op = nla_get_u32(tb[CTRL_ATTR_OP]);

		err = genl_get_cmd(ctx->op, rt, &op);
		if (err) {
			NL_SET_BAD_ATTR(cb->extack, tb[CTRL_ATTR_OP]);
			return err;
		}

		if (!op.policy)
			return -ENODATA;

		return netlink_policy_dump_add_policy(&ctx->state, op.policy,
						      op.maxattr);
	}

	for (i = 0; i < genl_get_cmd_cnt(rt); i++) {
		genl_get_cmd_by_index(i, rt, &op);

		if (op.policy) {
			err = netlink_policy_dump_add_policy(&ctx->state,
							     op.policy,
							     op.maxattr);
			if (err)
				goto err_free_state;
		}
	}

	if (!ctx->state)
		return -ENODATA;
	return 0;

err_free_state:
	netlink_policy_dump_free(ctx->state);
	return err;
}

static void *ctrl_dumppolicy_prep(struct sk_buff *skb,
				  struct netlink_callback *cb)
{
	struct ctrl_dump_policy_ctx *ctx = (void *)cb->ctx;
	void *hdr;

	hdr = genlmsg_put(skb, NETLINK_CB(cb->skb).portid,
			  cb->nlh->nlmsg_seq, &genl_ctrl,
			  NLM_F_MULTI, CTRL_CMD_GETPOLICY);
	if (!hdr)
		return NULL;

	if (nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, ctx->fam_id))
		return NULL;

	return hdr;
}

static int ctrl_dumppolicy_put_op(struct sk_buff *skb,
				  struct netlink_callback *cb,
			          struct genl_ops *op)
{
	struct ctrl_dump_policy_ctx *ctx = (void *)cb->ctx;
	struct nlattr *nest_pol, *nest_op;
	void *hdr;
	int idx;

	/* skip if we have nothing to show */
	if (!op->policy)
		return 0;
	if (!op->doit &&
	    (!op->dumpit || op->validate & GENL_DONT_VALIDATE_DUMP))
		return 0;

	hdr = ctrl_dumppolicy_prep(skb, cb);
	if (!hdr)
		return -ENOBUFS;

	nest_pol = nla_nest_start(skb, CTRL_ATTR_OP_POLICY);
	if (!nest_pol)
		goto err;

	nest_op = nla_nest_start(skb, op->cmd);
	if (!nest_op)
		goto err;

	/* for now both do/dump are always the same */
	idx = netlink_policy_dump_get_policy_idx(ctx->state,
						 op->policy,
						 op->maxattr);

	if (op->doit && nla_put_u32(skb, CTRL_ATTR_POLICY_DO, idx))
		goto err;

	if (op->dumpit && !(op->validate & GENL_DONT_VALIDATE_DUMP) &&
	    nla_put_u32(skb, CTRL_ATTR_POLICY_DUMP, idx))
		goto err;

	nla_nest_end(skb, nest_op);
	nla_nest_end(skb, nest_pol);
	genlmsg_end(skb, hdr);

	return 0;
err:
	genlmsg_cancel(skb, hdr);
	return -ENOBUFS;
}

static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
{
	struct ctrl_dump_policy_ctx *ctx = (void *)cb->ctx;
	void *hdr;

	if (!ctx->policies) {
		while (ctx->opidx < genl_get_cmd_cnt(ctx->rt)) {
			struct genl_ops op;

			if (ctx->single_op) {
				int err;

				err = genl_get_cmd(ctx->op, ctx->rt, &op);
				if (WARN_ON(err))
					return skb->len;

				/* break out of the loop after this one */
				ctx->opidx = genl_get_cmd_cnt(ctx->rt);
			} else {
				genl_get_cmd_by_index(ctx->opidx, ctx->rt, &op);
			}

			if (ctrl_dumppolicy_put_op(skb, cb, &op))
				return skb->len;

			ctx->opidx++;
		}

		/* completed with the per-op policy index list */
		ctx->policies = true;
	}

	while (netlink_policy_dump_loop(ctx->state)) {
		struct nlattr *nest;

		hdr = ctrl_dumppolicy_prep(skb, cb);
		if (!hdr)
			goto nla_put_failure;

		nest = nla_nest_start(skb, CTRL_ATTR_POLICY);
		if (!nest)
			goto nla_put_failure;

		if (netlink_policy_dump_write(skb, ctx->state))
			goto nla_put_failure;

		nla_nest_end(skb, nest);

		genlmsg_end(skb, hdr);
	}

	return skb->len;

nla_put_failure:
	genlmsg_cancel(skb, hdr);
	return skb->len;
}

static int ctrl_dumppolicy_done(struct netlink_callback *cb)
{
	struct ctrl_dump_policy_ctx *ctx = (void *)cb->ctx;

	netlink_policy_dump_free(ctx->state);
	return 0;
}

static const struct genl_ops genl_ctrl_ops[] = {
	{
		.cmd		= CTRL_CMD_GETFAMILY,
		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
		.policy		= ctrl_policy_family,
		.maxattr	= ARRAY_SIZE(ctrl_policy_family) - 1,
		.doit		= ctrl_getfamily,
		.dumpit		= ctrl_dumpfamily,
	},
	{
		.cmd		= CTRL_CMD_GETPOLICY,
		.policy		= ctrl_policy_policy,
		.maxattr	= ARRAY_SIZE(ctrl_policy_policy) - 1,
		.start		= ctrl_dumppolicy_start,
		.dumpit		= ctrl_dumppolicy,
		.done		= ctrl_dumppolicy_done,
	},
};

static const struct genl_multicast_group genl_ctrl_groups[] = {
	{ .name = "notify", },
};

static struct genl_family genl_ctrl __ro_after_init = {
	.module = THIS_MODULE,
	.ops = genl_ctrl_ops,
	.n_ops = ARRAY_SIZE(genl_ctrl_ops),
	.resv_start_op = CTRL_CMD_GETPOLICY + 1,
	.mcgrps = genl_ctrl_groups,
	.n_mcgrps = ARRAY_SIZE(genl_ctrl_groups),
	.id = GENL_ID_CTRL,
	.name = "nlctrl",
	.version = 0x2,
	.netnsok = true,
};

static int genl_bind(struct net *net, int group)
{
	const struct genl_family *family;
	unsigned int id;
	int ret = 0;

	down_read(&cb_lock);

	idr_for_each_entry(&genl_fam_idr, family, id) {
		const struct genl_multicast_group *grp;
		int i;

		if (family->n_mcgrps == 0)
			continue;

		i = group - family->mcgrp_offset;
		if (i < 0 || i >= family->n_mcgrps)
			continue;

		grp = &family->mcgrps[i];
		if ((grp->flags & GENL_UNS_ADMIN_PERM) &&
		    !ns_capable(net->user_ns, CAP_NET_ADMIN))
			ret = -EPERM;

		break;
	}

	up_read(&cb_lock);
	return ret;
}

static int __net_init genl_pernet_init(struct net *net)
{
	struct netlink_kernel_cfg cfg = {
		.input		= genl_rcv,
		.flags		= NL_CFG_F_NONROOT_RECV,
		.bind		= genl_bind,
	};

	/* we'll bump the group number right afterwards */
	net->genl_sock = netlink_kernel_create(net, NETLINK_GENERIC, &cfg);

	if (!net->genl_sock && net_eq(net, &init_net))
		panic("GENL: Cannot initialize generic netlink\n");

	if (!net->genl_sock)
		return -ENOMEM;

	return 0;
}

static void __net_exit genl_pernet_exit(struct net *net)
{
	netlink_kernel_release(net->genl_sock);
	net->genl_sock = NULL;
}

static struct pernet_operations genl_pernet_ops = {
	.init = genl_pernet_init,
	.exit = genl_pernet_exit,
};

static int __init genl_init(void)
{
	int err;

	err = genl_register_family(&genl_ctrl);
	if (err < 0)
		goto problem;

	err = register_pernet_subsys(&genl_pernet_ops);
	if (err)
		goto problem;

	return 0;

problem:
	panic("GENL: Cannot register controller: %d\n", err);
}

core_initcall(genl_init);

static int genlmsg_mcast(struct sk_buff *skb, u32 portid, unsigned long group,
			 gfp_t flags)
{
	struct sk_buff *tmp;
	struct net *net, *prev = NULL;
	bool delivered = false;
	int err;

	for_each_net_rcu(net) {
		if (prev) {
			tmp = skb_clone(skb, flags);
			if (!tmp) {
				err = -ENOMEM;
				goto error;
			}
			err = nlmsg_multicast(prev->genl_sock, tmp,
					      portid, group, flags);
			if (!err)
				delivered = true;
			else if (err != -ESRCH)
				goto error;
		}

		prev = net;
	}

	err = nlmsg_multicast(prev->genl_sock, skb, portid, group, flags);
	if (!err)
		delivered = true;
	else if (err != -ESRCH)
		return err;
	return delivered ? 0 : -ESRCH;
 error:
	kfree_skb(skb);
	return err;
}

int genlmsg_multicast_allns(const struct genl_family *family,
			    struct sk_buff *skb, u32 portid,
			    unsigned int group, gfp_t flags)
{
	if (WARN_ON_ONCE(group >= family->n_mcgrps))
		return -EINVAL;

	group = family->mcgrp_offset + group;
	return genlmsg_mcast(skb, portid, group, flags);
}
EXPORT_SYMBOL(genlmsg_multicast_allns);

void genl_notify(const struct genl_family *family, struct sk_buff *skb,
		 struct genl_info *info, u32 group, gfp_t flags)
{
	struct net *net = genl_info_net(info);
	struct sock *sk = net->genl_sock;

	if (WARN_ON_ONCE(group >= family->n_mcgrps))
		return;

	group = family->mcgrp_offset + group;
	nlmsg_notify(sk, skb, info->snd_portid, group,
		     nlmsg_report(info->nlhdr), flags);
}
EXPORT_SYMBOL(genl_notify);