summaryrefslogtreecommitdiff
path: root/fs/overlayfs/params.c
blob: 4860fcc4611bb766547218d1baa9fd802f24f547 (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
// SPDX-License-Identifier: GPL-2.0-only

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/namei.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/posix_acl_xattr.h>
#include <linux/seq_file.h>
#include <linux/xattr.h>
#include "overlayfs.h"
#include "params.h"

static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
MODULE_PARM_DESC(redirect_dir,
		 "Default to on or off for the redirect_dir feature");

static bool ovl_redirect_always_follow =
	IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
module_param_named(redirect_always_follow, ovl_redirect_always_follow,
		   bool, 0644);
MODULE_PARM_DESC(redirect_always_follow,
		 "Follow redirects even if redirect_dir feature is turned off");

static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
MODULE_PARM_DESC(xino_auto,
		 "Auto enable xino feature");

static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
module_param_named(index, ovl_index_def, bool, 0644);
MODULE_PARM_DESC(index,
		 "Default to on or off for the inodes index feature");

static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
MODULE_PARM_DESC(nfs_export,
		 "Default to on or off for the NFS export feature");

static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
MODULE_PARM_DESC(metacopy,
		 "Default to on or off for the metadata only copy up feature");

enum ovl_opt {
	Opt_lowerdir,
	Opt_lowerdir_add,
	Opt_datadir_add,
	Opt_upperdir,
	Opt_workdir,
	Opt_default_permissions,
	Opt_redirect_dir,
	Opt_index,
	Opt_uuid,
	Opt_nfs_export,
	Opt_userxattr,
	Opt_xino,
	Opt_metacopy,
	Opt_verity,
	Opt_volatile,
};

static const struct constant_table ovl_parameter_bool[] = {
	{ "on",		true  },
	{ "off",	false },
	{}
};

static const struct constant_table ovl_parameter_uuid[] = {
	{ "off",	OVL_UUID_OFF  },
	{ "null",	OVL_UUID_NULL },
	{ "auto",	OVL_UUID_AUTO },
	{ "on",		OVL_UUID_ON   },
	{}
};

static const char *ovl_uuid_mode(struct ovl_config *config)
{
	return ovl_parameter_uuid[config->uuid].name;
}

static int ovl_uuid_def(void)
{
	return OVL_UUID_AUTO;
}

static const struct constant_table ovl_parameter_xino[] = {
	{ "off",	OVL_XINO_OFF  },
	{ "auto",	OVL_XINO_AUTO },
	{ "on",		OVL_XINO_ON   },
	{}
};

const char *ovl_xino_mode(struct ovl_config *config)
{
	return ovl_parameter_xino[config->xino].name;
}

static int ovl_xino_def(void)
{
	return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
}

const struct constant_table ovl_parameter_redirect_dir[] = {
	{ "off",	OVL_REDIRECT_OFF      },
	{ "follow",	OVL_REDIRECT_FOLLOW   },
	{ "nofollow",	OVL_REDIRECT_NOFOLLOW },
	{ "on",		OVL_REDIRECT_ON       },
	{}
};

static const char *ovl_redirect_mode(struct ovl_config *config)
{
	return ovl_parameter_redirect_dir[config->redirect_mode].name;
}

static int ovl_redirect_mode_def(void)
{
	return ovl_redirect_dir_def	  ? OVL_REDIRECT_ON :
	       ovl_redirect_always_follow ? OVL_REDIRECT_FOLLOW :
					    OVL_REDIRECT_NOFOLLOW;
}

static const struct constant_table ovl_parameter_verity[] = {
	{ "off",	OVL_VERITY_OFF     },
	{ "on",		OVL_VERITY_ON      },
	{ "require",	OVL_VERITY_REQUIRE },
	{}
};

static const char *ovl_verity_mode(struct ovl_config *config)
{
	return ovl_parameter_verity[config->verity_mode].name;
}

static int ovl_verity_mode_def(void)
{
	return OVL_VERITY_OFF;
}

const struct fs_parameter_spec ovl_parameter_spec[] = {
	fsparam_string_empty("lowerdir",    Opt_lowerdir),
	fsparam_string("lowerdir+",         Opt_lowerdir_add),
	fsparam_string("datadir+",          Opt_datadir_add),
	fsparam_string("upperdir",          Opt_upperdir),
	fsparam_string("workdir",           Opt_workdir),
	fsparam_flag("default_permissions", Opt_default_permissions),
	fsparam_enum("redirect_dir",        Opt_redirect_dir, ovl_parameter_redirect_dir),
	fsparam_enum("index",               Opt_index, ovl_parameter_bool),
	fsparam_enum("uuid",                Opt_uuid, ovl_parameter_uuid),
	fsparam_enum("nfs_export",          Opt_nfs_export, ovl_parameter_bool),
	fsparam_flag("userxattr",           Opt_userxattr),
	fsparam_enum("xino",                Opt_xino, ovl_parameter_xino),
	fsparam_enum("metacopy",            Opt_metacopy, ovl_parameter_bool),
	fsparam_enum("verity",              Opt_verity, ovl_parameter_verity),
	fsparam_flag("volatile",            Opt_volatile),
	{}
};

static char *ovl_next_opt(char **s)
{
	char *sbegin = *s;
	char *p;

	if (sbegin == NULL)
		return NULL;

	for (p = sbegin; *p; p++) {
		if (*p == '\\') {
			p++;
			if (!*p)
				break;
		} else if (*p == ',') {
			*p = '\0';
			*s = p + 1;
			return sbegin;
		}
	}
	*s = NULL;
	return sbegin;
}

static int ovl_parse_monolithic(struct fs_context *fc, void *data)
{
	return vfs_parse_monolithic_sep(fc, data, ovl_next_opt);
}

static ssize_t ovl_parse_param_split_lowerdirs(char *str)
{
	ssize_t nr_layers = 1, nr_colons = 0;
	char *s, *d;

	for (s = d = str;; s++, d++) {
		if (*s == '\\') {
			/* keep esc chars in split lowerdir */
			*d++ = *s++;
		} else if (*s == ':') {
			bool next_colon = (*(s + 1) == ':');

			nr_colons++;
			if (nr_colons == 2 && next_colon) {
				pr_err("only single ':' or double '::' sequences of unescaped colons in lowerdir mount option allowed.\n");
				return -EINVAL;
			}
			/* count layers, not colons */
			if (!next_colon)
				nr_layers++;

			*d = '\0';
			continue;
		}

		*d = *s;
		if (!*s) {
			/* trailing colons */
			if (nr_colons) {
				pr_err("unescaped trailing colons in lowerdir mount option.\n");
				return -EINVAL;
			}
			break;
		}
		nr_colons = 0;
	}

	return nr_layers;
}

static int ovl_mount_dir_noesc(const char *name, struct path *path)
{
	int err = -EINVAL;

	if (!*name) {
		pr_err("empty lowerdir\n");
		goto out;
	}
	err = kern_path(name, LOOKUP_FOLLOW, path);
	if (err) {
		pr_err("failed to resolve '%s': %i\n", name, err);
		goto out;
	}
	return 0;

out:
	return err;
}

static void ovl_unescape(char *s)
{
	char *d = s;

	for (;; s++, d++) {
		if (*s == '\\')
			s++;
		*d = *s;
		if (!*s)
			break;
	}
}

static int ovl_mount_dir(const char *name, struct path *path)
{
	int err = -ENOMEM;
	char *tmp = kstrdup(name, GFP_KERNEL);

	if (tmp) {
		ovl_unescape(tmp);
		err = ovl_mount_dir_noesc(tmp, path);
		kfree(tmp);
	}
	return err;
}

static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
			       enum ovl_opt layer, const char *name, bool upper)
{
	struct ovl_fs_context *ctx = fc->fs_private;

	if (!d_is_dir(path->dentry))
		return invalfc(fc, "%s is not a directory", name);

	/*
	 * Root dentries of case-insensitive capable filesystems might
	 * not have the dentry operations set, but still be incompatible
	 * with overlayfs.  Check explicitly to prevent post-mount
	 * failures.
	 */
	if (sb_has_encoding(path->mnt->mnt_sb))
		return invalfc(fc, "case-insensitive capable filesystem on %s not supported", name);

	if (ovl_dentry_weird(path->dentry))
		return invalfc(fc, "filesystem on %s not supported", name);

	/*
	 * Check whether upper path is read-only here to report failures
	 * early. Don't forget to recheck when the superblock is created
	 * as the mount attributes could change.
	 */
	if (upper) {
		if (path->dentry->d_flags & DCACHE_OP_REAL)
			return invalfc(fc, "filesystem on %s not supported as upperdir", name);
		if (__mnt_is_readonly(path->mnt))
			return invalfc(fc, "filesystem on %s is read-only", name);
	} else {
		if (ctx->lowerdir_all && layer != Opt_lowerdir)
			return invalfc(fc, "lowerdir+ and datadir+ cannot follow lowerdir");
		if (ctx->nr_data && layer == Opt_lowerdir_add)
			return invalfc(fc, "regular lower layers cannot follow data layers");
		if (ctx->nr == OVL_MAX_STACK)
			return invalfc(fc, "too many lower directories, limit is %d",
				       OVL_MAX_STACK);
	}
	return 0;
}

static int ovl_ctx_realloc_lower(struct fs_context *fc)
{
	struct ovl_fs_context *ctx = fc->fs_private;
	struct ovl_fs_context_layer *l;
	size_t nr;

	if (ctx->nr < ctx->capacity)
		return 0;

	nr = min_t(size_t, max(4096 / sizeof(*l), ctx->capacity * 2),
		   OVL_MAX_STACK);
	l = krealloc_array(ctx->lower, nr, sizeof(*l), GFP_KERNEL_ACCOUNT);
	if (!l)
		return -ENOMEM;

	ctx->lower = l;
	ctx->capacity = nr;
	return 0;
}

static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
			 struct path *path, char **pname)
{
	struct ovl_fs *ofs = fc->s_fs_info;
	struct ovl_config *config = &ofs->config;
	struct ovl_fs_context *ctx = fc->fs_private;
	struct ovl_fs_context_layer *l;

	switch (layer) {
	case Opt_workdir:
		swap(config->workdir, *pname);
		swap(ctx->work, *path);
		break;
	case Opt_upperdir:
		swap(config->upperdir, *pname);
		swap(ctx->upper, *path);
		break;
	case Opt_datadir_add:
		ctx->nr_data++;
		fallthrough;
	case Opt_lowerdir_add:
		WARN_ON(ctx->nr >= ctx->capacity);
		l = &ctx->lower[ctx->nr++];
		memset(l, 0, sizeof(*l));
		swap(l->name, *pname);
		swap(l->path, *path);
		break;
	default:
		WARN_ON(1);
	}
}

static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
			   enum ovl_opt layer)
{
	char *name = kstrdup(param->string, GFP_KERNEL);
	bool upper = (layer == Opt_upperdir || layer == Opt_workdir);
	struct path path;
	int err;

	if (!name)
		return -ENOMEM;

	if (upper)
		err = ovl_mount_dir(name, &path);
	else
		err = ovl_mount_dir_noesc(name, &path);
	if (err)
		goto out_free;

	err = ovl_mount_dir_check(fc, &path, layer, name, upper);
	if (err)
		goto out_put;

	if (!upper) {
		err = ovl_ctx_realloc_lower(fc);
		if (err)
			goto out_put;
	}

	/* Store the user provided path string in ctx to show in mountinfo */
	ovl_add_layer(fc, layer, &path, &name);

out_put:
	path_put(&path);
out_free:
	kfree(name);
	return err;
}

static void ovl_reset_lowerdirs(struct ovl_fs_context *ctx)
{
	struct ovl_fs_context_layer *l = ctx->lower;

	// Reset old user provided lowerdir string
	kfree(ctx->lowerdir_all);
	ctx->lowerdir_all = NULL;

	for (size_t nr = 0; nr < ctx->nr; nr++, l++) {
		path_put(&l->path);
		kfree(l->name);
		l->name = NULL;
	}
	ctx->nr = 0;
	ctx->nr_data = 0;
}

/*
 * Parse lowerdir= mount option:
 *
 * e.g.: lowerdir=/lower1:/lower2:/lower3::/data1::/data2
 *     Set "/lower1", "/lower2", and "/lower3" as lower layers and
 *     "/data1" and "/data2" as data lower layers. Any existing lower
 *     layers are replaced.
 */
static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
{
	int err;
	struct ovl_fs_context *ctx = fc->fs_private;
	struct ovl_fs_context_layer *l;
	char *dup = NULL, *iter;
	ssize_t nr_lower, nr;
	bool data_layer = false;

	/*
	 * Ensure we're backwards compatible with mount(2)
	 * by allowing relative paths.
	 */

	/* drop all existing lower layers */
	ovl_reset_lowerdirs(ctx);

	if (!*name)
		return 0;

	if (*name == ':') {
		pr_err("cannot append lower layer");
		return -EINVAL;
	}

	// Store user provided lowerdir string to show in mount options
	ctx->lowerdir_all = kstrdup(name, GFP_KERNEL);
	if (!ctx->lowerdir_all)
		return -ENOMEM;

	dup = kstrdup(name, GFP_KERNEL);
	if (!dup)
		return -ENOMEM;

	err = -EINVAL;
	nr_lower = ovl_parse_param_split_lowerdirs(dup);
	if (nr_lower < 0)
		goto out_err;

	if (nr_lower > OVL_MAX_STACK) {
		pr_err("too many lower directories, limit is %d\n", OVL_MAX_STACK);
		goto out_err;
	}

	if (nr_lower > ctx->capacity) {
		err = -ENOMEM;
		l = krealloc_array(ctx->lower, nr_lower, sizeof(*ctx->lower),
				   GFP_KERNEL_ACCOUNT);
		if (!l)
			goto out_err;

		ctx->lower = l;
		ctx->capacity = nr_lower;
	}

	iter = dup;
	l = ctx->lower;
	for (nr = 0; nr < nr_lower; nr++, l++) {
		ctx->nr++;
		memset(l, 0, sizeof(*l));

		err = ovl_mount_dir(iter, &l->path);
		if (err)
			goto out_put;

		err = ovl_mount_dir_check(fc, &l->path, Opt_lowerdir, iter, false);
		if (err)
			goto out_put;

		err = -ENOMEM;
		l->name = kstrdup(iter, GFP_KERNEL_ACCOUNT);
		if (!l->name)
			goto out_put;

		if (data_layer)
			ctx->nr_data++;

		/* Calling strchr() again would overrun. */
		if (ctx->nr == nr_lower)
			break;

		err = -EINVAL;
		iter = strchr(iter, '\0') + 1;
		if (*iter) {
			/*
			 * This is a regular layer so we require that
			 * there are no data layers.
			 */
			if (ctx->nr_data > 0) {
				pr_err("regular lower layers cannot follow data lower layers");
				goto out_put;
			}

			data_layer = false;
			continue;
		}

		/* This is a data lower layer. */
		data_layer = true;
		iter++;
	}
	kfree(dup);
	return 0;

out_put:
	ovl_reset_lowerdirs(ctx);

out_err:
	kfree(dup);

	/* Intentionally don't realloc to a smaller size. */
	return err;
}

static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
	int err = 0;
	struct fs_parse_result result;
	struct ovl_fs *ofs = fc->s_fs_info;
	struct ovl_config *config = &ofs->config;
	struct ovl_fs_context *ctx = fc->fs_private;
	int opt;

	if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
		/*
		 * On remount overlayfs has always ignored all mount
		 * options no matter if malformed or not so for
		 * backwards compatibility we do the same here.
		 */
		if (fc->oldapi)
			return 0;

		/*
		 * Give us the freedom to allow changing mount options
		 * with the new mount api in the future. So instead of
		 * silently ignoring everything we report a proper
		 * error. This is only visible for users of the new
		 * mount api.
		 */
		return invalfc(fc, "No changes allowed in reconfigure");
	}

	opt = fs_parse(fc, ovl_parameter_spec, param, &result);
	if (opt < 0)
		return opt;

	switch (opt) {
	case Opt_lowerdir:
		err = ovl_parse_param_lowerdir(param->string, fc);
		break;
	case Opt_lowerdir_add:
	case Opt_datadir_add:
	case Opt_upperdir:
	case Opt_workdir:
		err = ovl_parse_layer(fc, param, opt);
		break;
	case Opt_default_permissions:
		config->default_permissions = true;
		break;
	case Opt_redirect_dir:
		config->redirect_mode = result.uint_32;
		if (config->redirect_mode == OVL_REDIRECT_OFF) {
			config->redirect_mode = ovl_redirect_always_follow ?
						OVL_REDIRECT_FOLLOW :
						OVL_REDIRECT_NOFOLLOW;
		}
		ctx->set.redirect = true;
		break;
	case Opt_index:
		config->index = result.uint_32;
		ctx->set.index = true;
		break;
	case Opt_uuid:
		config->uuid = result.uint_32;
		break;
	case Opt_nfs_export:
		config->nfs_export = result.uint_32;
		ctx->set.nfs_export = true;
		break;
	case Opt_xino:
		config->xino = result.uint_32;
		break;
	case Opt_metacopy:
		config->metacopy = result.uint_32;
		ctx->set.metacopy = true;
		break;
	case Opt_verity:
		config->verity_mode = result.uint_32;
		break;
	case Opt_volatile:
		config->ovl_volatile = true;
		break;
	case Opt_userxattr:
		config->userxattr = true;
		break;
	default:
		pr_err("unrecognized mount option \"%s\" or missing value\n",
		       param->key);
		return -EINVAL;
	}

	return err;
}

static int ovl_get_tree(struct fs_context *fc)
{
	return get_tree_nodev(fc, ovl_fill_super);
}

static inline void ovl_fs_context_free(struct ovl_fs_context *ctx)
{
	ovl_reset_lowerdirs(ctx);
	path_put(&ctx->upper);
	path_put(&ctx->work);
	kfree(ctx->lower);
	kfree(ctx);
}

static void ovl_free(struct fs_context *fc)
{
	struct ovl_fs *ofs = fc->s_fs_info;
	struct ovl_fs_context *ctx = fc->fs_private;

	/*
	 * ofs is stored in the fs_context when it is initialized.
	 * ofs is transferred to the superblock on a successful mount,
	 * but if an error occurs before the transfer we have to free
	 * it here.
	 */
	if (ofs)
		ovl_free_fs(ofs);

	if (ctx)
		ovl_fs_context_free(ctx);
}

static int ovl_reconfigure(struct fs_context *fc)
{
	struct super_block *sb = fc->root->d_sb;
	struct ovl_fs *ofs = OVL_FS(sb);
	struct super_block *upper_sb;
	int ret = 0;

	if (!(fc->sb_flags & SB_RDONLY) && ovl_force_readonly(ofs))
		return -EROFS;

	if (fc->sb_flags & SB_RDONLY && !sb_rdonly(sb)) {
		upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
		if (ovl_should_sync(ofs)) {
			down_read(&upper_sb->s_umount);
			ret = sync_filesystem(upper_sb);
			up_read(&upper_sb->s_umount);
		}
	}

	return ret;
}

static const struct fs_context_operations ovl_context_ops = {
	.parse_monolithic = ovl_parse_monolithic,
	.parse_param = ovl_parse_param,
	.get_tree    = ovl_get_tree,
	.reconfigure = ovl_reconfigure,
	.free        = ovl_free,
};

/*
 * This is called during fsopen() and will record the user namespace of
 * the caller in fc->user_ns since we've raised FS_USERNS_MOUNT. We'll
 * need it when we actually create the superblock to verify that the
 * process creating the superblock is in the same user namespace as
 * process that called fsopen().
 */
int ovl_init_fs_context(struct fs_context *fc)
{
	struct ovl_fs_context *ctx;
	struct ovl_fs *ofs;

	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
	if (!ctx)
		return -ENOMEM;

	/*
	 * By default we allocate for three lower layers. It's likely
	 * that it'll cover most users.
	 */
	ctx->lower = kmalloc_array(3, sizeof(*ctx->lower), GFP_KERNEL_ACCOUNT);
	if (!ctx->lower)
		goto out_err;
	ctx->capacity = 3;

	ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
	if (!ofs)
		goto out_err;

	ofs->config.redirect_mode	= ovl_redirect_mode_def();
	ofs->config.index		= ovl_index_def;
	ofs->config.uuid		= ovl_uuid_def();
	ofs->config.nfs_export		= ovl_nfs_export_def;
	ofs->config.xino		= ovl_xino_def();
	ofs->config.metacopy		= ovl_metacopy_def;

	fc->s_fs_info		= ofs;
	fc->fs_private		= ctx;
	fc->ops			= &ovl_context_ops;
	return 0;

out_err:
	ovl_fs_context_free(ctx);
	return -ENOMEM;

}

void ovl_free_fs(struct ovl_fs *ofs)
{
	struct vfsmount **mounts;
	unsigned i;

	iput(ofs->workbasedir_trap);
	iput(ofs->workdir_trap);
	dput(ofs->whiteout);
	dput(ofs->workdir);
	if (ofs->workdir_locked)
		ovl_inuse_unlock(ofs->workbasedir);
	dput(ofs->workbasedir);
	if (ofs->upperdir_locked)
		ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);

	/* Reuse ofs->config.lowerdirs as a vfsmount array before freeing it */
	mounts = (struct vfsmount **) ofs->config.lowerdirs;
	for (i = 0; i < ofs->numlayer; i++) {
		iput(ofs->layers[i].trap);
		kfree(ofs->config.lowerdirs[i]);
		mounts[i] = ofs->layers[i].mnt;
	}
	kern_unmount_array(mounts, ofs->numlayer);
	kfree(ofs->layers);
	for (i = 0; i < ofs->numfs; i++)
		free_anon_bdev(ofs->fs[i].pseudo_dev);
	kfree(ofs->fs);

	kfree(ofs->config.lowerdirs);
	kfree(ofs->config.upperdir);
	kfree(ofs->config.workdir);
	if (ofs->creator_cred)
		put_cred(ofs->creator_cred);
	kfree(ofs);
}

int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
			 struct ovl_config *config)
{
	struct ovl_opt_set set = ctx->set;

	if (ctx->nr_data > 0 && !config->metacopy) {
		pr_err("lower data-only dirs require metacopy support.\n");
		return -EINVAL;
	}

	/* Workdir/index are useless in non-upper mount */
	if (!config->upperdir) {
		if (config->workdir) {
			pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
				config->workdir);
			kfree(config->workdir);
			config->workdir = NULL;
		}
		if (config->index && set.index) {
			pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
			set.index = false;
		}
		config->index = false;
	}

	if (!config->upperdir && config->ovl_volatile) {
		pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
		config->ovl_volatile = false;
	}

	if (!config->upperdir && config->uuid == OVL_UUID_ON) {
		pr_info("option \"uuid=on\" requires an upper fs, falling back to uuid=null.\n");
		config->uuid = OVL_UUID_NULL;
	}

	/* Resolve verity -> metacopy dependency */
	if (config->verity_mode && !config->metacopy) {
		/* Don't allow explicit specified conflicting combinations */
		if (set.metacopy) {
			pr_err("conflicting options: metacopy=off,verity=%s\n",
			       ovl_verity_mode(config));
			return -EINVAL;
		}
		/* Otherwise automatically enable metacopy. */
		config->metacopy = true;
	}

	/*
	 * This is to make the logic below simpler.  It doesn't make any other
	 * difference, since redirect_dir=on is only used for upper.
	 */
	if (!config->upperdir && config->redirect_mode == OVL_REDIRECT_FOLLOW)
		config->redirect_mode = OVL_REDIRECT_ON;

	/* Resolve verity -> metacopy -> redirect_dir dependency */
	if (config->metacopy && config->redirect_mode != OVL_REDIRECT_ON) {
		if (set.metacopy && set.redirect) {
			pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
			       ovl_redirect_mode(config));
			return -EINVAL;
		}
		if (config->verity_mode && set.redirect) {
			pr_err("conflicting options: verity=%s,redirect_dir=%s\n",
			       ovl_verity_mode(config), ovl_redirect_mode(config));
			return -EINVAL;
		}
		if (set.redirect) {
			/*
			 * There was an explicit redirect_dir=... that resulted
			 * in this conflict.
			 */
			pr_info("disabling metacopy due to redirect_dir=%s\n",
				ovl_redirect_mode(config));
			config->metacopy = false;
		} else {
			/* Automatically enable redirect otherwise. */
			config->redirect_mode = OVL_REDIRECT_ON;
		}
	}

	/* Resolve nfs_export -> index dependency */
	if (config->nfs_export && !config->index) {
		if (!config->upperdir &&
		    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
			pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
			config->nfs_export = false;
		} else if (set.nfs_export && set.index) {
			pr_err("conflicting options: nfs_export=on,index=off\n");
			return -EINVAL;
		} else if (set.index) {
			/*
			 * There was an explicit index=off that resulted
			 * in this conflict.
			 */
			pr_info("disabling nfs_export due to index=off\n");
			config->nfs_export = false;
		} else {
			/* Automatically enable index otherwise. */
			config->index = true;
		}
	}

	/* Resolve nfs_export -> !metacopy && !verity dependency */
	if (config->nfs_export && config->metacopy) {
		if (set.nfs_export && set.metacopy) {
			pr_err("conflicting options: nfs_export=on,metacopy=on\n");
			return -EINVAL;
		}
		if (set.metacopy) {
			/*
			 * There was an explicit metacopy=on that resulted
			 * in this conflict.
			 */
			pr_info("disabling nfs_export due to metacopy=on\n");
			config->nfs_export = false;
		} else if (config->verity_mode) {
			/*
			 * There was an explicit verity=.. that resulted
			 * in this conflict.
			 */
			pr_info("disabling nfs_export due to verity=%s\n",
				ovl_verity_mode(config));
			config->nfs_export = false;
		} else {
			/*
			 * There was an explicit nfs_export=on that resulted
			 * in this conflict.
			 */
			pr_info("disabling metacopy due to nfs_export=on\n");
			config->metacopy = false;
		}
	}


	/* Resolve userxattr -> !redirect && !metacopy && !verity dependency */
	if (config->userxattr) {
		if (set.redirect &&
		    config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
			pr_err("conflicting options: userxattr,redirect_dir=%s\n",
			       ovl_redirect_mode(config));
			return -EINVAL;
		}
		if (config->metacopy && set.metacopy) {
			pr_err("conflicting options: userxattr,metacopy=on\n");
			return -EINVAL;
		}
		if (config->verity_mode) {
			pr_err("conflicting options: userxattr,verity=%s\n",
			       ovl_verity_mode(config));
			return -EINVAL;
		}
		/*
		 * Silently disable default setting of redirect and metacopy.
		 * This shall be the default in the future as well: these
		 * options must be explicitly enabled if used together with
		 * userxattr.
		 */
		config->redirect_mode = OVL_REDIRECT_NOFOLLOW;
		config->metacopy = false;
	}

	return 0;
}

/**
 * ovl_show_options
 * @m: the seq_file handle
 * @dentry: The dentry to query
 *
 * Prints the mount options for a given superblock.
 * Returns zero; does not fail.
 */
int ovl_show_options(struct seq_file *m, struct dentry *dentry)
{
	struct super_block *sb = dentry->d_sb;
	struct ovl_fs *ofs = OVL_FS(sb);
	size_t nr, nr_merged_lower, nr_lower = 0;
	char **lowerdirs = ofs->config.lowerdirs;

	/*
	 * lowerdirs[0] holds the colon separated list that user provided
	 * with lowerdir mount option.
	 * lowerdirs[1..numlayer] hold the lowerdir paths that were added
	 * using the lowerdir+ and datadir+ mount options.
	 * For now, we do not allow mixing the legacy lowerdir mount option
	 * with the new lowerdir+ and datadir+ mount options.
	 */
	if (lowerdirs[0]) {
		seq_show_option(m, "lowerdir", lowerdirs[0]);
	} else {
		nr_lower = ofs->numlayer;
		nr_merged_lower = nr_lower - ofs->numdatalayer;
	}
	for (nr = 1; nr < nr_lower; nr++) {
		if (nr < nr_merged_lower)
			seq_show_option(m, "lowerdir+", lowerdirs[nr]);
		else
			seq_show_option(m, "datadir+", lowerdirs[nr]);
	}
	if (ofs->config.upperdir) {
		seq_show_option(m, "upperdir", ofs->config.upperdir);
		seq_show_option(m, "workdir", ofs->config.workdir);
	}
	if (ofs->config.default_permissions)
		seq_puts(m, ",default_permissions");
	if (ofs->config.redirect_mode != ovl_redirect_mode_def())
		seq_printf(m, ",redirect_dir=%s",
			   ovl_redirect_mode(&ofs->config));
	if (ofs->config.index != ovl_index_def)
		seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
	if (ofs->config.uuid != ovl_uuid_def())
		seq_printf(m, ",uuid=%s", ovl_uuid_mode(&ofs->config));
	if (ofs->config.nfs_export != ovl_nfs_export_def)
		seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
						"on" : "off");
	if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(ofs))
		seq_printf(m, ",xino=%s", ovl_xino_mode(&ofs->config));
	if (ofs->config.metacopy != ovl_metacopy_def)
		seq_printf(m, ",metacopy=%s",
			   ofs->config.metacopy ? "on" : "off");
	if (ofs->config.ovl_volatile)
		seq_puts(m, ",volatile");
	if (ofs->config.userxattr)
		seq_puts(m, ",userxattr");
	if (ofs->config.verity_mode != ovl_verity_mode_def())
		seq_printf(m, ",verity=%s",
			   ovl_verity_mode(&ofs->config));
	return 0;
}