Home Home > GIT Browse
summaryrefslogtreecommitdiff
blob: 103643c68e3fdfa394bf7133b0803ce14e38786f (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
// SPDX-License-Identifier: GPL-2.0-or-later
/* Provide a way to create a superblock configuration context within the kernel
 * that allows a superblock to be set up prior to mounting.
 *
 * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/module.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/nsproxy.h>
#include <linux/slab.h>
#include <linux/magic.h>
#include <linux/security.h>
#include <linux/mnt_namespace.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <net/net_namespace.h>
#include <asm/sections.h>
#include "mount.h"
#include "internal.h"

enum legacy_fs_param {
	LEGACY_FS_UNSET_PARAMS,
	LEGACY_FS_MONOLITHIC_PARAMS,
	LEGACY_FS_INDIVIDUAL_PARAMS,
};

struct legacy_fs_context {
	char			*legacy_data;	/* Data page for legacy filesystems */
	size_t			data_size;
	enum legacy_fs_param	param_type;
};

static int legacy_init_fs_context(struct fs_context *fc);

static const struct constant_table common_set_sb_flag[] = {
	{ "dirsync",	SB_DIRSYNC },
	{ "lazytime",	SB_LAZYTIME },
	{ "mand",	SB_MANDLOCK },
	{ "posixacl",	SB_POSIXACL },
	{ "ro",		SB_RDONLY },
	{ "sync",	SB_SYNCHRONOUS },
};

static const struct constant_table common_clear_sb_flag[] = {
	{ "async",	SB_SYNCHRONOUS },
	{ "nolazytime",	SB_LAZYTIME },
	{ "nomand",	SB_MANDLOCK },
	{ "rw",		SB_RDONLY },
	{ "silent",	SB_SILENT },
};

static const char *const forbidden_sb_flag[] = {
	"bind",
	"dev",
	"exec",
	"move",
	"noatime",
	"nodev",
	"nodiratime",
	"noexec",
	"norelatime",
	"nostrictatime",
	"nosuid",
	"private",
	"rec",
	"relatime",
	"remount",
	"shared",
	"slave",
	"strictatime",
	"suid",
	"unbindable",
};

/*
 * Check for a common mount option that manipulates s_flags.
 */
static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
{
	unsigned int token;
	unsigned int i;

	for (i = 0; i < ARRAY_SIZE(forbidden_sb_flag); i++)
		if (strcmp(key, forbidden_sb_flag[i]) == 0)
			return -EINVAL;

	token = lookup_constant(common_set_sb_flag, key, 0);
	if (token) {
		fc->sb_flags |= token;
		fc->sb_flags_mask |= token;
		return 0;
	}

	token = lookup_constant(common_clear_sb_flag, key, 0);
	if (token) {
		fc->sb_flags &= ~token;
		fc->sb_flags_mask |= token;
		return 0;
	}

	return -ENOPARAM;
}

/**
 * vfs_parse_fs_param - Add a single parameter to a superblock config
 * @fc: The filesystem context to modify
 * @param: The parameter
 *
 * A single mount option in string form is applied to the filesystem context
 * being set up.  Certain standard options (for example "ro") are translated
 * into flag bits without going to the filesystem.  The active security module
 * is allowed to observe and poach options.  Any other options are passed over
 * to the filesystem to parse.
 *
 * This may be called multiple times for a context.
 *
 * Returns 0 on success and a negative error code on failure.  In the event of
 * failure, supplementary error information may have been set.
 */
int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
{
	int ret;

	if (!param->key)
		return invalf(fc, "Unnamed parameter\n");

	ret = vfs_parse_sb_flag(fc, param->key);
	if (ret != -ENOPARAM)
		return ret;

	ret = security_fs_context_parse_param(fc, param);
	if (ret != -ENOPARAM)
		/* Param belongs to the LSM or is disallowed by the LSM; so
		 * don't pass to the FS.
		 */
		return ret;

	if (fc->ops->parse_param) {
		ret = fc->ops->parse_param(fc, param);
		if (ret != -ENOPARAM)
			return ret;
	}

	/* If the filesystem doesn't take any arguments, give it the
	 * default handling of source.
	 */
	if (strcmp(param->key, "source") == 0) {
		if (param->type != fs_value_is_string)
			return invalf(fc, "VFS: Non-string source");
		if (fc->source)
			return invalf(fc, "VFS: Multiple sources");
		fc->source = param->string;
		param->string = NULL;
		return 0;
	}

	return invalf(fc, "%s: Unknown parameter '%s'",
		      fc->fs_type->name, param->key);
}
EXPORT_SYMBOL(vfs_parse_fs_param);

/**
 * vfs_parse_fs_string - Convenience function to just parse a string.
 */
int vfs_parse_fs_string(struct fs_context *fc, const char *key,
			const char *value, size_t v_size)
{
	int ret;

	struct fs_parameter param = {
		.key	= key,
		.type	= fs_value_is_string,
		.size	= v_size,
	};

	if (v_size > 0) {
		param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
		if (!param.string)
			return -ENOMEM;
	}

	ret = vfs_parse_fs_param(fc, &param);
	kfree(param.string);
	return ret;
}
EXPORT_SYMBOL(vfs_parse_fs_string);

/**
 * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
 * @ctx: The superblock configuration to fill in.
 * @data: The data to parse
 *
 * Parse a blob of data that's in key[=val][,key[=val]]* form.  This can be
 * called from the ->monolithic_mount_data() fs_context operation.
 *
 * Returns 0 on success or the error returned by the ->parse_option() fs_context
 * operation on failure.
 */
int generic_parse_monolithic(struct fs_context *fc, void *data)
{
	char *options = data, *key;
	int ret = 0;

	if (!options)
		return 0;

	ret = security_sb_eat_lsm_opts(options, &fc->security);
	if (ret)
		return ret;

	while ((key = strsep(&options, ",")) != NULL) {
		if (*key) {
			size_t v_len = 0;
			char *value = strchr(key, '=');

			if (value) {
				if (value == key)
					continue;
				*value++ = 0;
				v_len = strlen(value);
			}
			ret = vfs_parse_fs_string(fc, key, value, v_len);
			if (ret < 0)
				break;
		}
	}

	return ret;
}
EXPORT_SYMBOL(generic_parse_monolithic);

/**
 * alloc_fs_context - Create a filesystem context.
 * @fs_type: The filesystem type.
 * @reference: The dentry from which this one derives (or NULL)
 * @sb_flags: Filesystem/superblock flags (SB_*)
 * @sb_flags_mask: Applicable members of @sb_flags
 * @purpose: The purpose that this configuration shall be used for.
 *
 * Open a filesystem and create a mount context.  The mount context is
 * initialised with the supplied flags and, if a submount/automount from
 * another superblock (referred to by @reference) is supplied, may have
 * parameters such as namespaces copied across from that superblock.
 */
static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
				      struct dentry *reference,
				      unsigned int sb_flags,
				      unsigned int sb_flags_mask,
				      enum fs_context_purpose purpose)
{
	int (*init_fs_context)(struct fs_context *);
	struct fs_context *fc;
	int ret = -ENOMEM;

	fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL);
	if (!fc)
		return ERR_PTR(-ENOMEM);

	fc->purpose	= purpose;
	fc->sb_flags	= sb_flags;
	fc->sb_flags_mask = sb_flags_mask;
	fc->fs_type	= get_filesystem(fs_type);
	fc->cred	= get_current_cred();
	fc->net_ns	= get_net(current->nsproxy->net_ns);

	mutex_init(&fc->uapi_mutex);

	switch (purpose) {
	case FS_CONTEXT_FOR_MOUNT:
		fc->user_ns = get_user_ns(fc->cred->user_ns);
		break;
	case FS_CONTEXT_FOR_SUBMOUNT:
		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
		break;
	case FS_CONTEXT_FOR_RECONFIGURE:
		/* We don't pin any namespaces as the superblock's
		 * subscriptions cannot be changed at this point.
		 */
		atomic_inc(&reference->d_sb->s_active);
		fc->root = dget(reference);
		break;
	}

	/* TODO: Make all filesystems support this unconditionally */
	init_fs_context = fc->fs_type->init_fs_context;
	if (!init_fs_context)
		init_fs_context = legacy_init_fs_context;

	ret = init_fs_context(fc);
	if (ret < 0)
		goto err_fc;
	fc->need_free = true;
	return fc;

err_fc:
	put_fs_context(fc);
	return ERR_PTR(ret);
}

struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
					unsigned int sb_flags)
{
	return alloc_fs_context(fs_type, NULL, sb_flags, 0,
					FS_CONTEXT_FOR_MOUNT);
}
EXPORT_SYMBOL(fs_context_for_mount);

struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
					unsigned int sb_flags,
					unsigned int sb_flags_mask)
{
	return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
				sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
}
EXPORT_SYMBOL(fs_context_for_reconfigure);

struct fs_context *fs_context_for_submount(struct file_system_type *type,
					   struct dentry *reference)
{
	return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
}
EXPORT_SYMBOL(fs_context_for_submount);

void fc_drop_locked(struct fs_context *fc)
{
	struct super_block *sb = fc->root->d_sb;
	dput(fc->root);
	fc->root = NULL;
	deactivate_locked_super(sb);
}

static void legacy_fs_context_free(struct fs_context *fc);

/**
 * vfs_dup_fc_config: Duplicate a filesystem context.
 * @src_fc: The context to copy.
 */
struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
{
	struct fs_context *fc;
	int ret;

	if (!src_fc->ops->dup)
		return ERR_PTR(-EOPNOTSUPP);

	fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
	if (!fc)
		return ERR_PTR(-ENOMEM);

	mutex_init(&fc->uapi_mutex);

	fc->fs_private	= NULL;
	fc->s_fs_info	= NULL;
	fc->source	= NULL;
	fc->security	= NULL;
	get_filesystem(fc->fs_type);
	get_net(fc->net_ns);
	get_user_ns(fc->user_ns);
	get_cred(fc->cred);
	if (fc->log)
		refcount_inc(&fc->log->usage);

	/* Can't call put until we've called ->dup */
	ret = fc->ops->dup(fc, src_fc);
	if (ret < 0)
		goto err_fc;

	ret = security_fs_context_dup(fc, src_fc);
	if (ret < 0)
		goto err_fc;
	return fc;

err_fc:
	put_fs_context(fc);
	return ERR_PTR(ret);
}
EXPORT_SYMBOL(vfs_dup_fs_context);

/**
 * logfc - Log a message to a filesystem context
 * @fc: The filesystem context to log to.
 * @fmt: The format of the buffer.
 */
void logfc(struct fs_context *fc, const char *fmt, ...)
{
	static const char store_failure[] = "OOM: Can't store error string";
	struct fc_log *log = fc ? fc->log : NULL;
	const char *p;
	va_list va;
	char *q;
	u8 freeable;

	va_start(va, fmt);
	if (!strchr(fmt, '%')) {
		p = fmt;
		goto unformatted_string;
	}
	if (strcmp(fmt, "%s") == 0) {
		p = va_arg(va, const char *);
		goto unformatted_string;
	}

	q = kvasprintf(GFP_KERNEL, fmt, va);
copied_string:
	if (!q)
		goto store_failure;
	freeable = 1;
	goto store_string;

unformatted_string:
	if ((unsigned long)p >= (unsigned long)__start_rodata &&
	    (unsigned long)p <  (unsigned long)__end_rodata)
		goto const_string;
	if (log && within_module_core((unsigned long)p, log->owner))
		goto const_string;
	q = kstrdup(p, GFP_KERNEL);
	goto copied_string;

store_failure:
	p = store_failure;
const_string:
	q = (char *)p;
	freeable = 0;
store_string:
	if (!log) {
		switch (fmt[0]) {
		case 'w':
			printk(KERN_WARNING "%s\n", q + 2);
			break;
		case 'e':
			printk(KERN_ERR "%s\n", q + 2);
			break;
		default:
			printk(KERN_NOTICE "%s\n", q + 2);
			break;
		}
		if (freeable)
			kfree(q);
	} else {
		unsigned int logsize = ARRAY_SIZE(log->buffer);
		u8 index;

		index = log->head & (logsize - 1);
		BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
			     sizeof(log->tail) != sizeof(u8));
		if ((u8)(log->head - log->tail) == logsize) {
			/* The buffer is full, discard the oldest message */
			if (log->need_free & (1 << index))
				kfree(log->buffer[index]);
			log->tail++;
		}

		log->buffer[index] = q;
		log->need_free &= ~(1 << index);
		log->need_free |= freeable << index;
		log->head++;
	}
	va_end(va);
}
EXPORT_SYMBOL(logfc);

/*
 * Free a logging structure.
 */
static void put_fc_log(struct fs_context *fc)
{
	struct fc_log *log = fc->log;
	int i;

	if (log) {
		if (refcount_dec_and_test(&log->usage)) {
			fc->log = NULL;
			for (i = 0; i <= 7; i++)
				if (log->need_free & (1 << i))
					kfree(log->buffer[i]);
			kfree(log);
		}
	}
}

/**
 * put_fs_context - Dispose of a superblock configuration context.
 * @fc: The context to dispose of.
 */
void put_fs_context(struct fs_context *fc)
{
	struct super_block *sb;

	if (fc->root) {
		sb = fc->root->d_sb;
		dput(fc->root);
		fc->root = NULL;
		deactivate_super(sb);
	}

	if (fc->need_free && fc->ops && fc->ops->free)
		fc->ops->free(fc);

	security_free_mnt_opts(&fc->security);
	put_net(fc->net_ns);
	put_user_ns(fc->user_ns);
	put_cred(fc->cred);
	kfree(fc->subtype);
	put_fc_log(fc);
	put_filesystem(fc->fs_type);
	kfree(fc->source);
	kfree(fc);
}
EXPORT_SYMBOL(put_fs_context);

/*
 * Free the config for a filesystem that doesn't support fs_context.
 */
static void legacy_fs_context_free(struct fs_context *fc)
{
	struct legacy_fs_context *ctx = fc->fs_private;

	if (ctx) {
		if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
			kfree(ctx->legacy_data);
		kfree(ctx);
	}
}

/*
 * Duplicate a legacy config.
 */
static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
{
	struct legacy_fs_context *ctx;
	struct legacy_fs_context *src_ctx = src_fc->fs_private;

	ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
	if (!ctx)
		return -ENOMEM;

	if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
		ctx->legacy_data = kmemdup(src_ctx->legacy_data,
					   src_ctx->data_size, GFP_KERNEL);
		if (!ctx->legacy_data) {
			kfree(ctx);
			return -ENOMEM;
		}
	}

	fc->fs_private = ctx;
	return 0;
}

/*
 * Add a parameter to a legacy config.  We build up a comma-separated list of
 * options.
 */
static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
	struct legacy_fs_context *ctx = fc->fs_private;
	unsigned int size = ctx->data_size;
	size_t len = 0;

	if (strcmp(param->key, "source") == 0) {
		if (param->type != fs_value_is_string)
			return invalf(fc, "VFS: Legacy: Non-string source");
		if (fc->source)
			return invalf(fc, "VFS: Legacy: Multiple sources");
		fc->source = param->string;
		param->string = NULL;
		return 0;
	}

	if ((fc->fs_type->fs_flags & FS_HAS_SUBTYPE) &&
	    strcmp(param->key, "subtype") == 0) {
		if (param->type != fs_value_is_string)
			return invalf(fc, "VFS: Legacy: Non-string subtype");
		if (fc->subtype)
			return invalf(fc, "VFS: Legacy: Multiple subtype");
		fc->subtype = param->string;
		param->string = NULL;
		return 0;
	}

	if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
		return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");

	switch (param->type) {
	case fs_value_is_string:
		len = 1 + param->size;
		/* Fall through */
	case fs_value_is_flag:
		len += strlen(param->key);
		break;
	default:
		return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported",
			      param->key);
	}

	if (len > PAGE_SIZE - 2 - size)
		return invalf(fc, "VFS: Legacy: Cumulative options too large");
	if (strchr(param->key, ',') ||
	    (param->type == fs_value_is_string &&
	     memchr(param->string, ',', param->size)))
		return invalf(fc, "VFS: Legacy: Option '%s' contained comma",
			      param->key);
	if (!ctx->legacy_data) {
		ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
		if (!ctx->legacy_data)
			return -ENOMEM;
	}

	ctx->legacy_data[size++] = ',';
	len = strlen(param->key);
	memcpy(ctx->legacy_data + size, param->key, len);
	size += len;
	if (param->type == fs_value_is_string) {
		ctx->legacy_data[size++] = '=';
		memcpy(ctx->legacy_data + size, param->string, param->size);
		size += param->size;
	}
	ctx->legacy_data[size] = '\0';
	ctx->data_size = size;
	ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
	return 0;
}

/*
 * Add monolithic mount data.
 */
static int legacy_parse_monolithic(struct fs_context *fc, void *data)
{
	struct legacy_fs_context *ctx = fc->fs_private;

	if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
		pr_warn("VFS: Can't mix monolithic and individual options\n");
		return -EINVAL;
	}

	ctx->legacy_data = data;
	ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
	if (!ctx->legacy_data)
		return 0;

	if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
		return 0;
	return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
}

/*
 * Get a mountable root with the legacy mount command.
 */
static int legacy_get_tree(struct fs_context *fc)
{
	struct legacy_fs_context *ctx = fc->fs_private;
	struct super_block *sb;
	struct dentry *root;

	root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
				      fc->source, ctx->legacy_data);
	if (IS_ERR(root))
		return PTR_ERR(root);

	sb = root->d_sb;
	BUG_ON(!sb);

	fc->root = root;
	return 0;
}

/*
 * Handle remount.
 */
static int legacy_reconfigure(struct fs_context *fc)
{
	struct legacy_fs_context *ctx = fc->fs_private;
	struct super_block *sb = fc->root->d_sb;

	if (!sb->s_op->remount_fs)
		return 0;

	return sb->s_op->remount_fs(sb, &fc->sb_flags,
				    ctx ? ctx->legacy_data : NULL);
}

const struct fs_context_operations legacy_fs_context_ops = {
	.free			= legacy_fs_context_free,
	.dup			= legacy_fs_context_dup,
	.parse_param		= legacy_parse_param,
	.parse_monolithic	= legacy_parse_monolithic,
	.get_tree		= legacy_get_tree,
	.reconfigure		= legacy_reconfigure,
};

/*
 * Initialise a legacy context for a filesystem that doesn't support
 * fs_context.
 */
static int legacy_init_fs_context(struct fs_context *fc)
{
	fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL);
	if (!fc->fs_private)
		return -ENOMEM;
	fc->ops = &legacy_fs_context_ops;
	return 0;
}

int parse_monolithic_mount_data(struct fs_context *fc, void *data)
{
	int (*monolithic_mount_data)(struct fs_context *, void *);

	monolithic_mount_data = fc->ops->parse_monolithic;
	if (!monolithic_mount_data)
		monolithic_mount_data = generic_parse_monolithic;

	return monolithic_mount_data(fc, data);
}

/*
 * Clean up a context after performing an action on it and put it into a state
 * from where it can be used to reconfigure a superblock.
 *
 * Note that here we do only the parts that can't fail; the rest is in
 * finish_clean_context() below and in between those fs_context is marked
 * FS_CONTEXT_AWAITING_RECONF.  The reason for splitup is that after
 * successful mount or remount we need to report success to userland.
 * Trying to do full reinit (for the sake of possible subsequent remount)
 * and failing to allocate memory would've put us into a nasty situation.
 * So here we only discard the old state and reinitialization is left
 * until we actually try to reconfigure.
 */
void vfs_clean_context(struct fs_context *fc)
{
	if (fc->need_free && fc->ops && fc->ops->free)
		fc->ops->free(fc);
	fc->need_free = false;
	fc->fs_private = NULL;
	fc->s_fs_info = NULL;
	fc->sb_flags = 0;
	security_free_mnt_opts(&fc->security);
	kfree(fc->subtype);
	fc->subtype = NULL;
	kfree(fc->source);
	fc->source = NULL;

	fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
	fc->phase = FS_CONTEXT_AWAITING_RECONF;
}

int finish_clean_context(struct fs_context *fc)
{
	int error;

	if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
		return 0;

	if (fc->fs_type->init_fs_context)
		error = fc->fs_type->init_fs_context(fc);
	else
		error = legacy_init_fs_context(fc);
	if (unlikely(error)) {
		fc->phase = FS_CONTEXT_FAILED;
		return error;
	}
	fc->need_free = true;
	fc->phase = FS_CONTEXT_RECONF_PARAMS;
	return 0;
}