1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Provide a way to create a superblock configuration context within the kernel
3 * that allows a superblock to be set up prior to mounting.
4 *
5 * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
7 */
8
9#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
10#include <linux/module.h>
11#include <linux/fs_context.h>
12#include <linux/fs_parser.h>
13#include <linux/fs.h>
14#include <linux/mount.h>
15#include <linux/nsproxy.h>
16#include <linux/slab.h>
17#include <linux/magic.h>
18#include <linux/security.h>
19#include <linux/mnt_namespace.h>
20#include <linux/pid_namespace.h>
21#include <linux/user_namespace.h>
22#include <net/net_namespace.h>
23#include <asm/sections.h>
24#include "mount.h"
25#include "internal.h"
26
27enum legacy_fs_param {
28	LEGACY_FS_UNSET_PARAMS,
29	LEGACY_FS_MONOLITHIC_PARAMS,
30	LEGACY_FS_INDIVIDUAL_PARAMS,
31};
32
33struct legacy_fs_context {
34	char			*legacy_data;	/* Data page for legacy filesystems */
35	size_t			data_size;
36	enum legacy_fs_param	param_type;
37};
38
39static int legacy_init_fs_context(struct fs_context *fc);
40
41static const struct constant_table common_set_sb_flag[] = {
42	{ "dirsync",	SB_DIRSYNC },
43	{ "lazytime",	SB_LAZYTIME },
44	{ "mand",	SB_MANDLOCK },
45	{ "ro",		SB_RDONLY },
46	{ "sync",	SB_SYNCHRONOUS },
47	{ },
48};
49
50static const struct constant_table common_clear_sb_flag[] = {
51	{ "async",	SB_SYNCHRONOUS },
52	{ "nolazytime",	SB_LAZYTIME },
53	{ "nomand",	SB_MANDLOCK },
54	{ "rw",		SB_RDONLY },
55	{ },
56};
57
58/*
59 * Check for a common mount option that manipulates s_flags.
60 */
61static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
62{
63	unsigned int token;
64
65	token = lookup_constant(common_set_sb_flag, key, 0);
66	if (token) {
67		fc->sb_flags |= token;
68		fc->sb_flags_mask |= token;
69		return 0;
70	}
71
72	token = lookup_constant(common_clear_sb_flag, key, 0);
73	if (token) {
74		fc->sb_flags &= ~token;
75		fc->sb_flags_mask |= token;
76		return 0;
77	}
78
79	return -ENOPARAM;
80}
81
82/**
83 * vfs_parse_fs_param_source - Handle setting "source" via parameter
84 * @fc: The filesystem context to modify
85 * @param: The parameter
86 *
87 * This is a simple helper for filesystems to verify that the "source" they
88 * accept is sane.
89 *
90 * Returns 0 on success, -ENOPARAM if this is not  "source" parameter, and
91 * -EINVAL otherwise. In the event of failure, supplementary error information
92 *  is logged.
93 */
94int vfs_parse_fs_param_source(struct fs_context *fc, struct fs_parameter *param)
95{
96	if (strcmp(param->key, "source") != 0)
97		return -ENOPARAM;
98
99	if (param->type != fs_value_is_string)
100		return invalf(fc, "Non-string source");
101
102	if (fc->source)
103		return invalf(fc, "Multiple sources");
104
105	fc->source = param->string;
106	param->string = NULL;
107	return 0;
108}
109EXPORT_SYMBOL(vfs_parse_fs_param_source);
110
111/**
112 * vfs_parse_fs_param - Add a single parameter to a superblock config
113 * @fc: The filesystem context to modify
114 * @param: The parameter
115 *
116 * A single mount option in string form is applied to the filesystem context
117 * being set up.  Certain standard options (for example "ro") are translated
118 * into flag bits without going to the filesystem.  The active security module
119 * is allowed to observe and poach options.  Any other options are passed over
120 * to the filesystem to parse.
121 *
122 * This may be called multiple times for a context.
123 *
124 * Returns 0 on success and a negative error code on failure.  In the event of
125 * failure, supplementary error information may have been set.
126 */
127int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
128{
129	int ret;
130
131	if (!param->key)
132		return invalf(fc, "Unnamed parameter\n");
133
134	ret = vfs_parse_sb_flag(fc, param->key);
135	if (ret != -ENOPARAM)
136		return ret;
137
138	ret = security_fs_context_parse_param(fc, param);
139	if (ret != -ENOPARAM)
140		/* Param belongs to the LSM or is disallowed by the LSM; so
141		 * don't pass to the FS.
142		 */
143		return ret;
144
145	if (fc->ops->parse_param) {
146		ret = fc->ops->parse_param(fc, param);
147		if (ret != -ENOPARAM)
148			return ret;
149	}
150
151	/* If the filesystem doesn't take any arguments, give it the
152	 * default handling of source.
153	 */
154	ret = vfs_parse_fs_param_source(fc, param);
155	if (ret != -ENOPARAM)
156		return ret;
157
158	return invalf(fc, "%s: Unknown parameter '%s'",
159		      fc->fs_type->name, param->key);
160}
161EXPORT_SYMBOL(vfs_parse_fs_param);
162
163/**
164 * vfs_parse_fs_string - Convenience function to just parse a string.
165 * @fc: Filesystem context.
166 * @key: Parameter name.
167 * @value: Default value.
168 * @v_size: Maximum number of bytes in the value.
169 */
170int vfs_parse_fs_string(struct fs_context *fc, const char *key,
171			const char *value, size_t v_size)
172{
173	int ret;
174
175	struct fs_parameter param = {
176		.key	= key,
177		.type	= fs_value_is_flag,
178		.size	= v_size,
179	};
180
181	if (value) {
182		param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
183		if (!param.string)
184			return -ENOMEM;
185		param.type = fs_value_is_string;
186	}
187
188	ret = vfs_parse_fs_param(fc, &param);
189	kfree(param.string);
190	return ret;
191}
192EXPORT_SYMBOL(vfs_parse_fs_string);
193
194/**
195 * vfs_parse_monolithic_sep - Parse key[=val][,key[=val]]* mount data
196 * @fc: The superblock configuration to fill in.
197 * @data: The data to parse
198 * @sep: callback for separating next option
199 *
200 * Parse a blob of data that's in key[=val][,key[=val]]* form with a custom
201 * option separator callback.
202 *
203 * Returns 0 on success or the error returned by the ->parse_option() fs_context
204 * operation on failure.
205 */
206int vfs_parse_monolithic_sep(struct fs_context *fc, void *data,
207			     char *(*sep)(char **))
208{
209	char *options = data, *key;
210	int ret = 0;
211
212	if (!options)
213		return 0;
214
215	ret = security_sb_eat_lsm_opts(options, &fc->security);
216	if (ret)
217		return ret;
218
219	while ((key = sep(&options)) != NULL) {
220		if (*key) {
221			size_t v_len = 0;
222			char *value = strchr(key, '=');
223
224			if (value) {
225				if (value == key)
226					continue;
227				*value++ = 0;
228				v_len = strlen(value);
229			}
230			ret = vfs_parse_fs_string(fc, key, value, v_len);
231			if (ret < 0)
232				break;
233		}
234	}
235
236	return ret;
237}
238EXPORT_SYMBOL(vfs_parse_monolithic_sep);
239
240static char *vfs_parse_comma_sep(char **s)
241{
242	return strsep(s, ",");
243}
244
245/**
246 * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
247 * @fc: The superblock configuration to fill in.
248 * @data: The data to parse
249 *
250 * Parse a blob of data that's in key[=val][,key[=val]]* form.  This can be
251 * called from the ->monolithic_mount_data() fs_context operation.
252 *
253 * Returns 0 on success or the error returned by the ->parse_option() fs_context
254 * operation on failure.
255 */
256int generic_parse_monolithic(struct fs_context *fc, void *data)
257{
258	return vfs_parse_monolithic_sep(fc, data, vfs_parse_comma_sep);
259}
260EXPORT_SYMBOL(generic_parse_monolithic);
261
262/**
263 * alloc_fs_context - Create a filesystem context.
264 * @fs_type: The filesystem type.
265 * @reference: The dentry from which this one derives (or NULL)
266 * @sb_flags: Filesystem/superblock flags (SB_*)
267 * @sb_flags_mask: Applicable members of @sb_flags
268 * @purpose: The purpose that this configuration shall be used for.
269 *
270 * Open a filesystem and create a mount context.  The mount context is
271 * initialised with the supplied flags and, if a submount/automount from
272 * another superblock (referred to by @reference) is supplied, may have
273 * parameters such as namespaces copied across from that superblock.
274 */
275static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
276				      struct dentry *reference,
277				      unsigned int sb_flags,
278				      unsigned int sb_flags_mask,
279				      enum fs_context_purpose purpose)
280{
281	int (*init_fs_context)(struct fs_context *);
282	struct fs_context *fc;
283	int ret = -ENOMEM;
284
285	fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL_ACCOUNT);
286	if (!fc)
287		return ERR_PTR(-ENOMEM);
288
289	fc->purpose	= purpose;
290	fc->sb_flags	= sb_flags;
291	fc->sb_flags_mask = sb_flags_mask;
292	fc->fs_type	= get_filesystem(fs_type);
293	fc->cred	= get_current_cred();
294	fc->net_ns	= get_net(current->nsproxy->net_ns);
295	fc->log.prefix	= fs_type->name;
296
297	mutex_init(&fc->uapi_mutex);
298
299	switch (purpose) {
300	case FS_CONTEXT_FOR_MOUNT:
301		fc->user_ns = get_user_ns(fc->cred->user_ns);
302		break;
303	case FS_CONTEXT_FOR_SUBMOUNT:
304		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
305		break;
306	case FS_CONTEXT_FOR_RECONFIGURE:
307		atomic_inc(&reference->d_sb->s_active);
308		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
309		fc->root = dget(reference);
310		break;
311	}
312
313	/* TODO: Make all filesystems support this unconditionally */
314	init_fs_context = fc->fs_type->init_fs_context;
315	if (!init_fs_context)
316		init_fs_context = legacy_init_fs_context;
317
318	ret = init_fs_context(fc);
319	if (ret < 0)
320		goto err_fc;
321	fc->need_free = true;
322	return fc;
323
324err_fc:
325	put_fs_context(fc);
326	return ERR_PTR(ret);
327}
328
329struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
330					unsigned int sb_flags)
331{
332	return alloc_fs_context(fs_type, NULL, sb_flags, 0,
333					FS_CONTEXT_FOR_MOUNT);
334}
335EXPORT_SYMBOL(fs_context_for_mount);
336
337struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
338					unsigned int sb_flags,
339					unsigned int sb_flags_mask)
340{
341	return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
342				sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
343}
344EXPORT_SYMBOL(fs_context_for_reconfigure);
345
346/**
347 * fs_context_for_submount: allocate a new fs_context for a submount
348 * @type: file_system_type of the new context
349 * @reference: reference dentry from which to copy relevant info
350 *
351 * Allocate a new fs_context suitable for a submount. This also ensures that
352 * the fc->security object is inherited from @reference (if needed).
353 */
354struct fs_context *fs_context_for_submount(struct file_system_type *type,
355					   struct dentry *reference)
356{
357	struct fs_context *fc;
358	int ret;
359
360	fc = alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
361	if (IS_ERR(fc))
362		return fc;
363
364	ret = security_fs_context_submount(fc, reference->d_sb);
365	if (ret) {
366		put_fs_context(fc);
367		return ERR_PTR(ret);
368	}
369
370	return fc;
371}
372EXPORT_SYMBOL(fs_context_for_submount);
373
374void fc_drop_locked(struct fs_context *fc)
375{
376	struct super_block *sb = fc->root->d_sb;
377	dput(fc->root);
378	fc->root = NULL;
379	deactivate_locked_super(sb);
380}
381
382static void legacy_fs_context_free(struct fs_context *fc);
383
384/**
385 * vfs_dup_fs_context - Duplicate a filesystem context.
386 * @src_fc: The context to copy.
387 */
388struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
389{
390	struct fs_context *fc;
391	int ret;
392
393	if (!src_fc->ops->dup)
394		return ERR_PTR(-EOPNOTSUPP);
395
396	fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
397	if (!fc)
398		return ERR_PTR(-ENOMEM);
399
400	mutex_init(&fc->uapi_mutex);
401
402	fc->fs_private	= NULL;
403	fc->s_fs_info	= NULL;
404	fc->source	= NULL;
405	fc->security	= NULL;
406	get_filesystem(fc->fs_type);
407	get_net(fc->net_ns);
408	get_user_ns(fc->user_ns);
409	get_cred(fc->cred);
410	if (fc->log.log)
411		refcount_inc(&fc->log.log->usage);
412
413	/* Can't call put until we've called ->dup */
414	ret = fc->ops->dup(fc, src_fc);
415	if (ret < 0)
416		goto err_fc;
417
418	ret = security_fs_context_dup(fc, src_fc);
419	if (ret < 0)
420		goto err_fc;
421	return fc;
422
423err_fc:
424	put_fs_context(fc);
425	return ERR_PTR(ret);
426}
427EXPORT_SYMBOL(vfs_dup_fs_context);
428
429/**
430 * logfc - Log a message to a filesystem context
431 * @log: The filesystem context to log to, or NULL to use printk.
432 * @prefix: A string to prefix the output with, or NULL.
433 * @level: 'w' for a warning, 'e' for an error.  Anything else is a notice.
434 * @fmt: The format of the buffer.
435 */
436void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...)
437{
438	va_list va;
439	struct va_format vaf = {.fmt = fmt, .va = &va};
440
441	va_start(va, fmt);
442	if (!log) {
443		switch (level) {
444		case 'w':
445			printk(KERN_WARNING "%s%s%pV\n", prefix ? prefix : "",
446						prefix ? ": " : "", &vaf);
447			break;
448		case 'e':
449			printk(KERN_ERR "%s%s%pV\n", prefix ? prefix : "",
450						prefix ? ": " : "", &vaf);
451			break;
452		default:
453			printk(KERN_NOTICE "%s%s%pV\n", prefix ? prefix : "",
454						prefix ? ": " : "", &vaf);
455			break;
456		}
457	} else {
458		unsigned int logsize = ARRAY_SIZE(log->buffer);
459		u8 index;
460		char *q = kasprintf(GFP_KERNEL, "%c %s%s%pV\n", level,
461						prefix ? prefix : "",
462						prefix ? ": " : "", &vaf);
463
464		index = log->head & (logsize - 1);
465		BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
466			     sizeof(log->tail) != sizeof(u8));
467		if ((u8)(log->head - log->tail) == logsize) {
468			/* The buffer is full, discard the oldest message */
469			if (log->need_free & (1 << index))
470				kfree(log->buffer[index]);
471			log->tail++;
472		}
473
474		log->buffer[index] = q ? q : "OOM: Can't store error string";
475		if (q)
476			log->need_free |= 1 << index;
477		else
478			log->need_free &= ~(1 << index);
479		log->head++;
480	}
481	va_end(va);
482}
483EXPORT_SYMBOL(logfc);
484
485/*
486 * Free a logging structure.
487 */
488static void put_fc_log(struct fs_context *fc)
489{
490	struct fc_log *log = fc->log.log;
491	int i;
492
493	if (log) {
494		if (refcount_dec_and_test(&log->usage)) {
495			fc->log.log = NULL;
496			for (i = 0; i <= 7; i++)
497				if (log->need_free & (1 << i))
498					kfree(log->buffer[i]);
499			kfree(log);
500		}
501	}
502}
503
504/**
505 * put_fs_context - Dispose of a superblock configuration context.
506 * @fc: The context to dispose of.
507 */
508void put_fs_context(struct fs_context *fc)
509{
510	struct super_block *sb;
511
512	if (fc->root) {
513		sb = fc->root->d_sb;
514		dput(fc->root);
515		fc->root = NULL;
516		deactivate_super(sb);
517	}
518
519	if (fc->need_free && fc->ops && fc->ops->free)
520		fc->ops->free(fc);
521
522	security_free_mnt_opts(&fc->security);
523	put_net(fc->net_ns);
524	put_user_ns(fc->user_ns);
525	put_cred(fc->cred);
526	put_fc_log(fc);
527	put_filesystem(fc->fs_type);
528	kfree(fc->source);
529	kfree(fc);
530}
531EXPORT_SYMBOL(put_fs_context);
532
533/*
534 * Free the config for a filesystem that doesn't support fs_context.
535 */
536static void legacy_fs_context_free(struct fs_context *fc)
537{
538	struct legacy_fs_context *ctx = fc->fs_private;
539
540	if (ctx) {
541		if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
542			kfree(ctx->legacy_data);
543		kfree(ctx);
544	}
545}
546
547/*
548 * Duplicate a legacy config.
549 */
550static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
551{
552	struct legacy_fs_context *ctx;
553	struct legacy_fs_context *src_ctx = src_fc->fs_private;
554
555	ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
556	if (!ctx)
557		return -ENOMEM;
558
559	if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
560		ctx->legacy_data = kmemdup(src_ctx->legacy_data,
561					   src_ctx->data_size, GFP_KERNEL);
562		if (!ctx->legacy_data) {
563			kfree(ctx);
564			return -ENOMEM;
565		}
566	}
567
568	fc->fs_private = ctx;
569	return 0;
570}
571
572/*
573 * Add a parameter to a legacy config.  We build up a comma-separated list of
574 * options.
575 */
576static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
577{
578	struct legacy_fs_context *ctx = fc->fs_private;
579	unsigned int size = ctx->data_size;
580	size_t len = 0;
581	int ret;
582
583	ret = vfs_parse_fs_param_source(fc, param);
584	if (ret != -ENOPARAM)
585		return ret;
586
587	if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
588		return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");
589
590	switch (param->type) {
591	case fs_value_is_string:
592		len = 1 + param->size;
593		fallthrough;
594	case fs_value_is_flag:
595		len += strlen(param->key);
596		break;
597	default:
598		return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported",
599			      param->key);
600	}
601
602	if (size + len + 2 > PAGE_SIZE)
603		return invalf(fc, "VFS: Legacy: Cumulative options too large");
604	if (strchr(param->key, ',') ||
605	    (param->type == fs_value_is_string &&
606	     memchr(param->string, ',', param->size)))
607		return invalf(fc, "VFS: Legacy: Option '%s' contained comma",
608			      param->key);
609	if (!ctx->legacy_data) {
610		ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
611		if (!ctx->legacy_data)
612			return -ENOMEM;
613	}
614
615	if (size)
616		ctx->legacy_data[size++] = ',';
617	len = strlen(param->key);
618	memcpy(ctx->legacy_data + size, param->key, len);
619	size += len;
620	if (param->type == fs_value_is_string) {
621		ctx->legacy_data[size++] = '=';
622		memcpy(ctx->legacy_data + size, param->string, param->size);
623		size += param->size;
624	}
625	ctx->legacy_data[size] = '\0';
626	ctx->data_size = size;
627	ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
628	return 0;
629}
630
631/*
632 * Add monolithic mount data.
633 */
634static int legacy_parse_monolithic(struct fs_context *fc, void *data)
635{
636	struct legacy_fs_context *ctx = fc->fs_private;
637
638	if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
639		pr_warn("VFS: Can't mix monolithic and individual options\n");
640		return -EINVAL;
641	}
642
643	ctx->legacy_data = data;
644	ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
645	if (!ctx->legacy_data)
646		return 0;
647
648	if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
649		return 0;
650	return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
651}
652
653/*
654 * Get a mountable root with the legacy mount command.
655 */
656static int legacy_get_tree(struct fs_context *fc)
657{
658	struct legacy_fs_context *ctx = fc->fs_private;
659	struct super_block *sb;
660	struct dentry *root;
661
662	root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
663				      fc->source, ctx->legacy_data);
664	if (IS_ERR(root))
665		return PTR_ERR(root);
666
667	sb = root->d_sb;
668	BUG_ON(!sb);
669
670	fc->root = root;
671	return 0;
672}
673
674/*
675 * Handle remount.
676 */
677static int legacy_reconfigure(struct fs_context *fc)
678{
679	struct legacy_fs_context *ctx = fc->fs_private;
680	struct super_block *sb = fc->root->d_sb;
681
682	if (!sb->s_op->remount_fs)
683		return 0;
684
685	return sb->s_op->remount_fs(sb, &fc->sb_flags,
686				    ctx ? ctx->legacy_data : NULL);
687}
688
689const struct fs_context_operations legacy_fs_context_ops = {
690	.free			= legacy_fs_context_free,
691	.dup			= legacy_fs_context_dup,
692	.parse_param		= legacy_parse_param,
693	.parse_monolithic	= legacy_parse_monolithic,
694	.get_tree		= legacy_get_tree,
695	.reconfigure		= legacy_reconfigure,
696};
697
698/*
699 * Initialise a legacy context for a filesystem that doesn't support
700 * fs_context.
701 */
702static int legacy_init_fs_context(struct fs_context *fc)
703{
704	fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL_ACCOUNT);
705	if (!fc->fs_private)
706		return -ENOMEM;
707	fc->ops = &legacy_fs_context_ops;
708	return 0;
709}
710
711int parse_monolithic_mount_data(struct fs_context *fc, void *data)
712{
713	int (*monolithic_mount_data)(struct fs_context *, void *);
714
715	monolithic_mount_data = fc->ops->parse_monolithic;
716	if (!monolithic_mount_data)
717		monolithic_mount_data = generic_parse_monolithic;
718
719	return monolithic_mount_data(fc, data);
720}
721
722/*
723 * Clean up a context after performing an action on it and put it into a state
724 * from where it can be used to reconfigure a superblock.
725 *
726 * Note that here we do only the parts that can't fail; the rest is in
727 * finish_clean_context() below and in between those fs_context is marked
728 * FS_CONTEXT_AWAITING_RECONF.  The reason for splitup is that after
729 * successful mount or remount we need to report success to userland.
730 * Trying to do full reinit (for the sake of possible subsequent remount)
731 * and failing to allocate memory would've put us into a nasty situation.
732 * So here we only discard the old state and reinitialization is left
733 * until we actually try to reconfigure.
734 */
735void vfs_clean_context(struct fs_context *fc)
736{
737	if (fc->need_free && fc->ops && fc->ops->free)
738		fc->ops->free(fc);
739	fc->need_free = false;
740	fc->fs_private = NULL;
741	fc->s_fs_info = NULL;
742	fc->sb_flags = 0;
743	security_free_mnt_opts(&fc->security);
744	kfree(fc->source);
745	fc->source = NULL;
746	fc->exclusive = false;
747
748	fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
749	fc->phase = FS_CONTEXT_AWAITING_RECONF;
750}
751
752int finish_clean_context(struct fs_context *fc)
753{
754	int error;
755
756	if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
757		return 0;
758
759	if (fc->fs_type->init_fs_context)
760		error = fc->fs_type->init_fs_context(fc);
761	else
762		error = legacy_init_fs_context(fc);
763	if (unlikely(error)) {
764		fc->phase = FS_CONTEXT_FAILED;
765		return error;
766	}
767	fc->need_free = true;
768	fc->phase = FS_CONTEXT_RECONF_PARAMS;
769	return 0;
770}
771