xref: /openbmc/linux/fs/fs_context.c (revision 37744fee) 
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 
27 enum legacy_fs_param {
28 	LEGACY_FS_UNSET_PARAMS,
29 	LEGACY_FS_MONOLITHIC_PARAMS,
30 	LEGACY_FS_INDIVIDUAL_PARAMS,
31 };
32 
33 struct 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 
39 static int legacy_init_fs_context(struct fs_context *fc);
40 
41 static const struct constant_table common_set_sb_flag[] = {
42 	{ "dirsync",	SB_DIRSYNC },
43 	{ "lazytime",	SB_LAZYTIME },
44 	{ "mand",	SB_MANDLOCK },
45 	{ "posixacl",	SB_POSIXACL },
46 	{ "ro",		SB_RDONLY },
47 	{ "sync",	SB_SYNCHRONOUS },
48 	{ },
49 };
50 
51 static const struct constant_table common_clear_sb_flag[] = {
52 	{ "async",	SB_SYNCHRONOUS },
53 	{ "nolazytime",	SB_LAZYTIME },
54 	{ "nomand",	SB_MANDLOCK },
55 	{ "rw",		SB_RDONLY },
56 	{ "silent",	SB_SILENT },
57 	{ },
58 };
59 
60 static const char *const forbidden_sb_flag[] = {
61 	"bind",
62 	"dev",
63 	"exec",
64 	"move",
65 	"noatime",
66 	"nodev",
67 	"nodiratime",
68 	"noexec",
69 	"norelatime",
70 	"nostrictatime",
71 	"nosuid",
72 	"private",
73 	"rec",
74 	"relatime",
75 	"remount",
76 	"shared",
77 	"slave",
78 	"strictatime",
79 	"suid",
80 	"unbindable",
81 };
82 
83 /*
84  * Check for a common mount option that manipulates s_flags.
85  */
86 static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
87 {
88 	unsigned int token;
89 	unsigned int i;
90 
91 	for (i = 0; i < ARRAY_SIZE(forbidden_sb_flag); i++)
92 		if (strcmp(key, forbidden_sb_flag[i]) == 0)
93 			return -EINVAL;
94 
95 	token = lookup_constant(common_set_sb_flag, key, 0);
96 	if (token) {
97 		fc->sb_flags |= token;
98 		fc->sb_flags_mask |= token;
99 		return 0;
100 	}
101 
102 	token = lookup_constant(common_clear_sb_flag, key, 0);
103 	if (token) {
104 		fc->sb_flags &= ~token;
105 		fc->sb_flags_mask |= token;
106 		return 0;
107 	}
108 
109 	return -ENOPARAM;
110 }
111 
112 /**
113  * vfs_parse_fs_param - Add a single parameter to a superblock config
114  * @fc: The filesystem context to modify
115  * @param: The parameter
116  *
117  * A single mount option in string form is applied to the filesystem context
118  * being set up.  Certain standard options (for example "ro") are translated
119  * into flag bits without going to the filesystem.  The active security module
120  * is allowed to observe and poach options.  Any other options are passed over
121  * to the filesystem to parse.
122  *
123  * This may be called multiple times for a context.
124  *
125  * Returns 0 on success and a negative error code on failure.  In the event of
126  * failure, supplementary error information may have been set.
127  */
128 int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
129 {
130 	int ret;
131 
132 	if (!param->key)
133 		return invalf(fc, "Unnamed parameter\n");
134 
135 	ret = vfs_parse_sb_flag(fc, param->key);
136 	if (ret != -ENOPARAM)
137 		return ret;
138 
139 	ret = security_fs_context_parse_param(fc, param);
140 	if (ret != -ENOPARAM)
141 		/* Param belongs to the LSM or is disallowed by the LSM; so
142 		 * don't pass to the FS.
143 		 */
144 		return ret;
145 
146 	if (fc->ops->parse_param) {
147 		ret = fc->ops->parse_param(fc, param);
148 		if (ret != -ENOPARAM)
149 			return ret;
150 	}
151 
152 	/* If the filesystem doesn't take any arguments, give it the
153 	 * default handling of source.
154 	 */
155 	if (strcmp(param->key, "source") == 0) {
156 		if (param->type != fs_value_is_string)
157 			return invalf(fc, "VFS: Non-string source");
158 		if (fc->source)
159 			return invalf(fc, "VFS: Multiple sources");
160 		fc->source = param->string;
161 		param->string = NULL;
162 		return 0;
163 	}
164 
165 	return invalf(fc, "%s: Unknown parameter '%s'",
166 		      fc->fs_type->name, param->key);
167 }
168 EXPORT_SYMBOL(vfs_parse_fs_param);
169 
170 /**
171  * vfs_parse_fs_string - Convenience function to just parse a string.
172  */
173 int vfs_parse_fs_string(struct fs_context *fc, const char *key,
174 			const char *value, size_t v_size)
175 {
176 	int ret;
177 
178 	struct fs_parameter param = {
179 		.key	= key,
180 		.type	= fs_value_is_flag,
181 		.size	= v_size,
182 	};
183 
184 	if (value) {
185 		param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
186 		if (!param.string)
187 			return -ENOMEM;
188 		param.type = fs_value_is_string;
189 	}
190 
191 	ret = vfs_parse_fs_param(fc, &param);
192 	kfree(param.string);
193 	return ret;
194 }
195 EXPORT_SYMBOL(vfs_parse_fs_string);
196 
197 /**
198  * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
199  * @ctx: The superblock configuration to fill in.
200  * @data: The data to parse
201  *
202  * Parse a blob of data that's in key[=val][,key[=val]]* form.  This can be
203  * called from the ->monolithic_mount_data() fs_context operation.
204  *
205  * Returns 0 on success or the error returned by the ->parse_option() fs_context
206  * operation on failure.
207  */
208 int generic_parse_monolithic(struct fs_context *fc, void *data)
209 {
210 	char *options = data, *key;
211 	int ret = 0;
212 
213 	if (!options)
214 		return 0;
215 
216 	ret = security_sb_eat_lsm_opts(options, &fc->security);
217 	if (ret)
218 		return ret;
219 
220 	while ((key = strsep(&options, ",")) != NULL) {
221 		if (*key) {
222 			size_t v_len = 0;
223 			char *value = strchr(key, '=');
224 
225 			if (value) {
226 				if (value == key)
227 					continue;
228 				*value++ = 0;
229 				v_len = strlen(value);
230 			}
231 			ret = vfs_parse_fs_string(fc, key, value, v_len);
232 			if (ret < 0)
233 				break;
234 		}
235 	}
236 
237 	return ret;
238 }
239 EXPORT_SYMBOL(generic_parse_monolithic);
240 
241 /**
242  * alloc_fs_context - Create a filesystem context.
243  * @fs_type: The filesystem type.
244  * @reference: The dentry from which this one derives (or NULL)
245  * @sb_flags: Filesystem/superblock flags (SB_*)
246  * @sb_flags_mask: Applicable members of @sb_flags
247  * @purpose: The purpose that this configuration shall be used for.
248  *
249  * Open a filesystem and create a mount context.  The mount context is
250  * initialised with the supplied flags and, if a submount/automount from
251  * another superblock (referred to by @reference) is supplied, may have
252  * parameters such as namespaces copied across from that superblock.
253  */
254 static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
255 				      struct dentry *reference,
256 				      unsigned int sb_flags,
257 				      unsigned int sb_flags_mask,
258 				      enum fs_context_purpose purpose)
259 {
260 	int (*init_fs_context)(struct fs_context *);
261 	struct fs_context *fc;
262 	int ret = -ENOMEM;
263 
264 	fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL);
265 	if (!fc)
266 		return ERR_PTR(-ENOMEM);
267 
268 	fc->purpose	= purpose;
269 	fc->sb_flags	= sb_flags;
270 	fc->sb_flags_mask = sb_flags_mask;
271 	fc->fs_type	= get_filesystem(fs_type);
272 	fc->cred	= get_current_cred();
273 	fc->net_ns	= get_net(current->nsproxy->net_ns);
274 	fc->log.prefix	= fs_type->name;
275 
276 	mutex_init(&fc->uapi_mutex);
277 
278 	switch (purpose) {
279 	case FS_CONTEXT_FOR_MOUNT:
280 		fc->user_ns = get_user_ns(fc->cred->user_ns);
281 		break;
282 	case FS_CONTEXT_FOR_SUBMOUNT:
283 		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
284 		break;
285 	case FS_CONTEXT_FOR_RECONFIGURE:
286 		atomic_inc(&reference->d_sb->s_active);
287 		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
288 		fc->root = dget(reference);
289 		break;
290 	}
291 
292 	/* TODO: Make all filesystems support this unconditionally */
293 	init_fs_context = fc->fs_type->init_fs_context;
294 	if (!init_fs_context)
295 		init_fs_context = legacy_init_fs_context;
296 
297 	ret = init_fs_context(fc);
298 	if (ret < 0)
299 		goto err_fc;
300 	fc->need_free = true;
301 	return fc;
302 
303 err_fc:
304 	put_fs_context(fc);
305 	return ERR_PTR(ret);
306 }
307 
308 struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
309 					unsigned int sb_flags)
310 {
311 	return alloc_fs_context(fs_type, NULL, sb_flags, 0,
312 					FS_CONTEXT_FOR_MOUNT);
313 }
314 EXPORT_SYMBOL(fs_context_for_mount);
315 
316 struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
317 					unsigned int sb_flags,
318 					unsigned int sb_flags_mask)
319 {
320 	return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
321 				sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
322 }
323 EXPORT_SYMBOL(fs_context_for_reconfigure);
324 
325 struct fs_context *fs_context_for_submount(struct file_system_type *type,
326 					   struct dentry *reference)
327 {
328 	return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
329 }
330 EXPORT_SYMBOL(fs_context_for_submount);
331 
332 void fc_drop_locked(struct fs_context *fc)
333 {
334 	struct super_block *sb = fc->root->d_sb;
335 	dput(fc->root);
336 	fc->root = NULL;
337 	deactivate_locked_super(sb);
338 }
339 
340 static void legacy_fs_context_free(struct fs_context *fc);
341 
342 /**
343  * vfs_dup_fc_config: Duplicate a filesystem context.
344  * @src_fc: The context to copy.
345  */
346 struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
347 {
348 	struct fs_context *fc;
349 	int ret;
350 
351 	if (!src_fc->ops->dup)
352 		return ERR_PTR(-EOPNOTSUPP);
353 
354 	fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
355 	if (!fc)
356 		return ERR_PTR(-ENOMEM);
357 
358 	mutex_init(&fc->uapi_mutex);
359 
360 	fc->fs_private	= NULL;
361 	fc->s_fs_info	= NULL;
362 	fc->source	= NULL;
363 	fc->security	= NULL;
364 	get_filesystem(fc->fs_type);
365 	get_net(fc->net_ns);
366 	get_user_ns(fc->user_ns);
367 	get_cred(fc->cred);
368 	if (fc->log.log)
369 		refcount_inc(&fc->log.log->usage);
370 
371 	/* Can't call put until we've called ->dup */
372 	ret = fc->ops->dup(fc, src_fc);
373 	if (ret < 0)
374 		goto err_fc;
375 
376 	ret = security_fs_context_dup(fc, src_fc);
377 	if (ret < 0)
378 		goto err_fc;
379 	return fc;
380 
381 err_fc:
382 	put_fs_context(fc);
383 	return ERR_PTR(ret);
384 }
385 EXPORT_SYMBOL(vfs_dup_fs_context);
386 
387 /**
388  * logfc - Log a message to a filesystem context
389  * @fc: The filesystem context to log to.
390  * @fmt: The format of the buffer.
391  */
392 void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...)
393 {
394 	va_list va;
395 	struct va_format vaf = {.fmt = fmt, .va = &va};
396 
397 	va_start(va, fmt);
398 	if (!log) {
399 		switch (level) {
400 		case 'w':
401 			printk(KERN_WARNING "%s%s%pV\n", prefix ? prefix : "",
402 						prefix ? ": " : "", &vaf);
403 			break;
404 		case 'e':
405 			printk(KERN_ERR "%s%s%pV\n", prefix ? prefix : "",
406 						prefix ? ": " : "", &vaf);
407 			break;
408 		default:
409 			printk(KERN_NOTICE "%s%s%pV\n", prefix ? prefix : "",
410 						prefix ? ": " : "", &vaf);
411 			break;
412 		}
413 	} else {
414 		unsigned int logsize = ARRAY_SIZE(log->buffer);
415 		u8 index;
416 		char *q = kasprintf(GFP_KERNEL, "%c %s%s%pV\n", level,
417 						prefix ? prefix : "",
418 						prefix ? ": " : "", &vaf);
419 
420 		index = log->head & (logsize - 1);
421 		BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
422 			     sizeof(log->tail) != sizeof(u8));
423 		if ((u8)(log->head - log->tail) == logsize) {
424 			/* The buffer is full, discard the oldest message */
425 			if (log->need_free & (1 << index))
426 				kfree(log->buffer[index]);
427 			log->tail++;
428 		}
429 
430 		log->buffer[index] = q ? q : "OOM: Can't store error string";
431 		if (q)
432 			log->need_free |= 1 << index;
433 		else
434 			log->need_free &= ~(1 << index);
435 		log->head++;
436 	}
437 	va_end(va);
438 }
439 EXPORT_SYMBOL(logfc);
440 
441 /*
442  * Free a logging structure.
443  */
444 static void put_fc_log(struct fs_context *fc)
445 {
446 	struct fc_log *log = fc->log.log;
447 	int i;
448 
449 	if (log) {
450 		if (refcount_dec_and_test(&log->usage)) {
451 			fc->log.log = NULL;
452 			for (i = 0; i <= 7; i++)
453 				if (log->need_free & (1 << i))
454 					kfree(log->buffer[i]);
455 			kfree(log);
456 		}
457 	}
458 }
459 
460 /**
461  * put_fs_context - Dispose of a superblock configuration context.
462  * @fc: The context to dispose of.
463  */
464 void put_fs_context(struct fs_context *fc)
465 {
466 	struct super_block *sb;
467 
468 	if (fc->root) {
469 		sb = fc->root->d_sb;
470 		dput(fc->root);
471 		fc->root = NULL;
472 		deactivate_super(sb);
473 	}
474 
475 	if (fc->need_free && fc->ops && fc->ops->free)
476 		fc->ops->free(fc);
477 
478 	security_free_mnt_opts(&fc->security);
479 	put_net(fc->net_ns);
480 	put_user_ns(fc->user_ns);
481 	put_cred(fc->cred);
482 	put_fc_log(fc);
483 	put_filesystem(fc->fs_type);
484 	kfree(fc->source);
485 	kfree(fc);
486 }
487 EXPORT_SYMBOL(put_fs_context);
488 
489 /*
490  * Free the config for a filesystem that doesn't support fs_context.
491  */
492 static void legacy_fs_context_free(struct fs_context *fc)
493 {
494 	struct legacy_fs_context *ctx = fc->fs_private;
495 
496 	if (ctx) {
497 		if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
498 			kfree(ctx->legacy_data);
499 		kfree(ctx);
500 	}
501 }
502 
503 /*
504  * Duplicate a legacy config.
505  */
506 static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
507 {
508 	struct legacy_fs_context *ctx;
509 	struct legacy_fs_context *src_ctx = src_fc->fs_private;
510 
511 	ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
512 	if (!ctx)
513 		return -ENOMEM;
514 
515 	if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
516 		ctx->legacy_data = kmemdup(src_ctx->legacy_data,
517 					   src_ctx->data_size, GFP_KERNEL);
518 		if (!ctx->legacy_data) {
519 			kfree(ctx);
520 			return -ENOMEM;
521 		}
522 	}
523 
524 	fc->fs_private = ctx;
525 	return 0;
526 }
527 
528 /*
529  * Add a parameter to a legacy config.  We build up a comma-separated list of
530  * options.
531  */
532 static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
533 {
534 	struct legacy_fs_context *ctx = fc->fs_private;
535 	unsigned int size = ctx->data_size;
536 	size_t len = 0;
537 
538 	if (strcmp(param->key, "source") == 0) {
539 		if (param->type != fs_value_is_string)
540 			return invalf(fc, "VFS: Legacy: Non-string source");
541 		if (fc->source)
542 			return invalf(fc, "VFS: Legacy: Multiple sources");
543 		fc->source = param->string;
544 		param->string = NULL;
545 		return 0;
546 	}
547 
548 	if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
549 		return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");
550 
551 	switch (param->type) {
552 	case fs_value_is_string:
553 		len = 1 + param->size;
554 		/* Fall through */
555 	case fs_value_is_flag:
556 		len += strlen(param->key);
557 		break;
558 	default:
559 		return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported",
560 			      param->key);
561 	}
562 
563 	if (len > PAGE_SIZE - 2 - size)
564 		return invalf(fc, "VFS: Legacy: Cumulative options too large");
565 	if (strchr(param->key, ',') ||
566 	    (param->type == fs_value_is_string &&
567 	     memchr(param->string, ',', param->size)))
568 		return invalf(fc, "VFS: Legacy: Option '%s' contained comma",
569 			      param->key);
570 	if (!ctx->legacy_data) {
571 		ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
572 		if (!ctx->legacy_data)
573 			return -ENOMEM;
574 	}
575 
576 	ctx->legacy_data[size++] = ',';
577 	len = strlen(param->key);
578 	memcpy(ctx->legacy_data + size, param->key, len);
579 	size += len;
580 	if (param->type == fs_value_is_string) {
581 		ctx->legacy_data[size++] = '=';
582 		memcpy(ctx->legacy_data + size, param->string, param->size);
583 		size += param->size;
584 	}
585 	ctx->legacy_data[size] = '\0';
586 	ctx->data_size = size;
587 	ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
588 	return 0;
589 }
590 
591 /*
592  * Add monolithic mount data.
593  */
594 static int legacy_parse_monolithic(struct fs_context *fc, void *data)
595 {
596 	struct legacy_fs_context *ctx = fc->fs_private;
597 
598 	if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
599 		pr_warn("VFS: Can't mix monolithic and individual options\n");
600 		return -EINVAL;
601 	}
602 
603 	ctx->legacy_data = data;
604 	ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
605 	if (!ctx->legacy_data)
606 		return 0;
607 
608 	if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
609 		return 0;
610 	return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
611 }
612 
613 /*
614  * Get a mountable root with the legacy mount command.
615  */
616 static int legacy_get_tree(struct fs_context *fc)
617 {
618 	struct legacy_fs_context *ctx = fc->fs_private;
619 	struct super_block *sb;
620 	struct dentry *root;
621 
622 	root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
623 				      fc->source, ctx->legacy_data);
624 	if (IS_ERR(root))
625 		return PTR_ERR(root);
626 
627 	sb = root->d_sb;
628 	BUG_ON(!sb);
629 
630 	fc->root = root;
631 	return 0;
632 }
633 
634 /*
635  * Handle remount.
636  */
637 static int legacy_reconfigure(struct fs_context *fc)
638 {
639 	struct legacy_fs_context *ctx = fc->fs_private;
640 	struct super_block *sb = fc->root->d_sb;
641 
642 	if (!sb->s_op->remount_fs)
643 		return 0;
644 
645 	return sb->s_op->remount_fs(sb, &fc->sb_flags,
646 				    ctx ? ctx->legacy_data : NULL);
647 }
648 
649 const struct fs_context_operations legacy_fs_context_ops = {
650 	.free			= legacy_fs_context_free,
651 	.dup			= legacy_fs_context_dup,
652 	.parse_param		= legacy_parse_param,
653 	.parse_monolithic	= legacy_parse_monolithic,
654 	.get_tree		= legacy_get_tree,
655 	.reconfigure		= legacy_reconfigure,
656 };
657 
658 /*
659  * Initialise a legacy context for a filesystem that doesn't support
660  * fs_context.
661  */
662 static int legacy_init_fs_context(struct fs_context *fc)
663 {
664 	fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL);
665 	if (!fc->fs_private)
666 		return -ENOMEM;
667 	fc->ops = &legacy_fs_context_ops;
668 	return 0;
669 }
670 
671 int parse_monolithic_mount_data(struct fs_context *fc, void *data)
672 {
673 	int (*monolithic_mount_data)(struct fs_context *, void *);
674 
675 	monolithic_mount_data = fc->ops->parse_monolithic;
676 	if (!monolithic_mount_data)
677 		monolithic_mount_data = generic_parse_monolithic;
678 
679 	return monolithic_mount_data(fc, data);
680 }
681 
682 /*
683  * Clean up a context after performing an action on it and put it into a state
684  * from where it can be used to reconfigure a superblock.
685  *
686  * Note that here we do only the parts that can't fail; the rest is in
687  * finish_clean_context() below and in between those fs_context is marked
688  * FS_CONTEXT_AWAITING_RECONF.  The reason for splitup is that after
689  * successful mount or remount we need to report success to userland.
690  * Trying to do full reinit (for the sake of possible subsequent remount)
691  * and failing to allocate memory would've put us into a nasty situation.
692  * So here we only discard the old state and reinitialization is left
693  * until we actually try to reconfigure.
694  */
695 void vfs_clean_context(struct fs_context *fc)
696 {
697 	if (fc->need_free && fc->ops && fc->ops->free)
698 		fc->ops->free(fc);
699 	fc->need_free = false;
700 	fc->fs_private = NULL;
701 	fc->s_fs_info = NULL;
702 	fc->sb_flags = 0;
703 	security_free_mnt_opts(&fc->security);
704 	kfree(fc->source);
705 	fc->source = NULL;
706 
707 	fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
708 	fc->phase = FS_CONTEXT_AWAITING_RECONF;
709 }
710 
711 int finish_clean_context(struct fs_context *fc)
712 {
713 	int error;
714 
715 	if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
716 		return 0;
717 
718 	if (fc->fs_type->init_fs_context)
719 		error = fc->fs_type->init_fs_context(fc);
720 	else
721 		error = legacy_init_fs_context(fc);
722 	if (unlikely(error)) {
723 		fc->phase = FS_CONTEXT_FAILED;
724 		return error;
725 	}
726 	fc->need_free = true;
727 	fc->phase = FS_CONTEXT_RECONF_PARAMS;
728 	return 0;
729 }
730