xref: /openbmc/linux/fs/fs_context.c (revision 4e95bc26) 
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 static 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 	{ "silent",	SB_SILENT },
56 };
57 
58 static const char *const forbidden_sb_flag[] = {
59 	"bind",
60 	"dev",
61 	"exec",
62 	"move",
63 	"noatime",
64 	"nodev",
65 	"nodiratime",
66 	"noexec",
67 	"norelatime",
68 	"nostrictatime",
69 	"nosuid",
70 	"private",
71 	"rec",
72 	"relatime",
73 	"remount",
74 	"shared",
75 	"slave",
76 	"strictatime",
77 	"suid",
78 	"unbindable",
79 };
80 
81 /*
82  * Check for a common mount option that manipulates s_flags.
83  */
84 static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
85 {
86 	unsigned int token;
87 	unsigned int i;
88 
89 	for (i = 0; i < ARRAY_SIZE(forbidden_sb_flag); i++)
90 		if (strcmp(key, forbidden_sb_flag[i]) == 0)
91 			return -EINVAL;
92 
93 	token = lookup_constant(common_set_sb_flag, key, 0);
94 	if (token) {
95 		fc->sb_flags |= token;
96 		fc->sb_flags_mask |= token;
97 		return 0;
98 	}
99 
100 	token = lookup_constant(common_clear_sb_flag, key, 0);
101 	if (token) {
102 		fc->sb_flags &= ~token;
103 		fc->sb_flags_mask |= token;
104 		return 0;
105 	}
106 
107 	return -ENOPARAM;
108 }
109 
110 /**
111  * vfs_parse_fs_param - Add a single parameter to a superblock config
112  * @fc: The filesystem context to modify
113  * @param: The parameter
114  *
115  * A single mount option in string form is applied to the filesystem context
116  * being set up.  Certain standard options (for example "ro") are translated
117  * into flag bits without going to the filesystem.  The active security module
118  * is allowed to observe and poach options.  Any other options are passed over
119  * to the filesystem to parse.
120  *
121  * This may be called multiple times for a context.
122  *
123  * Returns 0 on success and a negative error code on failure.  In the event of
124  * failure, supplementary error information may have been set.
125  */
126 int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
127 {
128 	int ret;
129 
130 	if (!param->key)
131 		return invalf(fc, "Unnamed parameter\n");
132 
133 	ret = vfs_parse_sb_flag(fc, param->key);
134 	if (ret != -ENOPARAM)
135 		return ret;
136 
137 	ret = security_fs_context_parse_param(fc, param);
138 	if (ret != -ENOPARAM)
139 		/* Param belongs to the LSM or is disallowed by the LSM; so
140 		 * don't pass to the FS.
141 		 */
142 		return ret;
143 
144 	if (fc->ops->parse_param) {
145 		ret = fc->ops->parse_param(fc, param);
146 		if (ret != -ENOPARAM)
147 			return ret;
148 	}
149 
150 	/* If the filesystem doesn't take any arguments, give it the
151 	 * default handling of source.
152 	 */
153 	if (strcmp(param->key, "source") == 0) {
154 		if (param->type != fs_value_is_string)
155 			return invalf(fc, "VFS: Non-string source");
156 		if (fc->source)
157 			return invalf(fc, "VFS: Multiple sources");
158 		fc->source = param->string;
159 		param->string = NULL;
160 		return 0;
161 	}
162 
163 	return invalf(fc, "%s: Unknown parameter '%s'",
164 		      fc->fs_type->name, param->key);
165 }
166 EXPORT_SYMBOL(vfs_parse_fs_param);
167 
168 /**
169  * vfs_parse_fs_string - Convenience function to just parse a string.
170  */
171 int vfs_parse_fs_string(struct fs_context *fc, const char *key,
172 			const char *value, size_t v_size)
173 {
174 	int ret;
175 
176 	struct fs_parameter param = {
177 		.key	= key,
178 		.type	= fs_value_is_string,
179 		.size	= v_size,
180 	};
181 
182 	if (v_size > 0) {
183 		param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
184 		if (!param.string)
185 			return -ENOMEM;
186 	}
187 
188 	ret = vfs_parse_fs_param(fc, &param);
189 	kfree(param.string);
190 	return ret;
191 }
192 EXPORT_SYMBOL(vfs_parse_fs_string);
193 
194 /**
195  * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
196  * @ctx: The superblock configuration to fill in.
197  * @data: The data to parse
198  *
199  * Parse a blob of data that's in key[=val][,key[=val]]* form.  This can be
200  * called from the ->monolithic_mount_data() fs_context operation.
201  *
202  * Returns 0 on success or the error returned by the ->parse_option() fs_context
203  * operation on failure.
204  */
205 int generic_parse_monolithic(struct fs_context *fc, void *data)
206 {
207 	char *options = data, *key;
208 	int ret = 0;
209 
210 	if (!options)
211 		return 0;
212 
213 	ret = security_sb_eat_lsm_opts(options, &fc->security);
214 	if (ret)
215 		return ret;
216 
217 	while ((key = strsep(&options, ",")) != NULL) {
218 		if (*key) {
219 			size_t v_len = 0;
220 			char *value = strchr(key, '=');
221 
222 			if (value) {
223 				if (value == key)
224 					continue;
225 				*value++ = 0;
226 				v_len = strlen(value);
227 			}
228 			ret = vfs_parse_fs_string(fc, key, value, v_len);
229 			if (ret < 0)
230 				break;
231 		}
232 	}
233 
234 	return ret;
235 }
236 EXPORT_SYMBOL(generic_parse_monolithic);
237 
238 /**
239  * alloc_fs_context - Create a filesystem context.
240  * @fs_type: The filesystem type.
241  * @reference: The dentry from which this one derives (or NULL)
242  * @sb_flags: Filesystem/superblock flags (SB_*)
243  * @sb_flags_mask: Applicable members of @sb_flags
244  * @purpose: The purpose that this configuration shall be used for.
245  *
246  * Open a filesystem and create a mount context.  The mount context is
247  * initialised with the supplied flags and, if a submount/automount from
248  * another superblock (referred to by @reference) is supplied, may have
249  * parameters such as namespaces copied across from that superblock.
250  */
251 static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
252 				      struct dentry *reference,
253 				      unsigned int sb_flags,
254 				      unsigned int sb_flags_mask,
255 				      enum fs_context_purpose purpose)
256 {
257 	int (*init_fs_context)(struct fs_context *);
258 	struct fs_context *fc;
259 	int ret = -ENOMEM;
260 
261 	fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL);
262 	if (!fc)
263 		return ERR_PTR(-ENOMEM);
264 
265 	fc->purpose	= purpose;
266 	fc->sb_flags	= sb_flags;
267 	fc->sb_flags_mask = sb_flags_mask;
268 	fc->fs_type	= get_filesystem(fs_type);
269 	fc->cred	= get_current_cred();
270 	fc->net_ns	= get_net(current->nsproxy->net_ns);
271 
272 	mutex_init(&fc->uapi_mutex);
273 
274 	switch (purpose) {
275 	case FS_CONTEXT_FOR_MOUNT:
276 		fc->user_ns = get_user_ns(fc->cred->user_ns);
277 		break;
278 	case FS_CONTEXT_FOR_SUBMOUNT:
279 		fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
280 		break;
281 	case FS_CONTEXT_FOR_RECONFIGURE:
282 		/* We don't pin any namespaces as the superblock's
283 		 * subscriptions cannot be changed at this point.
284 		 */
285 		atomic_inc(&reference->d_sb->s_active);
286 		fc->root = dget(reference);
287 		break;
288 	}
289 
290 	/* TODO: Make all filesystems support this unconditionally */
291 	init_fs_context = fc->fs_type->init_fs_context;
292 	if (!init_fs_context)
293 		init_fs_context = legacy_init_fs_context;
294 
295 	ret = init_fs_context(fc);
296 	if (ret < 0)
297 		goto err_fc;
298 	fc->need_free = true;
299 	return fc;
300 
301 err_fc:
302 	put_fs_context(fc);
303 	return ERR_PTR(ret);
304 }
305 
306 struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
307 					unsigned int sb_flags)
308 {
309 	return alloc_fs_context(fs_type, NULL, sb_flags, 0,
310 					FS_CONTEXT_FOR_MOUNT);
311 }
312 EXPORT_SYMBOL(fs_context_for_mount);
313 
314 struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
315 					unsigned int sb_flags,
316 					unsigned int sb_flags_mask)
317 {
318 	return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
319 				sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
320 }
321 EXPORT_SYMBOL(fs_context_for_reconfigure);
322 
323 struct fs_context *fs_context_for_submount(struct file_system_type *type,
324 					   struct dentry *reference)
325 {
326 	return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
327 }
328 EXPORT_SYMBOL(fs_context_for_submount);
329 
330 void fc_drop_locked(struct fs_context *fc)
331 {
332 	struct super_block *sb = fc->root->d_sb;
333 	dput(fc->root);
334 	fc->root = NULL;
335 	deactivate_locked_super(sb);
336 }
337 
338 static void legacy_fs_context_free(struct fs_context *fc);
339 
340 /**
341  * vfs_dup_fc_config: Duplicate a filesystem context.
342  * @src_fc: The context to copy.
343  */
344 struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
345 {
346 	struct fs_context *fc;
347 	int ret;
348 
349 	if (!src_fc->ops->dup)
350 		return ERR_PTR(-EOPNOTSUPP);
351 
352 	fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
353 	if (!fc)
354 		return ERR_PTR(-ENOMEM);
355 
356 	mutex_init(&fc->uapi_mutex);
357 
358 	fc->fs_private	= NULL;
359 	fc->s_fs_info	= NULL;
360 	fc->source	= NULL;
361 	fc->security	= NULL;
362 	get_filesystem(fc->fs_type);
363 	get_net(fc->net_ns);
364 	get_user_ns(fc->user_ns);
365 	get_cred(fc->cred);
366 	if (fc->log)
367 		refcount_inc(&fc->log->usage);
368 
369 	/* Can't call put until we've called ->dup */
370 	ret = fc->ops->dup(fc, src_fc);
371 	if (ret < 0)
372 		goto err_fc;
373 
374 	ret = security_fs_context_dup(fc, src_fc);
375 	if (ret < 0)
376 		goto err_fc;
377 	return fc;
378 
379 err_fc:
380 	put_fs_context(fc);
381 	return ERR_PTR(ret);
382 }
383 EXPORT_SYMBOL(vfs_dup_fs_context);
384 
385 /**
386  * logfc - Log a message to a filesystem context
387  * @fc: The filesystem context to log to.
388  * @fmt: The format of the buffer.
389  */
390 void logfc(struct fs_context *fc, const char *fmt, ...)
391 {
392 	static const char store_failure[] = "OOM: Can't store error string";
393 	struct fc_log *log = fc ? fc->log : NULL;
394 	const char *p;
395 	va_list va;
396 	char *q;
397 	u8 freeable;
398 
399 	va_start(va, fmt);
400 	if (!strchr(fmt, '%')) {
401 		p = fmt;
402 		goto unformatted_string;
403 	}
404 	if (strcmp(fmt, "%s") == 0) {
405 		p = va_arg(va, const char *);
406 		goto unformatted_string;
407 	}
408 
409 	q = kvasprintf(GFP_KERNEL, fmt, va);
410 copied_string:
411 	if (!q)
412 		goto store_failure;
413 	freeable = 1;
414 	goto store_string;
415 
416 unformatted_string:
417 	if ((unsigned long)p >= (unsigned long)__start_rodata &&
418 	    (unsigned long)p <  (unsigned long)__end_rodata)
419 		goto const_string;
420 	if (log && within_module_core((unsigned long)p, log->owner))
421 		goto const_string;
422 	q = kstrdup(p, GFP_KERNEL);
423 	goto copied_string;
424 
425 store_failure:
426 	p = store_failure;
427 const_string:
428 	q = (char *)p;
429 	freeable = 0;
430 store_string:
431 	if (!log) {
432 		switch (fmt[0]) {
433 		case 'w':
434 			printk(KERN_WARNING "%s\n", q + 2);
435 			break;
436 		case 'e':
437 			printk(KERN_ERR "%s\n", q + 2);
438 			break;
439 		default:
440 			printk(KERN_NOTICE "%s\n", q + 2);
441 			break;
442 		}
443 		if (freeable)
444 			kfree(q);
445 	} else {
446 		unsigned int logsize = ARRAY_SIZE(log->buffer);
447 		u8 index;
448 
449 		index = log->head & (logsize - 1);
450 		BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
451 			     sizeof(log->tail) != sizeof(u8));
452 		if ((u8)(log->head - log->tail) == logsize) {
453 			/* The buffer is full, discard the oldest message */
454 			if (log->need_free & (1 << index))
455 				kfree(log->buffer[index]);
456 			log->tail++;
457 		}
458 
459 		log->buffer[index] = q;
460 		log->need_free &= ~(1 << index);
461 		log->need_free |= freeable << index;
462 		log->head++;
463 	}
464 	va_end(va);
465 }
466 EXPORT_SYMBOL(logfc);
467 
468 /*
469  * Free a logging structure.
470  */
471 static void put_fc_log(struct fs_context *fc)
472 {
473 	struct fc_log *log = fc->log;
474 	int i;
475 
476 	if (log) {
477 		if (refcount_dec_and_test(&log->usage)) {
478 			fc->log = NULL;
479 			for (i = 0; i <= 7; i++)
480 				if (log->need_free & (1 << i))
481 					kfree(log->buffer[i]);
482 			kfree(log);
483 		}
484 	}
485 }
486 
487 /**
488  * put_fs_context - Dispose of a superblock configuration context.
489  * @fc: The context to dispose of.
490  */
491 void put_fs_context(struct fs_context *fc)
492 {
493 	struct super_block *sb;
494 
495 	if (fc->root) {
496 		sb = fc->root->d_sb;
497 		dput(fc->root);
498 		fc->root = NULL;
499 		deactivate_super(sb);
500 	}
501 
502 	if (fc->need_free && fc->ops && fc->ops->free)
503 		fc->ops->free(fc);
504 
505 	security_free_mnt_opts(&fc->security);
506 	put_net(fc->net_ns);
507 	put_user_ns(fc->user_ns);
508 	put_cred(fc->cred);
509 	kfree(fc->subtype);
510 	put_fc_log(fc);
511 	put_filesystem(fc->fs_type);
512 	kfree(fc->source);
513 	kfree(fc);
514 }
515 EXPORT_SYMBOL(put_fs_context);
516 
517 /*
518  * Free the config for a filesystem that doesn't support fs_context.
519  */
520 static void legacy_fs_context_free(struct fs_context *fc)
521 {
522 	struct legacy_fs_context *ctx = fc->fs_private;
523 
524 	if (ctx) {
525 		if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
526 			kfree(ctx->legacy_data);
527 		kfree(ctx);
528 	}
529 }
530 
531 /*
532  * Duplicate a legacy config.
533  */
534 static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
535 {
536 	struct legacy_fs_context *ctx;
537 	struct legacy_fs_context *src_ctx = src_fc->fs_private;
538 
539 	ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
540 	if (!ctx)
541 		return -ENOMEM;
542 
543 	if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
544 		ctx->legacy_data = kmemdup(src_ctx->legacy_data,
545 					   src_ctx->data_size, GFP_KERNEL);
546 		if (!ctx->legacy_data) {
547 			kfree(ctx);
548 			return -ENOMEM;
549 		}
550 	}
551 
552 	fc->fs_private = ctx;
553 	return 0;
554 }
555 
556 /*
557  * Add a parameter to a legacy config.  We build up a comma-separated list of
558  * options.
559  */
560 static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
561 {
562 	struct legacy_fs_context *ctx = fc->fs_private;
563 	unsigned int size = ctx->data_size;
564 	size_t len = 0;
565 
566 	if (strcmp(param->key, "source") == 0) {
567 		if (param->type != fs_value_is_string)
568 			return invalf(fc, "VFS: Legacy: Non-string source");
569 		if (fc->source)
570 			return invalf(fc, "VFS: Legacy: Multiple sources");
571 		fc->source = param->string;
572 		param->string = NULL;
573 		return 0;
574 	}
575 
576 	if ((fc->fs_type->fs_flags & FS_HAS_SUBTYPE) &&
577 	    strcmp(param->key, "subtype") == 0) {
578 		if (param->type != fs_value_is_string)
579 			return invalf(fc, "VFS: Legacy: Non-string subtype");
580 		if (fc->subtype)
581 			return invalf(fc, "VFS: Legacy: Multiple subtype");
582 		fc->subtype = param->string;
583 		param->string = NULL;
584 		return 0;
585 	}
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 		/* Fall through */
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 (len > PAGE_SIZE - 2 - 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 	ctx->legacy_data[size++] = ',';
616 	len = strlen(param->key);
617 	memcpy(ctx->legacy_data + size, param->key, len);
618 	size += len;
619 	if (param->type == fs_value_is_string) {
620 		ctx->legacy_data[size++] = '=';
621 		memcpy(ctx->legacy_data + size, param->string, param->size);
622 		size += param->size;
623 	}
624 	ctx->legacy_data[size] = '\0';
625 	ctx->data_size = size;
626 	ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
627 	return 0;
628 }
629 
630 /*
631  * Add monolithic mount data.
632  */
633 static int legacy_parse_monolithic(struct fs_context *fc, void *data)
634 {
635 	struct legacy_fs_context *ctx = fc->fs_private;
636 
637 	if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
638 		pr_warn("VFS: Can't mix monolithic and individual options\n");
639 		return -EINVAL;
640 	}
641 
642 	ctx->legacy_data = data;
643 	ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
644 	if (!ctx->legacy_data)
645 		return 0;
646 
647 	if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
648 		return 0;
649 	return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
650 }
651 
652 /*
653  * Get a mountable root with the legacy mount command.
654  */
655 static int legacy_get_tree(struct fs_context *fc)
656 {
657 	struct legacy_fs_context *ctx = fc->fs_private;
658 	struct super_block *sb;
659 	struct dentry *root;
660 
661 	root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
662 				      fc->source, ctx->legacy_data);
663 	if (IS_ERR(root))
664 		return PTR_ERR(root);
665 
666 	sb = root->d_sb;
667 	BUG_ON(!sb);
668 
669 	fc->root = root;
670 	return 0;
671 }
672 
673 /*
674  * Handle remount.
675  */
676 static int legacy_reconfigure(struct fs_context *fc)
677 {
678 	struct legacy_fs_context *ctx = fc->fs_private;
679 	struct super_block *sb = fc->root->d_sb;
680 
681 	if (!sb->s_op->remount_fs)
682 		return 0;
683 
684 	return sb->s_op->remount_fs(sb, &fc->sb_flags,
685 				    ctx ? ctx->legacy_data : NULL);
686 }
687 
688 const struct fs_context_operations legacy_fs_context_ops = {
689 	.free			= legacy_fs_context_free,
690 	.dup			= legacy_fs_context_dup,
691 	.parse_param		= legacy_parse_param,
692 	.parse_monolithic	= legacy_parse_monolithic,
693 	.get_tree		= legacy_get_tree,
694 	.reconfigure		= legacy_reconfigure,
695 };
696 
697 /*
698  * Initialise a legacy context for a filesystem that doesn't support
699  * fs_context.
700  */
701 static int legacy_init_fs_context(struct fs_context *fc)
702 {
703 	fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL);
704 	if (!fc->fs_private)
705 		return -ENOMEM;
706 	fc->ops = &legacy_fs_context_ops;
707 	return 0;
708 }
709 
710 int parse_monolithic_mount_data(struct fs_context *fc, void *data)
711 {
712 	int (*monolithic_mount_data)(struct fs_context *, void *);
713 
714 	monolithic_mount_data = fc->ops->parse_monolithic;
715 	if (!monolithic_mount_data)
716 		monolithic_mount_data = generic_parse_monolithic;
717 
718 	return monolithic_mount_data(fc, data);
719 }
720 
721 /*
722  * Clean up a context after performing an action on it and put it into a state
723  * from where it can be used to reconfigure a superblock.
724  *
725  * Note that here we do only the parts that can't fail; the rest is in
726  * finish_clean_context() below and in between those fs_context is marked
727  * FS_CONTEXT_AWAITING_RECONF.  The reason for splitup is that after
728  * successful mount or remount we need to report success to userland.
729  * Trying to do full reinit (for the sake of possible subsequent remount)
730  * and failing to allocate memory would've put us into a nasty situation.
731  * So here we only discard the old state and reinitialization is left
732  * until we actually try to reconfigure.
733  */
734 void vfs_clean_context(struct fs_context *fc)
735 {
736 	if (fc->need_free && fc->ops && fc->ops->free)
737 		fc->ops->free(fc);
738 	fc->need_free = false;
739 	fc->fs_private = NULL;
740 	fc->s_fs_info = NULL;
741 	fc->sb_flags = 0;
742 	security_free_mnt_opts(&fc->security);
743 	kfree(fc->subtype);
744 	fc->subtype = NULL;
745 	kfree(fc->source);
746 	fc->source = NULL;
747 
748 	fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
749 	fc->phase = FS_CONTEXT_AWAITING_RECONF;
750 }
751 
752 int 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