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 { "ro", SB_RDONLY },
46 { "sync", SB_SYNCHRONOUS },
47 { },
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 { },
56 };
57
58 /*
59 * Check for a common mount option that manipulates s_flags.
60 */
vfs_parse_sb_flag(struct fs_context * fc,const char * key)61 static 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 */
vfs_parse_fs_param_source(struct fs_context * fc,struct fs_parameter * param)94 int 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 }
109 EXPORT_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 */
vfs_parse_fs_param(struct fs_context * fc,struct fs_parameter * param)127 int 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 }
161 EXPORT_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 */
vfs_parse_fs_string(struct fs_context * fc,const char * key,const char * value,size_t v_size)170 int 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, ¶m);
189 kfree(param.string);
190 return ret;
191 }
192 EXPORT_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 */
vfs_parse_monolithic_sep(struct fs_context * fc,void * data,char * (* sep)(char **))206 int 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 (unlikely(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 }
238 EXPORT_SYMBOL(vfs_parse_monolithic_sep);
239
vfs_parse_comma_sep(char ** s)240 static 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 */
generic_parse_monolithic(struct fs_context * fc,void * data)256 int generic_parse_monolithic(struct fs_context *fc, void *data)
257 {
258 return vfs_parse_monolithic_sep(fc, data, vfs_parse_comma_sep);
259 }
260 EXPORT_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 */
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)275 static 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
324 err_fc:
325 put_fs_context(fc);
326 return ERR_PTR(ret);
327 }
328
fs_context_for_mount(struct file_system_type * fs_type,unsigned int sb_flags)329 struct 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 }
335 EXPORT_SYMBOL(fs_context_for_mount);
336
fs_context_for_reconfigure(struct dentry * dentry,unsigned int sb_flags,unsigned int sb_flags_mask)337 struct 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 }
344 EXPORT_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 */
fs_context_for_submount(struct file_system_type * type,struct dentry * reference)354 struct 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 }
372 EXPORT_SYMBOL(fs_context_for_submount);
373
fc_drop_locked(struct fs_context * fc)374 void 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
382 static 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 */
vfs_dup_fs_context(struct fs_context * src_fc)388 struct 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
423 err_fc:
424 put_fs_context(fc);
425 return ERR_PTR(ret);
426 }
427 EXPORT_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 */
logfc(struct fc_log * log,const char * prefix,char level,const char * fmt,...)436 void 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 case 'i':
453 printk(KERN_INFO "%s%s%pV\n", prefix ? prefix : "",
454 prefix ? ": " : "", &vaf);
455 break;
456 default:
457 printk(KERN_NOTICE "%s%s%pV\n", prefix ? prefix : "",
458 prefix ? ": " : "", &vaf);
459 break;
460 }
461 } else {
462 unsigned int logsize = ARRAY_SIZE(log->buffer);
463 u8 index;
464 char *q = kasprintf(GFP_KERNEL, "%c %s%s%pV\n", level,
465 prefix ? prefix : "",
466 prefix ? ": " : "", &vaf);
467
468 index = log->head & (logsize - 1);
469 BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
470 sizeof(log->tail) != sizeof(u8));
471 if ((u8)(log->head - log->tail) == logsize) {
472 /* The buffer is full, discard the oldest message */
473 if (log->need_free & (1 << index))
474 kfree(log->buffer[index]);
475 log->tail++;
476 }
477
478 log->buffer[index] = q ? q : "OOM: Can't store error string";
479 if (q)
480 log->need_free |= 1 << index;
481 else
482 log->need_free &= ~(1 << index);
483 log->head++;
484 }
485 va_end(va);
486 }
487 EXPORT_SYMBOL(logfc);
488
489 /*
490 * Free a logging structure.
491 */
put_fc_log(struct fs_context * fc)492 static void put_fc_log(struct fs_context *fc)
493 {
494 struct fc_log *log = fc->log.log;
495 int i;
496
497 if (log) {
498 if (refcount_dec_and_test(&log->usage)) {
499 fc->log.log = NULL;
500 for (i = 0; i < ARRAY_SIZE(log->buffer) ; i++)
501 if (log->need_free & (1 << i))
502 kfree(log->buffer[i]);
503 kfree(log);
504 }
505 }
506 }
507
508 /**
509 * put_fs_context - Dispose of a superblock configuration context.
510 * @fc: The context to dispose of.
511 */
put_fs_context(struct fs_context * fc)512 void put_fs_context(struct fs_context *fc)
513 {
514 struct super_block *sb;
515
516 if (fc->root) {
517 sb = fc->root->d_sb;
518 dput(fc->root);
519 fc->root = NULL;
520 deactivate_super(sb);
521 }
522
523 if (fc->need_free && fc->ops && fc->ops->free)
524 fc->ops->free(fc);
525
526 security_free_mnt_opts(&fc->security);
527 put_net(fc->net_ns);
528 put_user_ns(fc->user_ns);
529 put_cred(fc->cred);
530 put_fc_log(fc);
531 put_filesystem(fc->fs_type);
532 kfree(fc->source);
533 kfree(fc);
534 }
535 EXPORT_SYMBOL(put_fs_context);
536
537 /*
538 * Free the config for a filesystem that doesn't support fs_context.
539 */
legacy_fs_context_free(struct fs_context * fc)540 static void legacy_fs_context_free(struct fs_context *fc)
541 {
542 struct legacy_fs_context *ctx = fc->fs_private;
543
544 if (ctx) {
545 if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
546 kfree(ctx->legacy_data);
547 kfree(ctx);
548 }
549 }
550
551 /*
552 * Duplicate a legacy config.
553 */
legacy_fs_context_dup(struct fs_context * fc,struct fs_context * src_fc)554 static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
555 {
556 struct legacy_fs_context *ctx;
557 struct legacy_fs_context *src_ctx = src_fc->fs_private;
558
559 ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
560 if (!ctx)
561 return -ENOMEM;
562
563 if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
564 ctx->legacy_data = kmemdup(src_ctx->legacy_data,
565 src_ctx->data_size, GFP_KERNEL);
566 if (!ctx->legacy_data) {
567 kfree(ctx);
568 return -ENOMEM;
569 }
570 }
571
572 fc->fs_private = ctx;
573 return 0;
574 }
575
576 /*
577 * Add a parameter to a legacy config. We build up a comma-separated list of
578 * options.
579 */
legacy_parse_param(struct fs_context * fc,struct fs_parameter * param)580 static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
581 {
582 struct legacy_fs_context *ctx = fc->fs_private;
583 unsigned int size = ctx->data_size;
584 size_t len = 0;
585 int ret;
586
587 ret = vfs_parse_fs_param_source(fc, param);
588 if (ret != -ENOPARAM)
589 return ret;
590
591 if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
592 return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");
593
594 switch (param->type) {
595 case fs_value_is_string:
596 len = 1 + param->size;
597 fallthrough;
598 case fs_value_is_flag:
599 len += strlen(param->key);
600 break;
601 default:
602 return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported",
603 param->key);
604 }
605
606 if (size + len + 2 > PAGE_SIZE)
607 return invalf(fc, "VFS: Legacy: Cumulative options too large");
608 if (strchr(param->key, ',') ||
609 (param->type == fs_value_is_string &&
610 memchr(param->string, ',', param->size)))
611 return invalf(fc, "VFS: Legacy: Option '%s' contained comma",
612 param->key);
613 if (!ctx->legacy_data) {
614 ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
615 if (!ctx->legacy_data)
616 return -ENOMEM;
617 }
618
619 if (size)
620 ctx->legacy_data[size++] = ',';
621 len = strlen(param->key);
622 memcpy(ctx->legacy_data + size, param->key, len);
623 size += len;
624 if (param->type == fs_value_is_string) {
625 ctx->legacy_data[size++] = '=';
626 memcpy(ctx->legacy_data + size, param->string, param->size);
627 size += param->size;
628 }
629 ctx->legacy_data[size] = '\0';
630 ctx->data_size = size;
631 ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
632 return 0;
633 }
634
635 /*
636 * Add monolithic mount data.
637 */
legacy_parse_monolithic(struct fs_context * fc,void * data)638 static int legacy_parse_monolithic(struct fs_context *fc, void *data)
639 {
640 struct legacy_fs_context *ctx = fc->fs_private;
641
642 if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
643 pr_warn("VFS: Can't mix monolithic and individual options\n");
644 return -EINVAL;
645 }
646
647 ctx->legacy_data = data;
648 ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
649 if (!ctx->legacy_data)
650 return 0;
651
652 if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
653 return 0;
654 return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
655 }
656
657 /*
658 * Get a mountable root with the legacy mount command.
659 */
legacy_get_tree(struct fs_context * fc)660 static int legacy_get_tree(struct fs_context *fc)
661 {
662 struct legacy_fs_context *ctx = fc->fs_private;
663 struct super_block *sb;
664 struct dentry *root;
665
666 root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
667 fc->source, ctx->legacy_data);
668 if (IS_ERR(root))
669 return PTR_ERR(root);
670
671 sb = root->d_sb;
672 BUG_ON(!sb);
673
674 fc->root = root;
675 return 0;
676 }
677
678 /*
679 * Handle remount.
680 */
legacy_reconfigure(struct fs_context * fc)681 static int legacy_reconfigure(struct fs_context *fc)
682 {
683 struct legacy_fs_context *ctx = fc->fs_private;
684 struct super_block *sb = fc->root->d_sb;
685
686 if (!sb->s_op->remount_fs)
687 return 0;
688
689 return sb->s_op->remount_fs(sb, &fc->sb_flags,
690 ctx ? ctx->legacy_data : NULL);
691 }
692
693 const struct fs_context_operations legacy_fs_context_ops = {
694 .free = legacy_fs_context_free,
695 .dup = legacy_fs_context_dup,
696 .parse_param = legacy_parse_param,
697 .parse_monolithic = legacy_parse_monolithic,
698 .get_tree = legacy_get_tree,
699 .reconfigure = legacy_reconfigure,
700 };
701
702 /*
703 * Initialise a legacy context for a filesystem that doesn't support
704 * fs_context.
705 */
legacy_init_fs_context(struct fs_context * fc)706 static int legacy_init_fs_context(struct fs_context *fc)
707 {
708 fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL_ACCOUNT);
709 if (!fc->fs_private)
710 return -ENOMEM;
711 fc->ops = &legacy_fs_context_ops;
712 return 0;
713 }
714
parse_monolithic_mount_data(struct fs_context * fc,void * data)715 int parse_monolithic_mount_data(struct fs_context *fc, void *data)
716 {
717 int (*monolithic_mount_data)(struct fs_context *, void *);
718
719 monolithic_mount_data = fc->ops->parse_monolithic;
720 if (!monolithic_mount_data)
721 monolithic_mount_data = generic_parse_monolithic;
722
723 return monolithic_mount_data(fc, data);
724 }
725
726 /*
727 * Clean up a context after performing an action on it and put it into a state
728 * from where it can be used to reconfigure a superblock.
729 *
730 * Note that here we do only the parts that can't fail; the rest is in
731 * finish_clean_context() below and in between those fs_context is marked
732 * FS_CONTEXT_AWAITING_RECONF. The reason for splitup is that after
733 * successful mount or remount we need to report success to userland.
734 * Trying to do full reinit (for the sake of possible subsequent remount)
735 * and failing to allocate memory would've put us into a nasty situation.
736 * So here we only discard the old state and reinitialization is left
737 * until we actually try to reconfigure.
738 */
vfs_clean_context(struct fs_context * fc)739 void vfs_clean_context(struct fs_context *fc)
740 {
741 if (fc->need_free && fc->ops && fc->ops->free)
742 fc->ops->free(fc);
743 fc->need_free = false;
744 fc->fs_private = NULL;
745 fc->s_fs_info = NULL;
746 fc->sb_flags = 0;
747 security_free_mnt_opts(&fc->security);
748 kfree(fc->source);
749 fc->source = NULL;
750 fc->exclusive = false;
751
752 fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
753 fc->phase = FS_CONTEXT_AWAITING_RECONF;
754 }
755
finish_clean_context(struct fs_context * fc)756 int finish_clean_context(struct fs_context *fc)
757 {
758 int error;
759
760 if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
761 return 0;
762
763 if (fc->fs_type->init_fs_context)
764 error = fc->fs_type->init_fs_context(fc);
765 else
766 error = legacy_init_fs_context(fc);
767 if (unlikely(error)) {
768 fc->phase = FS_CONTEXT_FAILED;
769 return error;
770 }
771 fc->need_free = true;
772 fc->phase = FS_CONTEXT_RECONF_PARAMS;
773 return 0;
774 }
775