fs/fs_context.c

   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                 atomic_inc(&reference->d_sb->s_active);
 283                 fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
 284                 fc->root = dget(reference);
 285                 break;
 286         }
 287
 288         /* TODO: Make all filesystems support this unconditionally */
 289         init_fs_context = fc->fs_type->init_fs_context;
 290         if (!init_fs_context)
 291                 init_fs_context = legacy_init_fs_context;
 292
 293         ret = init_fs_context(fc);
 294         if (ret < 0)
 295                 goto err_fc;
 296         fc->need_free = true;
 297         return fc;
 298
 299 err_fc:
 300         put_fs_context(fc);
 301         return ERR_PTR(ret);
 302 }
 303
 304 struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
 305                                         unsigned int sb_flags)
 306 {
 307         return alloc_fs_context(fs_type, NULL, sb_flags, 0,
 308                                         FS_CONTEXT_FOR_MOUNT);
 309 }
 310 EXPORT_SYMBOL(fs_context_for_mount);
 311
 312 struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
 313                                         unsigned int sb_flags,
 314                                         unsigned int sb_flags_mask)
 315 {
 316         return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
 317                                 sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
 318 }
 319 EXPORT_SYMBOL(fs_context_for_reconfigure);
 320
 321 struct fs_context *fs_context_for_submount(struct file_system_type *type,
 322                                            struct dentry *reference)
 323 {
 324         return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
 325 }
 326 EXPORT_SYMBOL(fs_context_for_submount);
 327
 328 void fc_drop_locked(struct fs_context *fc)
 329 {
 330         struct super_block *sb = fc->root->d_sb;
 331         dput(fc->root);
 332         fc->root = NULL;
 333         deactivate_locked_super(sb);
 334 }
 335
 336 static void legacy_fs_context_free(struct fs_context *fc);
 337
 338 /**
 339  * vfs_dup_fc_config: Duplicate a filesystem context.
 340  * @src_fc: The context to copy.
 341  */
 342 struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
 343 {
 344         struct fs_context *fc;
 345         int ret;
 346
 347         if (!src_fc->ops->dup)
 348                 return ERR_PTR(-EOPNOTSUPP);
 349
 350         fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
 351         if (!fc)
 352                 return ERR_PTR(-ENOMEM);
 353
 354         mutex_init(&fc->uapi_mutex);
 355
 356         fc->fs_private  = NULL;
 357         fc->s_fs_info   = NULL;
 358         fc->source      = NULL;
 359         fc->security    = NULL;
 360         get_filesystem(fc->fs_type);
 361         get_net(fc->net_ns);
 362         get_user_ns(fc->user_ns);
 363         get_cred(fc->cred);
 364         if (fc->log)
 365                 refcount_inc(&fc->log->usage);
 366
 367         /* Can't call put until we've called ->dup */
 368         ret = fc->ops->dup(fc, src_fc);
 369         if (ret < 0)
 370                 goto err_fc;
 371
 372         ret = security_fs_context_dup(fc, src_fc);
 373         if (ret < 0)
 374                 goto err_fc;
 375         return fc;
 376
 377 err_fc:
 378         put_fs_context(fc);
 379         return ERR_PTR(ret);
 380 }
 381 EXPORT_SYMBOL(vfs_dup_fs_context);
 382
 383 /**
 384  * logfc - Log a message to a filesystem context
 385  * @fc: The filesystem context to log to.
 386  * @fmt: The format of the buffer.
 387  */
 388 void logfc(struct fs_context *fc, const char *fmt, ...)
 389 {
 390         static const char store_failure[] = "OOM: Can't store error string";
 391         struct fc_log *log = fc ? fc->log : NULL;
 392         const char *p;
 393         va_list va;
 394         char *q;
 395         u8 freeable;
 396
 397         va_start(va, fmt);
 398         if (!strchr(fmt, '%')) {
 399                 p = fmt;
 400                 goto unformatted_string;
 401         }
 402         if (strcmp(fmt, "%s") == 0) {
 403                 p = va_arg(va, const char *);
 404                 goto unformatted_string;
 405         }
 406
 407         q = kvasprintf(GFP_KERNEL, fmt, va);
 408 copied_string:
 409         if (!q)
 410                 goto store_failure;
 411         freeable = 1;
 412         goto store_string;
 413
 414 unformatted_string:
 415         if ((unsigned long)p >= (unsigned long)__start_rodata &&
 416             (unsigned long)p <  (unsigned long)__end_rodata)
 417                 goto const_string;
 418         if (log && within_module_core((unsigned long)p, log->owner))
 419                 goto const_string;
 420         q = kstrdup(p, GFP_KERNEL);
 421         goto copied_string;
 422
 423 store_failure:
 424         p = store_failure;
 425 const_string:
 426         q = (char *)p;
 427         freeable = 0;
 428 store_string:
 429         if (!log) {
 430                 switch (fmt[0]) {
 431                 case 'w':
 432                         printk(KERN_WARNING "%s\n", q + 2);
 433                         break;
 434                 case 'e':
 435                         printk(KERN_ERR "%s\n", q + 2);
 436                         break;
 437                 default:
 438                         printk(KERN_NOTICE "%s\n", q + 2);
 439                         break;
 440                 }
 441                 if (freeable)
 442                         kfree(q);
 443         } else {
 444                 unsigned int logsize = ARRAY_SIZE(log->buffer);
 445                 u8 index;
 446
 447                 index = log->head & (logsize - 1);
 448                 BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
 449                              sizeof(log->tail) != sizeof(u8));
 450                 if ((u8)(log->head - log->tail) == logsize) {
 451                         /* The buffer is full, discard the oldest message */
 452                         if (log->need_free & (1 << index))
 453                                 kfree(log->buffer[index]);
 454                         log->tail++;
 455                 }
 456
 457                 log->buffer[index] = q;
 458                 log->need_free &= ~(1 << index);
 459                 log->need_free |= freeable << index;
 460                 log->head++;
 461         }
 462         va_end(va);
 463 }
 464 EXPORT_SYMBOL(logfc);
 465
 466 /*
 467  * Free a logging structure.
 468  */
 469 static void put_fc_log(struct fs_context *fc)
 470 {
 471         struct fc_log *log = fc->log;
 472         int i;
 473
 474         if (log) {
 475                 if (refcount_dec_and_test(&log->usage)) {
 476                         fc->log = NULL;
 477                         for (i = 0; i <= 7; i++)
 478                                 if (log->need_free & (1 << i))
 479                                         kfree(log->buffer[i]);
 480                         kfree(log);
 481                 }
 482         }
 483 }
 484
 485 /**
 486  * put_fs_context - Dispose of a superblock configuration context.
 487  * @fc: The context to dispose of.
 488  */
 489 void put_fs_context(struct fs_context *fc)
 490 {
 491         struct super_block *sb;
 492
 493         if (fc->root) {
 494                 sb = fc->root->d_sb;
 495                 dput(fc->root);
 496                 fc->root = NULL;
 497                 deactivate_super(sb);
 498         }
 499
 500         if (fc->need_free && fc->ops && fc->ops->free)
 501                 fc->ops->free(fc);
 502
 503         security_free_mnt_opts(&fc->security);
 504         put_net(fc->net_ns);
 505         put_user_ns(fc->user_ns);
 506         put_cred(fc->cred);
 507         kfree(fc->subtype);
 508         put_fc_log(fc);
 509         put_filesystem(fc->fs_type);
 510         kfree(fc->source);
 511         kfree(fc);
 512 }
 513 EXPORT_SYMBOL(put_fs_context);
 514
 515 /*
 516  * Free the config for a filesystem that doesn't support fs_context.
 517  */
 518 static void legacy_fs_context_free(struct fs_context *fc)
 519 {
 520         struct legacy_fs_context *ctx = fc->fs_private;
 521
 522         if (ctx) {
 523                 if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
 524                         kfree(ctx->legacy_data);
 525                 kfree(ctx);
 526         }
 527 }
 528
 529 /*
 530  * Duplicate a legacy config.
 531  */
 532 static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
 533 {
 534         struct legacy_fs_context *ctx;
 535         struct legacy_fs_context *src_ctx = src_fc->fs_private;
 536
 537         ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
 538         if (!ctx)
 539                 return -ENOMEM;
 540
 541         if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
 542                 ctx->legacy_data = kmemdup(src_ctx->legacy_data,
 543                                            src_ctx->data_size, GFP_KERNEL);
 544                 if (!ctx->legacy_data) {
 545                         kfree(ctx);
 546                         return -ENOMEM;
 547                 }
 548         }
 549
 550         fc->fs_private = ctx;
 551         return 0;
 552 }
 553
 554 /*
 555  * Add a parameter to a legacy config.  We build up a comma-separated list of
 556  * options.
 557  */
 558 static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
 559 {
 560         struct legacy_fs_context *ctx = fc->fs_private;
 561         unsigned int size = ctx->data_size;
 562         size_t len = 0;
 563
 564         if (strcmp(param->key, "source") == 0) {
 565                 if (param->type != fs_value_is_string)
 566                         return invalf(fc, "VFS: Legacy: Non-string source");
 567                 if (fc->source)
 568                         return invalf(fc, "VFS: Legacy: Multiple sources");
 569                 fc->source = param->string;
 570                 param->string = NULL;
 571                 return 0;
 572         }
 573
 574         if ((fc->fs_type->fs_flags & FS_HAS_SUBTYPE) &&
 575             strcmp(param->key, "subtype") == 0) {
 576                 if (param->type != fs_value_is_string)
 577                         return invalf(fc, "VFS: Legacy: Non-string subtype");
 578                 if (fc->subtype)
 579                         return invalf(fc, "VFS: Legacy: Multiple subtype");
 580                 fc->subtype = param->string;
 581                 param->string = NULL;
 582                 return 0;
 583         }
 584
 585         if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
 586                 return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");
 587
 588         switch (param->type) {
 589         case fs_value_is_string:
 590                 len = 1 + param->size;
 591                 /* Fall through */
 592         case fs_value_is_flag:
 593                 len += strlen(param->key);
 594                 break;
 595         default:
 596                 return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported",
 597                               param->key);
 598         }
 599
 600         if (len > PAGE_SIZE - 2 - size)
 601                 return invalf(fc, "VFS: Legacy: Cumulative options too large");
 602         if (strchr(param->key, ',') ||
 603             (param->type == fs_value_is_string &&
 604              memchr(param->string, ',', param->size)))
 605                 return invalf(fc, "VFS: Legacy: Option '%s' contained comma",
 606                               param->key);
 607         if (!ctx->legacy_data) {
 608                 ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
 609                 if (!ctx->legacy_data)
 610                         return -ENOMEM;
 611         }
 612
 613         ctx->legacy_data[size++] = ',';
 614         len = strlen(param->key);
 615         memcpy(ctx->legacy_data + size, param->key, len);
 616         size += len;
 617         if (param->type == fs_value_is_string) {
 618                 ctx->legacy_data[size++] = '=';
 619                 memcpy(ctx->legacy_data + size, param->string, param->size);
 620                 size += param->size;
 621         }
 622         ctx->legacy_data[size] = '\0';
 623         ctx->data_size = size;
 624         ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
 625         return 0;
 626 }
 627
 628 /*
 629  * Add monolithic mount data.
 630  */
 631 static int legacy_parse_monolithic(struct fs_context *fc, void *data)
 632 {
 633         struct legacy_fs_context *ctx = fc->fs_private;
 634
 635         if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
 636                 pr_warn("VFS: Can't mix monolithic and individual options\n");
 637                 return -EINVAL;
 638         }
 639
 640         ctx->legacy_data = data;
 641         ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
 642         if (!ctx->legacy_data)
 643                 return 0;
 644
 645         if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
 646                 return 0;
 647         return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
 648 }
 649
 650 /*
 651  * Get a mountable root with the legacy mount command.
 652  */
 653 static int legacy_get_tree(struct fs_context *fc)
 654 {
 655         struct legacy_fs_context *ctx = fc->fs_private;
 656         struct super_block *sb;
 657         struct dentry *root;
 658
 659         root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
 660                                       fc->source, ctx->legacy_data);
 661         if (IS_ERR(root))
 662                 return PTR_ERR(root);
 663
 664         sb = root->d_sb;
 665         BUG_ON(!sb);
 666
 667         fc->root = root;
 668         return 0;
 669 }
 670
 671 /*
 672  * Handle remount.
 673  */
 674 static int legacy_reconfigure(struct fs_context *fc)
 675 {
 676         struct legacy_fs_context *ctx = fc->fs_private;
 677         struct super_block *sb = fc->root->d_sb;
 678
 679         if (!sb->s_op->remount_fs)
 680                 return 0;
 681
 682         return sb->s_op->remount_fs(sb, &fc->sb_flags,
 683                                     ctx ? ctx->legacy_data : NULL);
 684 }
 685
 686 const struct fs_context_operations legacy_fs_context_ops = {
 687         .free                   = legacy_fs_context_free,
 688         .dup                    = legacy_fs_context_dup,
 689         .parse_param            = legacy_parse_param,
 690         .parse_monolithic       = legacy_parse_monolithic,
 691         .get_tree               = legacy_get_tree,
 692         .reconfigure            = legacy_reconfigure,
 693 };
 694
 695 /*
 696  * Initialise a legacy context for a filesystem that doesn't support
 697  * fs_context.
 698  */
 699 static int legacy_init_fs_context(struct fs_context *fc)
 700 {
 701         fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL);
 702         if (!fc->fs_private)
 703                 return -ENOMEM;
 704         fc->ops = &legacy_fs_context_ops;
 705         return 0;
 706 }
 707
 708 int parse_monolithic_mount_data(struct fs_context *fc, void *data)
 709 {
 710         int (*monolithic_mount_data)(struct fs_context *, void *);
 711
 712         monolithic_mount_data = fc->ops->parse_monolithic;
 713         if (!monolithic_mount_data)
 714                 monolithic_mount_data = generic_parse_monolithic;
 715
 716         return monolithic_mount_data(fc, data);
 717 }
 718
 719 /*
 720  * Clean up a context after performing an action on it and put it into a state
 721  * from where it can be used to reconfigure a superblock.
 722  *
 723  * Note that here we do only the parts that can't fail; the rest is in
 724  * finish_clean_context() below and in between those fs_context is marked
 725  * FS_CONTEXT_AWAITING_RECONF.  The reason for splitup is that after
 726  * successful mount or remount we need to report success to userland.
 727  * Trying to do full reinit (for the sake of possible subsequent remount)
 728  * and failing to allocate memory would've put us into a nasty situation.
 729  * So here we only discard the old state and reinitialization is left
 730  * until we actually try to reconfigure.
 731  */
 732 void vfs_clean_context(struct fs_context *fc)
 733 {
 734         if (fc->need_free && fc->ops && fc->ops->free)
 735                 fc->ops->free(fc);
 736         fc->need_free = false;
 737         fc->fs_private = NULL;
 738         fc->s_fs_info = NULL;
 739         fc->sb_flags = 0;
 740         security_free_mnt_opts(&fc->security);
 741         kfree(fc->subtype);
 742         fc->subtype = NULL;
 743         kfree(fc->source);
 744         fc->source = NULL;
 745
 746         fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
 747         fc->phase = FS_CONTEXT_AWAITING_RECONF;
 748 }
 749
 750 int finish_clean_context(struct fs_context *fc)
 751 {
 752         int error;
 753
 754         if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
 755                 return 0;
 756
 757         if (fc->fs_type->init_fs_context)
 758                 error = fc->fs_type->init_fs_context(fc);
 759         else
 760                 error = legacy_init_fs_context(fc);
 761         if (unlikely(error)) {
 762                 fc->phase = FS_CONTEXT_FAILED;
 763                 return error;
 764         }
 765         fc->need_free = true;
 766         fc->phase = FS_CONTEXT_RECONF_PARAMS;
 767         return 0;
 768 }