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                 /* 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 }