the-tree/fs/fs_context.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /* Provide a way to create a superblock configuration context within the kernel
0003  * that allows a superblock to be set up prior to mounting.
0004  *
0005  * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
0006  * Written by David Howells (dhowells@redhat.com)
0007  */
0008
0009 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
0010 #include <linux/module.h>
0011 #include <linux/fs_context.h>
0012 #include <linux/fs_parser.h>
0013 #include <linux/fs.h>
0014 #include <linux/mount.h>
0015 #include <linux/nsproxy.h>
0016 #include <linux/slab.h>
0017 #include <linux/magic.h>
0018 #include <linux/security.h>
0019 #include <linux/mnt_namespace.h>
0020 #include <linux/pid_namespace.h>
0021 #include <linux/user_namespace.h>
0022 #include <net/net_namespace.h>
0023 #include <asm/sections.h>
0024 #include "mount.h"
0025 #include "internal.h"
0026
0027 enum legacy_fs_param {
0028     LEGACY_FS_UNSET_PARAMS,
0029     LEGACY_FS_MONOLITHIC_PARAMS,
0030     LEGACY_FS_INDIVIDUAL_PARAMS,
0031 };
0032
0033 struct legacy_fs_context {
0034     char            *legacy_data;   /* Data page for legacy filesystems */
0035     size_t          data_size;
0036     enum legacy_fs_param    param_type;
0037 };
0038
0039 static int legacy_init_fs_context(struct fs_context *fc);
0040
0041 static const struct constant_table common_set_sb_flag[] = {
0042     { "dirsync",    SB_DIRSYNC },
0043     { "lazytime",   SB_LAZYTIME },
0044     { "mand",   SB_MANDLOCK },
0045     { "ro",     SB_RDONLY },
0046     { "sync",   SB_SYNCHRONOUS },
0047     { },
0048 };
0049
0050 static const struct constant_table common_clear_sb_flag[] = {
0051     { "async",  SB_SYNCHRONOUS },
0052     { "nolazytime", SB_LAZYTIME },
0053     { "nomand", SB_MANDLOCK },
0054     { "rw",     SB_RDONLY },
0055     { },
0056 };
0057
0058 /*
0059  * Check for a common mount option that manipulates s_flags.
0060  */
0061 static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
0062 {
0063     unsigned int token;
0064
0065     token = lookup_constant(common_set_sb_flag, key, 0);
0066     if (token) {
0067         fc->sb_flags |= token;
0068         fc->sb_flags_mask |= token;
0069         return 0;
0070     }
0071
0072     token = lookup_constant(common_clear_sb_flag, key, 0);
0073     if (token) {
0074         fc->sb_flags &= ~token;
0075         fc->sb_flags_mask |= token;
0076         return 0;
0077     }
0078
0079     return -ENOPARAM;
0080 }
0081
0082 /**
0083  * vfs_parse_fs_param_source - Handle setting "source" via parameter
0084  * @fc: The filesystem context to modify
0085  * @param: The parameter
0086  *
0087  * This is a simple helper for filesystems to verify that the "source" they
0088  * accept is sane.
0089  *
0090  * Returns 0 on success, -ENOPARAM if this is not  "source" parameter, and
0091  * -EINVAL otherwise. In the event of failure, supplementary error information
0092  *  is logged.
0093  */
0094 int vfs_parse_fs_param_source(struct fs_context *fc, struct fs_parameter *param)
0095 {
0096     if (strcmp(param->key, "source") != 0)
0097         return -ENOPARAM;
0098
0099     if (param->type != fs_value_is_string)
0100         return invalf(fc, "Non-string source");
0101
0102     if (fc->source)
0103         return invalf(fc, "Multiple sources");
0104
0105     fc->source = param->string;
0106     param->string = NULL;
0107     return 0;
0108 }
0109 EXPORT_SYMBOL(vfs_parse_fs_param_source);
0110
0111 /**
0112  * vfs_parse_fs_param - Add a single parameter to a superblock config
0113  * @fc: The filesystem context to modify
0114  * @param: The parameter
0115  *
0116  * A single mount option in string form is applied to the filesystem context
0117  * being set up.  Certain standard options (for example "ro") are translated
0118  * into flag bits without going to the filesystem.  The active security module
0119  * is allowed to observe and poach options.  Any other options are passed over
0120  * to the filesystem to parse.
0121  *
0122  * This may be called multiple times for a context.
0123  *
0124  * Returns 0 on success and a negative error code on failure.  In the event of
0125  * failure, supplementary error information may have been set.
0126  */
0127 int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
0128 {
0129     int ret;
0130
0131     if (!param->key)
0132         return invalf(fc, "Unnamed parameter\n");
0133
0134     ret = vfs_parse_sb_flag(fc, param->key);
0135     if (ret != -ENOPARAM)
0136         return ret;
0137
0138     ret = security_fs_context_parse_param(fc, param);
0139     if (ret != -ENOPARAM)
0140         /* Param belongs to the LSM or is disallowed by the LSM; so
0141          * don't pass to the FS.
0142          */
0143         return ret;
0144
0145     if (fc->ops->parse_param) {
0146         ret = fc->ops->parse_param(fc, param);
0147         if (ret != -ENOPARAM)
0148             return ret;
0149     }
0150
0151     /* If the filesystem doesn't take any arguments, give it the
0152      * default handling of source.
0153      */
0154     ret = vfs_parse_fs_param_source(fc, param);
0155     if (ret != -ENOPARAM)
0156         return ret;
0157
0158     return invalf(fc, "%s: Unknown parameter '%s'",
0159               fc->fs_type->name, param->key);
0160 }
0161 EXPORT_SYMBOL(vfs_parse_fs_param);
0162
0163 /**
0164  * vfs_parse_fs_string - Convenience function to just parse a string.
0165  */
0166 int vfs_parse_fs_string(struct fs_context *fc, const char *key,
0167             const char *value, size_t v_size)
0168 {
0169     int ret;
0170
0171     struct fs_parameter param = {
0172         .key    = key,
0173         .type   = fs_value_is_flag,
0174         .size   = v_size,
0175     };
0176
0177     if (value) {
0178         param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
0179         if (!param.string)
0180             return -ENOMEM;
0181         param.type = fs_value_is_string;
0182     }
0183
0184     ret = vfs_parse_fs_param(fc, &param);
0185     kfree(param.string);
0186     return ret;
0187 }
0188 EXPORT_SYMBOL(vfs_parse_fs_string);
0189
0190 /**
0191  * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
0192  * @ctx: The superblock configuration to fill in.
0193  * @data: The data to parse
0194  *
0195  * Parse a blob of data that's in key[=val][,key[=val]]* form.  This can be
0196  * called from the ->monolithic_mount_data() fs_context operation.
0197  *
0198  * Returns 0 on success or the error returned by the ->parse_option() fs_context
0199  * operation on failure.
0200  */
0201 int generic_parse_monolithic(struct fs_context *fc, void *data)
0202 {
0203     char *options = data, *key;
0204     int ret = 0;
0205
0206     if (!options)
0207         return 0;
0208
0209     ret = security_sb_eat_lsm_opts(options, &fc->security);
0210     if (ret)
0211         return ret;
0212
0213     while ((key = strsep(&options, ",")) != NULL) {
0214         if (*key) {
0215             size_t v_len = 0;
0216             char *value = strchr(key, '=');
0217
0218             if (value) {
0219                 if (value == key)
0220                     continue;
0221                 *value++ = 0;
0222                 v_len = strlen(value);
0223             }
0224             ret = vfs_parse_fs_string(fc, key, value, v_len);
0225             if (ret < 0)
0226                 break;
0227         }
0228     }
0229
0230     return ret;
0231 }
0232 EXPORT_SYMBOL(generic_parse_monolithic);
0233
0234 /**
0235  * alloc_fs_context - Create a filesystem context.
0236  * @fs_type: The filesystem type.
0237  * @reference: The dentry from which this one derives (or NULL)
0238  * @sb_flags: Filesystem/superblock flags (SB_*)
0239  * @sb_flags_mask: Applicable members of @sb_flags
0240  * @purpose: The purpose that this configuration shall be used for.
0241  *
0242  * Open a filesystem and create a mount context.  The mount context is
0243  * initialised with the supplied flags and, if a submount/automount from
0244  * another superblock (referred to by @reference) is supplied, may have
0245  * parameters such as namespaces copied across from that superblock.
0246  */
0247 static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
0248                       struct dentry *reference,
0249                       unsigned int sb_flags,
0250                       unsigned int sb_flags_mask,
0251                       enum fs_context_purpose purpose)
0252 {
0253     int (*init_fs_context)(struct fs_context *);
0254     struct fs_context *fc;
0255     int ret = -ENOMEM;
0256
0257     fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL_ACCOUNT);
0258     if (!fc)
0259         return ERR_PTR(-ENOMEM);
0260
0261     fc->purpose = purpose;
0262     fc->sb_flags    = sb_flags;
0263     fc->sb_flags_mask = sb_flags_mask;
0264     fc->fs_type = get_filesystem(fs_type);
0265     fc->cred    = get_current_cred();
0266     fc->net_ns  = get_net(current->nsproxy->net_ns);
0267     fc->log.prefix  = fs_type->name;
0268
0269     mutex_init(&fc->uapi_mutex);
0270
0271     switch (purpose) {
0272     case FS_CONTEXT_FOR_MOUNT:
0273         fc->user_ns = get_user_ns(fc->cred->user_ns);
0274         break;
0275     case FS_CONTEXT_FOR_SUBMOUNT:
0276         fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
0277         break;
0278     case FS_CONTEXT_FOR_RECONFIGURE:
0279         atomic_inc(&reference->d_sb->s_active);
0280         fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
0281         fc->root = dget(reference);
0282         break;
0283     }
0284
0285     /* TODO: Make all filesystems support this unconditionally */
0286     init_fs_context = fc->fs_type->init_fs_context;
0287     if (!init_fs_context)
0288         init_fs_context = legacy_init_fs_context;
0289
0290     ret = init_fs_context(fc);
0291     if (ret < 0)
0292         goto err_fc;
0293     fc->need_free = true;
0294     return fc;
0295
0296 err_fc:
0297     put_fs_context(fc);
0298     return ERR_PTR(ret);
0299 }
0300
0301 struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
0302                     unsigned int sb_flags)
0303 {
0304     return alloc_fs_context(fs_type, NULL, sb_flags, 0,
0305                     FS_CONTEXT_FOR_MOUNT);
0306 }
0307 EXPORT_SYMBOL(fs_context_for_mount);
0308
0309 struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
0310                     unsigned int sb_flags,
0311                     unsigned int sb_flags_mask)
0312 {
0313     return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
0314                 sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
0315 }
0316 EXPORT_SYMBOL(fs_context_for_reconfigure);
0317
0318 struct fs_context *fs_context_for_submount(struct file_system_type *type,
0319                        struct dentry *reference)
0320 {
0321     return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
0322 }
0323 EXPORT_SYMBOL(fs_context_for_submount);
0324
0325 void fc_drop_locked(struct fs_context *fc)
0326 {
0327     struct super_block *sb = fc->root->d_sb;
0328     dput(fc->root);
0329     fc->root = NULL;
0330     deactivate_locked_super(sb);
0331 }
0332
0333 static void legacy_fs_context_free(struct fs_context *fc);
0334
0335 /**
0336  * vfs_dup_fc_config: Duplicate a filesystem context.
0337  * @src_fc: The context to copy.
0338  */
0339 struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
0340 {
0341     struct fs_context *fc;
0342     int ret;
0343
0344     if (!src_fc->ops->dup)
0345         return ERR_PTR(-EOPNOTSUPP);
0346
0347     fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
0348     if (!fc)
0349         return ERR_PTR(-ENOMEM);
0350
0351     mutex_init(&fc->uapi_mutex);
0352
0353     fc->fs_private  = NULL;
0354     fc->s_fs_info   = NULL;
0355     fc->source  = NULL;
0356     fc->security    = NULL;
0357     get_filesystem(fc->fs_type);
0358     get_net(fc->net_ns);
0359     get_user_ns(fc->user_ns);
0360     get_cred(fc->cred);
0361     if (fc->log.log)
0362         refcount_inc(&fc->log.log->usage);
0363
0364     /* Can't call put until we've called ->dup */
0365     ret = fc->ops->dup(fc, src_fc);
0366     if (ret < 0)
0367         goto err_fc;
0368
0369     ret = security_fs_context_dup(fc, src_fc);
0370     if (ret < 0)
0371         goto err_fc;
0372     return fc;
0373
0374 err_fc:
0375     put_fs_context(fc);
0376     return ERR_PTR(ret);
0377 }
0378 EXPORT_SYMBOL(vfs_dup_fs_context);
0379
0380 /**
0381  * logfc - Log a message to a filesystem context
0382  * @fc: The filesystem context to log to.
0383  * @fmt: The format of the buffer.
0384  */
0385 void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...)
0386 {
0387     va_list va;
0388     struct va_format vaf = {.fmt = fmt, .va = &va};
0389
0390     va_start(va, fmt);
0391     if (!log) {
0392         switch (level) {
0393         case 'w':
0394             printk(KERN_WARNING "%s%s%pV\n", prefix ? prefix : "",
0395                         prefix ? ": " : "", &vaf);
0396             break;
0397         case 'e':
0398             printk(KERN_ERR "%s%s%pV\n", prefix ? prefix : "",
0399                         prefix ? ": " : "", &vaf);
0400             break;
0401         default:
0402             printk(KERN_NOTICE "%s%s%pV\n", prefix ? prefix : "",
0403                         prefix ? ": " : "", &vaf);
0404             break;
0405         }
0406     } else {
0407         unsigned int logsize = ARRAY_SIZE(log->buffer);
0408         u8 index;
0409         char *q = kasprintf(GFP_KERNEL, "%c %s%s%pV\n", level,
0410                         prefix ? prefix : "",
0411                         prefix ? ": " : "", &vaf);
0412
0413         index = log->head & (logsize - 1);
0414         BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
0415                  sizeof(log->tail) != sizeof(u8));
0416         if ((u8)(log->head - log->tail) == logsize) {
0417             /* The buffer is full, discard the oldest message */
0418             if (log->need_free & (1 << index))
0419                 kfree(log->buffer[index]);
0420             log->tail++;
0421         }
0422
0423         log->buffer[index] = q ? q : "OOM: Can't store error string";
0424         if (q)
0425             log->need_free |= 1 << index;
0426         else
0427             log->need_free &= ~(1 << index);
0428         log->head++;
0429     }
0430     va_end(va);
0431 }
0432 EXPORT_SYMBOL(logfc);
0433
0434 /*
0435  * Free a logging structure.
0436  */
0437 static void put_fc_log(struct fs_context *fc)
0438 {
0439     struct fc_log *log = fc->log.log;
0440     int i;
0441
0442     if (log) {
0443         if (refcount_dec_and_test(&log->usage)) {
0444             fc->log.log = NULL;
0445             for (i = 0; i <= 7; i++)
0446                 if (log->need_free & (1 << i))
0447                     kfree(log->buffer[i]);
0448             kfree(log);
0449         }
0450     }
0451 }
0452
0453 /**
0454  * put_fs_context - Dispose of a superblock configuration context.
0455  * @fc: The context to dispose of.
0456  */
0457 void put_fs_context(struct fs_context *fc)
0458 {
0459     struct super_block *sb;
0460
0461     if (fc->root) {
0462         sb = fc->root->d_sb;
0463         dput(fc->root);
0464         fc->root = NULL;
0465         deactivate_super(sb);
0466     }
0467
0468     if (fc->need_free && fc->ops && fc->ops->free)
0469         fc->ops->free(fc);
0470
0471     security_free_mnt_opts(&fc->security);
0472     put_net(fc->net_ns);
0473     put_user_ns(fc->user_ns);
0474     put_cred(fc->cred);
0475     put_fc_log(fc);
0476     put_filesystem(fc->fs_type);
0477     kfree(fc->source);
0478     kfree(fc);
0479 }
0480 EXPORT_SYMBOL(put_fs_context);
0481
0482 /*
0483  * Free the config for a filesystem that doesn't support fs_context.
0484  */
0485 static void legacy_fs_context_free(struct fs_context *fc)
0486 {
0487     struct legacy_fs_context *ctx = fc->fs_private;
0488
0489     if (ctx) {
0490         if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
0491             kfree(ctx->legacy_data);
0492         kfree(ctx);
0493     }
0494 }
0495
0496 /*
0497  * Duplicate a legacy config.
0498  */
0499 static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
0500 {
0501     struct legacy_fs_context *ctx;
0502     struct legacy_fs_context *src_ctx = src_fc->fs_private;
0503
0504     ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
0505     if (!ctx)
0506         return -ENOMEM;
0507
0508     if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
0509         ctx->legacy_data = kmemdup(src_ctx->legacy_data,
0510                        src_ctx->data_size, GFP_KERNEL);
0511         if (!ctx->legacy_data) {
0512             kfree(ctx);
0513             return -ENOMEM;
0514         }
0515     }
0516
0517     fc->fs_private = ctx;
0518     return 0;
0519 }
0520
0521 /*
0522  * Add a parameter to a legacy config.  We build up a comma-separated list of
0523  * options.
0524  */
0525 static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
0526 {
0527     struct legacy_fs_context *ctx = fc->fs_private;
0528     unsigned int size = ctx->data_size;
0529     size_t len = 0;
0530     int ret;
0531
0532     ret = vfs_parse_fs_param_source(fc, param);
0533     if (ret != -ENOPARAM)
0534         return ret;
0535
0536     if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS)
0537         return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options");
0538
0539     switch (param->type) {
0540     case fs_value_is_string:
0541         len = 1 + param->size;
0542         fallthrough;
0543     case fs_value_is_flag:
0544         len += strlen(param->key);
0545         break;
0546     default:
0547         return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported",
0548                   param->key);
0549     }
0550
0551     if (size + len + 2 > PAGE_SIZE)
0552         return invalf(fc, "VFS: Legacy: Cumulative options too large");
0553     if (strchr(param->key, ',') ||
0554         (param->type == fs_value_is_string &&
0555          memchr(param->string, ',', param->size)))
0556         return invalf(fc, "VFS: Legacy: Option '%s' contained comma",
0557                   param->key);
0558     if (!ctx->legacy_data) {
0559         ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL);
0560         if (!ctx->legacy_data)
0561             return -ENOMEM;
0562     }
0563
0564     ctx->legacy_data[size++] = ',';
0565     len = strlen(param->key);
0566     memcpy(ctx->legacy_data + size, param->key, len);
0567     size += len;
0568     if (param->type == fs_value_is_string) {
0569         ctx->legacy_data[size++] = '=';
0570         memcpy(ctx->legacy_data + size, param->string, param->size);
0571         size += param->size;
0572     }
0573     ctx->legacy_data[size] = '\0';
0574     ctx->data_size = size;
0575     ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;
0576     return 0;
0577 }
0578
0579 /*
0580  * Add monolithic mount data.
0581  */
0582 static int legacy_parse_monolithic(struct fs_context *fc, void *data)
0583 {
0584     struct legacy_fs_context *ctx = fc->fs_private;
0585
0586     if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {
0587         pr_warn("VFS: Can't mix monolithic and individual options\n");
0588         return -EINVAL;
0589     }
0590
0591     ctx->legacy_data = data;
0592     ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;
0593     if (!ctx->legacy_data)
0594         return 0;
0595
0596     if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)
0597         return 0;
0598     return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);
0599 }
0600
0601 /*
0602  * Get a mountable root with the legacy mount command.
0603  */
0604 static int legacy_get_tree(struct fs_context *fc)
0605 {
0606     struct legacy_fs_context *ctx = fc->fs_private;
0607     struct super_block *sb;
0608     struct dentry *root;
0609
0610     root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,
0611                       fc->source, ctx->legacy_data);
0612     if (IS_ERR(root))
0613         return PTR_ERR(root);
0614
0615     sb = root->d_sb;
0616     BUG_ON(!sb);
0617
0618     fc->root = root;
0619     return 0;
0620 }
0621
0622 /*
0623  * Handle remount.
0624  */
0625 static int legacy_reconfigure(struct fs_context *fc)
0626 {
0627     struct legacy_fs_context *ctx = fc->fs_private;
0628     struct super_block *sb = fc->root->d_sb;
0629
0630     if (!sb->s_op->remount_fs)
0631         return 0;
0632
0633     return sb->s_op->remount_fs(sb, &fc->sb_flags,
0634                     ctx ? ctx->legacy_data : NULL);
0635 }
0636
0637 const struct fs_context_operations legacy_fs_context_ops = {
0638     .free           = legacy_fs_context_free,
0639     .dup            = legacy_fs_context_dup,
0640     .parse_param        = legacy_parse_param,
0641     .parse_monolithic   = legacy_parse_monolithic,
0642     .get_tree       = legacy_get_tree,
0643     .reconfigure        = legacy_reconfigure,
0644 };
0645
0646 /*
0647  * Initialise a legacy context for a filesystem that doesn't support
0648  * fs_context.
0649  */
0650 static int legacy_init_fs_context(struct fs_context *fc)
0651 {
0652     fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL_ACCOUNT);
0653     if (!fc->fs_private)
0654         return -ENOMEM;
0655     fc->ops = &legacy_fs_context_ops;
0656     return 0;
0657 }
0658
0659 int parse_monolithic_mount_data(struct fs_context *fc, void *data)
0660 {
0661     int (*monolithic_mount_data)(struct fs_context *, void *);
0662
0663     monolithic_mount_data = fc->ops->parse_monolithic;
0664     if (!monolithic_mount_data)
0665         monolithic_mount_data = generic_parse_monolithic;
0666
0667     return monolithic_mount_data(fc, data);
0668 }
0669
0670 /*
0671  * Clean up a context after performing an action on it and put it into a state
0672  * from where it can be used to reconfigure a superblock.
0673  *
0674  * Note that here we do only the parts that can't fail; the rest is in
0675  * finish_clean_context() below and in between those fs_context is marked
0676  * FS_CONTEXT_AWAITING_RECONF.  The reason for splitup is that after
0677  * successful mount or remount we need to report success to userland.
0678  * Trying to do full reinit (for the sake of possible subsequent remount)
0679  * and failing to allocate memory would've put us into a nasty situation.
0680  * So here we only discard the old state and reinitialization is left
0681  * until we actually try to reconfigure.
0682  */
0683 void vfs_clean_context(struct fs_context *fc)
0684 {
0685     if (fc->need_free && fc->ops && fc->ops->free)
0686         fc->ops->free(fc);
0687     fc->need_free = false;
0688     fc->fs_private = NULL;
0689     fc->s_fs_info = NULL;
0690     fc->sb_flags = 0;
0691     security_free_mnt_opts(&fc->security);
0692     kfree(fc->source);
0693     fc->source = NULL;
0694
0695     fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;
0696     fc->phase = FS_CONTEXT_AWAITING_RECONF;
0697 }
0698
0699 int finish_clean_context(struct fs_context *fc)
0700 {
0701     int error;
0702
0703     if (fc->phase != FS_CONTEXT_AWAITING_RECONF)
0704         return 0;
0705
0706     if (fc->fs_type->init_fs_context)
0707         error = fc->fs_type->init_fs_context(fc);
0708     else
0709         error = legacy_init_fs_context(fc);
0710     if (unlikely(error)) {
0711         fc->phase = FS_CONTEXT_FAILED;
0712         return error;
0713     }
0714     fc->need_free = true;
0715     fc->phase = FS_CONTEXT_RECONF_PARAMS;
0716     return 0;
0717 }