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1// SPDX-License-Identifier: GPL-2.0-or-later2/* Provide a way to create a superblock configuration context within the kernel3 * 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 ": " fmt10#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 27enum legacy_fs_param {28 LEGACY_FS_UNSET_PARAMS,29 LEGACY_FS_MONOLITHIC_PARAMS,30 LEGACY_FS_INDIVIDUAL_PARAMS,31};32 33struct 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 39static int legacy_init_fs_context(struct fs_context *fc);40 41static 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 50static 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 */61static 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 parameter84 * @fc: The filesystem context to modify85 * @param: The parameter86 *87 * This is a simple helper for filesystems to verify that the "source" they88 * accept is sane.89 *90 * Returns 0 on success, -ENOPARAM if this is not "source" parameter, and91 * -EINVAL otherwise. In the event of failure, supplementary error information92 * is logged.93 */94int 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}109EXPORT_SYMBOL(vfs_parse_fs_param_source);110 111/**112 * vfs_parse_fs_param - Add a single parameter to a superblock config113 * @fc: The filesystem context to modify114 * @param: The parameter115 *116 * A single mount option in string form is applied to the filesystem context117 * being set up. Certain standard options (for example "ro") are translated118 * into flag bits without going to the filesystem. The active security module119 * is allowed to observe and poach options. Any other options are passed over120 * 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 of125 * failure, supplementary error information may have been set.126 */127int 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; so141 * 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 the152 * 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}161EXPORT_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 */170int 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}192EXPORT_SYMBOL(vfs_parse_fs_string);193 194/**195 * vfs_parse_monolithic_sep - Parse key[=val][,key[=val]]* mount data196 * @fc: The superblock configuration to fill in.197 * @data: The data to parse198 * @sep: callback for separating next option199 *200 * Parse a blob of data that's in key[=val][,key[=val]]* form with a custom201 * option separator callback.202 *203 * Returns 0 on success or the error returned by the ->parse_option() fs_context204 * operation on failure.205 */206int 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 (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}238EXPORT_SYMBOL(vfs_parse_monolithic_sep);239 240static 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 data247 * @fc: The superblock configuration to fill in.248 * @data: The data to parse249 *250 * Parse a blob of data that's in key[=val][,key[=val]]* form. This can be251 * called from the ->monolithic_mount_data() fs_context operation.252 *253 * Returns 0 on success or the error returned by the ->parse_option() fs_context254 * operation on failure.255 */256int generic_parse_monolithic(struct fs_context *fc, void *data)257{258 return vfs_parse_monolithic_sep(fc, data, vfs_parse_comma_sep);259}260EXPORT_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_flags268 * @purpose: The purpose that this configuration shall be used for.269 *270 * Open a filesystem and create a mount context. The mount context is271 * initialised with the supplied flags and, if a submount/automount from272 * another superblock (referred to by @reference) is supplied, may have273 * parameters such as namespaces copied across from that superblock.274 */275static HWJS_SUSPENDS 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 324err_fc:325 put_fs_context(fc);326 return ERR_PTR(ret);327}328 329struct 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}335EXPORT_SYMBOL(fs_context_for_mount);336 337struct 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}344EXPORT_SYMBOL(fs_context_for_reconfigure);345 346/**347 * fs_context_for_submount: allocate a new fs_context for a submount348 * @type: file_system_type of the new context349 * @reference: reference dentry from which to copy relevant info350 *351 * Allocate a new fs_context suitable for a submount. This also ensures that352 * the fc->security object is inherited from @reference (if needed).353 */354struct 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}372EXPORT_SYMBOL(fs_context_for_submount);373 374void 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 382static 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 */388struct 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 423err_fc:424 put_fs_context(fc);425 return ERR_PTR(ret);426}427EXPORT_SYMBOL(vfs_dup_fs_context);428 429/**430 * logfc - Log a message to a filesystem context431 * @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 */436void 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 default:453 printk(KERN_NOTICE "%s%s%pV\n", prefix ? prefix : "",454 prefix ? ": " : "", &vaf);455 break;456 }457 } else {458 unsigned int logsize = ARRAY_SIZE(log->buffer);459 u8 index;460 char *q = kasprintf(GFP_KERNEL, "%c %s%s%pV\n", level,461 prefix ? prefix : "",462 prefix ? ": " : "", &vaf);463 464 index = log->head & (logsize - 1);465 BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||466 sizeof(log->tail) != sizeof(u8));467 if ((u8)(log->head - log->tail) == logsize) {468 /* The buffer is full, discard the oldest message */469 if (log->need_free & (1 << index))470 kfree(log->buffer[index]);471 log->tail++;472 }473 474 log->buffer[index] = q ? q : "OOM: Can't store error string";475 if (q)476 log->need_free |= 1 << index;477 else478 log->need_free &= ~(1 << index);479 log->head++;480 }481 va_end(va);482}483EXPORT_SYMBOL(logfc);484 485/*486 * Free a logging structure.487 */488static void put_fc_log(struct fs_context *fc)489{490 struct fc_log *log = fc->log.log;491 int i;492 493 if (log) {494 if (refcount_dec_and_test(&log->usage)) {495 fc->log.log = NULL;496 for (i = 0; i <= 7; i++)497 if (log->need_free & (1 << i))498 kfree(log->buffer[i]);499 kfree(log);500 }501 }502}503 504/**505 * put_fs_context - Dispose of a superblock configuration context.506 * @fc: The context to dispose of.507 */508void put_fs_context(struct fs_context *fc)509{510 struct super_block *sb;511 512 if (fc->root) {513 sb = fc->root->d_sb;514 dput(fc->root);515 fc->root = NULL;516 deactivate_super(sb);517 }518 519 if (fc->need_free && fc->ops && fc->ops->free)520 fc->ops->free(fc);521 522 security_free_mnt_opts(&fc->security);523 put_net(fc->net_ns);524 put_user_ns(fc->user_ns);525 put_cred(fc->cred);526 put_fc_log(fc);527 put_filesystem(fc->fs_type);528 kfree(fc->source);529 kfree(fc);530}531EXPORT_SYMBOL(put_fs_context);532 533/*534 * Free the config for a filesystem that doesn't support fs_context.535 */536static void legacy_fs_context_free(struct fs_context *fc)537{538 struct legacy_fs_context *ctx = fc->fs_private;539 540 if (ctx) {541 if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)542 kfree(ctx->legacy_data);543 kfree(ctx);544 }545}546 547/*548 * Duplicate a legacy config.549 */550static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)551{552 struct legacy_fs_context *ctx;553 struct legacy_fs_context *src_ctx = src_fc->fs_private;554 555 ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);556 if (!ctx)557 return -ENOMEM;558 559 if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {560 ctx->legacy_data = kmemdup(src_ctx->legacy_data,561 src_ctx->data_size, GFP_KERNEL);562 if (!ctx->legacy_data) {563 kfree(ctx);564 return -ENOMEM;565 }566 }567 568 fc->fs_private = ctx;569 return 0;570}571 572/*573 * Add a parameter to a legacy config. We build up a comma-separated list of574 * options.575 */576static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)577{578 struct legacy_fs_context *ctx = fc->fs_private;579 unsigned int size = ctx->data_size;580 size_t len = 0;581 int ret;582 583 ret = vfs_parse_fs_param_source(fc, param);584 if (ret != -ENOPARAM)585 return ret;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 fallthrough;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 (size + len + 2 > PAGE_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 if (size)616 ctx->legacy_data[size++] = ',';617 len = strlen(param->key);618 memcpy(ctx->legacy_data + size, param->key, len);619 size += len;620 if (param->type == fs_value_is_string) {621 ctx->legacy_data[size++] = '=';622 memcpy(ctx->legacy_data + size, param->string, param->size);623 size += param->size;624 }625 ctx->legacy_data[size] = '\0';626 ctx->data_size = size;627 ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS;628 return 0;629}630 631/*632 * Add monolithic mount data.633 */634static int legacy_parse_monolithic(struct fs_context *fc, void *data)635{636 struct legacy_fs_context *ctx = fc->fs_private;637 638 if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) {639 pr_warn("VFS: Can't mix monolithic and individual options\n");640 return -EINVAL;641 }642 643 ctx->legacy_data = data;644 ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS;645 if (!ctx->legacy_data)646 return 0;647 648 if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA)649 return 0;650 return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security);651}652 653/*654 * Get a mountable root with the legacy mount command.655 */656static int legacy_get_tree(struct fs_context *fc)657{658 struct legacy_fs_context *ctx = fc->fs_private;659 struct super_block *sb;660 struct dentry *root;661 662 root = fc->fs_type->mount(fc->fs_type, fc->sb_flags,663 fc->source, ctx->legacy_data);664 if (IS_ERR(root))665 return PTR_ERR(root);666 667 sb = root->d_sb;668 BUG_ON(!sb);669 670 fc->root = root;671 return 0;672}673 674/*675 * Handle remount.676 */677static int legacy_reconfigure(struct fs_context *fc)678{679 struct legacy_fs_context *ctx = fc->fs_private;680 struct super_block *sb = fc->root->d_sb;681 682 if (!sb->s_op->remount_fs)683 return 0;684 685 return sb->s_op->remount_fs(sb, &fc->sb_flags,686 ctx ? ctx->legacy_data : NULL);687}688 689const struct fs_context_operations legacy_fs_context_ops = {690 .free = legacy_fs_context_free,691 .dup = legacy_fs_context_dup,692 .parse_param = legacy_parse_param,693 .parse_monolithic = legacy_parse_monolithic,694 .get_tree = legacy_get_tree,695 .reconfigure = legacy_reconfigure,696};697 698/*699 * Initialise a legacy context for a filesystem that doesn't support700 * fs_context.701 */702static int legacy_init_fs_context(struct fs_context *fc)703{704 fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL_ACCOUNT);705 if (!fc->fs_private)706 return -ENOMEM;707 fc->ops = &legacy_fs_context_ops;708 return 0;709}710 711int parse_monolithic_mount_data(struct fs_context *fc, void *data)712{713 int (*monolithic_mount_data)(struct fs_context *, void *);714 715 monolithic_mount_data = fc->ops->parse_monolithic;716 if (!monolithic_mount_data)717 monolithic_mount_data = generic_parse_monolithic;718 719 return monolithic_mount_data(fc, data);720}721 722/*723 * Clean up a context after performing an action on it and put it into a state724 * from where it can be used to reconfigure a superblock.725 *726 * Note that here we do only the parts that can't fail; the rest is in727 * finish_clean_context() below and in between those fs_context is marked728 * FS_CONTEXT_AWAITING_RECONF. The reason for splitup is that after729 * successful mount or remount we need to report success to userland.730 * Trying to do full reinit (for the sake of possible subsequent remount)731 * and failing to allocate memory would've put us into a nasty situation.732 * So here we only discard the old state and reinitialization is left733 * until we actually try to reconfigure.734 */735void vfs_clean_context(struct fs_context *fc)736{737 if (fc->need_free && fc->ops && fc->ops->free)738 fc->ops->free(fc);739 fc->need_free = false;740 fc->fs_private = NULL;741 fc->s_fs_info = NULL;742 fc->sb_flags = 0;743 security_free_mnt_opts(&fc->security);744 kfree(fc->source);745 fc->source = NULL;746 fc->exclusive = false;747 748 fc->purpose = FS_CONTEXT_FOR_RECONFIGURE;749 fc->phase = FS_CONTEXT_AWAITING_RECONF;750}751 752int 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 else762 error = legacy_init_fs_context(fc);763 if (unlikely(error)) {764 fc->phase = FS_CONTEXT_FAILED;765 return error;766 }767 fc->need_free = true;768 fc->phase = FS_CONTEXT_RECONF_PARAMS;769 return 0;770}771