diff options
Diffstat (limited to 'fs/fs_context.c')
| -rw-r--r-- | fs/fs_context.c | 642 |
1 files changed, 642 insertions, 0 deletions
diff --git a/fs/fs_context.c b/fs/fs_context.c new file mode 100644 index 000000000000..87e3546b9a52 --- /dev/null +++ b/fs/fs_context.c @@ -0,0 +1,642 @@ +/* Provide a way to create a superblock configuration context within the kernel + * that allows a superblock to be set up prior to mounting. + * + * Copyright (C) 2017 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public Licence + * as published by the Free Software Foundation; either version + * 2 of the Licence, or (at your option) any later version. + */ + +#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt +#include <linux/fs_context.h> +#include <linux/fs_parser.h> +#include <linux/fs.h> +#include <linux/mount.h> +#include <linux/nsproxy.h> +#include <linux/slab.h> +#include <linux/magic.h> +#include <linux/security.h> +#include <linux/mnt_namespace.h> +#include <linux/pid_namespace.h> +#include <linux/user_namespace.h> +#include <net/net_namespace.h> +#include "mount.h" +#include "internal.h" + +enum legacy_fs_param { + LEGACY_FS_UNSET_PARAMS, + LEGACY_FS_MONOLITHIC_PARAMS, + LEGACY_FS_INDIVIDUAL_PARAMS, +}; + +struct legacy_fs_context { + char *legacy_data; /* Data page for legacy filesystems */ + size_t data_size; + enum legacy_fs_param param_type; +}; + +static int legacy_init_fs_context(struct fs_context *fc); + +static const struct constant_table common_set_sb_flag[] = { + { "dirsync", SB_DIRSYNC }, + { "lazytime", SB_LAZYTIME }, + { "mand", SB_MANDLOCK }, + { "posixacl", SB_POSIXACL }, + { "ro", SB_RDONLY }, + { "sync", SB_SYNCHRONOUS }, +}; + +static const struct constant_table common_clear_sb_flag[] = { + { "async", SB_SYNCHRONOUS }, + { "nolazytime", SB_LAZYTIME }, + { "nomand", SB_MANDLOCK }, + { "rw", SB_RDONLY }, + { "silent", SB_SILENT }, +}; + +static const char *const forbidden_sb_flag[] = { + "bind", + "dev", + "exec", + "move", + "noatime", + "nodev", + "nodiratime", + "noexec", + "norelatime", + "nostrictatime", + "nosuid", + "private", + "rec", + "relatime", + "remount", + "shared", + "slave", + "strictatime", + "suid", + "unbindable", +}; + +/* + * Check for a common mount option that manipulates s_flags. + */ +static int vfs_parse_sb_flag(struct fs_context *fc, const char *key) +{ + unsigned int token; + unsigned int i; + + for (i = 0; i < ARRAY_SIZE(forbidden_sb_flag); i++) + if (strcmp(key, forbidden_sb_flag[i]) == 0) + return -EINVAL; + + token = lookup_constant(common_set_sb_flag, key, 0); + if (token) { + fc->sb_flags |= token; + fc->sb_flags_mask |= token; + return 0; + } + + token = lookup_constant(common_clear_sb_flag, key, 0); + if (token) { + fc->sb_flags &= ~token; + fc->sb_flags_mask |= token; + return 0; + } + + return -ENOPARAM; +} + +/** + * vfs_parse_fs_param - Add a single parameter to a superblock config + * @fc: The filesystem context to modify + * @param: The parameter + * + * A single mount option in string form is applied to the filesystem context + * being set up. Certain standard options (for example "ro") are translated + * into flag bits without going to the filesystem. The active security module + * is allowed to observe and poach options. Any other options are passed over + * to the filesystem to parse. + * + * This may be called multiple times for a context. + * + * Returns 0 on success and a negative error code on failure. In the event of + * failure, supplementary error information may have been set. + */ +int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param) +{ + int ret; + + if (!param->key) + return invalf(fc, "Unnamed parameter\n"); + + ret = vfs_parse_sb_flag(fc, param->key); + if (ret != -ENOPARAM) + return ret; + + ret = security_fs_context_parse_param(fc, param); + if (ret != -ENOPARAM) + /* Param belongs to the LSM or is disallowed by the LSM; so + * don't pass to the FS. + */ + return ret; + + if (fc->ops->parse_param) { + ret = fc->ops->parse_param(fc, param); + if (ret != -ENOPARAM) + return ret; + } + + /* If the filesystem doesn't take any arguments, give it the + * default handling of source. + */ + if (strcmp(param->key, "source") == 0) { + if (param->type != fs_value_is_string) + return invalf(fc, "VFS: Non-string source"); + if (fc->source) + return invalf(fc, "VFS: Multiple sources"); + fc->source = param->string; + param->string = NULL; + return 0; + } + + return invalf(fc, "%s: Unknown parameter '%s'", + fc->fs_type->name, param->key); +} +EXPORT_SYMBOL(vfs_parse_fs_param); + +/** + * vfs_parse_fs_string - Convenience function to just parse a string. + */ +int vfs_parse_fs_string(struct fs_context *fc, const char *key, + const char *value, size_t v_size) +{ + int ret; + + struct fs_parameter param = { + .key = key, + .type = fs_value_is_string, + .size = v_size, + }; + + if (v_size > 0) { + param.string = kmemdup_nul(value, v_size, GFP_KERNEL); + if (!param.string) + return -ENOMEM; + } + + ret = vfs_parse_fs_param(fc, ¶m); + kfree(param.string); + return ret; +} +EXPORT_SYMBOL(vfs_parse_fs_string); + +/** + * generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data + * @ctx: The superblock configuration to fill in. + * @data: The data to parse + * + * Parse a blob of data that's in key[=val][,key[=val]]* form. This can be + * called from the ->monolithic_mount_data() fs_context operation. + * + * Returns 0 on success or the error returned by the ->parse_option() fs_context + * operation on failure. + */ +int generic_parse_monolithic(struct fs_context *fc, void *data) +{ + char *options = data, *key; + int ret = 0; + + if (!options) + return 0; + + ret = security_sb_eat_lsm_opts(options, &fc->security); + if (ret) + return ret; + + while ((key = strsep(&options, ",")) != NULL) { + if (*key) { + size_t v_len = 0; + char *value = strchr(key, '='); + + if (value) { + if (value == key) + continue; + *value++ = 0; + v_len = strlen(value); + } + ret = vfs_parse_fs_string(fc, key, value, v_len); + if (ret < 0) + break; + } + } + + return ret; +} +EXPORT_SYMBOL(generic_parse_monolithic); + +/** + * alloc_fs_context - Create a filesystem context. + * @fs_type: The filesystem type. + * @reference: The dentry from which this one derives (or NULL) + * @sb_flags: Filesystem/superblock flags (SB_*) + * @sb_flags_mask: Applicable members of @sb_flags + * @purpose: The purpose that this configuration shall be used for. + * + * Open a filesystem and create a mount context. The mount context is + * initialised with the supplied flags and, if a submount/automount from + * another superblock (referred to by @reference) is supplied, may have + * parameters such as namespaces copied across from that superblock. + */ +static struct fs_context *alloc_fs_context(struct file_system_type *fs_type, + struct dentry *reference, + unsigned int sb_flags, + unsigned int sb_flags_mask, + enum fs_context_purpose purpose) +{ + int (*init_fs_context)(struct fs_context *); + struct fs_context *fc; + int ret = -ENOMEM; + + fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL); + if (!fc) + return ERR_PTR(-ENOMEM); + + fc->purpose = purpose; + fc->sb_flags = sb_flags; + fc->sb_flags_mask = sb_flags_mask; + fc->fs_type = get_filesystem(fs_type); + fc->cred = get_current_cred(); + fc->net_ns = get_net(current->nsproxy->net_ns); + + switch (purpose) { + case FS_CONTEXT_FOR_MOUNT: + fc->user_ns = get_user_ns(fc->cred->user_ns); + break; + case FS_CONTEXT_FOR_SUBMOUNT: + fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); + break; + case FS_CONTEXT_FOR_RECONFIGURE: + /* We don't pin any namespaces as the superblock's + * subscriptions cannot be changed at this point. + */ + atomic_inc(&reference->d_sb->s_active); + fc->root = dget(reference); + break; + } + + /* TODO: Make all filesystems support this unconditionally */ + init_fs_context = fc->fs_type->init_fs_context; + if (!init_fs_context) + init_fs_context = legacy_init_fs_context; + + ret = init_fs_context(fc); + if (ret < 0) + goto err_fc; + fc->need_free = true; + return fc; + +err_fc: + put_fs_context(fc); + return ERR_PTR(ret); +} + +struct fs_context *fs_context_for_mount(struct file_system_type *fs_type, + unsigned int sb_flags) +{ + return alloc_fs_context(fs_type, NULL, sb_flags, 0, + FS_CONTEXT_FOR_MOUNT); +} +EXPORT_SYMBOL(fs_context_for_mount); + +struct fs_context *fs_context_for_reconfigure(struct dentry *dentry, + unsigned int sb_flags, + unsigned int sb_flags_mask) +{ + return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags, + sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE); +} +EXPORT_SYMBOL(fs_context_for_reconfigure); + +struct fs_context *fs_context_for_submount(struct file_system_type *type, + struct dentry *reference) +{ + return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT); +} +EXPORT_SYMBOL(fs_context_for_submount); + +void fc_drop_locked(struct fs_context *fc) +{ + struct super_block *sb = fc->root->d_sb; + dput(fc->root); + fc->root = NULL; + deactivate_locked_super(sb); +} + +static void legacy_fs_context_free(struct fs_context *fc); + +/** + * vfs_dup_fc_config: Duplicate a filesystem context. + * @src_fc: The context to copy. + */ +struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc) +{ + struct fs_context *fc; + int ret; + + if (!src_fc->ops->dup) + return ERR_PTR(-EOPNOTSUPP); + + fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL); + if (!fc) + return ERR_PTR(-ENOMEM); + + fc->fs_private = NULL; + fc->s_fs_info = NULL; + fc->source = NULL; + fc->security = NULL; + get_filesystem(fc->fs_type); + get_net(fc->net_ns); + get_user_ns(fc->user_ns); + get_cred(fc->cred); + + /* Can't call put until we've called ->dup */ + ret = fc->ops->dup(fc, src_fc); + if (ret < 0) + goto err_fc; + + ret = security_fs_context_dup(fc, src_fc); + if (ret < 0) + goto err_fc; + return fc; + +err_fc: + put_fs_context(fc); + return ERR_PTR(ret); +} +EXPORT_SYMBOL(vfs_dup_fs_context); + +#ifdef CONFIG_PRINTK +/** + * logfc - Log a message to a filesystem context + * @fc: The filesystem context to log to. + * @fmt: The format of the buffer. + */ +void logfc(struct fs_context *fc, const char *fmt, ...) +{ + va_list va; + + va_start(va, fmt); + + switch (fmt[0]) { + case 'w': + vprintk_emit(0, LOGLEVEL_WARNING, NULL, 0, fmt, va); + break; + case 'e': + vprintk_emit(0, LOGLEVEL_ERR, NULL, 0, fmt, va); + break; + default: + vprintk_emit(0, LOGLEVEL_NOTICE, NULL, 0, fmt, va); + break; + } + + pr_cont("\n"); + va_end(va); +} +EXPORT_SYMBOL(logfc); +#endif + +/** + * put_fs_context - Dispose of a superblock configuration context. + * @fc: The context to dispose of. + */ +void put_fs_context(struct fs_context *fc) +{ + struct super_block *sb; + + if (fc->root) { + sb = fc->root->d_sb; + dput(fc->root); + fc->root = NULL; + deactivate_super(sb); + } + + if (fc->need_free && fc->ops && fc->ops->free) + fc->ops->free(fc); + + security_free_mnt_opts(&fc->security); + put_net(fc->net_ns); + put_user_ns(fc->user_ns); + put_cred(fc->cred); + kfree(fc->subtype); + put_filesystem(fc->fs_type); + kfree(fc->source); + kfree(fc); +} +EXPORT_SYMBOL(put_fs_context); + +/* + * Free the config for a filesystem that doesn't support fs_context. + */ +static void legacy_fs_context_free(struct fs_context *fc) +{ + struct legacy_fs_context *ctx = fc->fs_private; + + if (ctx) { + if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) + kfree(ctx->legacy_data); + kfree(ctx); + } +} + +/* + * Duplicate a legacy config. + */ +static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc) +{ + struct legacy_fs_context *ctx; + struct legacy_fs_context *src_ctx = src_fc->fs_private; + + ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL); + if (!ctx) + return -ENOMEM; + + if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) { + ctx->legacy_data = kmemdup(src_ctx->legacy_data, + src_ctx->data_size, GFP_KERNEL); + if (!ctx->legacy_data) { + kfree(ctx); + return -ENOMEM; + } + } + + fc->fs_private = ctx; + return 0; +} + +/* + * Add a parameter to a legacy config. We build up a comma-separated list of + * options. + */ +static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param) +{ + struct legacy_fs_context *ctx = fc->fs_private; + unsigned int size = ctx->data_size; + size_t len = 0; + + if (strcmp(param->key, "source") == 0) { + if (param->type != fs_value_is_string) + return invalf(fc, "VFS: Legacy: Non-string source"); + if (fc->source) + return invalf(fc, "VFS: Legacy: Multiple sources"); + fc->source = param->string; + param->string = NULL; + return 0; + } + + if ((fc->fs_type->fs_flags & FS_HAS_SUBTYPE) && + strcmp(param->key, "subtype") == 0) { + if (param->type != fs_value_is_string) + return invalf(fc, "VFS: Legacy: Non-string subtype"); + if (fc->subtype) + return invalf(fc, "VFS: Legacy: Multiple subtype"); + fc->subtype = param->string; + param->string = NULL; + return 0; + } + + if (ctx->param_type == LEGACY_FS_MONOLITHIC_PARAMS) + return invalf(fc, "VFS: Legacy: Can't mix monolithic and individual options"); + + switch (param->type) { + case fs_value_is_string: + len = 1 + param->size; + /* Fall through */ + case fs_value_is_flag: + len += strlen(param->key); + break; + default: + return invalf(fc, "VFS: Legacy: Parameter type for '%s' not supported", + param->key); + } + + if (len > PAGE_SIZE - 2 - size) + return invalf(fc, "VFS: Legacy: Cumulative options too large"); + if (strchr(param->key, ',') || + (param->type == fs_value_is_string && + memchr(param->string, ',', param->size))) + return invalf(fc, "VFS: Legacy: Option '%s' contained comma", + param->key); + if (!ctx->legacy_data) { + ctx->legacy_data = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!ctx->legacy_data) + return -ENOMEM; + } + + ctx->legacy_data[size++] = ','; + len = strlen(param->key); + memcpy(ctx->legacy_data + size, param->key, len); + size += len; + if (param->type == fs_value_is_string) { + ctx->legacy_data[size++] = '='; + memcpy(ctx->legacy_data + size, param->string, param->size); + size += param->size; + } + ctx->legacy_data[size] = '\0'; + ctx->data_size = size; + ctx->param_type = LEGACY_FS_INDIVIDUAL_PARAMS; + return 0; +} + +/* + * Add monolithic mount data. + */ +static int legacy_parse_monolithic(struct fs_context *fc, void *data) +{ + struct legacy_fs_context *ctx = fc->fs_private; + + if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) { + pr_warn("VFS: Can't mix monolithic and individual options\n"); + return -EINVAL; + } + + ctx->legacy_data = data; + ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS; + if (!ctx->legacy_data) + return 0; + + if (fc->fs_type->fs_flags & FS_BINARY_MOUNTDATA) + return 0; + return security_sb_eat_lsm_opts(ctx->legacy_data, &fc->security); +} + +/* + * Get a mountable root with the legacy mount command. + */ +static int legacy_get_tree(struct fs_context *fc) +{ + struct legacy_fs_context *ctx = fc->fs_private; + struct super_block *sb; + struct dentry *root; + + root = fc->fs_type->mount(fc->fs_type, fc->sb_flags, + fc->source, ctx->legacy_data); + if (IS_ERR(root)) + return PTR_ERR(root); + + sb = root->d_sb; + BUG_ON(!sb); + + fc->root = root; + return 0; +} + +/* + * Handle remount. + */ +static int legacy_reconfigure(struct fs_context *fc) +{ + struct legacy_fs_context *ctx = fc->fs_private; + struct super_block *sb = fc->root->d_sb; + + if (!sb->s_op->remount_fs) + return 0; + + return sb->s_op->remount_fs(sb, &fc->sb_flags, + ctx ? ctx->legacy_data : NULL); +} + +const struct fs_context_operations legacy_fs_context_ops = { + .free = legacy_fs_context_free, + .dup = legacy_fs_context_dup, + .parse_param = legacy_parse_param, + .parse_monolithic = legacy_parse_monolithic, + .get_tree = legacy_get_tree, + .reconfigure = legacy_reconfigure, +}; + +/* + * Initialise a legacy context for a filesystem that doesn't support + * fs_context. + */ +static int legacy_init_fs_context(struct fs_context *fc) +{ + fc->fs_private = kzalloc(sizeof(struct legacy_fs_context), GFP_KERNEL); + if (!fc->fs_private) + return -ENOMEM; + fc->ops = &legacy_fs_context_ops; + return 0; +} + +int parse_monolithic_mount_data(struct fs_context *fc, void *data) +{ + int (*monolithic_mount_data)(struct fs_context *, void *); + + monolithic_mount_data = fc->ops->parse_monolithic; + if (!monolithic_mount_data) + monolithic_mount_data = generic_parse_monolithic; + + return monolithic_mount_data(fc, data); +} |