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fs/fs_context.c
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// SPDX-License-Identifier: GPL-2.0-or-later |
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/* 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) |
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*/ #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
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#include <linux/module.h> |
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#include <linux/fs_context.h> |
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#include <linux/fs_parser.h> |
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#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> |
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#include <asm/sections.h> |
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#include "mount.h" #include "internal.h" |
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enum legacy_fs_param { LEGACY_FS_UNSET_PARAMS, LEGACY_FS_MONOLITHIC_PARAMS, LEGACY_FS_INDIVIDUAL_PARAMS, }; |
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struct legacy_fs_context { char *legacy_data; /* Data page for legacy filesystems */ size_t data_size; |
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enum legacy_fs_param param_type; |
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}; static int legacy_init_fs_context(struct fs_context *fc); |
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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 "); 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); |
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/** * 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) { |
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int (*init_fs_context)(struct fs_context *); |
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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); |
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mutex_init(&fc->uapi_mutex); |
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switch (purpose) { case FS_CONTEXT_FOR_MOUNT: fc->user_ns = get_user_ns(fc->cred->user_ns); break; |
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case FS_CONTEXT_FOR_SUBMOUNT: fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); break; |
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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; |
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} |
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/* 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); |
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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); |
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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); |
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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); |
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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); } |
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static void legacy_fs_context_free(struct fs_context *fc); |
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/** |
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* 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); |
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mutex_init(&fc->uapi_mutex); |
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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); |
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if (fc->log) refcount_inc(&fc->log->usage); |
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/* 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); |
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/** * 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, ...) { |
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static const char store_failure[] = "OOM: Can't store error string"; struct fc_log *log = fc ? fc->log : NULL; const char *p; |
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va_list va; |
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char *q; u8 freeable; |
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va_start(va, fmt); |
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if (!strchr(fmt, '%')) { p = fmt; goto unformatted_string; |
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} |
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if (strcmp(fmt, "%s") == 0) { p = va_arg(va, const char *); goto unformatted_string; } q = kvasprintf(GFP_KERNEL, fmt, va); copied_string: if (!q) goto store_failure; freeable = 1; goto store_string; unformatted_string: if ((unsigned long)p >= (unsigned long)__start_rodata && (unsigned long)p < (unsigned long)__end_rodata) goto const_string; if (log && within_module_core((unsigned long)p, log->owner)) goto const_string; q = kstrdup(p, GFP_KERNEL); goto copied_string; store_failure: p = store_failure; const_string: q = (char *)p; freeable = 0; store_string: if (!log) { switch (fmt[0]) { case 'w': printk(KERN_WARNING "%s ", q + 2); break; case 'e': printk(KERN_ERR "%s ", q + 2); break; default: printk(KERN_NOTICE "%s ", q + 2); break; } if (freeable) kfree(q); } else { unsigned int logsize = ARRAY_SIZE(log->buffer); u8 index; index = log->head & (logsize - 1); BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) || sizeof(log->tail) != sizeof(u8)); if ((u8)(log->head - log->tail) == logsize) { /* The buffer is full, discard the oldest message */ if (log->need_free & (1 << index)) kfree(log->buffer[index]); log->tail++; } |
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log->buffer[index] = q; log->need_free &= ~(1 << index); log->need_free |= freeable << index; log->head++; } |
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va_end(va); } EXPORT_SYMBOL(logfc); |
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/* * Free a logging structure. */ static void put_fc_log(struct fs_context *fc) { struct fc_log *log = fc->log; int i; if (log) { if (refcount_dec_and_test(&log->usage)) { fc->log = NULL; for (i = 0; i <= 7; i++) if (log->need_free & (1 << i)) kfree(log->buffer[i]); kfree(log); } } } |
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/** |
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* 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); } |
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if (fc->need_free && fc->ops && fc->ops->free) fc->ops->free(fc); |
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security_free_mnt_opts(&fc->security); |
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put_net(fc->net_ns); |
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put_user_ns(fc->user_ns); put_cred(fc->cred); kfree(fc->subtype); |
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put_fc_log(fc); |
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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) { |
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struct legacy_fs_context *ctx = fc->fs_private; if (ctx) { if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) kfree(ctx->legacy_data); kfree(ctx); } } /* |
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* 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; } /* |
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* 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; |
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} /* * Add monolithic mount data. */ static int legacy_parse_monolithic(struct fs_context *fc, void *data) { struct legacy_fs_context *ctx = fc->fs_private; |
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if (ctx->param_type != LEGACY_FS_UNSET_PARAMS) { pr_warn("VFS: Can't mix monolithic and individual options "); return -EINVAL; } |
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ctx->legacy_data = data; |
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ctx->param_type = LEGACY_FS_MONOLITHIC_PARAMS; |
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if (!ctx->legacy_data) return 0; |
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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. */ |
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static int legacy_get_tree(struct fs_context *fc) |
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{ 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; } /* |
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* Handle remount. */ |
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static int legacy_reconfigure(struct fs_context *fc) |
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{ 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); } |
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const struct fs_context_operations legacy_fs_context_ops = { .free = legacy_fs_context_free, |
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.dup = legacy_fs_context_dup, |
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.parse_param = legacy_parse_param, |
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.parse_monolithic = legacy_parse_monolithic, .get_tree = legacy_get_tree, .reconfigure = legacy_reconfigure, }; |
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/* |
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* 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; |
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fc->ops = &legacy_fs_context_ops; |
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return 0; } int parse_monolithic_mount_data(struct fs_context *fc, void *data) { |
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int (*monolithic_mount_data)(struct fs_context *, void *); |
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monolithic_mount_data = fc->ops->parse_monolithic; |
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if (!monolithic_mount_data) monolithic_mount_data = generic_parse_monolithic; |
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return monolithic_mount_data(fc, data); |
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} |
ecdab150f vfs: syscall: Add... |
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/* * Clean up a context after performing an action on it and put it into a state * from where it can be used to reconfigure a superblock. * * Note that here we do only the parts that can't fail; the rest is in * finish_clean_context() below and in between those fs_context is marked * FS_CONTEXT_AWAITING_RECONF. The reason for splitup is that after * successful mount or remount we need to report success to userland. * Trying to do full reinit (for the sake of possible subsequent remount) * and failing to allocate memory would've put us into a nasty situation. * So here we only discard the old state and reinitialization is left * until we actually try to reconfigure. */ void vfs_clean_context(struct fs_context *fc) { if (fc->need_free && fc->ops && fc->ops->free) fc->ops->free(fc); fc->need_free = false; fc->fs_private = NULL; fc->s_fs_info = NULL; fc->sb_flags = 0; security_free_mnt_opts(&fc->security); kfree(fc->subtype); fc->subtype = NULL; kfree(fc->source); fc->source = NULL; fc->purpose = FS_CONTEXT_FOR_RECONFIGURE; fc->phase = FS_CONTEXT_AWAITING_RECONF; } int finish_clean_context(struct fs_context *fc) { int error; if (fc->phase != FS_CONTEXT_AWAITING_RECONF) return 0; if (fc->fs_type->init_fs_context) error = fc->fs_type->init_fs_context(fc); else error = legacy_init_fs_context(fc); if (unlikely(error)) { fc->phase = FS_CONTEXT_FAILED; return error; } fc->need_free = true; fc->phase = FS_CONTEXT_RECONF_PARAMS; return 0; } |