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![Gustavo A. R. Silva](/assets/img/avatar_default.png)
Replace the existing /* fall through */ comments and its variants with the new pseudo-keyword macro fallthrough[1]. Also, remove unnecessary fall-through markings when it is the case. [1] https://www.kernel.org/doc/html/v5.7/process/deprecated.html?highlight=fallthrough#implicit-switch-case-fall-through Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
699 lines
17 KiB
C
699 lines
17 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/* Provide a way to create a superblock configuration context within the kernel
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* that allows a superblock to be set up prior to mounting.
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*
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* Copyright (C) 2017 Red Hat, Inc. All Rights Reserved.
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* Written by David Howells (dhowells@redhat.com)
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*/
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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>
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#include <linux/mount.h>
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#include <linux/nsproxy.h>
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#include <linux/slab.h>
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#include <linux/magic.h>
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#include <linux/security.h>
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#include <linux/mnt_namespace.h>
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#include <linux/pid_namespace.h>
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#include <linux/user_namespace.h>
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#include <net/net_namespace.h>
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#include <asm/sections.h>
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#include "mount.h"
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#include "internal.h"
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enum legacy_fs_param {
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LEGACY_FS_UNSET_PARAMS,
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LEGACY_FS_MONOLITHIC_PARAMS,
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LEGACY_FS_INDIVIDUAL_PARAMS,
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};
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struct legacy_fs_context {
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char *legacy_data; /* Data page for legacy filesystems */
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size_t data_size;
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enum legacy_fs_param param_type;
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};
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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[] = {
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{ "dirsync", SB_DIRSYNC },
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{ "lazytime", SB_LAZYTIME },
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{ "mand", SB_MANDLOCK },
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{ "ro", SB_RDONLY },
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{ "sync", SB_SYNCHRONOUS },
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{ },
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};
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static const struct constant_table common_clear_sb_flag[] = {
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{ "async", SB_SYNCHRONOUS },
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{ "nolazytime", SB_LAZYTIME },
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{ "nomand", SB_MANDLOCK },
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{ "rw", SB_RDONLY },
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{ },
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};
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/*
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* Check for a common mount option that manipulates s_flags.
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*/
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static int vfs_parse_sb_flag(struct fs_context *fc, const char *key)
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{
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unsigned int token;
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token = lookup_constant(common_set_sb_flag, key, 0);
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if (token) {
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fc->sb_flags |= token;
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fc->sb_flags_mask |= token;
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return 0;
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}
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token = lookup_constant(common_clear_sb_flag, key, 0);
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if (token) {
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fc->sb_flags &= ~token;
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fc->sb_flags_mask |= token;
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return 0;
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}
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return -ENOPARAM;
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}
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/**
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* vfs_parse_fs_param - Add a single parameter to a superblock config
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* @fc: The filesystem context to modify
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* @param: The parameter
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*
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* A single mount option in string form is applied to the filesystem context
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* being set up. Certain standard options (for example "ro") are translated
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* into flag bits without going to the filesystem. The active security module
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* is allowed to observe and poach options. Any other options are passed over
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* to the filesystem to parse.
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*
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* This may be called multiple times for a context.
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*
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* Returns 0 on success and a negative error code on failure. In the event of
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* failure, supplementary error information may have been set.
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*/
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int vfs_parse_fs_param(struct fs_context *fc, struct fs_parameter *param)
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{
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int ret;
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if (!param->key)
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return invalf(fc, "Unnamed parameter\n");
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ret = vfs_parse_sb_flag(fc, param->key);
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if (ret != -ENOPARAM)
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return ret;
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ret = security_fs_context_parse_param(fc, param);
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if (ret != -ENOPARAM)
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/* Param belongs to the LSM or is disallowed by the LSM; so
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* don't pass to the FS.
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*/
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return ret;
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if (fc->ops->parse_param) {
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ret = fc->ops->parse_param(fc, param);
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if (ret != -ENOPARAM)
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return ret;
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}
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/* If the filesystem doesn't take any arguments, give it the
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* default handling of source.
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*/
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if (strcmp(param->key, "source") == 0) {
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if (param->type != fs_value_is_string)
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return invalf(fc, "VFS: Non-string source");
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if (fc->source)
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return invalf(fc, "VFS: Multiple sources");
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fc->source = param->string;
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param->string = NULL;
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return 0;
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}
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return invalf(fc, "%s: Unknown parameter '%s'",
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fc->fs_type->name, param->key);
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}
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EXPORT_SYMBOL(vfs_parse_fs_param);
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/**
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* vfs_parse_fs_string - Convenience function to just parse a string.
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*/
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int vfs_parse_fs_string(struct fs_context *fc, const char *key,
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const char *value, size_t v_size)
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{
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int ret;
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struct fs_parameter param = {
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.key = key,
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.type = fs_value_is_flag,
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.size = v_size,
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};
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if (value) {
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param.string = kmemdup_nul(value, v_size, GFP_KERNEL);
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if (!param.string)
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return -ENOMEM;
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param.type = fs_value_is_string;
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}
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ret = vfs_parse_fs_param(fc, ¶m);
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kfree(param.string);
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return ret;
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}
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EXPORT_SYMBOL(vfs_parse_fs_string);
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/**
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* generic_parse_monolithic - Parse key[=val][,key[=val]]* mount data
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* @ctx: The superblock configuration to fill in.
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* @data: The data to parse
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*
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* Parse a blob of data that's in key[=val][,key[=val]]* form. This can be
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* called from the ->monolithic_mount_data() fs_context operation.
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*
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* Returns 0 on success or the error returned by the ->parse_option() fs_context
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* operation on failure.
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*/
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int generic_parse_monolithic(struct fs_context *fc, void *data)
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{
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char *options = data, *key;
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int ret = 0;
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if (!options)
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return 0;
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ret = security_sb_eat_lsm_opts(options, &fc->security);
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if (ret)
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return ret;
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while ((key = strsep(&options, ",")) != NULL) {
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if (*key) {
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size_t v_len = 0;
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char *value = strchr(key, '=');
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if (value) {
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if (value == key)
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continue;
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*value++ = 0;
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v_len = strlen(value);
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}
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ret = vfs_parse_fs_string(fc, key, value, v_len);
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if (ret < 0)
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break;
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}
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}
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return ret;
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}
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EXPORT_SYMBOL(generic_parse_monolithic);
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/**
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* alloc_fs_context - Create a filesystem context.
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* @fs_type: The filesystem type.
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* @reference: The dentry from which this one derives (or NULL)
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* @sb_flags: Filesystem/superblock flags (SB_*)
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* @sb_flags_mask: Applicable members of @sb_flags
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* @purpose: The purpose that this configuration shall be used for.
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*
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* Open a filesystem and create a mount context. The mount context is
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* initialised with the supplied flags and, if a submount/automount from
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* another superblock (referred to by @reference) is supplied, may have
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* parameters such as namespaces copied across from that superblock.
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*/
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static struct fs_context *alloc_fs_context(struct file_system_type *fs_type,
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struct dentry *reference,
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unsigned int sb_flags,
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unsigned int sb_flags_mask,
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enum fs_context_purpose purpose)
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{
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int (*init_fs_context)(struct fs_context *);
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struct fs_context *fc;
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int ret = -ENOMEM;
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fc = kzalloc(sizeof(struct fs_context), GFP_KERNEL);
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if (!fc)
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return ERR_PTR(-ENOMEM);
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fc->purpose = purpose;
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fc->sb_flags = sb_flags;
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fc->sb_flags_mask = sb_flags_mask;
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fc->fs_type = get_filesystem(fs_type);
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fc->cred = get_current_cred();
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fc->net_ns = get_net(current->nsproxy->net_ns);
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fc->log.prefix = fs_type->name;
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mutex_init(&fc->uapi_mutex);
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switch (purpose) {
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case FS_CONTEXT_FOR_MOUNT:
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fc->user_ns = get_user_ns(fc->cred->user_ns);
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break;
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case FS_CONTEXT_FOR_SUBMOUNT:
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fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
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break;
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case FS_CONTEXT_FOR_RECONFIGURE:
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atomic_inc(&reference->d_sb->s_active);
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fc->user_ns = get_user_ns(reference->d_sb->s_user_ns);
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fc->root = dget(reference);
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break;
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}
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/* TODO: Make all filesystems support this unconditionally */
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init_fs_context = fc->fs_type->init_fs_context;
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if (!init_fs_context)
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init_fs_context = legacy_init_fs_context;
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ret = init_fs_context(fc);
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if (ret < 0)
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goto err_fc;
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fc->need_free = true;
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return fc;
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err_fc:
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put_fs_context(fc);
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return ERR_PTR(ret);
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}
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struct fs_context *fs_context_for_mount(struct file_system_type *fs_type,
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unsigned int sb_flags)
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{
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return alloc_fs_context(fs_type, NULL, sb_flags, 0,
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FS_CONTEXT_FOR_MOUNT);
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}
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EXPORT_SYMBOL(fs_context_for_mount);
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struct fs_context *fs_context_for_reconfigure(struct dentry *dentry,
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unsigned int sb_flags,
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unsigned int sb_flags_mask)
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{
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return alloc_fs_context(dentry->d_sb->s_type, dentry, sb_flags,
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sb_flags_mask, FS_CONTEXT_FOR_RECONFIGURE);
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}
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EXPORT_SYMBOL(fs_context_for_reconfigure);
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struct fs_context *fs_context_for_submount(struct file_system_type *type,
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struct dentry *reference)
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{
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return alloc_fs_context(type, reference, 0, 0, FS_CONTEXT_FOR_SUBMOUNT);
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}
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EXPORT_SYMBOL(fs_context_for_submount);
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void fc_drop_locked(struct fs_context *fc)
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{
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struct super_block *sb = fc->root->d_sb;
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dput(fc->root);
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fc->root = NULL;
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deactivate_locked_super(sb);
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}
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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.
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* @src_fc: The context to copy.
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*/
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struct fs_context *vfs_dup_fs_context(struct fs_context *src_fc)
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{
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struct fs_context *fc;
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int ret;
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if (!src_fc->ops->dup)
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return ERR_PTR(-EOPNOTSUPP);
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fc = kmemdup(src_fc, sizeof(struct fs_context), GFP_KERNEL);
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if (!fc)
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return ERR_PTR(-ENOMEM);
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mutex_init(&fc->uapi_mutex);
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fc->fs_private = NULL;
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fc->s_fs_info = NULL;
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fc->source = NULL;
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fc->security = NULL;
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get_filesystem(fc->fs_type);
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get_net(fc->net_ns);
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get_user_ns(fc->user_ns);
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get_cred(fc->cred);
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if (fc->log.log)
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refcount_inc(&fc->log.log->usage);
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/* Can't call put until we've called ->dup */
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ret = fc->ops->dup(fc, src_fc);
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if (ret < 0)
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goto err_fc;
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ret = security_fs_context_dup(fc, src_fc);
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if (ret < 0)
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goto err_fc;
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return fc;
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err_fc:
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put_fs_context(fc);
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return ERR_PTR(ret);
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}
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EXPORT_SYMBOL(vfs_dup_fs_context);
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/**
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* logfc - Log a message to a filesystem context
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* @fc: The filesystem context to log to.
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* @fmt: The format of the buffer.
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*/
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void logfc(struct fc_log *log, const char *prefix, char level, const char *fmt, ...)
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{
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va_list va;
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struct va_format vaf = {.fmt = fmt, .va = &va};
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va_start(va, fmt);
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if (!log) {
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switch (level) {
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case 'w':
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printk(KERN_WARNING "%s%s%pV\n", prefix ? prefix : "",
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prefix ? ": " : "", &vaf);
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break;
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case 'e':
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printk(KERN_ERR "%s%s%pV\n", prefix ? prefix : "",
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prefix ? ": " : "", &vaf);
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break;
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default:
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printk(KERN_NOTICE "%s%s%pV\n", prefix ? prefix : "",
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prefix ? ": " : "", &vaf);
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break;
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}
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} else {
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unsigned int logsize = ARRAY_SIZE(log->buffer);
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u8 index;
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char *q = kasprintf(GFP_KERNEL, "%c %s%s%pV\n", level,
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prefix ? prefix : "",
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prefix ? ": " : "", &vaf);
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index = log->head & (logsize - 1);
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BUILD_BUG_ON(sizeof(log->head) != sizeof(u8) ||
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sizeof(log->tail) != sizeof(u8));
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if ((u8)(log->head - log->tail) == logsize) {
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/* The buffer is full, discard the oldest message */
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if (log->need_free & (1 << index))
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kfree(log->buffer[index]);
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log->tail++;
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}
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log->buffer[index] = q ? q : "OOM: Can't store error string";
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if (q)
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log->need_free |= 1 << index;
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else
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log->need_free &= ~(1 << index);
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log->head++;
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}
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va_end(va);
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}
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EXPORT_SYMBOL(logfc);
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/*
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* Free a logging structure.
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*/
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static void put_fc_log(struct fs_context *fc)
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{
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struct fc_log *log = fc->log.log;
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int i;
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if (log) {
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if (refcount_dec_and_test(&log->usage)) {
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fc->log.log = NULL;
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for (i = 0; i <= 7; i++)
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if (log->need_free & (1 << i))
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kfree(log->buffer[i]);
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kfree(log);
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}
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}
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}
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/**
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* put_fs_context - Dispose of a superblock configuration context.
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* @fc: The context to dispose of.
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*/
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void put_fs_context(struct fs_context *fc)
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{
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struct super_block *sb;
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if (fc->root) {
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sb = fc->root->d_sb;
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dput(fc->root);
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fc->root = NULL;
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deactivate_super(sb);
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}
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if (fc->need_free && fc->ops && fc->ops->free)
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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);
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put_cred(fc->cred);
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put_fc_log(fc);
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put_filesystem(fc->fs_type);
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kfree(fc->source);
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kfree(fc);
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}
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EXPORT_SYMBOL(put_fs_context);
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/*
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* Free the config for a filesystem that doesn't support fs_context.
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*/
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static void legacy_fs_context_free(struct fs_context *fc)
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{
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struct legacy_fs_context *ctx = fc->fs_private;
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if (ctx) {
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if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS)
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kfree(ctx->legacy_data);
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kfree(ctx);
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}
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}
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/*
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* Duplicate a legacy config.
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*/
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static int legacy_fs_context_dup(struct fs_context *fc, struct fs_context *src_fc)
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{
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struct legacy_fs_context *ctx;
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struct legacy_fs_context *src_ctx = src_fc->fs_private;
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ctx = kmemdup(src_ctx, sizeof(*src_ctx), GFP_KERNEL);
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if (!ctx)
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return -ENOMEM;
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if (ctx->param_type == LEGACY_FS_INDIVIDUAL_PARAMS) {
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ctx->legacy_data = kmemdup(src_ctx->legacy_data,
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src_ctx->data_size, GFP_KERNEL);
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if (!ctx->legacy_data) {
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kfree(ctx);
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return -ENOMEM;
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}
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}
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fc->fs_private = ctx;
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return 0;
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}
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/*
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* Add a parameter to a legacy config. We build up a comma-separated list of
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* options.
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*/
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static int legacy_parse_param(struct fs_context *fc, struct fs_parameter *param)
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{
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struct legacy_fs_context *ctx = fc->fs_private;
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unsigned int size = ctx->data_size;
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size_t len = 0;
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if (strcmp(param->key, "source") == 0) {
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if (param->type != fs_value_is_string)
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return invalf(fc, "VFS: Legacy: Non-string source");
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if (fc->source)
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return invalf(fc, "VFS: Legacy: Multiple sources");
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fc->source = param->string;
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param->string = NULL;
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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;
|
|
fallthrough;
|
|
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);
|
|
}
|
|
|
|
/*
|
|
* 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->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;
|
|
}
|