331 lines
8.8 KiB
C
331 lines
8.8 KiB
C
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/*
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* inode.c - securityfs
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*
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* Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License version
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* 2 as published by the Free Software Foundation.
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*
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* Based on fs/debugfs/inode.c which had the following copyright notice:
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* Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
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* Copyright (C) 2004 IBM Inc.
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*/
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/* #define DEBUG */
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#include <linux/module.h>
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#include <linux/fs.h>
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#include <linux/mount.h>
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#include <linux/pagemap.h>
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#include <linux/init.h>
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#include <linux/namei.h>
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#include <linux/security.h>
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#include <linux/magic.h>
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static struct vfsmount *mount;
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static int mount_count;
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/*
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* TODO:
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* I think I can get rid of these default_file_ops, but not quite sure...
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*/
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static ssize_t default_read_file(struct file *file, char __user *buf,
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size_t count, loff_t *ppos)
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{
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return 0;
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}
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static ssize_t default_write_file(struct file *file, const char __user *buf,
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size_t count, loff_t *ppos)
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{
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return count;
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}
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static int default_open(struct inode *inode, struct file *file)
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{
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if (inode->i_private)
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file->private_data = inode->i_private;
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return 0;
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}
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static const struct file_operations default_file_ops = {
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.read = default_read_file,
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.write = default_write_file,
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.open = default_open,
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};
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static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
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{
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struct inode *inode = new_inode(sb);
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if (inode) {
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inode->i_mode = mode;
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inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
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switch (mode & S_IFMT) {
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default:
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init_special_inode(inode, mode, dev);
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break;
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case S_IFREG:
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inode->i_fop = &default_file_ops;
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break;
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case S_IFDIR:
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inode->i_op = &simple_dir_inode_operations;
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inode->i_fop = &simple_dir_operations;
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/* directory inodes start off with i_nlink == 2 (for "." entry) */
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inc_nlink(inode);
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break;
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}
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}
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return inode;
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}
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/* SMP-safe */
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static int mknod(struct inode *dir, struct dentry *dentry,
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int mode, dev_t dev)
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{
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struct inode *inode;
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int error = -EPERM;
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if (dentry->d_inode)
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return -EEXIST;
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inode = get_inode(dir->i_sb, mode, dev);
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if (inode) {
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d_instantiate(dentry, inode);
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dget(dentry);
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error = 0;
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}
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return error;
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}
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static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
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{
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int res;
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mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
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res = mknod(dir, dentry, mode, 0);
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if (!res)
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inc_nlink(dir);
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return res;
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}
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static int create(struct inode *dir, struct dentry *dentry, int mode)
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{
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mode = (mode & S_IALLUGO) | S_IFREG;
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return mknod(dir, dentry, mode, 0);
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}
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static inline int positive(struct dentry *dentry)
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{
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return dentry->d_inode && !d_unhashed(dentry);
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}
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static int fill_super(struct super_block *sb, void *data, int silent)
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{
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static struct tree_descr files[] = {{""}};
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return simple_fill_super(sb, SECURITYFS_MAGIC, files);
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}
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static int get_sb(struct file_system_type *fs_type,
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int flags, const char *dev_name,
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void *data, struct vfsmount *mnt)
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{
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return get_sb_single(fs_type, flags, data, fill_super, mnt);
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}
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static struct file_system_type fs_type = {
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.owner = THIS_MODULE,
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.name = "securityfs",
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.get_sb = get_sb,
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.kill_sb = kill_litter_super,
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};
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static int create_by_name(const char *name, mode_t mode,
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struct dentry *parent,
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struct dentry **dentry)
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{
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int error = 0;
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*dentry = NULL;
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/* If the parent is not specified, we create it in the root.
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* We need the root dentry to do this, which is in the super
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* block. A pointer to that is in the struct vfsmount that we
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* have around.
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*/
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if (!parent ) {
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if (mount && mount->mnt_sb) {
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parent = mount->mnt_sb->s_root;
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}
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}
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if (!parent) {
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pr_debug("securityfs: Ah! can not find a parent!\n");
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return -EFAULT;
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}
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mutex_lock(&parent->d_inode->i_mutex);
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*dentry = lookup_one_len(name, parent, strlen(name));
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if (!IS_ERR(*dentry)) {
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if ((mode & S_IFMT) == S_IFDIR)
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error = mkdir(parent->d_inode, *dentry, mode);
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else
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error = create(parent->d_inode, *dentry, mode);
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} else
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error = PTR_ERR(*dentry);
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mutex_unlock(&parent->d_inode->i_mutex);
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return error;
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}
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/**
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* securityfs_create_file - create a file in the securityfs filesystem
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*
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* @name: a pointer to a string containing the name of the file to create.
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* @mode: the permission that the file should have
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* @parent: a pointer to the parent dentry for this file. This should be a
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* directory dentry if set. If this parameter is %NULL, then the
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* file will be created in the root of the securityfs filesystem.
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* @data: a pointer to something that the caller will want to get to later
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* on. The inode.i_private pointer will point to this value on
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* the open() call.
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* @fops: a pointer to a struct file_operations that should be used for
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* this file.
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*
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* This is the basic "create a file" function for securityfs. It allows for a
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* wide range of flexibility in creating a file, or a directory (if you
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* want to create a directory, the securityfs_create_dir() function is
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* recommended to be used instead).
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*
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* This function returns a pointer to a dentry if it succeeds. This
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* pointer must be passed to the securityfs_remove() function when the file is
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* to be removed (no automatic cleanup happens if your module is unloaded,
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* you are responsible here). If an error occurs, the function will return
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* the erorr value (via ERR_PTR).
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*
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* If securityfs is not enabled in the kernel, the value %-ENODEV is
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* returned.
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*/
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struct dentry *securityfs_create_file(const char *name, mode_t mode,
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struct dentry *parent, void *data,
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const struct file_operations *fops)
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{
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struct dentry *dentry = NULL;
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int error;
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pr_debug("securityfs: creating file '%s'\n",name);
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error = simple_pin_fs(&fs_type, &mount, &mount_count);
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if (error) {
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dentry = ERR_PTR(error);
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goto exit;
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}
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error = create_by_name(name, mode, parent, &dentry);
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if (error) {
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dentry = ERR_PTR(error);
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simple_release_fs(&mount, &mount_count);
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goto exit;
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}
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if (dentry->d_inode) {
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if (fops)
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dentry->d_inode->i_fop = fops;
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if (data)
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dentry->d_inode->i_private = data;
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}
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exit:
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return dentry;
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}
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EXPORT_SYMBOL_GPL(securityfs_create_file);
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/**
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* securityfs_create_dir - create a directory in the securityfs filesystem
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*
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* @name: a pointer to a string containing the name of the directory to
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* create.
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* @parent: a pointer to the parent dentry for this file. This should be a
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* directory dentry if set. If this parameter is %NULL, then the
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* directory will be created in the root of the securityfs filesystem.
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*
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* This function creates a directory in securityfs with the given @name.
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*
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* This function returns a pointer to a dentry if it succeeds. This
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* pointer must be passed to the securityfs_remove() function when the file is
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* to be removed (no automatic cleanup happens if your module is unloaded,
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* you are responsible here). If an error occurs, %NULL will be returned.
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*
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* If securityfs is not enabled in the kernel, the value %-ENODEV is
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* returned. It is not wise to check for this value, but rather, check for
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* %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
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* code.
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*/
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struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
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{
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return securityfs_create_file(name,
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S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
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parent, NULL, NULL);
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}
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EXPORT_SYMBOL_GPL(securityfs_create_dir);
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/**
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* securityfs_remove - removes a file or directory from the securityfs filesystem
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*
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* @dentry: a pointer to a the dentry of the file or directory to be removed.
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*
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* This function removes a file or directory in securityfs that was previously
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* created with a call to another securityfs function (like
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* securityfs_create_file() or variants thereof.)
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*
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* This function is required to be called in order for the file to be
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* removed. No automatic cleanup of files will happen when a module is
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* removed; you are responsible here.
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*/
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void securityfs_remove(struct dentry *dentry)
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{
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struct dentry *parent;
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if (!dentry || IS_ERR(dentry))
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return;
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parent = dentry->d_parent;
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if (!parent || !parent->d_inode)
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return;
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mutex_lock(&parent->d_inode->i_mutex);
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if (positive(dentry)) {
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if (dentry->d_inode) {
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if (S_ISDIR(dentry->d_inode->i_mode))
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simple_rmdir(parent->d_inode, dentry);
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else
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simple_unlink(parent->d_inode, dentry);
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dput(dentry);
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}
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}
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mutex_unlock(&parent->d_inode->i_mutex);
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simple_release_fs(&mount, &mount_count);
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}
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EXPORT_SYMBOL_GPL(securityfs_remove);
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static struct kobject *security_kobj;
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static int __init securityfs_init(void)
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{
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int retval;
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security_kobj = kobject_create_and_add("security", kernel_kobj);
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if (!security_kobj)
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return -EINVAL;
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retval = register_filesystem(&fs_type);
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if (retval)
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kobject_put(security_kobj);
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return retval;
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}
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core_initcall(securityfs_init);
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MODULE_LICENSE("GPL");
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