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![Arjan van de Ven](/assets/img/avatar_default.png)
Many struct file_operations in the kernel can be "const". Marking them const moves these to the .rodata section, which avoids false sharing with potential dirty data. In addition it'll catch accidental writes at compile time to these shared resources. Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
345 lines
9.2 KiB
C
345 lines
9.2 KiB
C
/*
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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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#define SECURITYFS_MAGIC 0x73636673
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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_uid = 0;
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inode->i_gid = 0;
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inode->i_blocks = 0;
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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 paramater 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 createing 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 will return 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 will be
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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_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 paramater 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 will return 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 will be
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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
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* 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)
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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 decl_subsys(security, NULL, NULL);
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static int __init securityfs_init(void)
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{
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int retval;
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kset_set_kset_s(&security_subsys, kernel_subsys);
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retval = subsystem_register(&security_subsys);
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if (retval)
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return retval;
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retval = register_filesystem(&fs_type);
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if (retval)
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subsystem_unregister(&security_subsys);
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return retval;
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}
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static void __exit securityfs_exit(void)
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{
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simple_release_fs(&mount, &mount_count);
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unregister_filesystem(&fs_type);
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subsystem_unregister(&security_subsys);
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}
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core_initcall(securityfs_init);
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module_exit(securityfs_exit);
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MODULE_LICENSE("GPL");
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