// SPDX-License-Identifier: GPL-2.0-only

  /*
   *  inode.c - securityfs
   *
   *  Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
   *

   *  Based on fs/debugfs/inode.c which had the following copyright notice:
   *    Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
   *    Copyright (C) 2004 IBM Inc.
   */
  
  /* #define DEBUG */

  #include <linux/sysfs.h>
  #include <linux/kobject.h>

  #include <linux/fs.h>

  #include <linux/fs_context.h>

  #include <linux/mount.h>
  #include <linux/pagemap.h>
  #include <linux/init.h>
  #include <linux/namei.h>
  #include <linux/security.h>

  #include <linux/lsm_hooks.h>

  #include <linux/magic.h>

  
  static struct vfsmount *mount;
  static int mount_count;

  static void securityfs_free_inode(struct inode *inode)

  {

  	if (S_ISLNK(inode->i_mode))
  		kfree(inode->i_link);

  	free_inode_nonrcu(inode);
  }

  static const struct super_operations securityfs_super_operations = {
  	.statfs		= simple_statfs,

  	.free_inode	= securityfs_free_inode,

  };

  static int securityfs_fill_super(struct super_block *sb, struct fs_context *fc)

  {

  	static const struct tree_descr files[] = {{""}};

  	int error;
  
  	error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
  	if (error)
  		return error;
  
  	sb->s_op = &securityfs_super_operations;

  	return 0;

  }

  static int securityfs_get_tree(struct fs_context *fc)

  {

  	return get_tree_single(fc, securityfs_fill_super);
  }
  
  static const struct fs_context_operations securityfs_context_ops = {
  	.get_tree	= securityfs_get_tree,
  };
  
  static int securityfs_init_fs_context(struct fs_context *fc)
  {
  	fc->ops = &securityfs_context_ops;
  	return 0;

  }
  
  static struct file_system_type fs_type = {
  	.owner =	THIS_MODULE,
  	.name =		"securityfs",

  	.init_fs_context = securityfs_init_fs_context,

  	.kill_sb =	kill_litter_super,
  };

  /**

   * securityfs_create_dentry - create a dentry in the securityfs filesystem

   *
   * @name: a pointer to a string containing the name of the file to create.
   * @mode: the permission that the file should have
   * @parent: a pointer to the parent dentry for this file.  This should be a

   *          directory dentry if set.  If this parameter is %NULL, then the

   *          file will be created in the root of the securityfs filesystem.
   * @data: a pointer to something that the caller will want to get to later

   *        on.  The inode.i_private pointer will point to this value on

   *        the open() call.
   * @fops: a pointer to a struct file_operations that should be used for
   *        this file.

   * @iops: a point to a struct of inode_operations that should be used for
   *        this file/dir

   *

   * This is the basic "create a file/dir/symlink" function for
   * securityfs.  It allows for a wide range of flexibility in creating
   * a file, or a directory (if you want to create a directory, the
   * securityfs_create_dir() function is recommended to be used
   * instead).

   *

   * This function returns a pointer to a dentry if it succeeds.  This

   * pointer must be passed to the securityfs_remove() function when the
   * file is to be removed (no automatic cleanup happens if your module
   * is unloaded, you are responsible here).  If an error occurs, the
   * function will return the error value (via ERR_PTR).

   *

   * If securityfs is not enabled in the kernel, the value %-ENODEV is

   * returned.

   */

  static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
  					struct dentry *parent, void *data,
  					const struct file_operations *fops,
  					const struct inode_operations *iops)

  {

  	struct dentry *dentry;

  	struct inode *dir, *inode;

  	int error;

  	if (!(mode & S_IFMT))

  		mode = (mode & S_IALLUGO) | S_IFREG;

  	pr_debug("securityfs: creating file '%s'
  ",name);

  	error = simple_pin_fs(&fs_type, &mount, &mount_count);

  	if (error)
  		return ERR_PTR(error);
  
  	if (!parent)
  		parent = mount->mnt_root;

  	dir = d_inode(parent);

  	inode_lock(dir);

  	dentry = lookup_one_len(name, parent, strlen(name));

  	if (IS_ERR(dentry))
  		goto out;

  	if (d_really_is_positive(dentry)) {

  		error = -EEXIST;
  		goto out1;

  	}

  	inode = new_inode(dir->i_sb);
  	if (!inode) {
  		error = -ENOMEM;
  		goto out1;

  	}

  	inode->i_ino = get_next_ino();
  	inode->i_mode = mode;

  	inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);

  	inode->i_private = data;

  	if (S_ISDIR(mode)) {

  		inode->i_op = &simple_dir_inode_operations;
  		inode->i_fop = &simple_dir_operations;
  		inc_nlink(inode);
  		inc_nlink(dir);

  	} else if (S_ISLNK(mode)) {
  		inode->i_op = iops ? iops : &simple_symlink_inode_operations;
  		inode->i_link = data;

  	} else {
  		inode->i_fop = fops;

  	}

  	d_instantiate(dentry, inode);
  	dget(dentry);

  	inode_unlock(dir);

  	return dentry;
  
  out1:
  	dput(dentry);
  	dentry = ERR_PTR(error);
  out:

  	inode_unlock(dir);

  	simple_release_fs(&mount, &mount_count);

  	return dentry;
  }

  
  /**
   * securityfs_create_file - create a file in the securityfs filesystem
   *
   * @name: a pointer to a string containing the name of the file to create.
   * @mode: the permission that the file should have
   * @parent: a pointer to the parent dentry for this file.  This should be a
   *          directory dentry if set.  If this parameter is %NULL, then the
   *          file will be created in the root of the securityfs filesystem.
   * @data: a pointer to something that the caller will want to get to later
   *        on.  The inode.i_private pointer will point to this value on
   *        the open() call.
   * @fops: a pointer to a struct file_operations that should be used for
   *        this file.
   *
   * This function creates a file in securityfs with the given @name.
   *
   * This function returns a pointer to a dentry if it succeeds.  This
   * pointer must be passed to the securityfs_remove() function when the file is
   * to be removed (no automatic cleanup happens if your module is unloaded,
   * you are responsible here).  If an error occurs, the function will return
   * the error value (via ERR_PTR).
   *
   * If securityfs is not enabled in the kernel, the value %-ENODEV is
   * returned.
   */
  struct dentry *securityfs_create_file(const char *name, umode_t mode,
  				      struct dentry *parent, void *data,
  				      const struct file_operations *fops)
  {
  	return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
  }

  EXPORT_SYMBOL_GPL(securityfs_create_file);
  
  /**
   * securityfs_create_dir - create a directory in the securityfs filesystem
   *
   * @name: a pointer to a string containing the name of the directory to
   *        create.
   * @parent: a pointer to the parent dentry for this file.  This should be a

   *          directory dentry if set.  If this parameter is %NULL, then the

   *          directory will be created in the root of the securityfs filesystem.
   *

   * This function creates a directory in securityfs with the given @name.

   *

   * This function returns a pointer to a dentry if it succeeds.  This

   * pointer must be passed to the securityfs_remove() function when the file is
   * to be removed (no automatic cleanup happens if your module is unloaded,

   * you are responsible here).  If an error occurs, the function will return
   * the error value (via ERR_PTR).

   *

   * If securityfs is not enabled in the kernel, the value %-ENODEV is

   * returned.

   */
  struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
  {

  	return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);

  }
  EXPORT_SYMBOL_GPL(securityfs_create_dir);
  
  /**

   * securityfs_create_symlink - create a symlink in the securityfs filesystem
   *
   * @name: a pointer to a string containing the name of the symlink to
   *        create.
   * @parent: a pointer to the parent dentry for the symlink.  This should be a
   *          directory dentry if set.  If this parameter is %NULL, then the
   *          directory will be created in the root of the securityfs filesystem.
   * @target: a pointer to a string containing the name of the symlink's target.
   *          If this parameter is %NULL, then the @iops parameter needs to be
   *          setup to handle .readlink and .get_link inode_operations.
   * @iops: a pointer to the struct inode_operations to use for the symlink. If
   *        this parameter is %NULL, then the default simple_symlink_inode
   *        operations will be used.
   *
   * This function creates a symlink in securityfs with the given @name.
   *
   * This function returns a pointer to a dentry if it succeeds.  This
   * pointer must be passed to the securityfs_remove() function when the file is
   * to be removed (no automatic cleanup happens if your module is unloaded,
   * you are responsible here).  If an error occurs, the function will return
   * the error value (via ERR_PTR).
   *
   * If securityfs is not enabled in the kernel, the value %-ENODEV is
   * returned.
   */
  struct dentry *securityfs_create_symlink(const char *name,
  					 struct dentry *parent,
  					 const char *target,
  					 const struct inode_operations *iops)
  {
  	struct dentry *dent;
  	char *link = NULL;
  
  	if (target) {
  		link = kstrdup(target, GFP_KERNEL);
  		if (!link)
  			return ERR_PTR(-ENOMEM);
  	}
  	dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
  					link, NULL, iops);
  	if (IS_ERR(dent))
  		kfree(link);
  
  	return dent;
  }
  EXPORT_SYMBOL_GPL(securityfs_create_symlink);
  
  /**

   * securityfs_remove - removes a file or directory from the securityfs filesystem
   *

   * @dentry: a pointer to a the dentry of the file or directory to be removed.

   *
   * This function removes a file or directory in securityfs that was previously
   * created with a call to another securityfs function (like
   * securityfs_create_file() or variants thereof.)
   *
   * This function is required to be called in order for the file to be

   * removed. No automatic cleanup of files will happen when a module is
   * removed; you are responsible here.

   */
  void securityfs_remove(struct dentry *dentry)
  {

  	struct inode *dir;

  	if (!dentry || IS_ERR(dentry))

  		return;

  	dir = d_inode(dentry->d_parent);
  	inode_lock(dir);

  	if (simple_positive(dentry)) {
  		if (d_is_dir(dentry))

  			simple_rmdir(dir, dentry);

  		else

  			simple_unlink(dir, dentry);

  		dput(dentry);

  	}

  	inode_unlock(dir);

  	simple_release_fs(&mount, &mount_count);
  }
  EXPORT_SYMBOL_GPL(securityfs_remove);

  #ifdef CONFIG_SECURITY
  static struct dentry *lsm_dentry;
  static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
  			loff_t *ppos)
  {
  	return simple_read_from_buffer(buf, count, ppos, lsm_names,
  		strlen(lsm_names));
  }
  
  static const struct file_operations lsm_ops = {
  	.read = lsm_read,
  	.llseek = generic_file_llseek,
  };
  #endif

  static int __init securityfs_init(void)
  {
  	int retval;

  	retval = sysfs_create_mount_point(kernel_kobj, "security");
  	if (retval)
  		return retval;

  
  	retval = register_filesystem(&fs_type);

  	if (retval) {

  		sysfs_remove_mount_point(kernel_kobj, "security");

  		return retval;
  	}
  #ifdef CONFIG_SECURITY
  	lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
  						&lsm_ops);
  #endif
  	return 0;

  }

  core_initcall(securityfs_init);