FreeBSD/Linux Kernel Cross Reference
sys/security/inode.c

     /*
      *  inode.c - securityfs
      *
      *  Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
      *
      *      This program is free software; you can redistribute it and/or
      *      modify it under the terms of the GNU General Public License version
      *      2 as published by the Free Software Foundation.
      *
     *  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/module.h>
    #include <linux/fs.h>
    #include <linux/mount.h>
    #include <linux/pagemap.h>
    #include <linux/init.h>
    #include <linux/namei.h>
    #include <linux/security.h>
    #include <linux/magic.h>
    
    static struct vfsmount *mount;
    static int mount_count;
    
    static inline int positive(struct dentry *dentry)
    {
            return dentry->d_inode && !d_unhashed(dentry);
    }
    
    static int fill_super(struct super_block *sb, void *data, int silent)
    {
            static struct tree_descr files[] = {{""}};
    
            return simple_fill_super(sb, SECURITYFS_MAGIC, files);
    }
    
    static struct dentry *get_sb(struct file_system_type *fs_type,
                      int flags, const char *dev_name,
                      void *data)
    {
            return mount_single(fs_type, flags, data, fill_super);
    }
    
    static struct file_system_type fs_type = {
            .owner =        THIS_MODULE,
            .name =         "securityfs",
            .mount =        get_sb,
            .kill_sb =      kill_litter_super,
    };
    
    /**
     * 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 is the basic "create a file" 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 erorr 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)
    {
            struct dentry *dentry;
            int is_dir = S_ISDIR(mode);
            struct inode *dir, *inode;
            int error;
    
            if (!is_dir) {
                    BUG_ON(!fops);
                    mode = (mode & S_IALLUGO) | S_IFREG;
            }
    
            pr_debug("securityfs: creating file '%s'\n",name);
    
            error = simple_pin_fs(&fs_type, &mount, &mount_count);
            if (error)
                   return ERR_PTR(error);
   
           if (!parent)
                   parent = mount->mnt_root;
   
           dir = parent->d_inode;
   
           mutex_lock(&dir->i_mutex);
           dentry = lookup_one_len(name, parent, strlen(name));
           if (IS_ERR(dentry))
                   goto out;
   
           if (dentry->d_inode) {
                   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->i_private = data;
           if (is_dir) {
                   inode->i_op = &simple_dir_inode_operations;
                   inode->i_fop = &simple_dir_operations;
                   inc_nlink(inode);
                   inc_nlink(dir);
           } else {
                   inode->i_fop = fops;
           }
           d_instantiate(dentry, inode);
           dget(dentry);
           mutex_unlock(&dir->i_mutex);
           return dentry;
   
   out1:
           dput(dentry);
           dentry = ERR_PTR(error);
   out:
           mutex_unlock(&dir->i_mutex);
           simple_release_fs(&mount, &mount_count);
           return dentry;
   }
   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, %NULL will be returned.
    *
    * If securityfs is not enabled in the kernel, the value %-ENODEV is
    * returned.  It is not wise to check for this value, but rather, check for
    * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
    * code.
    */
   struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
   {
           return securityfs_create_file(name,
                                         S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
                                         parent, NULL, NULL);
   }
   EXPORT_SYMBOL_GPL(securityfs_create_dir);
   
   /**
    * 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 dentry *parent;
   
           if (!dentry || IS_ERR(dentry))
                   return;
   
           parent = dentry->d_parent;
           if (!parent || !parent->d_inode)
                   return;
   
           mutex_lock(&parent->d_inode->i_mutex);
           if (positive(dentry)) {
                   if (dentry->d_inode) {
                           if (S_ISDIR(dentry->d_inode->i_mode))
                                   simple_rmdir(parent->d_inode, dentry);
                           else
                                   simple_unlink(parent->d_inode, dentry);
                           dput(dentry);
                   }
           }
           mutex_unlock(&parent->d_inode->i_mutex);
           simple_release_fs(&mount, &mount_count);
   }
   EXPORT_SYMBOL_GPL(securityfs_remove);
   
   static struct kobject *security_kobj;
   
   static int __init securityfs_init(void)
   {
           int retval;
   
           security_kobj = kobject_create_and_add("security", kernel_kobj);
           if (!security_kobj)
                   return -EINVAL;
   
           retval = register_filesystem(&fs_type);
           if (retval)
                   kobject_put(security_kobj);
           return retval;
   }
   
   core_initcall(securityfs_init);
   MODULE_LICENSE("GPL");
   

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