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/*

 *  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>

#define SECURITYFS_MAGIC        0x73636673

static struct vfsmount *mount;

static int mount_count;

/*

 * TODO:

 *   I think I can get rid of these default_file_ops, but not quite sure...

 */

static ssize_t default_read_file(struct file *file, char __user *buf,

                                 size_t count, loff_t *ppos)

{

        return 0;

}

static ssize_t default_write_file(struct file *file, const char __user *buf,

                                   size_t count, loff_t *ppos)

{

        return count;

}

static int default_open(struct inode *inode, struct file *file)

{

        if (inode->i_private)

                file->private_data = inode->i_private;

        return 0;

}

static const struct file_operations default_file_ops = {

        .read =         default_read_file,

        .write =        default_write_file,

        .open =         default_open,

};

static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)

{

        struct inode *inode = new_inode(sb);

        if (inode) {

                inode->i_mode = mode;

                inode->i_uid = 0;

                inode->i_gid = 0;

                inode->i_blocks = 0;

                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;

                switch (mode & S_IFMT) {

                default:

                        init_special_inode(inode, mode, dev);

                        break;

                case S_IFREG:

                        inode->i_fop = &default_file_ops;

                        break;

                case S_IFDIR:

                        inode->i_op = &simple_dir_inode_operations;

                        inode->i_fop = &simple_dir_operations;

                        /* directory inodes start off with i_nlink == 2 (for "." entry) */

                        inc_nlink(inode);

                        break;

                }

        }

        return inode;

}

/* SMP-safe */

static int mknod(struct inode *dir, struct dentry *dentry,

                         int mode, dev_t dev)

{

        struct inode *inode;

        int error = -EPERM;

        if (dentry->d_inode)

                return -EEXIST;

        inode = get_inode(dir->i_sb, mode, dev);

        if (inode) {

                d_instantiate(dentry, inode);

                dget(dentry);

                error = 0;

        }

        return error;

}

static int mkdir(struct inode *dir, struct dentry *dentry, int mode)

{

        int res;

        mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;

        res = mknod(dir, dentry, mode, 0);

        if (!res)

                inc_nlink(dir);

        return res;

}

static int create(struct inode *dir, struct dentry *dentry, int mode)

{

        mode = (mode & S_IALLUGO) | S_IFREG;

        return mknod(dir, dentry, mode, 0);

}

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 int get_sb(struct file_system_type *fs_type,

                  int flags, const char *dev_name,

                  void *data, struct vfsmount *mnt)

{

        return get_sb_single(fs_type, flags, data, fill_super, mnt);

}

static struct file_system_type fs_type = {

        .owner =        THIS_MODULE,

        .name =         "securityfs",

        .get_sb =       get_sb,

        .kill_sb =      kill_litter_super,

};

static int create_by_name(const char *name, mode_t mode,

                          struct dentry *parent,

                          struct dentry **dentry)

{

        int error = 0;

        *dentry = NULL;

        /* If the parent is not specified, we create it in the root.

         * We need the root dentry to do this, which is in the super

         * block. A pointer to that is in the struct vfsmount that we

         * have around.

         */

        if (!parent ) {

                if (mount && mount->mnt_sb) {

                        parent = mount->mnt_sb->s_root;

                }

        }

        if (!parent) {

                pr_debug("securityfs: Ah! can not find a parent!\n");

                return -EFAULT;

        }

        mutex_lock(&parent->d_inode->i_mutex);

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

        if (!IS_ERR(dentry)) {

                if ((mode & S_IFMT) == S_IFDIR)

                        error = mkdir(parent->d_inode, *dentry, mode);

                else

                        error = create(parent->d_inode, *dentry, mode);

        } else

                error = PTR_ERR(dentry);

        mutex_unlock(&parent->d_inode->i_mutex);

        return error;

}

/**

 * 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 paramater 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 createing 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 will return 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 will be

 * 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_file(const char *name, mode_t mode,

                                   struct dentry *parent, void *data,

                                   const struct file_operations *fops)

{

        struct dentry *dentry = NULL;

        int error;

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

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

        if (error) {

                dentry = ERR_PTR(error);

                goto exit;

        }

        error = create_by_name(name, mode, parent, &dentry);

        if (error) {

                dentry = ERR_PTR(error);

                simple_release_fs(&mount, &mount_count);

                goto exit;

        }

        if (dentry->d_inode) {

                if (fops)

                        dentry->d_inode->i_fop = fops;

                if (data)

                        dentry->d_inode->i_private = data;

        }

exit:

        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 paramater 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 will return 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 will be

 * 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)

                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 decl_subsys(security, NULL, NULL);

static int __init securityfs_init(void)

{

        int retval;

        kobj_set_kset_s(&security_subsys, kernel_subsys);

        retval = subsystem_register(&security_subsys);

        if (retval)

                return retval;

        retval = register_filesystem(&fs_type);

        if (retval)

                subsystem_unregister(&security_subsys);

        return retval;

}

core_initcall(securityfs_init);

MODULE_LICENSE("GPL");