Root/security/inode.c

1/*
2 * inode.c - securityfs
3 *
4 * Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de>
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License version
8 * 2 as published by the Free Software Foundation.
9 *
10 * Based on fs/debugfs/inode.c which had the following copyright notice:
11 * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
12 * Copyright (C) 2004 IBM Inc.
13 */
14
15/* #define DEBUG */
16#include <linux/module.h>
17#include <linux/fs.h>
18#include <linux/mount.h>
19#include <linux/pagemap.h>
20#include <linux/init.h>
21#include <linux/namei.h>
22#include <linux/security.h>
23#include <linux/magic.h>
24
25static struct vfsmount *mount;
26static int mount_count;
27
28static inline int positive(struct dentry *dentry)
29{
30    return dentry->d_inode && !d_unhashed(dentry);
31}
32
33static int fill_super(struct super_block *sb, void *data, int silent)
34{
35    static struct tree_descr files[] = {{""}};
36
37    return simple_fill_super(sb, SECURITYFS_MAGIC, files);
38}
39
40static struct dentry *get_sb(struct file_system_type *fs_type,
41          int flags, const char *dev_name,
42          void *data)
43{
44    return mount_single(fs_type, flags, data, fill_super);
45}
46
47static struct file_system_type fs_type = {
48    .owner = THIS_MODULE,
49    .name = "securityfs",
50    .mount = get_sb,
51    .kill_sb = kill_litter_super,
52};
53
54/**
55 * securityfs_create_file - create a file in the securityfs filesystem
56 *
57 * @name: a pointer to a string containing the name of the file to create.
58 * @mode: the permission that the file should have
59 * @parent: a pointer to the parent dentry for this file. This should be a
60 * directory dentry if set. If this parameter is %NULL, then the
61 * file will be created in the root of the securityfs filesystem.
62 * @data: a pointer to something that the caller will want to get to later
63 * on. The inode.i_private pointer will point to this value on
64 * the open() call.
65 * @fops: a pointer to a struct file_operations that should be used for
66 * this file.
67 *
68 * This is the basic "create a file" function for securityfs. It allows for a
69 * wide range of flexibility in creating a file, or a directory (if you
70 * want to create a directory, the securityfs_create_dir() function is
71 * recommended to be used instead).
72 *
73 * This function returns a pointer to a dentry if it succeeds. This
74 * pointer must be passed to the securityfs_remove() function when the file is
75 * to be removed (no automatic cleanup happens if your module is unloaded,
76 * you are responsible here). If an error occurs, the function will return
77 * the erorr value (via ERR_PTR).
78 *
79 * If securityfs is not enabled in the kernel, the value %-ENODEV is
80 * returned.
81 */
82struct dentry *securityfs_create_file(const char *name, umode_t mode,
83                   struct dentry *parent, void *data,
84                   const struct file_operations *fops)
85{
86    struct dentry *dentry;
87    int is_dir = S_ISDIR(mode);
88    struct inode *dir, *inode;
89    int error;
90
91    if (!is_dir) {
92        BUG_ON(!fops);
93        mode = (mode & S_IALLUGO) | S_IFREG;
94    }
95
96    pr_debug("securityfs: creating file '%s'\n",name);
97
98    error = simple_pin_fs(&fs_type, &mount, &mount_count);
99    if (error)
100        return ERR_PTR(error);
101
102    if (!parent)
103        parent = mount->mnt_root;
104
105    dir = parent->d_inode;
106
107    mutex_lock(&dir->i_mutex);
108    dentry = lookup_one_len(name, parent, strlen(name));
109    if (IS_ERR(dentry))
110        goto out;
111
112    if (dentry->d_inode) {
113        error = -EEXIST;
114        goto out1;
115    }
116
117    inode = new_inode(dir->i_sb);
118    if (!inode) {
119        error = -ENOMEM;
120        goto out1;
121    }
122
123    inode->i_ino = get_next_ino();
124    inode->i_mode = mode;
125    inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
126    inode->i_private = data;
127    if (is_dir) {
128        inode->i_op = &simple_dir_inode_operations;
129        inode->i_fop = &simple_dir_operations;
130        inc_nlink(inode);
131        inc_nlink(dir);
132    } else {
133        inode->i_fop = fops;
134    }
135    d_instantiate(dentry, inode);
136    dget(dentry);
137    mutex_unlock(&dir->i_mutex);
138    return dentry;
139
140out1:
141    dput(dentry);
142    dentry = ERR_PTR(error);
143out:
144    mutex_unlock(&dir->i_mutex);
145    simple_release_fs(&mount, &mount_count);
146    return dentry;
147}
148EXPORT_SYMBOL_GPL(securityfs_create_file);
149
150/**
151 * securityfs_create_dir - create a directory in the securityfs filesystem
152 *
153 * @name: a pointer to a string containing the name of the directory to
154 * create.
155 * @parent: a pointer to the parent dentry for this file. This should be a
156 * directory dentry if set. If this parameter is %NULL, then the
157 * directory will be created in the root of the securityfs filesystem.
158 *
159 * This function creates a directory in securityfs with the given @name.
160 *
161 * This function returns a pointer to a dentry if it succeeds. This
162 * pointer must be passed to the securityfs_remove() function when the file is
163 * to be removed (no automatic cleanup happens if your module is unloaded,
164 * you are responsible here). If an error occurs, %NULL will be returned.
165 *
166 * If securityfs is not enabled in the kernel, the value %-ENODEV is
167 * returned. It is not wise to check for this value, but rather, check for
168 * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
169 * code.
170 */
171struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
172{
173    return securityfs_create_file(name,
174                      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
175                      parent, NULL, NULL);
176}
177EXPORT_SYMBOL_GPL(securityfs_create_dir);
178
179/**
180 * securityfs_remove - removes a file or directory from the securityfs filesystem
181 *
182 * @dentry: a pointer to a the dentry of the file or directory to be removed.
183 *
184 * This function removes a file or directory in securityfs that was previously
185 * created with a call to another securityfs function (like
186 * securityfs_create_file() or variants thereof.)
187 *
188 * This function is required to be called in order for the file to be
189 * removed. No automatic cleanup of files will happen when a module is
190 * removed; you are responsible here.
191 */
192void securityfs_remove(struct dentry *dentry)
193{
194    struct dentry *parent;
195
196    if (!dentry || IS_ERR(dentry))
197        return;
198
199    parent = dentry->d_parent;
200    if (!parent || !parent->d_inode)
201        return;
202
203    mutex_lock(&parent->d_inode->i_mutex);
204    if (positive(dentry)) {
205        if (dentry->d_inode) {
206            if (S_ISDIR(dentry->d_inode->i_mode))
207                simple_rmdir(parent->d_inode, dentry);
208            else
209                simple_unlink(parent->d_inode, dentry);
210            dput(dentry);
211        }
212    }
213    mutex_unlock(&parent->d_inode->i_mutex);
214    simple_release_fs(&mount, &mount_count);
215}
216EXPORT_SYMBOL_GPL(securityfs_remove);
217
218static struct kobject *security_kobj;
219
220static int __init securityfs_init(void)
221{
222    int retval;
223
224    security_kobj = kobject_create_and_add("security", kernel_kobj);
225    if (!security_kobj)
226        return -EINVAL;
227
228    retval = register_filesystem(&fs_type);
229    if (retval)
230        kobject_put(security_kobj);
231    return retval;
232}
233
234core_initcall(securityfs_init);
235MODULE_LICENSE("GPL");
236
237

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