Root/security/inode.c

Source at commit be977234bfb4a6dca8a39e7c52165e4cd536ad71 created 9 years 4 months ago.
By Lars-Peter Clausen, jz4740: Fix compile error
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
28/*
29 * TODO:
30 * I think I can get rid of these default_file_ops, but not quite sure...
31 */
32static ssize_t default_read_file(struct file *file, char __user *buf,
33                 size_t count, loff_t *ppos)
34{
35    return 0;
36}
37
38static ssize_t default_write_file(struct file *file, const char __user *buf,
39                   size_t count, loff_t *ppos)
40{
41    return count;
42}
43
44static int default_open(struct inode *inode, struct file *file)
45{
46    if (inode->i_private)
47        file->private_data = inode->i_private;
48
49    return 0;
50}
51
52static const struct file_operations default_file_ops = {
53    .read = default_read_file,
54    .write = default_write_file,
55    .open = default_open,
56    .llseek = noop_llseek,
57};
58
59static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev)
60{
61    struct inode *inode = new_inode(sb);
62
63    if (inode) {
64        inode->i_ino = get_next_ino();
65        inode->i_mode = mode;
66        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
67        switch (mode & S_IFMT) {
68        default:
69            init_special_inode(inode, mode, dev);
70            break;
71        case S_IFREG:
72            inode->i_fop = &default_file_ops;
73            break;
74        case S_IFDIR:
75            inode->i_op = &simple_dir_inode_operations;
76            inode->i_fop = &simple_dir_operations;
77
78            /* directory inodes start off with i_nlink == 2 (for "." entry) */
79            inc_nlink(inode);
80            break;
81        }
82    }
83    return inode;
84}
85
86/* SMP-safe */
87static int mknod(struct inode *dir, struct dentry *dentry,
88             int mode, dev_t dev)
89{
90    struct inode *inode;
91    int error = -ENOMEM;
92
93    if (dentry->d_inode)
94        return -EEXIST;
95
96    inode = get_inode(dir->i_sb, mode, dev);
97    if (inode) {
98        d_instantiate(dentry, inode);
99        dget(dentry);
100        error = 0;
101    }
102    return error;
103}
104
105static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
106{
107    int res;
108
109    mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
110    res = mknod(dir, dentry, mode, 0);
111    if (!res)
112        inc_nlink(dir);
113    return res;
114}
115
116static int create(struct inode *dir, struct dentry *dentry, int mode)
117{
118    mode = (mode & S_IALLUGO) | S_IFREG;
119    return mknod(dir, dentry, mode, 0);
120}
121
122static inline int positive(struct dentry *dentry)
123{
124    return dentry->d_inode && !d_unhashed(dentry);
125}
126
127static int fill_super(struct super_block *sb, void *data, int silent)
128{
129    static struct tree_descr files[] = {{""}};
130
131    return simple_fill_super(sb, SECURITYFS_MAGIC, files);
132}
133
134static struct dentry *get_sb(struct file_system_type *fs_type,
135          int flags, const char *dev_name,
136          void *data)
137{
138    return mount_single(fs_type, flags, data, fill_super);
139}
140
141static struct file_system_type fs_type = {
142    .owner = THIS_MODULE,
143    .name = "securityfs",
144    .mount = get_sb,
145    .kill_sb = kill_litter_super,
146};
147
148static int create_by_name(const char *name, mode_t mode,
149              struct dentry *parent,
150              struct dentry **dentry)
151{
152    int error = 0;
153
154    *dentry = NULL;
155
156    /* If the parent is not specified, we create it in the root.
157     * We need the root dentry to do this, which is in the super
158     * block. A pointer to that is in the struct vfsmount that we
159     * have around.
160     */
161    if (!parent)
162        parent = mount->mnt_sb->s_root;
163
164    mutex_lock(&parent->d_inode->i_mutex);
165    *dentry = lookup_one_len(name, parent, strlen(name));
166    if (!IS_ERR(*dentry)) {
167        if ((mode & S_IFMT) == S_IFDIR)
168            error = mkdir(parent->d_inode, *dentry, mode);
169        else
170            error = create(parent->d_inode, *dentry, mode);
171        if (error)
172            dput(*dentry);
173    } else
174        error = PTR_ERR(*dentry);
175    mutex_unlock(&parent->d_inode->i_mutex);
176
177    return error;
178}
179
180/**
181 * securityfs_create_file - create a file in the securityfs filesystem
182 *
183 * @name: a pointer to a string containing the name of the file to create.
184 * @mode: the permission that the file should have
185 * @parent: a pointer to the parent dentry for this file. This should be a
186 * directory dentry if set. If this parameter is %NULL, then the
187 * file will be created in the root of the securityfs filesystem.
188 * @data: a pointer to something that the caller will want to get to later
189 * on. The inode.i_private pointer will point to this value on
190 * the open() call.
191 * @fops: a pointer to a struct file_operations that should be used for
192 * this file.
193 *
194 * This is the basic "create a file" function for securityfs. It allows for a
195 * wide range of flexibility in creating a file, or a directory (if you
196 * want to create a directory, the securityfs_create_dir() function is
197 * recommended to be used instead).
198 *
199 * This function returns a pointer to a dentry if it succeeds. This
200 * pointer must be passed to the securityfs_remove() function when the file is
201 * to be removed (no automatic cleanup happens if your module is unloaded,
202 * you are responsible here). If an error occurs, the function will return
203 * the erorr value (via ERR_PTR).
204 *
205 * If securityfs is not enabled in the kernel, the value %-ENODEV is
206 * returned.
207 */
208struct dentry *securityfs_create_file(const char *name, mode_t mode,
209                   struct dentry *parent, void *data,
210                   const struct file_operations *fops)
211{
212    struct dentry *dentry = NULL;
213    int error;
214
215    pr_debug("securityfs: creating file '%s'\n",name);
216
217    error = simple_pin_fs(&fs_type, &mount, &mount_count);
218    if (error) {
219        dentry = ERR_PTR(error);
220        goto exit;
221    }
222
223    error = create_by_name(name, mode, parent, &dentry);
224    if (error) {
225        dentry = ERR_PTR(error);
226        simple_release_fs(&mount, &mount_count);
227        goto exit;
228    }
229
230    if (dentry->d_inode) {
231        if (fops)
232            dentry->d_inode->i_fop = fops;
233        if (data)
234            dentry->d_inode->i_private = data;
235    }
236exit:
237    return dentry;
238}
239EXPORT_SYMBOL_GPL(securityfs_create_file);
240
241/**
242 * securityfs_create_dir - create a directory in the securityfs filesystem
243 *
244 * @name: a pointer to a string containing the name of the directory to
245 * create.
246 * @parent: a pointer to the parent dentry for this file. This should be a
247 * directory dentry if set. If this parameter is %NULL, then the
248 * directory will be created in the root of the securityfs filesystem.
249 *
250 * This function creates a directory in securityfs with the given @name.
251 *
252 * This function returns a pointer to a dentry if it succeeds. This
253 * pointer must be passed to the securityfs_remove() function when the file is
254 * to be removed (no automatic cleanup happens if your module is unloaded,
255 * you are responsible here). If an error occurs, %NULL will be returned.
256 *
257 * If securityfs is not enabled in the kernel, the value %-ENODEV is
258 * returned. It is not wise to check for this value, but rather, check for
259 * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling
260 * code.
261 */
262struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
263{
264    return securityfs_create_file(name,
265                      S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
266                      parent, NULL, NULL);
267}
268EXPORT_SYMBOL_GPL(securityfs_create_dir);
269
270/**
271 * securityfs_remove - removes a file or directory from the securityfs filesystem
272 *
273 * @dentry: a pointer to a the dentry of the file or directory to be removed.
274 *
275 * This function removes a file or directory in securityfs that was previously
276 * created with a call to another securityfs function (like
277 * securityfs_create_file() or variants thereof.)
278 *
279 * This function is required to be called in order for the file to be
280 * removed. No automatic cleanup of files will happen when a module is
281 * removed; you are responsible here.
282 */
283void securityfs_remove(struct dentry *dentry)
284{
285    struct dentry *parent;
286
287    if (!dentry || IS_ERR(dentry))
288        return;
289
290    parent = dentry->d_parent;
291    if (!parent || !parent->d_inode)
292        return;
293
294    mutex_lock(&parent->d_inode->i_mutex);
295    if (positive(dentry)) {
296        if (dentry->d_inode) {
297            if (S_ISDIR(dentry->d_inode->i_mode))
298                simple_rmdir(parent->d_inode, dentry);
299            else
300                simple_unlink(parent->d_inode, dentry);
301            dput(dentry);
302        }
303    }
304    mutex_unlock(&parent->d_inode->i_mutex);
305    simple_release_fs(&mount, &mount_count);
306}
307EXPORT_SYMBOL_GPL(securityfs_remove);
308
309static struct kobject *security_kobj;
310
311static int __init securityfs_init(void)
312{
313    int retval;
314
315    security_kobj = kobject_create_and_add("security", kernel_kobj);
316    if (!security_kobj)
317        return -EINVAL;
318
319    retval = register_filesystem(&fs_type);
320    if (retval)
321        kobject_put(security_kobj);
322    return retval;
323}
324
325core_initcall(securityfs_init);
326MODULE_LICENSE("GPL");
327
328

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