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

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