projects/linux·blob v2.6.21 · refs

345 lines · 9.2 KiB

1/*
2 * inode.c - securityfs
3 *
4 * Copyright (C) 2005 Greg Kroah-Hartman <[email protected]>
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 <[email protected]>
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
24#define SECURITYFS_MAGIC 0x73636673
25
26static struct vfsmount *mount;
27static int mount_count;
28
29/*
30 * TODO:
31 * I think I can get rid of these default_file_ops, but not quite sure...
32 */
33static ssize_t default_read_file(struct file *file, char __user *buf,
34 size_t count, loff_t *ppos)
35{
36 return 0;
37}
38
39static ssize_t default_write_file(struct file *file, const char __user *buf,
40 size_t count, loff_t *ppos)
41{
42 return count;
43}
44
45static int default_open(struct inode *inode, struct file *file)
46{
47 if (inode->i_private)
48 file->private_data = inode->i_private;
49
50 return 0;
51}
52
53static const struct file_operations default_file_ops = {
54 .read = default_read_file,
55 .write = default_write_file,
56 .open = default_open,
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_mode = mode;
65 inode->i_uid = 0;
66 inode->i_gid = 0;
67 inode->i_blocks = 0;
68 inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
69 switch (mode & S_IFMT) {
70 default:
71 init_special_inode(inode, mode, dev);
72 break;
73 case S_IFREG:
74 inode->i_fop = &default_file_ops;
75 break;
76 case S_IFDIR:
77 inode->i_op = &simple_dir_inode_operations;
78 inode->i_fop = &simple_dir_operations;
79
80 /* directory inodes start off with i_nlink == 2 (for "." entry) */
81 inc_nlink(inode);
82 break;
83 }
84 }
85 return inode;
86}
87
88/* SMP-safe */
89static int mknod(struct inode *dir, struct dentry *dentry,
90 int mode, dev_t dev)
91{
92 struct inode *inode;
93 int error = -EPERM;
94
95 if (dentry->d_inode)
96 return -EEXIST;
97
98 inode = get_inode(dir->i_sb, mode, dev);
99 if (inode) {
100 d_instantiate(dentry, inode);
101 dget(dentry);
102 error = 0;
103 }
104 return error;
105}
106
107static int mkdir(struct inode *dir, struct dentry *dentry, int mode)
108{
109 int res;
110
111 mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR;
112 res = mknod(dir, dentry, mode, 0);
113 if (!res)
114 inc_nlink(dir);
115 return res;
116}
117
118static int create(struct inode *dir, struct dentry *dentry, int mode)
119{
120 mode = (mode & S_IALLUGO) | S_IFREG;
121 return mknod(dir, dentry, mode, 0);
122}
123
124static inline int positive(struct dentry *dentry)
125{
126 return dentry->d_inode && !d_unhashed(dentry);
127}
128
129static int fill_super(struct super_block *sb, void *data, int silent)
130{
131 static struct tree_descr files[] = {{""}};
132
133 return simple_fill_super(sb, SECURITYFS_MAGIC, files);
134}
135
136static int get_sb(struct file_system_type *fs_type,
137 int flags, const char *dev_name,
138 void *data, struct vfsmount *mnt)
139{
140 return get_sb_single(fs_type, flags, data, fill_super, mnt);
141}
142
143static struct file_system_type fs_type = {
144 .owner = THIS_MODULE,
145 .name = "securityfs",
146 .get_sb = get_sb,
147 .kill_sb = kill_litter_super,
148};
149
150static int create_by_name(const char *name, mode_t mode,
151 struct dentry *parent,
152 struct dentry **dentry)
153{
154 int error = 0;
155
156 *dentry = NULL;
157
158 /* If the parent is not specified, we create it in the root.
159 * We need the root dentry to do this, which is in the super
160 * block. A pointer to that is in the struct vfsmount that we
161 * have around.
162 */
163 if (!parent ) {
164 if (mount && mount->mnt_sb) {
165 parent = mount->mnt_sb->s_root;
166 }
167 }
168 if (!parent) {
169 pr_debug("securityfs: Ah! can not find a parent!\n");
170 return -EFAULT;
171 }
172
173 mutex_lock(&parent->d_inode->i_mutex);
174 *dentry = lookup_one_len(name, parent, strlen(name));
175 if (!IS_ERR(dentry)) {
176 if ((mode & S_IFMT) == S_IFDIR)
177 error = mkdir(parent->d_inode, *dentry, mode);
178 else
179 error = create(parent->d_inode, *dentry, mode);
180 } else
181 error = PTR_ERR(dentry);
182 mutex_unlock(&parent->d_inode->i_mutex);
183
184 return error;
185}
186
187/**
188 * securityfs_create_file - create a file in the securityfs filesystem
189 *
190 * @name: a pointer to a string containing the name of the file to create.
191 * @mode: the permission that the file should have
192 * @parent: a pointer to the parent dentry for this file. This should be a
193 * directory dentry if set. If this paramater is NULL, then the
194 * file will be created in the root of the securityfs filesystem.
195 * @data: a pointer to something that the caller will want to get to later
196 * on. The inode.i_private pointer will point to this value on
197 * the open() call.
198 * @fops: a pointer to a struct file_operations that should be used for
199 * this file.
200 *
201 * This is the basic "create a file" function for securityfs. It allows for a
202 * wide range of flexibility in createing a file, or a directory (if you
203 * want to create a directory, the securityfs_create_dir() function is
204 * recommended to be used instead.)
205 *
206 * This function will return a pointer to a dentry if it succeeds. This
207 * pointer must be passed to the securityfs_remove() function when the file is
208 * to be removed (no automatic cleanup happens if your module is unloaded,
209 * you are responsible here.) If an error occurs, NULL will be returned.
210 *
211 * If securityfs is not enabled in the kernel, the value -ENODEV will be
212 * returned. It is not wise to check for this value, but rather, check for
213 * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
214 * code.
215 */
216struct dentry *securityfs_create_file(const char *name, mode_t mode,
217 struct dentry *parent, void *data,
218 const struct file_operations *fops)
219{
220 struct dentry *dentry = NULL;
221 int error;
222
223 pr_debug("securityfs: creating file '%s'\n",name);
224
225 error = simple_pin_fs(&fs_type, &mount, &mount_count);
226 if (error) {
227 dentry = ERR_PTR(error);
228 goto exit;
229 }
230
231 error = create_by_name(name, mode, parent, &dentry);
232 if (error) {
233 dentry = ERR_PTR(error);
234 simple_release_fs(&mount, &mount_count);
235 goto exit;
236 }
237
238 if (dentry->d_inode) {
239 if (fops)
240 dentry->d_inode->i_fop = fops;
241 if (data)
242 dentry->d_inode->i_private = data;
243 }
244exit:
245 return dentry;
246}
247EXPORT_SYMBOL_GPL(securityfs_create_file);
248
249/**
250 * securityfs_create_dir - create a directory in the securityfs filesystem
251 *
252 * @name: a pointer to a string containing the name of the directory to
253 * create.
254 * @parent: a pointer to the parent dentry for this file. This should be a
255 * directory dentry if set. If this paramater is NULL, then the
256 * directory will be created in the root of the securityfs filesystem.
257 *
258 * This function creates a directory in securityfs with the given name.
259 *
260 * This function will return a pointer to a dentry if it succeeds. This
261 * pointer must be passed to the securityfs_remove() function when the file is
262 * to be removed (no automatic cleanup happens if your module is unloaded,
263 * you are responsible here.) If an error occurs, NULL will be returned.
264 *
265 * If securityfs is not enabled in the kernel, the value -ENODEV will be
266 * returned. It is not wise to check for this value, but rather, check for
267 * NULL or !NULL instead as to eliminate the need for #ifdef in the calling
268 * code.
269 */
270struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
271{
272 return securityfs_create_file(name,
273 S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO,
274 parent, NULL, NULL);
275}
276EXPORT_SYMBOL_GPL(securityfs_create_dir);
277
278/**
279 * securityfs_remove - removes a file or directory from the securityfs filesystem
280 *
281 * @dentry: a pointer to a the dentry of the file or directory to be
282 * removed.
283 *
284 * This function removes a file or directory in securityfs that was previously
285 * created with a call to another securityfs function (like
286 * securityfs_create_file() or variants thereof.)
287 *
288 * This function is required to be called in order for the file to be
289 * removed, no automatic cleanup of files will happen when a module is
290 * removed, you are responsible here.
291 */
292void securityfs_remove(struct dentry *dentry)
293{
294 struct dentry *parent;
295
296 if (!dentry)
297 return;
298
299 parent = dentry->d_parent;
300 if (!parent || !parent->d_inode)
301 return;
302
303 mutex_lock(&parent->d_inode->i_mutex);
304 if (positive(dentry)) {
305 if (dentry->d_inode) {
306 if (S_ISDIR(dentry->d_inode->i_mode))
307 simple_rmdir(parent->d_inode, dentry);
308 else
309 simple_unlink(parent->d_inode, dentry);
310 dput(dentry);
311 }
312 }
313 mutex_unlock(&parent->d_inode->i_mutex);
314 simple_release_fs(&mount, &mount_count);
315}
316EXPORT_SYMBOL_GPL(securityfs_remove);
317
318static decl_subsys(security, NULL, NULL);
319
320static int __init securityfs_init(void)
321{
322 int retval;
323
324 kset_set_kset_s(&security_subsys, kernel_subsys);
325 retval = subsystem_register(&security_subsys);
326 if (retval)
327 return retval;
328
329 retval = register_filesystem(&fs_type);
330 if (retval)
331 subsystem_unregister(&security_subsys);
332 return retval;
333}
334
335static void __exit securityfs_exit(void)
336{
337 simple_release_fs(&mount, &mount_count);
338 unregister_filesystem(&fs_type);
339 subsystem_unregister(&security_subsys);
340}
341
342core_initcall(securityfs_init);
343module_exit(securityfs_exit);
344MODULE_LICENSE("GPL");
345