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/sysfs.h>
17#include <linux/kobject.h>
18#include <linux/fs.h>
19#include <linux/mount.h>
20#include <linux/pagemap.h>
21#include <linux/init.h>
22#include <linux/namei.h>
23#include <linux/security.h>
24#include <linux/lsm_hooks.h>
25#include <linux/magic.h>
26
27static struct vfsmount *mount;
28static int mount_count;
29
30static void securityfs_evict_inode(struct inode *inode)
31{
32 truncate_inode_pages_final(&inode->i_data);
33 clear_inode(inode);
34 if (S_ISLNK(inode->i_mode))
35 kfree(inode->i_link);
36}
37
38static const struct super_operations securityfs_super_operations = {
39 .statfs = simple_statfs,
40 .evict_inode = securityfs_evict_inode,
41};
42
43static int fill_super(struct super_block *sb, void *data, int silent)
44{
45 static const struct tree_descr files[] = {{""}};
46 int error;
47
48 error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
49 if (error)
50 return error;
51
52 sb->s_op = &securityfs_super_operations;
53
54 return 0;
55}
56
57static struct dentry *get_sb(struct file_system_type *fs_type,
58 int flags, const char *dev_name,
59 void *data)
60{
61 return mount_single(fs_type, flags, data, fill_super);
62}
63
64static struct file_system_type fs_type = {
65 .owner = THIS_MODULE,
66 .name = "securityfs",
67 .mount = get_sb,
68 .kill_sb = kill_litter_super,
69};
70
71/**
72 * securityfs_create_dentry - create a dentry in the securityfs filesystem
73 *
74 * @name: a pointer to a string containing the name of the file to create.
75 * @mode: the permission that the file should have
76 * @parent: a pointer to the parent dentry for this file. This should be a
77 * directory dentry if set. If this parameter is %NULL, then the
78 * file will be created in the root of the securityfs filesystem.
79 * @data: a pointer to something that the caller will want to get to later
80 * on. The inode.i_private pointer will point to this value on
81 * the open() call.
82 * @fops: a pointer to a struct file_operations that should be used for
83 * this file.
84 * @iops: a point to a struct of inode_operations that should be used for
85 * this file/dir
86 *
87 * This is the basic "create a file/dir/symlink" function for
88 * securityfs. It allows for a wide range of flexibility in creating
89 * a file, or a directory (if you want to create a directory, the
90 * securityfs_create_dir() function is recommended to be used
91 * instead).
92 *
93 * This function returns a pointer to a dentry if it succeeds. This
94 * pointer must be passed to the securityfs_remove() function when the
95 * file is to be removed (no automatic cleanup happens if your module
96 * is unloaded, you are responsible here). If an error occurs, the
97 * function will return the error value (via ERR_PTR).
98 *
99 * If securityfs is not enabled in the kernel, the value %-ENODEV is
100 * returned.
101 */
102static struct dentry *securityfs_create_dentry(const char *name, umode_t mode,
103 struct dentry *parent, void *data,
104 const struct file_operations *fops,
105 const struct inode_operations *iops)
106{
107 struct dentry *dentry;
108 struct inode *dir, *inode;
109 int error;
110
111 if (!(mode & S_IFMT))
112 mode = (mode & S_IALLUGO) | S_IFREG;
113
114 pr_debug("securityfs: creating file '%s'\n",name);
115
116 error = simple_pin_fs(&fs_type, &mount, &mount_count);
117 if (error)
118 return ERR_PTR(error);
119
120 if (!parent)
121 parent = mount->mnt_root;
122
123 dir = d_inode(parent);
124
125 inode_lock(dir);
126 dentry = lookup_one_len(name, parent, strlen(name));
127 if (IS_ERR(dentry))
128 goto out;
129
130 if (d_really_is_positive(dentry)) {
131 error = -EEXIST;
132 goto out1;
133 }
134
135 inode = new_inode(dir->i_sb);
136 if (!inode) {
137 error = -ENOMEM;
138 goto out1;
139 }
140
141 inode->i_ino = get_next_ino();
142 inode->i_mode = mode;
143 inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
144 inode->i_private = data;
145 if (S_ISDIR(mode)) {
146 inode->i_op = &simple_dir_inode_operations;
147 inode->i_fop = &simple_dir_operations;
148 inc_nlink(inode);
149 inc_nlink(dir);
150 } else if (S_ISLNK(mode)) {
151 inode->i_op = iops ? iops : &simple_symlink_inode_operations;
152 inode->i_link = data;
153 } else {
154 inode->i_fop = fops;
155 }
156 d_instantiate(dentry, inode);
157 dget(dentry);
158 inode_unlock(dir);
159 return dentry;
160
161out1:
162 dput(dentry);
163 dentry = ERR_PTR(error);
164out:
165 inode_unlock(dir);
166 simple_release_fs(&mount, &mount_count);
167 return dentry;
168}
169
170/**
171 * securityfs_create_file - create a file in the securityfs filesystem
172 *
173 * @name: a pointer to a string containing the name of the file to create.
174 * @mode: the permission that the file should have
175 * @parent: a pointer to the parent dentry for this file. This should be a
176 * directory dentry if set. If this parameter is %NULL, then the
177 * file will be created in the root of the securityfs filesystem.
178 * @data: a pointer to something that the caller will want to get to later
179 * on. The inode.i_private pointer will point to this value on
180 * the open() call.
181 * @fops: a pointer to a struct file_operations that should be used for
182 * this file.
183 *
184 * This function creates a file in securityfs with the given @name.
185 *
186 * This function returns a pointer to a dentry if it succeeds. This
187 * pointer must be passed to the securityfs_remove() function when the file is
188 * to be removed (no automatic cleanup happens if your module is unloaded,
189 * you are responsible here). If an error occurs, the function will return
190 * the error value (via ERR_PTR).
191 *
192 * If securityfs is not enabled in the kernel, the value %-ENODEV is
193 * returned.
194 */
195struct dentry *securityfs_create_file(const char *name, umode_t mode,
196 struct dentry *parent, void *data,
197 const struct file_operations *fops)
198{
199 return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
200}
201EXPORT_SYMBOL_GPL(securityfs_create_file);
202
203/**
204 * securityfs_create_dir - create a directory in the securityfs filesystem
205 *
206 * @name: a pointer to a string containing the name of the directory to
207 * create.
208 * @parent: a pointer to the parent dentry for this file. This should be a
209 * directory dentry if set. If this parameter is %NULL, then the
210 * directory will be created in the root of the securityfs filesystem.
211 *
212 * This function creates a directory in securityfs with the given @name.
213 *
214 * This function returns a pointer to a dentry if it succeeds. This
215 * pointer must be passed to the securityfs_remove() function when the file is
216 * to be removed (no automatic cleanup happens if your module is unloaded,
217 * you are responsible here). If an error occurs, the function will return
218 * the error value (via ERR_PTR).
219 *
220 * If securityfs is not enabled in the kernel, the value %-ENODEV is
221 * returned.
222 */
223struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
224{
225 return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);
226}
227EXPORT_SYMBOL_GPL(securityfs_create_dir);
228
229/**
230 * securityfs_create_symlink - create a symlink in the securityfs filesystem
231 *
232 * @name: a pointer to a string containing the name of the symlink to
233 * create.
234 * @parent: a pointer to the parent dentry for the symlink. This should be a
235 * directory dentry if set. If this parameter is %NULL, then the
236 * directory will be created in the root of the securityfs filesystem.
237 * @target: a pointer to a string containing the name of the symlink's target.
238 * If this parameter is %NULL, then the @iops parameter needs to be
239 * setup to handle .readlink and .get_link inode_operations.
240 * @iops: a pointer to the struct inode_operations to use for the symlink. If
241 * this parameter is %NULL, then the default simple_symlink_inode
242 * operations will be used.
243 *
244 * This function creates a symlink in securityfs with the given @name.
245 *
246 * This function returns a pointer to a dentry if it succeeds. This
247 * pointer must be passed to the securityfs_remove() function when the file is
248 * to be removed (no automatic cleanup happens if your module is unloaded,
249 * you are responsible here). If an error occurs, the function will return
250 * the error value (via ERR_PTR).
251 *
252 * If securityfs is not enabled in the kernel, the value %-ENODEV is
253 * returned.
254 */
255struct dentry *securityfs_create_symlink(const char *name,
256 struct dentry *parent,
257 const char *target,
258 const struct inode_operations *iops)
259{
260 struct dentry *dent;
261 char *link = NULL;
262
263 if (target) {
264 link = kstrdup(target, GFP_KERNEL);
265 if (!link)
266 return ERR_PTR(-ENOMEM);
267 }
268 dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
269 link, NULL, iops);
270 if (IS_ERR(dent))
271 kfree(link);
272
273 return dent;
274}
275EXPORT_SYMBOL_GPL(securityfs_create_symlink);
276
277/**
278 * securityfs_remove - removes a file or directory from the securityfs filesystem
279 *
280 * @dentry: a pointer to a the dentry of the file or directory to be removed.
281 *
282 * This function removes a file or directory in securityfs that was previously
283 * created with a call to another securityfs function (like
284 * securityfs_create_file() or variants thereof.)
285 *
286 * This function is required to be called in order for the file to be
287 * removed. No automatic cleanup of files will happen when a module is
288 * removed; you are responsible here.
289 */
290void securityfs_remove(struct dentry *dentry)
291{
292 struct inode *dir;
293
294 if (!dentry || IS_ERR(dentry))
295 return;
296
297 dir = d_inode(dentry->d_parent);
298 inode_lock(dir);
299 if (simple_positive(dentry)) {
300 if (d_is_dir(dentry))
301 simple_rmdir(dir, dentry);
302 else
303 simple_unlink(dir, dentry);
304 dput(dentry);
305 }
306 inode_unlock(dir);
307 simple_release_fs(&mount, &mount_count);
308}
309EXPORT_SYMBOL_GPL(securityfs_remove);
310
311#ifdef CONFIG_SECURITY
312static struct dentry *lsm_dentry;
313static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
314 loff_t *ppos)
315{
316 return simple_read_from_buffer(buf, count, ppos, lsm_names,
317 strlen(lsm_names));
318}
319
320static const struct file_operations lsm_ops = {
321 .read = lsm_read,
322 .llseek = generic_file_llseek,
323};
324#endif
325
326static int __init securityfs_init(void)
327{
328 int retval;
329
330 retval = sysfs_create_mount_point(kernel_kobj, "security");
331 if (retval)
332 return retval;
333
334 retval = register_filesystem(&fs_type);
335 if (retval) {
336 sysfs_remove_mount_point(kernel_kobj, "security");
337 return retval;
338 }
339#ifdef CONFIG_SECURITY
340 lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
341 &lsm_ops);
342#endif
343 return 0;
344}
345core_initcall(securityfs_init);
346