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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/lsm_hooks.h> | |
24 | #include <linux/magic.h> | |
25 | ||
26 | static struct vfsmount *mount; | |
27 | static int mount_count; | |
28 | ||
29 | static void securityfs_i_callback(struct rcu_head *head) | |
30 | { | |
31 | struct inode *inode = container_of(head, struct inode, i_rcu); | |
32 | if (S_ISLNK(inode->i_mode)) | |
33 | kfree(inode->i_link); | |
34 | free_inode_nonrcu(inode); | |
35 | } | |
36 | ||
37 | static void securityfs_destroy_inode(struct inode *inode) | |
38 | { | |
39 | call_rcu(&inode->i_rcu, securityfs_i_callback); | |
40 | } | |
41 | ||
42 | static const struct super_operations securityfs_super_operations = { | |
43 | .statfs = simple_statfs, | |
44 | .destroy_inode = securityfs_destroy_inode, | |
45 | }; | |
46 | ||
47 | static int fill_super(struct super_block *sb, void *data, int silent) | |
48 | { | |
49 | static const struct tree_descr files[] = {{""}}; | |
50 | int error; | |
51 | ||
52 | error = simple_fill_super(sb, SECURITYFS_MAGIC, files); | |
53 | if (error) | |
54 | return error; | |
55 | ||
56 | sb->s_op = &securityfs_super_operations; | |
57 | ||
58 | return 0; | |
59 | } | |
60 | ||
61 | static struct dentry *get_sb(struct file_system_type *fs_type, | |
62 | int flags, const char *dev_name, | |
63 | void *data) | |
64 | { | |
65 | return mount_single(fs_type, flags, data, fill_super); | |
66 | } | |
67 | ||
68 | static struct file_system_type fs_type = { | |
69 | .owner = THIS_MODULE, | |
70 | .name = "securityfs", | |
71 | .mount = get_sb, | |
72 | .kill_sb = kill_litter_super, | |
73 | }; | |
74 | ||
75 | /** | |
76 | * securityfs_create_dentry - create a dentry in the securityfs filesystem | |
77 | * | |
78 | * @name: a pointer to a string containing the name of the file to create. | |
79 | * @mode: the permission that the file should have | |
80 | * @parent: a pointer to the parent dentry for this file. This should be a | |
81 | * directory dentry if set. If this parameter is %NULL, then the | |
82 | * file will be created in the root of the securityfs filesystem. | |
83 | * @data: a pointer to something that the caller will want to get to later | |
84 | * on. The inode.i_private pointer will point to this value on | |
85 | * the open() call. | |
86 | * @fops: a pointer to a struct file_operations that should be used for | |
87 | * this file. | |
88 | * @iops: a point to a struct of inode_operations that should be used for | |
89 | * this file/dir | |
90 | * | |
91 | * This is the basic "create a file/dir/symlink" function for | |
92 | * securityfs. It allows for a wide range of flexibility in creating | |
93 | * a file, or a directory (if you want to create a directory, the | |
94 | * securityfs_create_dir() function is recommended to be used | |
95 | * instead). | |
96 | * | |
97 | * This function returns a pointer to a dentry if it succeeds. This | |
98 | * pointer must be passed to the securityfs_remove() function when the | |
99 | * file is to be removed (no automatic cleanup happens if your module | |
100 | * is unloaded, you are responsible here). If an error occurs, the | |
101 | * function will return the error value (via ERR_PTR). | |
102 | * | |
103 | * If securityfs is not enabled in the kernel, the value %-ENODEV is | |
104 | * returned. | |
105 | */ | |
106 | static struct dentry *securityfs_create_dentry(const char *name, umode_t mode, | |
107 | struct dentry *parent, void *data, | |
108 | const struct file_operations *fops, | |
109 | const struct inode_operations *iops) | |
110 | { | |
111 | struct dentry *dentry; | |
112 | struct inode *dir, *inode; | |
113 | int error; | |
114 | ||
115 | if (!(mode & S_IFMT)) | |
116 | mode = (mode & S_IALLUGO) | S_IFREG; | |
117 | ||
118 | pr_debug("securityfs: creating file '%s'\n",name); | |
119 | ||
120 | error = simple_pin_fs(&fs_type, &mount, &mount_count); | |
121 | if (error) | |
122 | return ERR_PTR(error); | |
123 | ||
124 | if (!parent) | |
125 | parent = mount->mnt_root; | |
126 | ||
127 | dir = d_inode(parent); | |
128 | ||
129 | inode_lock(dir); | |
130 | dentry = lookup_one_len(name, parent, strlen(name)); | |
131 | if (IS_ERR(dentry)) | |
132 | goto out; | |
133 | ||
134 | if (d_really_is_positive(dentry)) { | |
135 | error = -EEXIST; | |
136 | goto out1; | |
137 | } | |
138 | ||
139 | inode = new_inode(dir->i_sb); | |
140 | if (!inode) { | |
141 | error = -ENOMEM; | |
142 | goto out1; | |
143 | } | |
144 | ||
145 | inode->i_ino = get_next_ino(); | |
146 | inode->i_mode = mode; | |
147 | inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode); | |
148 | inode->i_private = data; | |
149 | if (S_ISDIR(mode)) { | |
150 | inode->i_op = &simple_dir_inode_operations; | |
151 | inode->i_fop = &simple_dir_operations; | |
152 | inc_nlink(inode); | |
153 | inc_nlink(dir); | |
154 | } else if (S_ISLNK(mode)) { | |
155 | inode->i_op = iops ? iops : &simple_symlink_inode_operations; | |
156 | inode->i_link = data; | |
157 | } else { | |
158 | inode->i_fop = fops; | |
159 | } | |
160 | d_instantiate(dentry, inode); | |
161 | dget(dentry); | |
162 | inode_unlock(dir); | |
163 | return dentry; | |
164 | ||
165 | out1: | |
166 | dput(dentry); | |
167 | dentry = ERR_PTR(error); | |
168 | out: | |
169 | inode_unlock(dir); | |
170 | simple_release_fs(&mount, &mount_count); | |
171 | return dentry; | |
172 | } | |
173 | ||
174 | /** | |
175 | * securityfs_create_file - create a file in the securityfs filesystem | |
176 | * | |
177 | * @name: a pointer to a string containing the name of the file to create. | |
178 | * @mode: the permission that the file should have | |
179 | * @parent: a pointer to the parent dentry for this file. This should be a | |
180 | * directory dentry if set. If this parameter is %NULL, then the | |
181 | * file will be created in the root of the securityfs filesystem. | |
182 | * @data: a pointer to something that the caller will want to get to later | |
183 | * on. The inode.i_private pointer will point to this value on | |
184 | * the open() call. | |
185 | * @fops: a pointer to a struct file_operations that should be used for | |
186 | * this file. | |
187 | * | |
188 | * This function creates a file in securityfs with the given @name. | |
189 | * | |
190 | * This function returns a pointer to a dentry if it succeeds. This | |
191 | * pointer must be passed to the securityfs_remove() function when the file is | |
192 | * to be removed (no automatic cleanup happens if your module is unloaded, | |
193 | * you are responsible here). If an error occurs, the function will return | |
194 | * the error value (via ERR_PTR). | |
195 | * | |
196 | * If securityfs is not enabled in the kernel, the value %-ENODEV is | |
197 | * returned. | |
198 | */ | |
199 | struct dentry *securityfs_create_file(const char *name, umode_t mode, | |
200 | struct dentry *parent, void *data, | |
201 | const struct file_operations *fops) | |
202 | { | |
203 | return securityfs_create_dentry(name, mode, parent, data, fops, NULL); | |
204 | } | |
205 | EXPORT_SYMBOL_GPL(securityfs_create_file); | |
206 | ||
207 | /** | |
208 | * securityfs_create_dir - create a directory in the securityfs filesystem | |
209 | * | |
210 | * @name: a pointer to a string containing the name of the directory to | |
211 | * create. | |
212 | * @parent: a pointer to the parent dentry for this file. This should be a | |
213 | * directory dentry if set. If this parameter is %NULL, then the | |
214 | * directory will be created in the root of the securityfs filesystem. | |
215 | * | |
216 | * This function creates a directory in securityfs with the given @name. | |
217 | * | |
218 | * This function returns a pointer to a dentry if it succeeds. This | |
219 | * pointer must be passed to the securityfs_remove() function when the file is | |
220 | * to be removed (no automatic cleanup happens if your module is unloaded, | |
221 | * you are responsible here). If an error occurs, the function will return | |
222 | * the error value (via ERR_PTR). | |
223 | * | |
224 | * If securityfs is not enabled in the kernel, the value %-ENODEV is | |
225 | * returned. | |
226 | */ | |
227 | struct dentry *securityfs_create_dir(const char *name, struct dentry *parent) | |
228 | { | |
229 | return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL); | |
230 | } | |
231 | EXPORT_SYMBOL_GPL(securityfs_create_dir); | |
232 | ||
233 | /** | |
234 | * securityfs_create_symlink - create a symlink in the securityfs filesystem | |
235 | * | |
236 | * @name: a pointer to a string containing the name of the symlink to | |
237 | * create. | |
238 | * @parent: a pointer to the parent dentry for the symlink. This should be a | |
239 | * directory dentry if set. If this parameter is %NULL, then the | |
240 | * directory will be created in the root of the securityfs filesystem. | |
241 | * @target: a pointer to a string containing the name of the symlink's target. | |
242 | * If this parameter is %NULL, then the @iops parameter needs to be | |
243 | * setup to handle .readlink and .get_link inode_operations. | |
244 | * @iops: a pointer to the struct inode_operations to use for the symlink. If | |
245 | * this parameter is %NULL, then the default simple_symlink_inode | |
246 | * operations will be used. | |
247 | * | |
248 | * This function creates a symlink 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, the function will return | |
254 | * the error value (via ERR_PTR). | |
255 | * | |
256 | * If securityfs is not enabled in the kernel, the value %-ENODEV is | |
257 | * returned. | |
258 | */ | |
259 | struct dentry *securityfs_create_symlink(const char *name, | |
260 | struct dentry *parent, | |
261 | const char *target, | |
262 | const struct inode_operations *iops) | |
263 | { | |
264 | struct dentry *dent; | |
265 | char *link = NULL; | |
266 | ||
267 | if (target) { | |
268 | link = kstrdup(target, GFP_KERNEL); | |
269 | if (!link) | |
270 | return ERR_PTR(-ENOMEM); | |
271 | } | |
272 | dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent, | |
273 | link, NULL, iops); | |
274 | if (IS_ERR(dent)) | |
275 | kfree(link); | |
276 | ||
277 | return dent; | |
278 | } | |
279 | EXPORT_SYMBOL_GPL(securityfs_create_symlink); | |
280 | ||
281 | /** | |
282 | * securityfs_remove - removes a file or directory from the securityfs filesystem | |
283 | * | |
284 | * @dentry: a pointer to a the dentry of the file or directory to be removed. | |
285 | * | |
286 | * This function removes a file or directory in securityfs that was previously | |
287 | * created with a call to another securityfs function (like | |
288 | * securityfs_create_file() or variants thereof.) | |
289 | * | |
290 | * This function is required to be called in order for the file to be | |
291 | * removed. No automatic cleanup of files will happen when a module is | |
292 | * removed; you are responsible here. | |
293 | */ | |
294 | void securityfs_remove(struct dentry *dentry) | |
295 | { | |
296 | struct inode *dir; | |
297 | ||
298 | if (!dentry || IS_ERR(dentry)) | |
299 | return; | |
300 | ||
301 | dir = d_inode(dentry->d_parent); | |
302 | inode_lock(dir); | |
303 | if (simple_positive(dentry)) { | |
304 | if (d_is_dir(dentry)) | |
305 | simple_rmdir(dir, dentry); | |
306 | else | |
307 | simple_unlink(dir, dentry); | |
308 | dput(dentry); | |
309 | } | |
310 | inode_unlock(dir); | |
311 | simple_release_fs(&mount, &mount_count); | |
312 | } | |
313 | EXPORT_SYMBOL_GPL(securityfs_remove); | |
314 | ||
315 | #ifdef CONFIG_SECURITY | |
316 | static struct dentry *lsm_dentry; | |
317 | static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count, | |
318 | loff_t *ppos) | |
319 | { | |
320 | return simple_read_from_buffer(buf, count, ppos, lsm_names, | |
321 | strlen(lsm_names)); | |
322 | } | |
323 | ||
324 | static const struct file_operations lsm_ops = { | |
325 | .read = lsm_read, | |
326 | .llseek = generic_file_llseek, | |
327 | }; | |
328 | #endif | |
329 | ||
330 | static int __init securityfs_init(void) | |
331 | { | |
332 | int retval; | |
333 | ||
334 | retval = sysfs_create_mount_point(kernel_kobj, "security"); | |
335 | if (retval) | |
336 | return retval; | |
337 | ||
338 | retval = register_filesystem(&fs_type); | |
339 | if (retval) { | |
340 | sysfs_remove_mount_point(kernel_kobj, "security"); | |
341 | return retval; | |
342 | } | |
343 | #ifdef CONFIG_SECURITY | |
344 | lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL, | |
345 | &lsm_ops); | |
346 | #endif | |
347 | return 0; | |
348 | } | |
349 | ||
350 | core_initcall(securityfs_init); | |
351 | MODULE_LICENSE("GPL"); | |
352 |