1 | // SPDX-License-Identifier: GPL-2.0-only |
2 | /* |
3 | * inode.c - securityfs |
4 | * |
5 | * Copyright (C) 2005 Greg Kroah-Hartman <gregkh@suse.de> |
6 | * |
7 | * Based on fs/debugfs/inode.c which had the following copyright notice: |
8 | * Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com> |
9 | * Copyright (C) 2004 IBM Inc. |
10 | */ |
11 | |
12 | /* #define DEBUG */ |
13 | #include <linux/sysfs.h> |
14 | #include <linux/kobject.h> |
15 | #include <linux/fs.h> |
16 | #include <linux/fs_context.h> |
17 | #include <linux/mount.h> |
18 | #include <linux/pagemap.h> |
19 | #include <linux/init.h> |
20 | #include <linux/namei.h> |
21 | #include <linux/security.h> |
22 | #include <linux/lsm_hooks.h> |
23 | #include <linux/magic.h> |
24 | |
25 | static struct vfsmount *mount; |
26 | static int mount_count; |
27 | |
28 | static void securityfs_free_inode(struct inode *inode) |
29 | { |
30 | if (S_ISLNK(inode->i_mode)) |
31 | kfree(objp: inode->i_link); |
32 | free_inode_nonrcu(inode); |
33 | } |
34 | |
35 | static const struct super_operations securityfs_super_operations = { |
36 | .statfs = simple_statfs, |
37 | .free_inode = securityfs_free_inode, |
38 | }; |
39 | |
40 | static int securityfs_fill_super(struct super_block *sb, struct fs_context *fc) |
41 | { |
42 | static const struct tree_descr files[] = {{"" }}; |
43 | int error; |
44 | |
45 | error = simple_fill_super(sb, SECURITYFS_MAGIC, files); |
46 | if (error) |
47 | return error; |
48 | |
49 | sb->s_op = &securityfs_super_operations; |
50 | |
51 | return 0; |
52 | } |
53 | |
54 | static int securityfs_get_tree(struct fs_context *fc) |
55 | { |
56 | return get_tree_single(fc, fill_super: securityfs_fill_super); |
57 | } |
58 | |
59 | static const struct fs_context_operations securityfs_context_ops = { |
60 | .get_tree = securityfs_get_tree, |
61 | }; |
62 | |
63 | static int securityfs_init_fs_context(struct fs_context *fc) |
64 | { |
65 | fc->ops = &securityfs_context_ops; |
66 | return 0; |
67 | } |
68 | |
69 | static struct file_system_type fs_type = { |
70 | .owner = THIS_MODULE, |
71 | .name = "securityfs" , |
72 | .init_fs_context = securityfs_init_fs_context, |
73 | .kill_sb = kill_litter_super, |
74 | }; |
75 | |
76 | /** |
77 | * securityfs_create_dentry - create a dentry in the securityfs filesystem |
78 | * |
79 | * @name: a pointer to a string containing the name of the file to create. |
80 | * @mode: the permission that the file should have |
81 | * @parent: a pointer to the parent dentry for this file. This should be a |
82 | * directory dentry if set. If this parameter is %NULL, then the |
83 | * file will be created in the root of the securityfs filesystem. |
84 | * @data: a pointer to something that the caller will want to get to later |
85 | * on. The inode.i_private pointer will point to this value on |
86 | * the open() call. |
87 | * @fops: a pointer to a struct file_operations that should be used for |
88 | * this file. |
89 | * @iops: a point to a struct of inode_operations that should be used for |
90 | * this file/dir |
91 | * |
92 | * This is the basic "create a file/dir/symlink" function for |
93 | * securityfs. It allows for a wide range of flexibility in creating |
94 | * a file, or a directory (if you want to create a directory, the |
95 | * securityfs_create_dir() function is recommended to be used |
96 | * instead). |
97 | * |
98 | * This function returns a pointer to a dentry if it succeeds. This |
99 | * pointer must be passed to the securityfs_remove() function when the |
100 | * file is to be removed (no automatic cleanup happens if your module |
101 | * is unloaded, you are responsible here). If an error occurs, the |
102 | * function will return the error value (via ERR_PTR). |
103 | * |
104 | * If securityfs is not enabled in the kernel, the value %-ENODEV is |
105 | * returned. |
106 | */ |
107 | static struct dentry *securityfs_create_dentry(const char *name, umode_t mode, |
108 | struct dentry *parent, void *data, |
109 | const struct file_operations *fops, |
110 | const struct inode_operations *iops) |
111 | { |
112 | struct dentry *dentry; |
113 | struct inode *dir, *inode; |
114 | int error; |
115 | |
116 | if (!(mode & S_IFMT)) |
117 | mode = (mode & S_IALLUGO) | S_IFREG; |
118 | |
119 | pr_debug("securityfs: creating file '%s'\n" ,name); |
120 | |
121 | error = simple_pin_fs(&fs_type, mount: &mount, count: &mount_count); |
122 | if (error) |
123 | return ERR_PTR(error); |
124 | |
125 | if (!parent) |
126 | parent = mount->mnt_root; |
127 | |
128 | dir = d_inode(dentry: parent); |
129 | |
130 | inode_lock(inode: dir); |
131 | dentry = lookup_one_len(name, parent, strlen(name)); |
132 | if (IS_ERR(ptr: dentry)) |
133 | goto out; |
134 | |
135 | if (d_really_is_positive(dentry)) { |
136 | error = -EEXIST; |
137 | goto out1; |
138 | } |
139 | |
140 | inode = new_inode(sb: dir->i_sb); |
141 | if (!inode) { |
142 | error = -ENOMEM; |
143 | goto out1; |
144 | } |
145 | |
146 | inode->i_ino = get_next_ino(); |
147 | inode->i_mode = mode; |
148 | simple_inode_init_ts(inode); |
149 | inode->i_private = data; |
150 | if (S_ISDIR(mode)) { |
151 | inode->i_op = &simple_dir_inode_operations; |
152 | inode->i_fop = &simple_dir_operations; |
153 | inc_nlink(inode); |
154 | inc_nlink(inode: dir); |
155 | } else if (S_ISLNK(mode)) { |
156 | inode->i_op = iops ? iops : &simple_symlink_inode_operations; |
157 | inode->i_link = data; |
158 | } else { |
159 | inode->i_fop = fops; |
160 | } |
161 | d_instantiate(dentry, inode); |
162 | dget(dentry); |
163 | inode_unlock(inode: dir); |
164 | return dentry; |
165 | |
166 | out1: |
167 | dput(dentry); |
168 | dentry = ERR_PTR(error); |
169 | out: |
170 | inode_unlock(inode: dir); |
171 | simple_release_fs(mount: &mount, count: &mount_count); |
172 | return dentry; |
173 | } |
174 | |
175 | /** |
176 | * securityfs_create_file - create a file in the securityfs filesystem |
177 | * |
178 | * @name: a pointer to a string containing the name of the file to create. |
179 | * @mode: the permission that the file should have |
180 | * @parent: a pointer to the parent dentry for this file. This should be a |
181 | * directory dentry if set. If this parameter is %NULL, then the |
182 | * file will be created in the root of the securityfs filesystem. |
183 | * @data: a pointer to something that the caller will want to get to later |
184 | * on. The inode.i_private pointer will point to this value on |
185 | * the open() call. |
186 | * @fops: a pointer to a struct file_operations that should be used for |
187 | * this file. |
188 | * |
189 | * This function creates a file in securityfs with the given @name. |
190 | * |
191 | * This function returns a pointer to a dentry if it succeeds. This |
192 | * pointer must be passed to the securityfs_remove() function when the file is |
193 | * to be removed (no automatic cleanup happens if your module is unloaded, |
194 | * you are responsible here). If an error occurs, the function will return |
195 | * the error value (via ERR_PTR). |
196 | * |
197 | * If securityfs is not enabled in the kernel, the value %-ENODEV is |
198 | * returned. |
199 | */ |
200 | struct dentry *securityfs_create_file(const char *name, umode_t mode, |
201 | struct dentry *parent, void *data, |
202 | const struct file_operations *fops) |
203 | { |
204 | return securityfs_create_dentry(name, mode, parent, data, fops, NULL); |
205 | } |
206 | EXPORT_SYMBOL_GPL(securityfs_create_file); |
207 | |
208 | /** |
209 | * securityfs_create_dir - create a directory in the securityfs filesystem |
210 | * |
211 | * @name: a pointer to a string containing the name of the directory to |
212 | * create. |
213 | * @parent: a pointer to the parent dentry for this file. This should be a |
214 | * directory dentry if set. If this parameter is %NULL, then the |
215 | * directory will be created in the root of the securityfs filesystem. |
216 | * |
217 | * This function creates a directory in securityfs with the given @name. |
218 | * |
219 | * This function returns a pointer to a dentry if it succeeds. This |
220 | * pointer must be passed to the securityfs_remove() function when the file is |
221 | * to be removed (no automatic cleanup happens if your module is unloaded, |
222 | * you are responsible here). If an error occurs, the function will return |
223 | * the error value (via ERR_PTR). |
224 | * |
225 | * If securityfs is not enabled in the kernel, the value %-ENODEV is |
226 | * returned. |
227 | */ |
228 | struct dentry *securityfs_create_dir(const char *name, struct dentry *parent) |
229 | { |
230 | return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL); |
231 | } |
232 | EXPORT_SYMBOL_GPL(securityfs_create_dir); |
233 | |
234 | /** |
235 | * securityfs_create_symlink - create a symlink in the securityfs filesystem |
236 | * |
237 | * @name: a pointer to a string containing the name of the symlink to |
238 | * create. |
239 | * @parent: a pointer to the parent dentry for the symlink. This should be a |
240 | * directory dentry if set. If this parameter is %NULL, then the |
241 | * directory will be created in the root of the securityfs filesystem. |
242 | * @target: a pointer to a string containing the name of the symlink's target. |
243 | * If this parameter is %NULL, then the @iops parameter needs to be |
244 | * setup to handle .readlink and .get_link inode_operations. |
245 | * @iops: a pointer to the struct inode_operations to use for the symlink. If |
246 | * this parameter is %NULL, then the default simple_symlink_inode |
247 | * operations will be used. |
248 | * |
249 | * This function creates a symlink in securityfs with the given @name. |
250 | * |
251 | * This function returns a pointer to a dentry if it succeeds. This |
252 | * pointer must be passed to the securityfs_remove() function when the file is |
253 | * to be removed (no automatic cleanup happens if your module is unloaded, |
254 | * you are responsible here). If an error occurs, the function will return |
255 | * the error value (via ERR_PTR). |
256 | * |
257 | * If securityfs is not enabled in the kernel, the value %-ENODEV is |
258 | * returned. |
259 | */ |
260 | struct dentry *securityfs_create_symlink(const char *name, |
261 | struct dentry *parent, |
262 | const char *target, |
263 | const struct inode_operations *iops) |
264 | { |
265 | struct dentry *dent; |
266 | char *link = NULL; |
267 | |
268 | if (target) { |
269 | link = kstrdup(s: target, GFP_KERNEL); |
270 | if (!link) |
271 | return ERR_PTR(error: -ENOMEM); |
272 | } |
273 | dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent, |
274 | data: link, NULL, iops); |
275 | if (IS_ERR(ptr: dent)) |
276 | kfree(objp: link); |
277 | |
278 | return dent; |
279 | } |
280 | EXPORT_SYMBOL_GPL(securityfs_create_symlink); |
281 | |
282 | /** |
283 | * securityfs_remove - removes a file or directory from the securityfs filesystem |
284 | * |
285 | * @dentry: a pointer to a the dentry of the file or directory to be removed. |
286 | * |
287 | * This function removes a file or directory in securityfs that was previously |
288 | * created with a call to another securityfs function (like |
289 | * securityfs_create_file() or variants thereof.) |
290 | * |
291 | * This function is required to be called in order for the file to be |
292 | * removed. No automatic cleanup of files will happen when a module is |
293 | * removed; you are responsible here. |
294 | */ |
295 | void securityfs_remove(struct dentry *dentry) |
296 | { |
297 | struct inode *dir; |
298 | |
299 | if (!dentry || IS_ERR(ptr: dentry)) |
300 | return; |
301 | |
302 | dir = d_inode(dentry: dentry->d_parent); |
303 | inode_lock(inode: dir); |
304 | if (simple_positive(dentry)) { |
305 | if (d_is_dir(dentry)) |
306 | simple_rmdir(dir, dentry); |
307 | else |
308 | simple_unlink(dir, dentry); |
309 | dput(dentry); |
310 | } |
311 | inode_unlock(inode: dir); |
312 | simple_release_fs(mount: &mount, count: &mount_count); |
313 | } |
314 | EXPORT_SYMBOL_GPL(securityfs_remove); |
315 | |
316 | #ifdef CONFIG_SECURITY |
317 | static struct dentry *lsm_dentry; |
318 | static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count, |
319 | loff_t *ppos) |
320 | { |
321 | return simple_read_from_buffer(to: buf, count, ppos, from: lsm_names, |
322 | strlen(lsm_names)); |
323 | } |
324 | |
325 | static const struct file_operations lsm_ops = { |
326 | .read = lsm_read, |
327 | .llseek = generic_file_llseek, |
328 | }; |
329 | #endif |
330 | |
331 | static int __init securityfs_init(void) |
332 | { |
333 | int retval; |
334 | |
335 | retval = sysfs_create_mount_point(parent_kobj: kernel_kobj, name: "security" ); |
336 | if (retval) |
337 | return retval; |
338 | |
339 | retval = register_filesystem(&fs_type); |
340 | if (retval) { |
341 | sysfs_remove_mount_point(parent_kobj: kernel_kobj, name: "security" ); |
342 | return retval; |
343 | } |
344 | #ifdef CONFIG_SECURITY |
345 | lsm_dentry = securityfs_create_file("lsm" , 0444, NULL, NULL, |
346 | &lsm_ops); |
347 | #endif |
348 | return 0; |
349 | } |
350 | core_initcall(securityfs_init); |
351 | |