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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 : 0 : static void securityfs_free_inode(struct inode *inode)
29 : : {
30 [ # # ]: 0 : if (S_ISLNK(inode->i_mode))
31 : 0 : kfree(inode->i_link);
32 : 0 : free_inode_nonrcu(inode);
33 : 0 : }
34 : :
35 : : static const struct super_operations securityfs_super_operations = {
36 : : .statfs = simple_statfs,
37 : : .free_inode = securityfs_free_inode,
38 : : };
39 : :
40 : 207 : 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 : 207 : error = simple_fill_super(sb, SECURITYFS_MAGIC, files);
46 [ + - ]: 207 : if (error)
47 : : return error;
48 : :
49 : 207 : sb->s_op = &securityfs_super_operations;
50 : :
51 : 207 : return 0;
52 : : }
53 : :
54 : 414 : static int securityfs_get_tree(struct fs_context *fc)
55 : : {
56 : 414 : return get_tree_single(fc, securityfs_fill_super);
57 : : }
58 : :
59 : : static const struct fs_context_operations securityfs_context_ops = {
60 : : .get_tree = securityfs_get_tree,
61 : : };
62 : :
63 : 414 : static int securityfs_init_fs_context(struct fs_context *fc)
64 : : {
65 : 414 : fc->ops = &securityfs_context_ops;
66 : 414 : 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 : 414 : 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 [ + + ]: 414 : if (!(mode & S_IFMT))
117 : 207 : mode = (mode & S_IALLUGO) | S_IFREG;
118 : :
119 : : pr_debug("securityfs: creating file '%s'\n",name);
120 : :
121 : 414 : error = simple_pin_fs(&fs_type, &mount, &mount_count);
122 [ - + ]: 414 : if (error)
123 : 0 : return ERR_PTR(error);
124 : :
125 [ + - ]: 414 : if (!parent)
126 : 414 : parent = mount->mnt_root;
127 : :
128 : : dir = d_inode(parent);
129 : :
130 : : inode_lock(dir);
131 : 414 : dentry = lookup_one_len(name, parent, strlen(name));
132 [ + - ]: 414 : if (IS_ERR(dentry))
133 : : goto out;
134 : :
135 [ + - ]: 414 : if (d_really_is_positive(dentry)) {
136 : : error = -EEXIST;
137 : : goto out1;
138 : : }
139 : :
140 : 414 : inode = new_inode(dir->i_sb);
141 [ + - ]: 414 : if (!inode) {
142 : : error = -ENOMEM;
143 : : goto out1;
144 : : }
145 : :
146 : 414 : inode->i_ino = get_next_ino();
147 : 414 : inode->i_mode = mode;
148 : 414 : inode->i_atime = inode->i_mtime = inode->i_ctime = current_time(inode);
149 : 414 : inode->i_private = data;
150 [ + + ]: 414 : if (S_ISDIR(mode)) {
151 : 207 : inode->i_op = &simple_dir_inode_operations;
152 : 207 : inode->i_fop = &simple_dir_operations;
153 : 207 : inc_nlink(inode);
154 : 207 : inc_nlink(dir);
155 [ - + ]: 207 : } else if (S_ISLNK(mode)) {
156 [ # # ]: 0 : inode->i_op = iops ? iops : &simple_symlink_inode_operations;
157 : 0 : inode->i_link = data;
158 : : } else {
159 : 207 : inode->i_fop = fops;
160 : : }
161 : 414 : d_instantiate(dentry, inode);
162 : : dget(dentry);
163 : : inode_unlock(dir);
164 : 414 : return dentry;
165 : :
166 : : out1:
167 : 0 : dput(dentry);
168 : : dentry = ERR_PTR(error);
169 : : out:
170 : : inode_unlock(dir);
171 : 0 : simple_release_fs(&mount, &mount_count);
172 : 0 : 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 : 0 : 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 : 414 : 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 : 207 : struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
229 : : {
230 : 207 : 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 : 0 : 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 [ # # ]: 0 : if (target) {
269 : 0 : link = kstrdup(target, GFP_KERNEL);
270 [ # # ]: 0 : if (!link)
271 : : return ERR_PTR(-ENOMEM);
272 : : }
273 : 0 : dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
274 : : link, NULL, iops);
275 [ # # ]: 0 : if (IS_ERR(dent))
276 : 0 : kfree(link);
277 : :
278 : 0 : 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 : 0 : void securityfs_remove(struct dentry *dentry)
296 : : {
297 : : struct inode *dir;
298 : :
299 [ # # # # ]: 0 : if (!dentry || IS_ERR(dentry))
300 : 0 : return;
301 : :
302 : 0 : dir = d_inode(dentry->d_parent);
303 : : inode_lock(dir);
304 [ # # ]: 0 : if (simple_positive(dentry)) {
305 [ # # ]: 0 : if (d_is_dir(dentry))
306 : 0 : simple_rmdir(dir, dentry);
307 : : else
308 : 0 : simple_unlink(dir, dentry);
309 : 0 : dput(dentry);
310 : : }
311 : : inode_unlock(dir);
312 : 0 : simple_release_fs(&mount, &mount_count);
313 : : }
314 : : EXPORT_SYMBOL_GPL(securityfs_remove);
315 : :
316 : : #ifdef CONFIG_SECURITY
317 : : static struct dentry *lsm_dentry;
318 : 0 : static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
319 : : loff_t *ppos)
320 : : {
321 : 0 : return simple_read_from_buffer(buf, count, ppos, 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 : 207 : static int __init securityfs_init(void)
332 : : {
333 : : int retval;
334 : :
335 : 207 : retval = sysfs_create_mount_point(kernel_kobj, "security");
336 [ + - ]: 207 : if (retval)
337 : : return retval;
338 : :
339 : 207 : retval = register_filesystem(&fs_type);
340 [ - + ]: 207 : if (retval) {
341 : 0 : sysfs_remove_mount_point(kernel_kobj, "security");
342 : 0 : return retval;
343 : : }
344 : : #ifdef CONFIG_SECURITY
345 : 207 : lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
346 : : &lsm_ops);
347 : : #endif
348 : 207 : return 0;
349 : : }
350 : : core_initcall(securityfs_init);
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