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
securityfs_free_inode(struct inode * inode)28 static void securityfs_free_inode(struct inode *inode)
29 {
30 if (S_ISLNK(inode->i_mode))
31 kfree(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
securityfs_fill_super(struct super_block * sb,struct fs_context * fc)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
securityfs_get_tree(struct fs_context * fc)54 static int securityfs_get_tree(struct fs_context *fc)
55 {
56 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
securityfs_init_fs_context(struct fs_context * fc)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 */
securityfs_create_dentry(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops,const struct inode_operations * iops)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 bool pinned = false;
116
117 if (!(mode & S_IFMT))
118 mode = (mode & S_IALLUGO) | S_IFREG;
119
120 pr_debug("securityfs: creating file '%s'\n",name);
121
122 if (!parent) {
123 error = simple_pin_fs(&fs_type, &mount, &mount_count);
124 if (error)
125 return ERR_PTR(error);
126 pinned = true;
127 parent = mount->mnt_root;
128 }
129
130 dir = d_inode(parent);
131
132 inode_lock(dir);
133 dentry = lookup_noperm(&QSTR(name), parent);
134 if (IS_ERR(dentry))
135 goto out;
136
137 if (d_really_is_positive(dentry)) {
138 error = -EEXIST;
139 goto out1;
140 }
141
142 inode = new_inode(dir->i_sb);
143 if (!inode) {
144 error = -ENOMEM;
145 goto out1;
146 }
147
148 inode->i_ino = get_next_ino();
149 inode->i_mode = mode;
150 simple_inode_init_ts(inode);
151 inode->i_private = data;
152 if (S_ISDIR(mode)) {
153 inode->i_op = &simple_dir_inode_operations;
154 inode->i_fop = &simple_dir_operations;
155 inc_nlink(inode);
156 inc_nlink(dir);
157 } else if (S_ISLNK(mode)) {
158 inode->i_op = iops ? iops : &simple_symlink_inode_operations;
159 inode->i_link = data;
160 } else {
161 inode->i_fop = fops;
162 }
163 d_instantiate(dentry, inode);
164 inode_unlock(dir);
165 return dentry;
166
167 out1:
168 dput(dentry);
169 dentry = ERR_PTR(error);
170 out:
171 inode_unlock(dir);
172 if (pinned)
173 simple_release_fs(&mount, &mount_count);
174 return dentry;
175 }
176
177 /**
178 * securityfs_create_file - create a file in the securityfs filesystem
179 *
180 * @name: a pointer to a string containing the name of the file to create.
181 * @mode: the permission that the file should have
182 * @parent: a pointer to the parent dentry for this file. This should be a
183 * directory dentry if set. If this parameter is %NULL, then the
184 * file will be created in the root of the securityfs filesystem.
185 * @data: a pointer to something that the caller will want to get to later
186 * on. The inode.i_private pointer will point to this value on
187 * the open() call.
188 * @fops: a pointer to a struct file_operations that should be used for
189 * this file.
190 *
191 * This function creates a file in securityfs with the given @name.
192 *
193 * This function returns a pointer to a dentry if it succeeds. This
194 * pointer must be passed to the securityfs_remove() function when the file is
195 * to be removed (no automatic cleanup happens if your module is unloaded,
196 * you are responsible here). If an error occurs, the function will return
197 * the error value (via ERR_PTR).
198 *
199 * If securityfs is not enabled in the kernel, the value %-ENODEV is
200 * returned.
201 */
securityfs_create_file(const char * name,umode_t mode,struct dentry * parent,void * data,const struct file_operations * fops)202 struct dentry *securityfs_create_file(const char *name, umode_t mode,
203 struct dentry *parent, void *data,
204 const struct file_operations *fops)
205 {
206 return securityfs_create_dentry(name, mode, parent, data, fops, NULL);
207 }
208 EXPORT_SYMBOL_GPL(securityfs_create_file);
209
210 /**
211 * securityfs_create_dir - create a directory in the securityfs filesystem
212 *
213 * @name: a pointer to a string containing the name of the directory to
214 * create.
215 * @parent: a pointer to the parent dentry for this file. This should be a
216 * directory dentry if set. If this parameter is %NULL, then the
217 * directory will be created in the root of the securityfs filesystem.
218 *
219 * This function creates a directory in securityfs with the given @name.
220 *
221 * This function returns a pointer to a dentry if it succeeds. This
222 * pointer must be passed to the securityfs_remove() function when the file is
223 * to be removed (no automatic cleanup happens if your module is unloaded,
224 * you are responsible here). If an error occurs, the function will return
225 * the error value (via ERR_PTR).
226 *
227 * If securityfs is not enabled in the kernel, the value %-ENODEV is
228 * returned.
229 */
securityfs_create_dir(const char * name,struct dentry * parent)230 struct dentry *securityfs_create_dir(const char *name, struct dentry *parent)
231 {
232 return securityfs_create_file(name, S_IFDIR | 0755, parent, NULL, NULL);
233 }
234 EXPORT_SYMBOL_GPL(securityfs_create_dir);
235
236 /**
237 * securityfs_create_symlink - create a symlink in the securityfs filesystem
238 *
239 * @name: a pointer to a string containing the name of the symlink to
240 * create.
241 * @parent: a pointer to the parent dentry for the symlink. This should be a
242 * directory dentry if set. If this parameter is %NULL, then the
243 * directory will be created in the root of the securityfs filesystem.
244 * @target: a pointer to a string containing the name of the symlink's target.
245 * If this parameter is %NULL, then the @iops parameter needs to be
246 * setup to handle .readlink and .get_link inode_operations.
247 * @iops: a pointer to the struct inode_operations to use for the symlink. If
248 * this parameter is %NULL, then the default simple_symlink_inode
249 * operations will be used.
250 *
251 * This function creates a symlink in securityfs with the given @name.
252 *
253 * This function returns a pointer to a dentry if it succeeds. This
254 * pointer must be passed to the securityfs_remove() function when the file is
255 * to be removed (no automatic cleanup happens if your module is unloaded,
256 * you are responsible here). If an error occurs, the function will return
257 * the error value (via ERR_PTR).
258 *
259 * If securityfs is not enabled in the kernel, the value %-ENODEV is
260 * returned.
261 */
securityfs_create_symlink(const char * name,struct dentry * parent,const char * target,const struct inode_operations * iops)262 struct dentry *securityfs_create_symlink(const char *name,
263 struct dentry *parent,
264 const char *target,
265 const struct inode_operations *iops)
266 {
267 struct dentry *dent;
268 char *link = NULL;
269
270 if (target) {
271 link = kstrdup(target, GFP_KERNEL);
272 if (!link)
273 return ERR_PTR(-ENOMEM);
274 }
275 dent = securityfs_create_dentry(name, S_IFLNK | 0444, parent,
276 link, NULL, iops);
277 if (IS_ERR(dent))
278 kfree(link);
279
280 return dent;
281 }
282 EXPORT_SYMBOL_GPL(securityfs_create_symlink);
283
remove_one(struct dentry * victim)284 static void remove_one(struct dentry *victim)
285 {
286 if (victim->d_parent == victim->d_sb->s_root)
287 simple_release_fs(&mount, &mount_count);
288 }
289
290 /**
291 * securityfs_remove - removes a file or directory from the securityfs filesystem
292 *
293 * @dentry: a pointer to a the dentry of the file or directory to be removed.
294 *
295 * This function removes a file or directory in securityfs that was previously
296 * created with a call to another securityfs function (like
297 * securityfs_create_file() or variants thereof.)
298 *
299 * This function is required to be called in order for the file to be
300 * removed. No automatic cleanup of files will happen when a module is
301 * removed; you are responsible here.
302 *
303 * AV: when applied to directory it will take all children out; no need to call
304 * it for descendents if ancestor is getting killed.
305 */
securityfs_remove(struct dentry * dentry)306 void securityfs_remove(struct dentry *dentry)
307 {
308 if (IS_ERR_OR_NULL(dentry))
309 return;
310
311 simple_pin_fs(&fs_type, &mount, &mount_count);
312 simple_recursive_removal(dentry, remove_one);
313 simple_release_fs(&mount, &mount_count);
314 }
315 EXPORT_SYMBOL_GPL(securityfs_remove);
316
317 #ifdef CONFIG_SECURITY
318 static struct dentry *lsm_dentry;
lsm_read(struct file * filp,char __user * buf,size_t count,loff_t * ppos)319 static ssize_t lsm_read(struct file *filp, char __user *buf, size_t count,
320 loff_t *ppos)
321 {
322 return simple_read_from_buffer(buf, count, ppos, lsm_names,
323 strlen(lsm_names));
324 }
325
326 static const struct file_operations lsm_ops = {
327 .read = lsm_read,
328 .llseek = generic_file_llseek,
329 };
330 #endif
331
securityfs_init(void)332 static int __init securityfs_init(void)
333 {
334 int retval;
335
336 retval = sysfs_create_mount_point(kernel_kobj, "security");
337 if (retval)
338 return retval;
339
340 retval = register_filesystem(&fs_type);
341 if (retval) {
342 sysfs_remove_mount_point(kernel_kobj, "security");
343 return retval;
344 }
345 #ifdef CONFIG_SECURITY
346 lsm_dentry = securityfs_create_file("lsm", 0444, NULL, NULL,
347 &lsm_ops);
348 #endif
349 return 0;
350 }
351 core_initcall(securityfs_init);
352