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