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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/magic.h> |
24 | |
25 | static struct vfsmount *mount; |
26 | static int mount_count; |
27 | |
28 | /* |
29 | * TODO: |
30 | * I think I can get rid of these default_file_ops, but not quite sure... |
31 | */ |
32 | static ssize_t default_read_file(struct file *file, char __user *buf, |
33 | size_t count, loff_t *ppos) |
34 | { |
35 | return 0; |
36 | } |
37 | |
38 | static ssize_t default_write_file(struct file *file, const char __user *buf, |
39 | size_t count, loff_t *ppos) |
40 | { |
41 | return count; |
42 | } |
43 | |
44 | static int default_open(struct inode *inode, struct file *file) |
45 | { |
46 | if (inode->i_private) |
47 | file->private_data = inode->i_private; |
48 | |
49 | return 0; |
50 | } |
51 | |
52 | static const struct file_operations default_file_ops = { |
53 | .read = default_read_file, |
54 | .write = default_write_file, |
55 | .open = default_open, |
56 | }; |
57 | |
58 | static struct inode *get_inode(struct super_block *sb, int mode, dev_t dev) |
59 | { |
60 | struct inode *inode = new_inode(sb); |
61 | |
62 | if (inode) { |
63 | inode->i_mode = mode; |
64 | inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
65 | switch (mode & S_IFMT) { |
66 | default: |
67 | init_special_inode(inode, mode, dev); |
68 | break; |
69 | case S_IFREG: |
70 | inode->i_fop = &default_file_ops; |
71 | break; |
72 | case S_IFDIR: |
73 | inode->i_op = &simple_dir_inode_operations; |
74 | inode->i_fop = &simple_dir_operations; |
75 | |
76 | /* directory inodes start off with i_nlink == 2 (for "." entry) */ |
77 | inc_nlink(inode); |
78 | break; |
79 | } |
80 | } |
81 | return inode; |
82 | } |
83 | |
84 | /* SMP-safe */ |
85 | static int mknod(struct inode *dir, struct dentry *dentry, |
86 | int mode, dev_t dev) |
87 | { |
88 | struct inode *inode; |
89 | int error = -EPERM; |
90 | |
91 | if (dentry->d_inode) |
92 | return -EEXIST; |
93 | |
94 | inode = get_inode(dir->i_sb, mode, dev); |
95 | if (inode) { |
96 | d_instantiate(dentry, inode); |
97 | dget(dentry); |
98 | error = 0; |
99 | } |
100 | return error; |
101 | } |
102 | |
103 | static int mkdir(struct inode *dir, struct dentry *dentry, int mode) |
104 | { |
105 | int res; |
106 | |
107 | mode = (mode & (S_IRWXUGO | S_ISVTX)) | S_IFDIR; |
108 | res = mknod(dir, dentry, mode, 0); |
109 | if (!res) |
110 | inc_nlink(dir); |
111 | return res; |
112 | } |
113 | |
114 | static int create(struct inode *dir, struct dentry *dentry, int mode) |
115 | { |
116 | mode = (mode & S_IALLUGO) | S_IFREG; |
117 | return mknod(dir, dentry, mode, 0); |
118 | } |
119 | |
120 | static inline int positive(struct dentry *dentry) |
121 | { |
122 | return dentry->d_inode && !d_unhashed(dentry); |
123 | } |
124 | |
125 | static int fill_super(struct super_block *sb, void *data, int silent) |
126 | { |
127 | static struct tree_descr files[] = {{""}}; |
128 | |
129 | return simple_fill_super(sb, SECURITYFS_MAGIC, files); |
130 | } |
131 | |
132 | static int get_sb(struct file_system_type *fs_type, |
133 | int flags, const char *dev_name, |
134 | void *data, struct vfsmount *mnt) |
135 | { |
136 | return get_sb_single(fs_type, flags, data, fill_super, mnt); |
137 | } |
138 | |
139 | static struct file_system_type fs_type = { |
140 | .owner = THIS_MODULE, |
141 | .name = "securityfs", |
142 | .get_sb = get_sb, |
143 | .kill_sb = kill_litter_super, |
144 | }; |
145 | |
146 | static int create_by_name(const char *name, mode_t mode, |
147 | struct dentry *parent, |
148 | struct dentry **dentry) |
149 | { |
150 | int error = 0; |
151 | |
152 | *dentry = NULL; |
153 | |
154 | /* If the parent is not specified, we create it in the root. |
155 | * We need the root dentry to do this, which is in the super |
156 | * block. A pointer to that is in the struct vfsmount that we |
157 | * have around. |
158 | */ |
159 | if (!parent) |
160 | parent = mount->mnt_sb->s_root; |
161 | |
162 | mutex_lock(&parent->d_inode->i_mutex); |
163 | *dentry = lookup_one_len(name, parent, strlen(name)); |
164 | if (!IS_ERR(dentry)) { |
165 | if ((mode & S_IFMT) == S_IFDIR) |
166 | error = mkdir(parent->d_inode, *dentry, mode); |
167 | else |
168 | error = create(parent->d_inode, *dentry, mode); |
169 | } else |
170 | error = PTR_ERR(dentry); |
171 | mutex_unlock(&parent->d_inode->i_mutex); |
172 | |
173 | return error; |
174 | } |
175 | |
176 | /** |
177 | * securityfs_create_file - create a file in the securityfs filesystem |
178 | * |
179 | * @name: a pointer to a string containing the name of the file to create. |
180 | * @mode: the permission that the file should have |
181 | * @parent: a pointer to the parent dentry for this file. This should be a |
182 | * directory dentry if set. If this parameter is %NULL, then the |
183 | * file will be created in the root of the securityfs filesystem. |
184 | * @data: a pointer to something that the caller will want to get to later |
185 | * on. The inode.i_private pointer will point to this value on |
186 | * the open() call. |
187 | * @fops: a pointer to a struct file_operations that should be used for |
188 | * this file. |
189 | * |
190 | * This is the basic "create a file" function for securityfs. It allows for a |
191 | * wide range of flexibility in creating a file, or a directory (if you |
192 | * want to create a directory, the securityfs_create_dir() function is |
193 | * recommended to be used instead). |
194 | * |
195 | * This function returns a pointer to a dentry if it succeeds. This |
196 | * pointer must be passed to the securityfs_remove() function when the file is |
197 | * to be removed (no automatic cleanup happens if your module is unloaded, |
198 | * you are responsible here). If an error occurs, the function will return |
199 | * the erorr value (via ERR_PTR). |
200 | * |
201 | * If securityfs is not enabled in the kernel, the value %-ENODEV is |
202 | * returned. |
203 | */ |
204 | struct dentry *securityfs_create_file(const char *name, mode_t mode, |
205 | struct dentry *parent, void *data, |
206 | const struct file_operations *fops) |
207 | { |
208 | struct dentry *dentry = NULL; |
209 | int error; |
210 | |
211 | pr_debug("securityfs: creating file '%s'\n",name); |
212 | |
213 | error = simple_pin_fs(&fs_type, &mount, &mount_count); |
214 | if (error) { |
215 | dentry = ERR_PTR(error); |
216 | goto exit; |
217 | } |
218 | |
219 | error = create_by_name(name, mode, parent, &dentry); |
220 | if (error) { |
221 | dentry = ERR_PTR(error); |
222 | simple_release_fs(&mount, &mount_count); |
223 | goto exit; |
224 | } |
225 | |
226 | if (dentry->d_inode) { |
227 | if (fops) |
228 | dentry->d_inode->i_fop = fops; |
229 | if (data) |
230 | dentry->d_inode->i_private = data; |
231 | } |
232 | exit: |
233 | return dentry; |
234 | } |
235 | EXPORT_SYMBOL_GPL(securityfs_create_file); |
236 | |
237 | /** |
238 | * securityfs_create_dir - create a directory in the securityfs filesystem |
239 | * |
240 | * @name: a pointer to a string containing the name of the directory to |
241 | * create. |
242 | * @parent: a pointer to the parent dentry for this file. This should be a |
243 | * directory dentry if set. If this parameter is %NULL, then the |
244 | * directory will be created in the root of the securityfs filesystem. |
245 | * |
246 | * This function creates a directory in securityfs with the given @name. |
247 | * |
248 | * This function returns a pointer to a dentry if it succeeds. This |
249 | * pointer must be passed to the securityfs_remove() function when the file is |
250 | * to be removed (no automatic cleanup happens if your module is unloaded, |
251 | * you are responsible here). If an error occurs, %NULL will be returned. |
252 | * |
253 | * If securityfs is not enabled in the kernel, the value %-ENODEV is |
254 | * returned. It is not wise to check for this value, but rather, check for |
255 | * %NULL or !%NULL instead as to eliminate the need for #ifdef in the calling |
256 | * code. |
257 | */ |
258 | struct dentry *securityfs_create_dir(const char *name, struct dentry *parent) |
259 | { |
260 | return securityfs_create_file(name, |
261 | S_IFDIR | S_IRWXU | S_IRUGO | S_IXUGO, |
262 | parent, NULL, NULL); |
263 | } |
264 | EXPORT_SYMBOL_GPL(securityfs_create_dir); |
265 | |
266 | /** |
267 | * securityfs_remove - removes a file or directory from the securityfs filesystem |
268 | * |
269 | * @dentry: a pointer to a the dentry of the file or directory to be removed. |
270 | * |
271 | * This function removes a file or directory in securityfs that was previously |
272 | * created with a call to another securityfs function (like |
273 | * securityfs_create_file() or variants thereof.) |
274 | * |
275 | * This function is required to be called in order for the file to be |
276 | * removed. No automatic cleanup of files will happen when a module is |
277 | * removed; you are responsible here. |
278 | */ |
279 | void securityfs_remove(struct dentry *dentry) |
280 | { |
281 | struct dentry *parent; |
282 | |
283 | if (!dentry || IS_ERR(dentry)) |
284 | return; |
285 | |
286 | parent = dentry->d_parent; |
287 | if (!parent || !parent->d_inode) |
288 | return; |
289 | |
290 | mutex_lock(&parent->d_inode->i_mutex); |
291 | if (positive(dentry)) { |
292 | if (dentry->d_inode) { |
293 | if (S_ISDIR(dentry->d_inode->i_mode)) |
294 | simple_rmdir(parent->d_inode, dentry); |
295 | else |
296 | simple_unlink(parent->d_inode, dentry); |
297 | dput(dentry); |
298 | } |
299 | } |
300 | mutex_unlock(&parent->d_inode->i_mutex); |
301 | simple_release_fs(&mount, &mount_count); |
302 | } |
303 | EXPORT_SYMBOL_GPL(securityfs_remove); |
304 | |
305 | static struct kobject *security_kobj; |
306 | |
307 | static int __init securityfs_init(void) |
308 | { |
309 | int retval; |
310 | |
311 | security_kobj = kobject_create_and_add("security", kernel_kobj); |
312 | if (!security_kobj) |
313 | return -EINVAL; |
314 | |
315 | retval = register_filesystem(&fs_type); |
316 | if (retval) |
317 | kobject_put(security_kobj); |
318 | return retval; |
319 | } |
320 | |
321 | core_initcall(securityfs_init); |
322 | MODULE_LICENSE("GPL"); |
323 | |
324 |
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