1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * fs/kernfs/inode.c - kernfs inode implementation
4 *
5 * Copyright (c) 2001-3 Patrick Mochel
6 * Copyright (c) 2007 SUSE Linux Products GmbH
7 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
8 */
9
10 #include <linux/pagemap.h>
11 #include <linux/backing-dev.h>
12 #include <linux/capability.h>
13 #include <linux/errno.h>
14 #include <linux/slab.h>
15 #include <linux/xattr.h>
16 #include <linux/security.h>
17
18 #include "kernfs-internal.h"
19
20 static const struct inode_operations kernfs_iops = {
21 .permission = kernfs_iop_permission,
22 .setattr = kernfs_iop_setattr,
23 .getattr = kernfs_iop_getattr,
24 .listxattr = kernfs_iop_listxattr,
25 };
26
27 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
28 {
29 static DEFINE_MUTEX(iattr_mutex);
30 struct kernfs_iattrs *ret;
31
32 mutex_lock(&iattr_mutex);
33
34 if (kn->iattr || !alloc)
35 goto out_unlock;
36
37 kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
38 if (!kn->iattr)
39 goto out_unlock;
40
41 /* assign default attributes */
42 kn->iattr->ia_uid = GLOBAL_ROOT_UID;
43 kn->iattr->ia_gid = GLOBAL_ROOT_GID;
44
45 ktime_get_real_ts64(&kn->iattr->ia_atime);
46 kn->iattr->ia_mtime = kn->iattr->ia_atime;
47 kn->iattr->ia_ctime = kn->iattr->ia_atime;
48
49 simple_xattrs_init(&kn->iattr->xattrs);
50 atomic_set(&kn->iattr->nr_user_xattrs, 0);
51 atomic_set(&kn->iattr->user_xattr_size, 0);
52 out_unlock:
53 ret = kn->iattr;
54 mutex_unlock(&iattr_mutex);
55 return ret;
56 }
57
58 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
59 {
60 return __kernfs_iattrs(kn, 1);
61 }
62
63 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
64 {
65 return __kernfs_iattrs(kn, 0);
66 }
67
68 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
69 {
70 struct kernfs_iattrs *attrs;
71 unsigned int ia_valid = iattr->ia_valid;
72
73 attrs = kernfs_iattrs(kn);
74 if (!attrs)
75 return -ENOMEM;
76
77 if (ia_valid & ATTR_UID)
78 attrs->ia_uid = iattr->ia_uid;
79 if (ia_valid & ATTR_GID)
80 attrs->ia_gid = iattr->ia_gid;
81 if (ia_valid & ATTR_ATIME)
82 attrs->ia_atime = iattr->ia_atime;
83 if (ia_valid & ATTR_MTIME)
84 attrs->ia_mtime = iattr->ia_mtime;
85 if (ia_valid & ATTR_CTIME)
86 attrs->ia_ctime = iattr->ia_ctime;
87 if (ia_valid & ATTR_MODE)
88 kn->mode = iattr->ia_mode;
89 return 0;
90 }
91
92 /**
93 * kernfs_setattr - set iattr on a node
94 * @kn: target node
95 * @iattr: iattr to set
96 *
97 * Return: %0 on success, -errno on failure.
98 */
99 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
100 {
101 int ret;
102 struct kernfs_root *root = kernfs_root(kn);
103
104 down_write(&root->kernfs_iattr_rwsem);
105 ret = __kernfs_setattr(kn, iattr);
106 up_write(&root->kernfs_iattr_rwsem);
107 return ret;
108 }
109
110 int kernfs_iop_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
111 struct iattr *iattr)
112 {
113 struct inode *inode = d_inode(dentry);
114 struct kernfs_node *kn = inode->i_private;
115 struct kernfs_root *root;
116 int error;
117
118 if (!kn)
119 return -EINVAL;
120
121 root = kernfs_root(kn);
122 down_write(&root->kernfs_iattr_rwsem);
123 error = setattr_prepare(&nop_mnt_idmap, dentry, iattr);
124 if (error)
125 goto out;
126
127 error = __kernfs_setattr(kn, iattr);
128 if (error)
129 goto out;
130
131 /* this ignores size changes */
132 setattr_copy(&nop_mnt_idmap, inode, iattr);
133
134 out:
135 up_write(&root->kernfs_iattr_rwsem);
136 return error;
137 }
138
139 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
140 {
141 struct kernfs_node *kn = kernfs_dentry_node(dentry);
142 struct kernfs_iattrs *attrs;
143
144 attrs = kernfs_iattrs(kn);
145 if (!attrs)
146 return -ENOMEM;
147
148 return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
149 }
150
151 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
152 {
153 inode->i_mode = mode;
154 simple_inode_init_ts(inode);
155 }
156
157 static inline void set_inode_attr(struct inode *inode,
158 struct kernfs_iattrs *attrs)
159 {
160 inode->i_uid = attrs->ia_uid;
161 inode->i_gid = attrs->ia_gid;
162 inode_set_atime_to_ts(inode, attrs->ia_atime);
163 inode_set_mtime_to_ts(inode, attrs->ia_mtime);
164 inode_set_ctime_to_ts(inode, attrs->ia_ctime);
165 }
166
167 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
168 {
169 struct kernfs_iattrs *attrs = kn->iattr;
170
171 inode->i_mode = kn->mode;
172 if (attrs)
173 /*
174 * kernfs_node has non-default attributes get them from
175 * persistent copy in kernfs_node.
176 */
177 set_inode_attr(inode, attrs);
178
179 if (kernfs_type(kn) == KERNFS_DIR)
180 set_nlink(inode, kn->dir.subdirs + 2);
181 }
182
183 int kernfs_iop_getattr(struct mnt_idmap *idmap,
184 const struct path *path, struct kstat *stat,
185 u32 request_mask, unsigned int query_flags)
186 {
187 struct inode *inode = d_inode(path->dentry);
188 struct kernfs_node *kn = inode->i_private;
189 struct kernfs_root *root = kernfs_root(kn);
190
191 down_read(&root->kernfs_iattr_rwsem);
192 kernfs_refresh_inode(kn, inode);
193 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
194 up_read(&root->kernfs_iattr_rwsem);
195
196 return 0;
197 }
198
199 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
200 {
201 kernfs_get(kn);
202 inode->i_private = kn;
203 inode->i_mapping->a_ops = &ram_aops;
204 inode->i_op = &kernfs_iops;
205 inode->i_generation = kernfs_gen(kn);
206
207 set_default_inode_attr(inode, kn->mode);
208 kernfs_refresh_inode(kn, inode);
209
210 /* initialize inode according to type */
211 switch (kernfs_type(kn)) {
212 case KERNFS_DIR:
213 inode->i_op = &kernfs_dir_iops;
214 inode->i_fop = &kernfs_dir_fops;
215 if (kn->flags & KERNFS_EMPTY_DIR)
216 make_empty_dir_inode(inode);
217 break;
218 case KERNFS_FILE:
219 inode->i_size = kn->attr.size;
220 inode->i_fop = &kernfs_file_fops;
221 break;
222 case KERNFS_LINK:
223 inode->i_op = &kernfs_symlink_iops;
224 break;
225 default:
226 BUG();
227 }
228
229 unlock_new_inode(inode);
230 }
231
232 /**
233 * kernfs_get_inode - get inode for kernfs_node
234 * @sb: super block
235 * @kn: kernfs_node to allocate inode for
236 *
237 * Get inode for @kn. If such inode doesn't exist, a new inode is
238 * allocated and basics are initialized. New inode is returned
239 * locked.
240 *
241 * Locking:
242 * Kernel thread context (may sleep).
243 *
244 * Return:
245 * Pointer to allocated inode on success, %NULL on failure.
246 */
247 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
248 {
249 struct inode *inode;
250
251 inode = iget_locked(sb, kernfs_ino(kn));
252 if (inode && (inode->i_state & I_NEW))
253 kernfs_init_inode(kn, inode);
254
255 return inode;
256 }
257
258 /*
259 * The kernfs_node serves as both an inode and a directory entry for
260 * kernfs. To prevent the kernfs inode numbers from being freed
261 * prematurely we take a reference to kernfs_node from the kernfs inode. A
262 * super_operations.evict_inode() implementation is needed to drop that
263 * reference upon inode destruction.
264 */
265 void kernfs_evict_inode(struct inode *inode)
266 {
267 struct kernfs_node *kn = inode->i_private;
268
269 truncate_inode_pages_final(&inode->i_data);
270 clear_inode(inode);
271 kernfs_put(kn);
272 }
273
274 int kernfs_iop_permission(struct mnt_idmap *idmap,
275 struct inode *inode, int mask)
276 {
277 struct kernfs_node *kn;
278 struct kernfs_root *root;
279 int ret;
280
281 if (mask & MAY_NOT_BLOCK)
282 return -ECHILD;
283
284 kn = inode->i_private;
285 root = kernfs_root(kn);
286
287 down_read(&root->kernfs_iattr_rwsem);
288 kernfs_refresh_inode(kn, inode);
289 ret = generic_permission(&nop_mnt_idmap, inode, mask);
290 up_read(&root->kernfs_iattr_rwsem);
291
292 return ret;
293 }
294
295 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
296 void *value, size_t size)
297 {
298 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
299 if (!attrs)
300 return -ENODATA;
301
302 return simple_xattr_get(&attrs->xattrs, name, value, size);
303 }
304
305 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
306 const void *value, size_t size, int flags)
307 {
308 struct simple_xattr *old_xattr;
309 struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
310 if (!attrs)
311 return -ENOMEM;
312
313 old_xattr = simple_xattr_set(&attrs->xattrs, name, value, size, flags);
314 if (IS_ERR(old_xattr))
315 return PTR_ERR(old_xattr);
316
317 simple_xattr_free(old_xattr);
318 return 0;
319 }
320
321 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
322 struct dentry *unused, struct inode *inode,
323 const char *suffix, void *value, size_t size)
324 {
325 const char *name = xattr_full_name(handler, suffix);
326 struct kernfs_node *kn = inode->i_private;
327
328 return kernfs_xattr_get(kn, name, value, size);
329 }
330
331 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
332 struct mnt_idmap *idmap,
333 struct dentry *unused, struct inode *inode,
334 const char *suffix, const void *value,
335 size_t size, int flags)
336 {
337 const char *name = xattr_full_name(handler, suffix);
338 struct kernfs_node *kn = inode->i_private;
339
340 return kernfs_xattr_set(kn, name, value, size, flags);
341 }
342
343 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
344 const char *full_name,
345 struct simple_xattrs *xattrs,
346 const void *value, size_t size, int flags)
347 {
348 atomic_t *sz = &kn->iattr->user_xattr_size;
349 atomic_t *nr = &kn->iattr->nr_user_xattrs;
350 struct simple_xattr *old_xattr;
351 int ret;
352
353 if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
354 ret = -ENOSPC;
355 goto dec_count_out;
356 }
357
358 if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) {
359 ret = -ENOSPC;
360 goto dec_size_out;
361 }
362
363 old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);
364 if (!old_xattr)
365 return 0;
366
367 if (IS_ERR(old_xattr)) {
368 ret = PTR_ERR(old_xattr);
369 goto dec_size_out;
370 }
371
372 ret = 0;
373 size = old_xattr->size;
374 simple_xattr_free(old_xattr);
375 dec_size_out:
376 atomic_sub(size, sz);
377 dec_count_out:
378 atomic_dec(nr);
379 return ret;
380 }
381
382 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
383 const char *full_name,
384 struct simple_xattrs *xattrs,
385 const void *value, size_t size, int flags)
386 {
387 atomic_t *sz = &kn->iattr->user_xattr_size;
388 atomic_t *nr = &kn->iattr->nr_user_xattrs;
389 struct simple_xattr *old_xattr;
390
391 old_xattr = simple_xattr_set(xattrs, full_name, value, size, flags);
392 if (!old_xattr)
393 return 0;
394
395 if (IS_ERR(old_xattr))
396 return PTR_ERR(old_xattr);
397
398 atomic_sub(old_xattr->size, sz);
399 atomic_dec(nr);
400 simple_xattr_free(old_xattr);
401 return 0;
402 }
403
404 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
405 struct mnt_idmap *idmap,
406 struct dentry *unused, struct inode *inode,
407 const char *suffix, const void *value,
408 size_t size, int flags)
409 {
410 const char *full_name = xattr_full_name(handler, suffix);
411 struct kernfs_node *kn = inode->i_private;
412 struct kernfs_iattrs *attrs;
413
414 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
415 return -EOPNOTSUPP;
416
417 attrs = kernfs_iattrs(kn);
418 if (!attrs)
419 return -ENOMEM;
420
421 if (value)
422 return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs,
423 value, size, flags);
424 else
425 return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs,
426 value, size, flags);
427
428 }
429
430 static const struct xattr_handler kernfs_trusted_xattr_handler = {
431 .prefix = XATTR_TRUSTED_PREFIX,
432 .get = kernfs_vfs_xattr_get,
433 .set = kernfs_vfs_xattr_set,
434 };
435
436 static const struct xattr_handler kernfs_security_xattr_handler = {
437 .prefix = XATTR_SECURITY_PREFIX,
438 .get = kernfs_vfs_xattr_get,
439 .set = kernfs_vfs_xattr_set,
440 };
441
442 static const struct xattr_handler kernfs_user_xattr_handler = {
443 .prefix = XATTR_USER_PREFIX,
444 .get = kernfs_vfs_xattr_get,
445 .set = kernfs_vfs_user_xattr_set,
446 };
447
448 const struct xattr_handler * const kernfs_xattr_handlers[] = {
449 &kernfs_trusted_xattr_handler,
450 &kernfs_security_xattr_handler,
451 &kernfs_user_xattr_handler,
452 NULL
453 };
454
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