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
20static 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
27static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, bool alloc)
28{
29 struct kernfs_iattrs *ret __free(kfree) = NULL;
30 struct kernfs_iattrs *attr;
31
32 attr = READ_ONCE(kn->iattr);
33 if (attr || !alloc)
34 return attr;
35
36 ret = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
37 if (!ret)
38 return NULL;
39
40 /* assign default attributes */
41 ret->ia_uid = GLOBAL_ROOT_UID;
42 ret->ia_gid = GLOBAL_ROOT_GID;
43
44 ktime_get_real_ts64(&ret->ia_atime);
45 ret->ia_mtime = ret->ia_atime;
46 ret->ia_ctime = ret->ia_atime;
47
48 simple_xattrs_init(&ret->xattrs);
49 atomic_set(&ret->nr_user_xattrs, 0);
50 atomic_set(&ret->user_xattr_size, 0);
51
52 /* If someone raced us, recognize it. */
53 if (!try_cmpxchg(&kn->iattr, &attr, ret))
54 return READ_ONCE(kn->iattr);
55
56 return no_free_ptr(ret);
57}
58
59static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
60{
61 return __kernfs_iattrs(kn, alloc: true);
62}
63
64static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
65{
66 return __kernfs_iattrs(kn, alloc: false);
67}
68
69int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
70{
71 struct kernfs_iattrs *attrs;
72 unsigned int ia_valid = iattr->ia_valid;
73
74 attrs = kernfs_iattrs(kn);
75 if (!attrs)
76 return -ENOMEM;
77
78 if (ia_valid & ATTR_UID)
79 attrs->ia_uid = iattr->ia_uid;
80 if (ia_valid & ATTR_GID)
81 attrs->ia_gid = iattr->ia_gid;
82 if (ia_valid & ATTR_ATIME)
83 attrs->ia_atime = iattr->ia_atime;
84 if (ia_valid & ATTR_MTIME)
85 attrs->ia_mtime = iattr->ia_mtime;
86 if (ia_valid & ATTR_CTIME)
87 attrs->ia_ctime = iattr->ia_ctime;
88 if (ia_valid & ATTR_MODE)
89 kn->mode = iattr->ia_mode;
90 return 0;
91}
92
93/**
94 * kernfs_setattr - set iattr on a node
95 * @kn: target node
96 * @iattr: iattr to set
97 *
98 * Return: %0 on success, -errno on failure.
99 */
100int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
101{
102 int ret;
103 struct kernfs_root *root = kernfs_root(kn);
104
105 down_write(sem: &root->kernfs_iattr_rwsem);
106 ret = __kernfs_setattr(kn, iattr);
107 up_write(sem: &root->kernfs_iattr_rwsem);
108 return ret;
109}
110
111int kernfs_iop_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
112 struct iattr *iattr)
113{
114 struct inode *inode = d_inode(dentry);
115 struct kernfs_node *kn = inode->i_private;
116 struct kernfs_root *root;
117 int error;
118
119 if (!kn)
120 return -EINVAL;
121
122 root = kernfs_root(kn);
123 down_write(sem: &root->kernfs_iattr_rwsem);
124 error = setattr_prepare(&nop_mnt_idmap, dentry, iattr);
125 if (error)
126 goto out;
127
128 error = __kernfs_setattr(kn, iattr);
129 if (error)
130 goto out;
131
132 /* this ignores size changes */
133 setattr_copy(&nop_mnt_idmap, inode, attr: iattr);
134
135out:
136 up_write(sem: &root->kernfs_iattr_rwsem);
137 return error;
138}
139
140ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
141{
142 struct kernfs_node *kn = kernfs_dentry_node(dentry);
143 struct kernfs_iattrs *attrs;
144
145 attrs = kernfs_iattrs(kn);
146 if (!attrs)
147 return -ENOMEM;
148
149 return simple_xattr_list(inode: d_inode(dentry), xattrs: &attrs->xattrs, buffer: buf, size);
150}
151
152static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
153{
154 inode->i_mode = mode;
155 simple_inode_init_ts(inode);
156}
157
158static inline void set_inode_attr(struct inode *inode,
159 struct kernfs_iattrs *attrs)
160{
161 inode->i_uid = attrs->ia_uid;
162 inode->i_gid = attrs->ia_gid;
163 inode_set_atime_to_ts(inode, ts: attrs->ia_atime);
164 inode_set_mtime_to_ts(inode, ts: attrs->ia_mtime);
165 inode_set_ctime_to_ts(inode, ts: attrs->ia_ctime);
166}
167
168static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
169{
170 struct kernfs_iattrs *attrs;
171
172 inode->i_mode = kn->mode;
173 attrs = kernfs_iattrs_noalloc(kn);
174 if (attrs)
175 /*
176 * kernfs_node has non-default attributes get them from
177 * persistent copy in kernfs_node.
178 */
179 set_inode_attr(inode, attrs);
180
181 if (kernfs_type(kn) == KERNFS_DIR)
182 set_nlink(inode, nlink: kn->dir.subdirs + 2);
183}
184
185int kernfs_iop_getattr(struct mnt_idmap *idmap,
186 const struct path *path, struct kstat *stat,
187 u32 request_mask, unsigned int query_flags)
188{
189 struct inode *inode = d_inode(dentry: path->dentry);
190 struct kernfs_node *kn = inode->i_private;
191 struct kernfs_root *root = kernfs_root(kn);
192
193 down_read(sem: &root->kernfs_iattr_rwsem);
194 kernfs_refresh_inode(kn, inode);
195 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
196 up_read(sem: &root->kernfs_iattr_rwsem);
197
198 return 0;
199}
200
201static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
202{
203 kernfs_get(kn);
204 inode->i_private = kn;
205 inode->i_mapping->a_ops = &ram_aops;
206 inode->i_op = &kernfs_iops;
207 inode->i_generation = kernfs_gen(kn);
208
209 set_default_inode_attr(inode, mode: kn->mode);
210 kernfs_refresh_inode(kn, inode);
211
212 /* initialize inode according to type */
213 switch (kernfs_type(kn)) {
214 case KERNFS_DIR:
215 inode->i_op = &kernfs_dir_iops;
216 inode->i_fop = &kernfs_dir_fops;
217 if (kn->flags & KERNFS_EMPTY_DIR)
218 make_empty_dir_inode(inode);
219 break;
220 case KERNFS_FILE:
221 inode->i_size = kn->attr.size;
222 inode->i_fop = &kernfs_file_fops;
223 break;
224 case KERNFS_LINK:
225 inode->i_op = &kernfs_symlink_iops;
226 break;
227 default:
228 BUG();
229 }
230
231 unlock_new_inode(inode);
232}
233
234/**
235 * kernfs_get_inode - get inode for kernfs_node
236 * @sb: super block
237 * @kn: kernfs_node to allocate inode for
238 *
239 * Get inode for @kn. If such inode doesn't exist, a new inode is
240 * allocated and basics are initialized. New inode is returned
241 * locked.
242 *
243 * Locking:
244 * Kernel thread context (may sleep).
245 *
246 * Return:
247 * Pointer to allocated inode on success, %NULL on failure.
248 */
249struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
250{
251 struct inode *inode;
252
253 inode = iget_locked(sb, kernfs_ino(kn));
254 if (inode && (inode->i_state & I_NEW))
255 kernfs_init_inode(kn, inode);
256
257 return inode;
258}
259
260/*
261 * The kernfs_node serves as both an inode and a directory entry for
262 * kernfs. To prevent the kernfs inode numbers from being freed
263 * prematurely we take a reference to kernfs_node from the kernfs inode. A
264 * super_operations.evict_inode() implementation is needed to drop that
265 * reference upon inode destruction.
266 */
267void kernfs_evict_inode(struct inode *inode)
268{
269 struct kernfs_node *kn = inode->i_private;
270
271 truncate_inode_pages_final(&inode->i_data);
272 clear_inode(inode);
273 kernfs_put(kn);
274}
275
276int kernfs_iop_permission(struct mnt_idmap *idmap,
277 struct inode *inode, int mask)
278{
279 struct kernfs_node *kn;
280 struct kernfs_root *root;
281 int ret;
282
283 if (mask & MAY_NOT_BLOCK)
284 return -ECHILD;
285
286 kn = inode->i_private;
287 root = kernfs_root(kn);
288
289 down_read(sem: &root->kernfs_iattr_rwsem);
290 kernfs_refresh_inode(kn, inode);
291 ret = generic_permission(&nop_mnt_idmap, inode, mask);
292 up_read(sem: &root->kernfs_iattr_rwsem);
293
294 return ret;
295}
296
297int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
298 void *value, size_t size)
299{
300 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
301 if (!attrs)
302 return -ENODATA;
303
304 return simple_xattr_get(xattrs: &attrs->xattrs, name, buffer: value, size);
305}
306
307int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
308 const void *value, size_t size, int flags)
309{
310 struct simple_xattr *old_xattr;
311 struct kernfs_iattrs *attrs;
312
313 attrs = kernfs_iattrs(kn);
314 if (!attrs)
315 return -ENOMEM;
316
317 old_xattr = simple_xattr_set(xattrs: &attrs->xattrs, name, value, size, flags);
318 if (IS_ERR(ptr: old_xattr))
319 return PTR_ERR(ptr: old_xattr);
320
321 simple_xattr_free(xattr: old_xattr);
322 return 0;
323}
324
325static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
326 struct dentry *unused, struct inode *inode,
327 const char *suffix, void *value, size_t size)
328{
329 const char *name = xattr_full_name(handler, suffix);
330 struct kernfs_node *kn = inode->i_private;
331
332 return kernfs_xattr_get(kn, name, value, size);
333}
334
335static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
336 struct mnt_idmap *idmap,
337 struct dentry *unused, struct inode *inode,
338 const char *suffix, const void *value,
339 size_t size, int flags)
340{
341 const char *name = xattr_full_name(handler, suffix);
342 struct kernfs_node *kn = inode->i_private;
343
344 return kernfs_xattr_set(kn, name, value, size, flags);
345}
346
347static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
348 const char *full_name,
349 struct simple_xattrs *xattrs,
350 const void *value, size_t size, int flags)
351{
352 struct kernfs_iattrs *attr = kernfs_iattrs_noalloc(kn);
353 atomic_t *sz = &attr->user_xattr_size;
354 atomic_t *nr = &attr->nr_user_xattrs;
355 struct simple_xattr *old_xattr;
356 int ret;
357
358 if (atomic_inc_return(v: nr) > KERNFS_MAX_USER_XATTRS) {
359 ret = -ENOSPC;
360 goto dec_count_out;
361 }
362
363 if (atomic_add_return(i: size, v: sz) > KERNFS_USER_XATTR_SIZE_LIMIT) {
364 ret = -ENOSPC;
365 goto dec_size_out;
366 }
367
368 old_xattr = simple_xattr_set(xattrs, name: full_name, value, size, flags);
369 if (!old_xattr)
370 return 0;
371
372 if (IS_ERR(ptr: old_xattr)) {
373 ret = PTR_ERR(ptr: old_xattr);
374 goto dec_size_out;
375 }
376
377 ret = 0;
378 size = old_xattr->size;
379 simple_xattr_free(xattr: old_xattr);
380dec_size_out:
381 atomic_sub(i: size, v: sz);
382dec_count_out:
383 atomic_dec(v: nr);
384 return ret;
385}
386
387static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
388 const char *full_name,
389 struct simple_xattrs *xattrs,
390 const void *value, size_t size, int flags)
391{
392 struct kernfs_iattrs *attr = kernfs_iattrs_noalloc(kn);
393 atomic_t *sz = &attr->user_xattr_size;
394 atomic_t *nr = &attr->nr_user_xattrs;
395 struct simple_xattr *old_xattr;
396
397 old_xattr = simple_xattr_set(xattrs, name: full_name, value, size, flags);
398 if (!old_xattr)
399 return 0;
400
401 if (IS_ERR(ptr: old_xattr))
402 return PTR_ERR(ptr: old_xattr);
403
404 atomic_sub(i: old_xattr->size, v: sz);
405 atomic_dec(v: nr);
406 simple_xattr_free(xattr: old_xattr);
407 return 0;
408}
409
410static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
411 struct mnt_idmap *idmap,
412 struct dentry *unused, struct inode *inode,
413 const char *suffix, const void *value,
414 size_t size, int flags)
415{
416 const char *full_name = xattr_full_name(handler, suffix);
417 struct kernfs_node *kn = inode->i_private;
418 struct kernfs_iattrs *attrs;
419
420 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
421 return -EOPNOTSUPP;
422
423 attrs = kernfs_iattrs(kn);
424 if (!attrs)
425 return -ENOMEM;
426
427 if (value)
428 return kernfs_vfs_user_xattr_add(kn, full_name, xattrs: &attrs->xattrs,
429 value, size, flags);
430 else
431 return kernfs_vfs_user_xattr_rm(kn, full_name, xattrs: &attrs->xattrs,
432 value, size, flags);
433
434}
435
436static const struct xattr_handler kernfs_trusted_xattr_handler = {
437 .prefix = XATTR_TRUSTED_PREFIX,
438 .get = kernfs_vfs_xattr_get,
439 .set = kernfs_vfs_xattr_set,
440};
441
442static const struct xattr_handler kernfs_security_xattr_handler = {
443 .prefix = XATTR_SECURITY_PREFIX,
444 .get = kernfs_vfs_xattr_get,
445 .set = kernfs_vfs_xattr_set,
446};
447
448static const struct xattr_handler kernfs_user_xattr_handler = {
449 .prefix = XATTR_USER_PREFIX,
450 .get = kernfs_vfs_xattr_get,
451 .set = kernfs_vfs_user_xattr_set,
452};
453
454const struct xattr_handler * const kernfs_xattr_handlers[] = {
455 &kernfs_trusted_xattr_handler,
456 &kernfs_security_xattr_handler,
457 &kernfs_user_xattr_handler,
458 NULL
459};
460