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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 <[email protected]>
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 INIT_LIST_HEAD_RCU(&ret->xattrs);
41 /* assign default attributes */
42 ret->ia_uid = GLOBAL_ROOT_UID;
43 ret->ia_gid = GLOBAL_ROOT_GID;
44
45 ktime_get_real_ts64(&ret->ia_atime);
46 ret->ia_mtime = ret->ia_atime;
47 ret->ia_ctime = ret->ia_atime;
48
49 simple_xattr_limits_init(&ret->xattr_limits);
50
51 /* If someone raced us, recognize it. */
52 if (!try_cmpxchg(&kn->iattr, &attr, ret))
53 return READ_ONCE(kn->iattr);
54
55 return no_free_ptr(ret);
56}
57
58static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
59{
60 return __kernfs_iattrs(kn, true);
61}
62
63static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
64{
65 return __kernfs_iattrs(kn, false);
66}
67
68int __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 */
99int 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
110int kernfs_iop_setattr(const 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
134out:
135 up_write(&root->kernfs_iattr_rwsem);
136 return error;
137}
138
139ssize_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_noalloc(kn);
145
146 return simple_xattr_list(d_inode(dentry), attrs ? &attrs->xattrs : NULL, buf, size);
147}
148
149static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
150{
151 inode->i_mode = mode;
152 simple_inode_init_ts(inode);
153}
154
155static inline void set_inode_attr(struct inode *inode,
156 struct kernfs_iattrs *attrs)
157{
158 inode->i_uid = attrs->ia_uid;
159 inode->i_gid = attrs->ia_gid;
160 inode_set_atime_to_ts(inode, attrs->ia_atime);
161 inode_set_mtime_to_ts(inode, attrs->ia_mtime);
162 inode_set_ctime_to_ts(inode, attrs->ia_ctime);
163}
164
165static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
166{
167 struct kernfs_iattrs *attrs;
168
169 inode->i_mode = kn->mode;
170 attrs = kernfs_iattrs_noalloc(kn);
171 if (attrs)
172 /*
173 * kernfs_node has non-default attributes get them from
174 * persistent copy in kernfs_node.
175 */
176 set_inode_attr(inode, attrs);
177
178 if (kernfs_type(kn) == KERNFS_DIR && !(kn->flags & KERNFS_REMOVING))
179 set_nlink(inode, kn->dir.subdirs + 2);
180}
181
182int kernfs_iop_getattr(const struct mnt_idmap *idmap,
183 const struct path *path, struct kstat *stat,
184 u32 request_mask, unsigned int query_flags)
185{
186 struct inode *inode = d_inode(path->dentry);
187 struct kernfs_node *kn = inode->i_private;
188 struct kernfs_root *root = kernfs_root(kn);
189
190 down_read(&root->kernfs_iattr_rwsem);
191 kernfs_refresh_inode(kn, inode);
192 generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
193 up_read(&root->kernfs_iattr_rwsem);
194
195 return 0;
196}
197
198static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
199{
200 kernfs_get(kn);
201 inode->i_private = kn;
202 inode->i_mapping->a_ops = &ram_aops;
203 inode->i_op = &kernfs_iops;
204 inode->i_generation = kernfs_gen(kn);
205
206 set_default_inode_attr(inode, kn->mode);
207 kernfs_refresh_inode(kn, inode);
208
209 /* initialize inode according to type */
210 switch (kernfs_type(kn)) {
211 case KERNFS_DIR:
212 inode->i_op = &kernfs_dir_iops;
213 inode->i_fop = &kernfs_dir_fops;
214 if (kn->flags & KERNFS_EMPTY_DIR)
215 make_empty_dir_inode(inode);
216 break;
217 case KERNFS_FILE:
218 inode->i_size = kn->attr.size;
219 inode->i_fop = &kernfs_file_fops;
220 break;
221 case KERNFS_LINK:
222 inode->i_op = &kernfs_symlink_iops;
223 break;
224 default:
225 BUG();
226 }
227
228 unlock_new_inode(inode);
229}
230
231/**
232 * kernfs_get_inode - get inode for kernfs_node
233 * @sb: super block
234 * @kn: kernfs_node to allocate inode for
235 *
236 * Get inode for @kn. If such inode doesn't exist, a new inode is
237 * allocated and basics are initialized. New inode is returned
238 * locked.
239 *
240 * Locking:
241 * Kernel thread context (may sleep).
242 *
243 * Return:
244 * Pointer to allocated inode on success, %NULL on failure.
245 */
246struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
247{
248 struct inode *inode;
249
250 inode = iget_locked(sb, kernfs_ino(kn));
251 if (inode && (inode_state_read_once(inode) & I_NEW))
252 kernfs_init_inode(kn, inode);
253
254 return inode;
255}
256
257/*
258 * The kernfs_node serves as both an inode and a directory entry for
259 * kernfs. To prevent the kernfs inode numbers from being freed
260 * prematurely we take a reference to kernfs_node from the kernfs inode. A
261 * super_operations.evict_inode() implementation is needed to drop that
262 * reference upon inode destruction.
263 */
264void kernfs_evict_inode(struct inode *inode)
265{
266 struct kernfs_node *kn = inode->i_private;
267
268 truncate_inode_pages_final(&inode->i_data);
269 clear_inode(inode);
270 kernfs_put(kn);
271}
272
273int kernfs_iop_permission(const struct mnt_idmap *idmap,
274 struct inode *inode, int mask)
275{
276 struct kernfs_node *kn;
277 struct kernfs_root *root;
278 int ret;
279
280 if (mask & MAY_NOT_BLOCK)
281 return -ECHILD;
282
283 kn = inode->i_private;
284 root = kernfs_root(kn);
285
286 down_read(&root->kernfs_iattr_rwsem);
287 kernfs_refresh_inode(kn, inode);
288 ret = generic_permission(&nop_mnt_idmap, inode, mask);
289 up_read(&root->kernfs_iattr_rwsem);
290
291 return ret;
292}
293
294int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
295 void *value, size_t size)
296{
297 struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
298 struct simple_xattr_cache *cache = &kernfs_root(kn)->xa_cache;
299
300 if (!attrs)
301 return -ENODATA;
302
303 return simple_xattr_get(cache, &attrs->xattrs, name, value, size);
304}
305
306int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
307 const void *value, size_t size, int flags)
308{
309 struct simple_xattr *old_xattr;
310 struct kernfs_iattrs *attrs;
311 struct simple_xattr_cache *cache = &kernfs_root(kn)->xa_cache;
312
313 attrs = kernfs_iattrs(kn);
314 if (!attrs)
315 return -ENOMEM;
316
317 /*
318 * Protect xattr modifications with the hashed per-node mutex.
319 * Multiple superblocks (with different namespaces) can share the same
320 * kernfs_node, so inode locking alone is insufficient. The hashed mutex
321 * ensures serialization of concurrent xattr operations on the same node,
322 * including the lazy allocation of the xattrs structure itself.
323 */
324 CLASS(kernfs_node_lock, lock)(kn);
325
326 old_xattr = simple_xattr_set(cache, &attrs->xattrs, name, value, size, flags);
327 if (IS_ERR(old_xattr))
328 return PTR_ERR(old_xattr);
329
330 simple_xattr_free_rcu(old_xattr);
331 return 0;
332}
333
334static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
335 struct dentry *unused, struct inode *inode,
336 const char *suffix, void *value, size_t size)
337{
338 const char *name = xattr_full_name(handler, suffix);
339 struct kernfs_node *kn = inode->i_private;
340
341 return kernfs_xattr_get(kn, name, value, size);
342}
343
344static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
345 const struct mnt_idmap *idmap,
346 struct dentry *unused, struct inode *inode,
347 const char *suffix, const void *value,
348 size_t size, int flags)
349{
350 const char *name = xattr_full_name(handler, suffix);
351 struct kernfs_node *kn = inode->i_private;
352
353 return kernfs_xattr_set(kn, name, value, size, flags);
354}
355
356static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
357 const struct mnt_idmap *idmap,
358 struct dentry *unused, struct inode *inode,
359 const char *suffix, const void *value,
360 size_t size, int flags)
361{
362 const char *full_name = xattr_full_name(handler, suffix);
363 struct kernfs_node *kn = inode->i_private;
364 struct kernfs_iattrs *attrs;
365
366 if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
367 return -EOPNOTSUPP;
368
369 attrs = kernfs_iattrs(kn);
370 if (!attrs)
371 return -ENOMEM;
372
373 /* See comment in kernfs_xattr_set() about locking. */
374 CLASS(kernfs_node_lock, lock)(kn);
375
376 return simple_xattr_set_limited(&kernfs_root(kn)->xa_cache,
377 &attrs->xattrs, &attrs->xattr_limits,
378 full_name, value, size, flags);
379}
380
381static const struct xattr_handler kernfs_trusted_xattr_handler = {
382 .prefix = XATTR_TRUSTED_PREFIX,
383 .get = kernfs_vfs_xattr_get,
384 .set = kernfs_vfs_xattr_set,
385};
386
387static const struct xattr_handler kernfs_security_xattr_handler = {
388 .prefix = XATTR_SECURITY_PREFIX,
389 .get = kernfs_vfs_xattr_get,
390 .set = kernfs_vfs_xattr_set,
391};
392
393static const struct xattr_handler kernfs_user_xattr_handler = {
394 .prefix = XATTR_USER_PREFIX,
395 .get = kernfs_vfs_xattr_get,
396 .set = kernfs_vfs_user_xattr_set,
397};
398
399const struct xattr_handler * const kernfs_xattr_handlers[] = {
400 &kernfs_trusted_xattr_handler,
401 &kernfs_security_xattr_handler,
402 &kernfs_user_xattr_handler,
403 NULL
404};