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, 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);
52out_unlock:
53	ret = kn->iattr;
54	mutex_unlock(&iattr_mutex);
55	return ret;
56}
57
58static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
59{
60	return __kernfs_iattrs(kn, 1);
61}
62
63static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
64{
65	return __kernfs_iattrs(kn, 0);
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(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(kn);
145	if (!attrs)
146		return -ENOMEM;
147
148	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
149}
150
151static 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
157static 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
167static 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
183int 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
199static 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 */
247struct 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 */
265void 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
274int 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
295int 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
305int 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
321static 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
331static 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
343static 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);
375dec_size_out:
376	atomic_sub(size, sz);
377dec_count_out:
378	atomic_dec(nr);
379	return ret;
380}
381
382static 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
404static 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
430static 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
436static 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
442static 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
448const 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