1/*
2 * fs/kernfs/inode.c - kernfs inode implementation
3 *
4 * Copyright (c) 2001-3 Patrick Mochel
5 * Copyright (c) 2007 SUSE Linux Products GmbH
6 * Copyright (c) 2007, 2013 Tejun Heo <tj@kernel.org>
7 *
8 * This file is released under the GPLv2.
9 */
10
11#include <linux/pagemap.h>
12#include <linux/backing-dev.h>
13#include <linux/capability.h>
14#include <linux/errno.h>
15#include <linux/slab.h>
16#include <linux/xattr.h>
17#include <linux/security.h>
18
19#include "kernfs-internal.h"
20
21static const struct address_space_operations kernfs_aops = {
22	.readpage	= simple_readpage,
23	.write_begin	= simple_write_begin,
24	.write_end	= simple_write_end,
25};
26
27static const struct inode_operations kernfs_iops = {
28	.permission	= kernfs_iop_permission,
29	.setattr	= kernfs_iop_setattr,
30	.getattr	= kernfs_iop_getattr,
31	.setxattr	= kernfs_iop_setxattr,
32	.removexattr	= kernfs_iop_removexattr,
33	.getxattr	= kernfs_iop_getxattr,
34	.listxattr	= kernfs_iop_listxattr,
35};
36
37static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
38{
39	static DEFINE_MUTEX(iattr_mutex);
40	struct kernfs_iattrs *ret;
41	struct iattr *iattrs;
42
43	mutex_lock(&iattr_mutex);
44
45	if (kn->iattr)
46		goto out_unlock;
47
48	kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
49	if (!kn->iattr)
50		goto out_unlock;
51	iattrs = &kn->iattr->ia_iattr;
52
53	/* assign default attributes */
54	iattrs->ia_mode = kn->mode;
55	iattrs->ia_uid = GLOBAL_ROOT_UID;
56	iattrs->ia_gid = GLOBAL_ROOT_GID;
57	iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
58
59	simple_xattrs_init(&kn->iattr->xattrs);
60out_unlock:
61	ret = kn->iattr;
62	mutex_unlock(&iattr_mutex);
63	return ret;
64}
65
66static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
67{
68	struct kernfs_iattrs *attrs;
69	struct iattr *iattrs;
70	unsigned int ia_valid = iattr->ia_valid;
71
72	attrs = kernfs_iattrs(kn);
73	if (!attrs)
74		return -ENOMEM;
75
76	iattrs = &attrs->ia_iattr;
77
78	if (ia_valid & ATTR_UID)
79		iattrs->ia_uid = iattr->ia_uid;
80	if (ia_valid & ATTR_GID)
81		iattrs->ia_gid = iattr->ia_gid;
82	if (ia_valid & ATTR_ATIME)
83		iattrs->ia_atime = iattr->ia_atime;
84	if (ia_valid & ATTR_MTIME)
85		iattrs->ia_mtime = iattr->ia_mtime;
86	if (ia_valid & ATTR_CTIME)
87		iattrs->ia_ctime = iattr->ia_ctime;
88	if (ia_valid & ATTR_MODE) {
89		umode_t mode = iattr->ia_mode;
90		iattrs->ia_mode = kn->mode = mode;
91	}
92	return 0;
93}
94
95/**
96 * kernfs_setattr - set iattr on a node
97 * @kn: target node
98 * @iattr: iattr to set
99 *
100 * Returns 0 on success, -errno on failure.
101 */
102int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
103{
104	int ret;
105
106	mutex_lock(&kernfs_mutex);
107	ret = __kernfs_setattr(kn, iattr);
108	mutex_unlock(&kernfs_mutex);
109	return ret;
110}
111
112int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
113{
114	struct inode *inode = d_inode(dentry);
115	struct kernfs_node *kn = dentry->d_fsdata;
116	int error;
117
118	if (!kn)
119		return -EINVAL;
120
121	mutex_lock(&kernfs_mutex);
122	error = inode_change_ok(inode, iattr);
123	if (error)
124		goto out;
125
126	error = __kernfs_setattr(kn, iattr);
127	if (error)
128		goto out;
129
130	/* this ignores size changes */
131	setattr_copy(inode, iattr);
132
133out:
134	mutex_unlock(&kernfs_mutex);
135	return error;
136}
137
138static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
139				  u32 *secdata_len)
140{
141	struct kernfs_iattrs *attrs;
142	void *old_secdata;
143	size_t old_secdata_len;
144
145	attrs = kernfs_iattrs(kn);
146	if (!attrs)
147		return -ENOMEM;
148
149	old_secdata = attrs->ia_secdata;
150	old_secdata_len = attrs->ia_secdata_len;
151
152	attrs->ia_secdata = *secdata;
153	attrs->ia_secdata_len = *secdata_len;
154
155	*secdata = old_secdata;
156	*secdata_len = old_secdata_len;
157	return 0;
158}
159
160int kernfs_iop_setxattr(struct dentry *dentry, const char *name,
161			const void *value, size_t size, int flags)
162{
163	struct kernfs_node *kn = dentry->d_fsdata;
164	struct kernfs_iattrs *attrs;
165	void *secdata;
166	int error;
167	u32 secdata_len = 0;
168
169	attrs = kernfs_iattrs(kn);
170	if (!attrs)
171		return -ENOMEM;
172
173	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
174		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
175		error = security_inode_setsecurity(d_inode(dentry), suffix,
176						value, size, flags);
177		if (error)
178			return error;
179		error = security_inode_getsecctx(d_inode(dentry),
180						&secdata, &secdata_len);
181		if (error)
182			return error;
183
184		mutex_lock(&kernfs_mutex);
185		error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
186		mutex_unlock(&kernfs_mutex);
187
188		if (secdata)
189			security_release_secctx(secdata, secdata_len);
190		return error;
191	} else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
192		return simple_xattr_set(&attrs->xattrs, name, value, size,
193					flags);
194	}
195
196	return -EINVAL;
197}
198
199int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
200{
201	struct kernfs_node *kn = dentry->d_fsdata;
202	struct kernfs_iattrs *attrs;
203
204	attrs = kernfs_iattrs(kn);
205	if (!attrs)
206		return -ENOMEM;
207
208	return simple_xattr_remove(&attrs->xattrs, name);
209}
210
211ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
212			    size_t size)
213{
214	struct kernfs_node *kn = dentry->d_fsdata;
215	struct kernfs_iattrs *attrs;
216
217	attrs = kernfs_iattrs(kn);
218	if (!attrs)
219		return -ENOMEM;
220
221	return simple_xattr_get(&attrs->xattrs, name, buf, size);
222}
223
224ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
225{
226	struct kernfs_node *kn = dentry->d_fsdata;
227	struct kernfs_iattrs *attrs;
228
229	attrs = kernfs_iattrs(kn);
230	if (!attrs)
231		return -ENOMEM;
232
233	return simple_xattr_list(&attrs->xattrs, buf, size);
234}
235
236static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
237{
238	inode->i_mode = mode;
239	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
240}
241
242static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
243{
244	inode->i_uid = iattr->ia_uid;
245	inode->i_gid = iattr->ia_gid;
246	inode->i_atime = iattr->ia_atime;
247	inode->i_mtime = iattr->ia_mtime;
248	inode->i_ctime = iattr->ia_ctime;
249}
250
251static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
252{
253	struct kernfs_iattrs *attrs = kn->iattr;
254
255	inode->i_mode = kn->mode;
256	if (attrs) {
257		/*
258		 * kernfs_node has non-default attributes get them from
259		 * persistent copy in kernfs_node.
260		 */
261		set_inode_attr(inode, &attrs->ia_iattr);
262		security_inode_notifysecctx(inode, attrs->ia_secdata,
263					    attrs->ia_secdata_len);
264	}
265
266	if (kernfs_type(kn) == KERNFS_DIR)
267		set_nlink(inode, kn->dir.subdirs + 2);
268}
269
270int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
271		   struct kstat *stat)
272{
273	struct kernfs_node *kn = dentry->d_fsdata;
274	struct inode *inode = d_inode(dentry);
275
276	mutex_lock(&kernfs_mutex);
277	kernfs_refresh_inode(kn, inode);
278	mutex_unlock(&kernfs_mutex);
279
280	generic_fillattr(inode, stat);
281	return 0;
282}
283
284static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
285{
286	kernfs_get(kn);
287	inode->i_private = kn;
288	inode->i_mapping->a_ops = &kernfs_aops;
289	inode->i_op = &kernfs_iops;
290
291	set_default_inode_attr(inode, kn->mode);
292	kernfs_refresh_inode(kn, inode);
293
294	/* initialize inode according to type */
295	switch (kernfs_type(kn)) {
296	case KERNFS_DIR:
297		inode->i_op = &kernfs_dir_iops;
298		inode->i_fop = &kernfs_dir_fops;
299		if (kn->flags & KERNFS_EMPTY_DIR)
300			make_empty_dir_inode(inode);
301		break;
302	case KERNFS_FILE:
303		inode->i_size = kn->attr.size;
304		inode->i_fop = &kernfs_file_fops;
305		break;
306	case KERNFS_LINK:
307		inode->i_op = &kernfs_symlink_iops;
308		break;
309	default:
310		BUG();
311	}
312
313	unlock_new_inode(inode);
314}
315
316/**
317 *	kernfs_get_inode - get inode for kernfs_node
318 *	@sb: super block
319 *	@kn: kernfs_node to allocate inode for
320 *
321 *	Get inode for @kn.  If such inode doesn't exist, a new inode is
322 *	allocated and basics are initialized.  New inode is returned
323 *	locked.
324 *
325 *	LOCKING:
326 *	Kernel thread context (may sleep).
327 *
328 *	RETURNS:
329 *	Pointer to allocated inode on success, NULL on failure.
330 */
331struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
332{
333	struct inode *inode;
334
335	inode = iget_locked(sb, kn->ino);
336	if (inode && (inode->i_state & I_NEW))
337		kernfs_init_inode(kn, inode);
338
339	return inode;
340}
341
342/*
343 * The kernfs_node serves as both an inode and a directory entry for
344 * kernfs.  To prevent the kernfs inode numbers from being freed
345 * prematurely we take a reference to kernfs_node from the kernfs inode.  A
346 * super_operations.evict_inode() implementation is needed to drop that
347 * reference upon inode destruction.
348 */
349void kernfs_evict_inode(struct inode *inode)
350{
351	struct kernfs_node *kn = inode->i_private;
352
353	truncate_inode_pages_final(&inode->i_data);
354	clear_inode(inode);
355	kernfs_put(kn);
356}
357
358int kernfs_iop_permission(struct inode *inode, int mask)
359{
360	struct kernfs_node *kn;
361
362	if (mask & MAY_NOT_BLOCK)
363		return -ECHILD;
364
365	kn = inode->i_private;
366
367	mutex_lock(&kernfs_mutex);
368	kernfs_refresh_inode(kn, inode);
369	mutex_unlock(&kernfs_mutex);
370
371	return generic_permission(inode, mask);
372}
373