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 struct backing_dev_info kernfs_bdi = {
 28	.name		= "kernfs",
 29	.ra_pages	= 0,	/* No readahead */
 30	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
 31};
 32
 33static const struct inode_operations kernfs_iops = {
 34	.permission	= kernfs_iop_permission,
 35	.setattr	= kernfs_iop_setattr,
 36	.getattr	= kernfs_iop_getattr,
 37	.setxattr	= kernfs_iop_setxattr,
 38	.removexattr	= kernfs_iop_removexattr,
 39	.getxattr	= kernfs_iop_getxattr,
 40	.listxattr	= kernfs_iop_listxattr,
 41};
 42
 43void __init kernfs_inode_init(void)
 44{
 45	if (bdi_init(&kernfs_bdi))
 46		panic("failed to init kernfs_bdi");
 47}
 48
 49static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
 50{
 51	static DEFINE_MUTEX(iattr_mutex);
 52	struct kernfs_iattrs *ret;
 53	struct iattr *iattrs;
 54
 55	mutex_lock(&iattr_mutex);
 56
 57	if (kn->iattr)
 58		goto out_unlock;
 59
 60	kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
 61	if (!kn->iattr)
 62		goto out_unlock;
 63	iattrs = &kn->iattr->ia_iattr;
 64
 65	/* assign default attributes */
 66	iattrs->ia_mode = kn->mode;
 67	iattrs->ia_uid = GLOBAL_ROOT_UID;
 68	iattrs->ia_gid = GLOBAL_ROOT_GID;
 69	iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
 70
 71	simple_xattrs_init(&kn->iattr->xattrs);
 72out_unlock:
 73	ret = kn->iattr;
 74	mutex_unlock(&iattr_mutex);
 75	return ret;
 76}
 77
 78static int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
 79{
 80	struct kernfs_iattrs *attrs;
 81	struct iattr *iattrs;
 82	unsigned int ia_valid = iattr->ia_valid;
 83
 84	attrs = kernfs_iattrs(kn);
 85	if (!attrs)
 86		return -ENOMEM;
 87
 88	iattrs = &attrs->ia_iattr;
 89
 90	if (ia_valid & ATTR_UID)
 91		iattrs->ia_uid = iattr->ia_uid;
 92	if (ia_valid & ATTR_GID)
 93		iattrs->ia_gid = iattr->ia_gid;
 94	if (ia_valid & ATTR_ATIME)
 95		iattrs->ia_atime = iattr->ia_atime;
 96	if (ia_valid & ATTR_MTIME)
 97		iattrs->ia_mtime = iattr->ia_mtime;
 98	if (ia_valid & ATTR_CTIME)
 99		iattrs->ia_ctime = iattr->ia_ctime;
100	if (ia_valid & ATTR_MODE) {
101		umode_t mode = iattr->ia_mode;
102		iattrs->ia_mode = kn->mode = mode;
103	}
104	return 0;
105}
106
107/**
108 * kernfs_setattr - set iattr on a node
109 * @kn: target node
110 * @iattr: iattr to set
111 *
112 * Returns 0 on success, -errno on failure.
113 */
114int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
115{
116	int ret;
117
118	mutex_lock(&kernfs_mutex);
119	ret = __kernfs_setattr(kn, iattr);
120	mutex_unlock(&kernfs_mutex);
121	return ret;
122}
123
124int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
125{
126	struct inode *inode = dentry->d_inode;
127	struct kernfs_node *kn = dentry->d_fsdata;
128	int error;
129
130	if (!kn)
131		return -EINVAL;
132
133	mutex_lock(&kernfs_mutex);
134	error = inode_change_ok(inode, iattr);
135	if (error)
136		goto out;
137
138	error = __kernfs_setattr(kn, iattr);
139	if (error)
140		goto out;
141
142	/* this ignores size changes */
143	setattr_copy(inode, iattr);
144
145out:
146	mutex_unlock(&kernfs_mutex);
147	return error;
148}
149
150static int kernfs_node_setsecdata(struct kernfs_node *kn, void **secdata,
151				  u32 *secdata_len)
152{
153	struct kernfs_iattrs *attrs;
154	void *old_secdata;
155	size_t old_secdata_len;
156
157	attrs = kernfs_iattrs(kn);
158	if (!attrs)
159		return -ENOMEM;
160
161	old_secdata = attrs->ia_secdata;
162	old_secdata_len = attrs->ia_secdata_len;
163
164	attrs->ia_secdata = *secdata;
165	attrs->ia_secdata_len = *secdata_len;
166
167	*secdata = old_secdata;
168	*secdata_len = old_secdata_len;
169	return 0;
170}
171
172int kernfs_iop_setxattr(struct dentry *dentry, const char *name,
173			const void *value, size_t size, int flags)
174{
175	struct kernfs_node *kn = dentry->d_fsdata;
176	struct kernfs_iattrs *attrs;
177	void *secdata;
178	int error;
179	u32 secdata_len = 0;
180
181	attrs = kernfs_iattrs(kn);
182	if (!attrs)
183		return -ENOMEM;
184
185	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
186		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
187		error = security_inode_setsecurity(dentry->d_inode, suffix,
188						value, size, flags);
189		if (error)
190			return error;
191		error = security_inode_getsecctx(dentry->d_inode,
192						&secdata, &secdata_len);
193		if (error)
194			return error;
195
196		mutex_lock(&kernfs_mutex);
197		error = kernfs_node_setsecdata(kn, &secdata, &secdata_len);
198		mutex_unlock(&kernfs_mutex);
199
200		if (secdata)
201			security_release_secctx(secdata, secdata_len);
202		return error;
203	} else if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN)) {
204		return simple_xattr_set(&attrs->xattrs, name, value, size,
205					flags);
206	}
207
208	return -EINVAL;
209}
210
211int kernfs_iop_removexattr(struct dentry *dentry, const char *name)
212{
213	struct kernfs_node *kn = dentry->d_fsdata;
214	struct kernfs_iattrs *attrs;
215
216	attrs = kernfs_iattrs(kn);
217	if (!attrs)
218		return -ENOMEM;
219
220	return simple_xattr_remove(&attrs->xattrs, name);
221}
222
223ssize_t kernfs_iop_getxattr(struct dentry *dentry, const char *name, void *buf,
224			    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_get(&attrs->xattrs, name, buf, size);
234}
235
236ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
237{
238	struct kernfs_node *kn = dentry->d_fsdata;
239	struct kernfs_iattrs *attrs;
240
241	attrs = kernfs_iattrs(kn);
242	if (!attrs)
243		return -ENOMEM;
244
245	return simple_xattr_list(&attrs->xattrs, buf, size);
246}
247
248static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
249{
250	inode->i_mode = mode;
251	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
252}
253
254static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
255{
256	inode->i_uid = iattr->ia_uid;
257	inode->i_gid = iattr->ia_gid;
258	inode->i_atime = iattr->ia_atime;
259	inode->i_mtime = iattr->ia_mtime;
260	inode->i_ctime = iattr->ia_ctime;
261}
262
263static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
264{
265	struct kernfs_iattrs *attrs = kn->iattr;
266
267	inode->i_mode = kn->mode;
268	if (attrs) {
269		/*
270		 * kernfs_node has non-default attributes get them from
271		 * persistent copy in kernfs_node.
272		 */
273		set_inode_attr(inode, &attrs->ia_iattr);
274		security_inode_notifysecctx(inode, attrs->ia_secdata,
275					    attrs->ia_secdata_len);
276	}
277
278	if (kernfs_type(kn) == KERNFS_DIR)
279		set_nlink(inode, kn->dir.subdirs + 2);
280}
281
282int kernfs_iop_getattr(struct vfsmount *mnt, struct dentry *dentry,
283		   struct kstat *stat)
284{
285	struct kernfs_node *kn = dentry->d_fsdata;
286	struct inode *inode = dentry->d_inode;
287
288	mutex_lock(&kernfs_mutex);
289	kernfs_refresh_inode(kn, inode);
290	mutex_unlock(&kernfs_mutex);
291
292	generic_fillattr(inode, stat);
293	return 0;
294}
295
296static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
297{
298	kernfs_get(kn);
299	inode->i_private = kn;
300	inode->i_mapping->a_ops = &kernfs_aops;
301	inode->i_mapping->backing_dev_info = &kernfs_bdi;
302	inode->i_op = &kernfs_iops;
303
304	set_default_inode_attr(inode, kn->mode);
305	kernfs_refresh_inode(kn, inode);
306
307	/* initialize inode according to type */
308	switch (kernfs_type(kn)) {
309	case KERNFS_DIR:
310		inode->i_op = &kernfs_dir_iops;
311		inode->i_fop = &kernfs_dir_fops;
312		break;
313	case KERNFS_FILE:
314		inode->i_size = kn->attr.size;
315		inode->i_fop = &kernfs_file_fops;
316		break;
317	case KERNFS_LINK:
318		inode->i_op = &kernfs_symlink_iops;
319		break;
320	default:
321		BUG();
322	}
323
324	unlock_new_inode(inode);
325}
326
327/**
328 *	kernfs_get_inode - get inode for kernfs_node
329 *	@sb: super block
330 *	@kn: kernfs_node to allocate inode for
331 *
332 *	Get inode for @kn.  If such inode doesn't exist, a new inode is
333 *	allocated and basics are initialized.  New inode is returned
334 *	locked.
335 *
336 *	LOCKING:
337 *	Kernel thread context (may sleep).
338 *
339 *	RETURNS:
340 *	Pointer to allocated inode on success, NULL on failure.
341 */
342struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
343{
344	struct inode *inode;
345
346	inode = iget_locked(sb, kn->ino);
347	if (inode && (inode->i_state & I_NEW))
348		kernfs_init_inode(kn, inode);
349
350	return inode;
351}
352
353/*
354 * The kernfs_node serves as both an inode and a directory entry for
355 * kernfs.  To prevent the kernfs inode numbers from being freed
356 * prematurely we take a reference to kernfs_node from the kernfs inode.  A
357 * super_operations.evict_inode() implementation is needed to drop that
358 * reference upon inode destruction.
359 */
360void kernfs_evict_inode(struct inode *inode)
361{
362	struct kernfs_node *kn = inode->i_private;
363
364	truncate_inode_pages_final(&inode->i_data);
365	clear_inode(inode);
366	kernfs_put(kn);
367}
368
369int kernfs_iop_permission(struct inode *inode, int mask)
370{
371	struct kernfs_node *kn;
372
373	if (mask & MAY_NOT_BLOCK)
374		return -ECHILD;
375
376	kn = inode->i_private;
377
378	mutex_lock(&kernfs_mutex);
379	kernfs_refresh_inode(kn, inode);
380	mutex_unlock(&kernfs_mutex);
381
382	return generic_permission(inode, mask);
383}