1/*
  2 * fs/sysfs/inode.c - basic sysfs inode and dentry operations
  3 *
  4 * Copyright (c) 2001-3 Patrick Mochel
  5 * Copyright (c) 2007 SUSE Linux Products GmbH
  6 * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
  7 *
  8 * This file is released under the GPLv2.
  9 *
 10 * Please see Documentation/filesystems/sysfs.txt for more information.
 11 */
 12
 13#undef DEBUG 
 14
 15#include <linux/pagemap.h>
 16#include <linux/namei.h>
 17#include <linux/backing-dev.h>
 18#include <linux/capability.h>
 19#include <linux/errno.h>
 20#include <linux/sched.h>
 21#include <linux/slab.h>
 22#include <linux/sysfs.h>
 23#include <linux/xattr.h>
 24#include <linux/security.h>
 25#include "sysfs.h"
 26
 27extern struct super_block * sysfs_sb;
 28
 29static const struct address_space_operations sysfs_aops = {
 30	.readpage	= simple_readpage,
 31	.write_begin	= simple_write_begin,
 32	.write_end	= simple_write_end,
 33};
 34
 35static struct backing_dev_info sysfs_backing_dev_info = {
 36	.name		= "sysfs",
 37	.ra_pages	= 0,	/* No readahead */
 38	.capabilities	= BDI_CAP_NO_ACCT_AND_WRITEBACK,
 39};
 40
 41static const struct inode_operations sysfs_inode_operations ={
 42	.permission	= sysfs_permission,
 43	.setattr	= sysfs_setattr,
 44	.getattr	= sysfs_getattr,
 45	.setxattr	= sysfs_setxattr,
 46};
 47
 48int __init sysfs_inode_init(void)
 49{
 50	return bdi_init(&sysfs_backing_dev_info);
 51}
 52
 53static struct sysfs_inode_attrs *sysfs_init_inode_attrs(struct sysfs_dirent *sd)
 54{
 55	struct sysfs_inode_attrs *attrs;
 56	struct iattr *iattrs;
 57
 58	attrs = kzalloc(sizeof(struct sysfs_inode_attrs), GFP_KERNEL);
 59	if (!attrs)
 60		return NULL;
 61	iattrs = &attrs->ia_iattr;
 62
 63	/* assign default attributes */
 64	iattrs->ia_mode = sd->s_mode;
 65	iattrs->ia_uid = 0;
 66	iattrs->ia_gid = 0;
 67	iattrs->ia_atime = iattrs->ia_mtime = iattrs->ia_ctime = CURRENT_TIME;
 68
 69	return attrs;
 70}
 71
 72int sysfs_sd_setattr(struct sysfs_dirent *sd, struct iattr * iattr)
 73{
 74	struct sysfs_inode_attrs *sd_attrs;
 75	struct iattr *iattrs;
 76	unsigned int ia_valid = iattr->ia_valid;
 77
 78	sd_attrs = sd->s_iattr;
 79
 80	if (!sd_attrs) {
 81		/* setting attributes for the first time, allocate now */
 82		sd_attrs = sysfs_init_inode_attrs(sd);
 83		if (!sd_attrs)
 84			return -ENOMEM;
 85		sd->s_iattr = sd_attrs;
 86	}
 87	/* attributes were changed at least once in past */
 88	iattrs = &sd_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 = sd->s_mode = mode;
103	}
104	return 0;
105}
106
107int sysfs_setattr(struct dentry *dentry, struct iattr *iattr)
108{
109	struct inode *inode = dentry->d_inode;
110	struct sysfs_dirent *sd = dentry->d_fsdata;
111	int error;
112
113	if (!sd)
114		return -EINVAL;
115
116	mutex_lock(&sysfs_mutex);
117	error = inode_change_ok(inode, iattr);
118	if (error)
119		goto out;
120
121	error = sysfs_sd_setattr(sd, iattr);
122	if (error)
123		goto out;
124
125	/* this ignores size changes */
126	setattr_copy(inode, iattr);
127
128out:
129	mutex_unlock(&sysfs_mutex);
130	return error;
131}
132
133static int sysfs_sd_setsecdata(struct sysfs_dirent *sd, void **secdata, u32 *secdata_len)
134{
135	struct sysfs_inode_attrs *iattrs;
136	void *old_secdata;
137	size_t old_secdata_len;
138
139	iattrs = sd->s_iattr;
140	if (!iattrs)
141		iattrs = sysfs_init_inode_attrs(sd);
142	if (!iattrs)
143		return -ENOMEM;
144
145	old_secdata = iattrs->ia_secdata;
146	old_secdata_len = iattrs->ia_secdata_len;
147
148	iattrs->ia_secdata = *secdata;
149	iattrs->ia_secdata_len = *secdata_len;
150
151	*secdata = old_secdata;
152	*secdata_len = old_secdata_len;
153	return 0;
154}
155
156int sysfs_setxattr(struct dentry *dentry, const char *name, const void *value,
157		size_t size, int flags)
158{
159	struct sysfs_dirent *sd = dentry->d_fsdata;
160	void *secdata;
161	int error;
162	u32 secdata_len = 0;
163
164	if (!sd)
165		return -EINVAL;
166
167	if (!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN)) {
168		const char *suffix = name + XATTR_SECURITY_PREFIX_LEN;
169		error = security_inode_setsecurity(dentry->d_inode, suffix,
170						value, size, flags);
171		if (error)
172			goto out;
173		error = security_inode_getsecctx(dentry->d_inode,
174						&secdata, &secdata_len);
175		if (error)
176			goto out;
177
178		mutex_lock(&sysfs_mutex);
179		error = sysfs_sd_setsecdata(sd, &secdata, &secdata_len);
180		mutex_unlock(&sysfs_mutex);
181
182		if (secdata)
183			security_release_secctx(secdata, secdata_len);
184	} else
185		return -EINVAL;
186out:
187	return error;
188}
189
190static inline void set_default_inode_attr(struct inode * inode, mode_t mode)
191{
192	inode->i_mode = mode;
193	inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
194}
195
196static inline void set_inode_attr(struct inode * inode, struct iattr * iattr)
197{
198	inode->i_uid = iattr->ia_uid;
199	inode->i_gid = iattr->ia_gid;
200	inode->i_atime = iattr->ia_atime;
201	inode->i_mtime = iattr->ia_mtime;
202	inode->i_ctime = iattr->ia_ctime;
203}
204
205static int sysfs_count_nlink(struct sysfs_dirent *sd)
206{
207	struct sysfs_dirent *child;
208	int nr = 0;
209
210	for (child = sd->s_dir.children; child; child = child->s_sibling)
211		if (sysfs_type(child) == SYSFS_DIR)
212			nr++;
213
214	return nr + 2;
215}
216
217static void sysfs_refresh_inode(struct sysfs_dirent *sd, struct inode *inode)
218{
219	struct sysfs_inode_attrs *iattrs = sd->s_iattr;
220
221	inode->i_mode = sd->s_mode;
222	if (iattrs) {
223		/* sysfs_dirent has non-default attributes
224		 * get them from persistent copy in sysfs_dirent
225		 */
226		set_inode_attr(inode, &iattrs->ia_iattr);
227		security_inode_notifysecctx(inode,
228					    iattrs->ia_secdata,
229					    iattrs->ia_secdata_len);
230	}
231
232	if (sysfs_type(sd) == SYSFS_DIR)
233		inode->i_nlink = sysfs_count_nlink(sd);
234}
235
236int sysfs_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *stat)
237{
238	struct sysfs_dirent *sd = dentry->d_fsdata;
239	struct inode *inode = dentry->d_inode;
240
241	mutex_lock(&sysfs_mutex);
242	sysfs_refresh_inode(sd, inode);
243	mutex_unlock(&sysfs_mutex);
244
245	generic_fillattr(inode, stat);
246	return 0;
247}
248
249static void sysfs_init_inode(struct sysfs_dirent *sd, struct inode *inode)
250{
251	struct bin_attribute *bin_attr;
252
253	inode->i_private = sysfs_get(sd);
254	inode->i_mapping->a_ops = &sysfs_aops;
255	inode->i_mapping->backing_dev_info = &sysfs_backing_dev_info;
256	inode->i_op = &sysfs_inode_operations;
257
258	set_default_inode_attr(inode, sd->s_mode);
259	sysfs_refresh_inode(sd, inode);
260
261	/* initialize inode according to type */
262	switch (sysfs_type(sd)) {
263	case SYSFS_DIR:
264		inode->i_op = &sysfs_dir_inode_operations;
265		inode->i_fop = &sysfs_dir_operations;
266		break;
267	case SYSFS_KOBJ_ATTR:
268		inode->i_size = PAGE_SIZE;
269		inode->i_fop = &sysfs_file_operations;
270		break;
271	case SYSFS_KOBJ_BIN_ATTR:
272		bin_attr = sd->s_bin_attr.bin_attr;
273		inode->i_size = bin_attr->size;
274		inode->i_fop = &bin_fops;
275		break;
276	case SYSFS_KOBJ_LINK:
277		inode->i_op = &sysfs_symlink_inode_operations;
278		break;
279	default:
280		BUG();
281	}
282
283	unlock_new_inode(inode);
284}
285
286/**
287 *	sysfs_get_inode - get inode for sysfs_dirent
288 *	@sb: super block
289 *	@sd: sysfs_dirent to allocate inode for
290 *
291 *	Get inode for @sd.  If such inode doesn't exist, a new inode
292 *	is allocated and basics are initialized.  New inode is
293 *	returned locked.
294 *
295 *	LOCKING:
296 *	Kernel thread context (may sleep).
297 *
298 *	RETURNS:
299 *	Pointer to allocated inode on success, NULL on failure.
300 */
301struct inode * sysfs_get_inode(struct super_block *sb, struct sysfs_dirent *sd)
302{
303	struct inode *inode;
304
305	inode = iget_locked(sb, sd->s_ino);
306	if (inode && (inode->i_state & I_NEW))
307		sysfs_init_inode(sd, inode);
308
309	return inode;
310}
311
312/*
313 * The sysfs_dirent serves as both an inode and a directory entry for sysfs.
314 * To prevent the sysfs inode numbers from being freed prematurely we take a
315 * reference to sysfs_dirent from the sysfs inode.  A
316 * super_operations.evict_inode() implementation is needed to drop that
317 * reference upon inode destruction.
318 */
319void sysfs_evict_inode(struct inode *inode)
320{
321	struct sysfs_dirent *sd  = inode->i_private;
322
323	truncate_inode_pages(&inode->i_data, 0);
324	end_writeback(inode);
325	sysfs_put(sd);
326}
327
328int sysfs_hash_and_remove(struct sysfs_dirent *dir_sd, const void *ns, const char *name)
329{
330	struct sysfs_addrm_cxt acxt;
331	struct sysfs_dirent *sd;
332
333	if (!dir_sd)
334		return -ENOENT;
335
336	sysfs_addrm_start(&acxt, dir_sd);
337
338	sd = sysfs_find_dirent(dir_sd, ns, name);
339	if (sd && (sd->s_ns != ns))
340		sd = NULL;
341	if (sd)
342		sysfs_remove_one(&acxt, sd);
343
344	sysfs_addrm_finish(&acxt);
345
346	if (sd)
347		return 0;
348	else
349		return -ENOENT;
350}
351
352int sysfs_permission(struct inode *inode, int mask)
353{
354	struct sysfs_dirent *sd;
355
356	if (mask & MAY_NOT_BLOCK)
357		return -ECHILD;
358
359	sd = inode->i_private;
360
361	mutex_lock(&sysfs_mutex);
362	sysfs_refresh_inode(sd, inode);
363	mutex_unlock(&sysfs_mutex);
364
365	return generic_permission(inode, mask);
366}