xref: /linux/fs/kernfs/inode.c (revision e0bf6c5ca2d3281f231c5f0c9bf145e9513644de)
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 
21 static 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 
27 static 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 
37 static 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);
60 out_unlock:
61 	ret = kn->iattr;
62 	mutex_unlock(&iattr_mutex);
63 	return ret;
64 }
65 
66 static 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  */
102 int 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 
112 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
113 {
114 	struct inode *inode = dentry->d_inode;
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 
133 out:
134 	mutex_unlock(&kernfs_mutex);
135 	return error;
136 }
137 
138 static 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 
160 int 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(dentry->d_inode, suffix,
176 						value, size, flags);
177 		if (error)
178 			return error;
179 		error = security_inode_getsecctx(dentry->d_inode,
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 
199 int 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 
211 ssize_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 
224 ssize_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 
236 static 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 
242 static 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 
251 static 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 
270 int 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 = dentry->d_inode;
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 
284 static 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 		break;
300 	case KERNFS_FILE:
301 		inode->i_size = kn->attr.size;
302 		inode->i_fop = &kernfs_file_fops;
303 		break;
304 	case KERNFS_LINK:
305 		inode->i_op = &kernfs_symlink_iops;
306 		break;
307 	default:
308 		BUG();
309 	}
310 
311 	unlock_new_inode(inode);
312 }
313 
314 /**
315  *	kernfs_get_inode - get inode for kernfs_node
316  *	@sb: super block
317  *	@kn: kernfs_node to allocate inode for
318  *
319  *	Get inode for @kn.  If such inode doesn't exist, a new inode is
320  *	allocated and basics are initialized.  New inode is returned
321  *	locked.
322  *
323  *	LOCKING:
324  *	Kernel thread context (may sleep).
325  *
326  *	RETURNS:
327  *	Pointer to allocated inode on success, NULL on failure.
328  */
329 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
330 {
331 	struct inode *inode;
332 
333 	inode = iget_locked(sb, kn->ino);
334 	if (inode && (inode->i_state & I_NEW))
335 		kernfs_init_inode(kn, inode);
336 
337 	return inode;
338 }
339 
340 /*
341  * The kernfs_node serves as both an inode and a directory entry for
342  * kernfs.  To prevent the kernfs inode numbers from being freed
343  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
344  * super_operations.evict_inode() implementation is needed to drop that
345  * reference upon inode destruction.
346  */
347 void kernfs_evict_inode(struct inode *inode)
348 {
349 	struct kernfs_node *kn = inode->i_private;
350 
351 	truncate_inode_pages_final(&inode->i_data);
352 	clear_inode(inode);
353 	kernfs_put(kn);
354 }
355 
356 int kernfs_iop_permission(struct inode *inode, int mask)
357 {
358 	struct kernfs_node *kn;
359 
360 	if (mask & MAY_NOT_BLOCK)
361 		return -ECHILD;
362 
363 	kn = inode->i_private;
364 
365 	mutex_lock(&kernfs_mutex);
366 	kernfs_refresh_inode(kn, inode);
367 	mutex_unlock(&kernfs_mutex);
368 
369 	return generic_permission(inode, mask);
370 }
371