xref: /openbmc/linux/fs/kernfs/inode.c (revision 4bb1eb3c) 
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 
20 static const struct address_space_operations kernfs_aops = {
21 	.readpage	= simple_readpage,
22 	.write_begin	= simple_write_begin,
23 	.write_end	= simple_write_end,
24 };
25 
26 static const struct inode_operations kernfs_iops = {
27 	.permission	= kernfs_iop_permission,
28 	.setattr	= kernfs_iop_setattr,
29 	.getattr	= kernfs_iop_getattr,
30 	.listxattr	= kernfs_iop_listxattr,
31 };
32 
33 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
34 {
35 	static DEFINE_MUTEX(iattr_mutex);
36 	struct kernfs_iattrs *ret;
37 
38 	mutex_lock(&iattr_mutex);
39 
40 	if (kn->iattr || !alloc)
41 		goto out_unlock;
42 
43 	kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
44 	if (!kn->iattr)
45 		goto out_unlock;
46 
47 	/* assign default attributes */
48 	kn->iattr->ia_uid = GLOBAL_ROOT_UID;
49 	kn->iattr->ia_gid = GLOBAL_ROOT_GID;
50 
51 	ktime_get_real_ts64(&kn->iattr->ia_atime);
52 	kn->iattr->ia_mtime = kn->iattr->ia_atime;
53 	kn->iattr->ia_ctime = kn->iattr->ia_atime;
54 
55 	simple_xattrs_init(&kn->iattr->xattrs);
56 	atomic_set(&kn->iattr->nr_user_xattrs, 0);
57 	atomic_set(&kn->iattr->user_xattr_size, 0);
58 out_unlock:
59 	ret = kn->iattr;
60 	mutex_unlock(&iattr_mutex);
61 	return ret;
62 }
63 
64 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
65 {
66 	return __kernfs_iattrs(kn, 1);
67 }
68 
69 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
70 {
71 	return __kernfs_iattrs(kn, 0);
72 }
73 
74 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
75 {
76 	struct kernfs_iattrs *attrs;
77 	unsigned int ia_valid = iattr->ia_valid;
78 
79 	attrs = kernfs_iattrs(kn);
80 	if (!attrs)
81 		return -ENOMEM;
82 
83 	if (ia_valid & ATTR_UID)
84 		attrs->ia_uid = iattr->ia_uid;
85 	if (ia_valid & ATTR_GID)
86 		attrs->ia_gid = iattr->ia_gid;
87 	if (ia_valid & ATTR_ATIME)
88 		attrs->ia_atime = iattr->ia_atime;
89 	if (ia_valid & ATTR_MTIME)
90 		attrs->ia_mtime = iattr->ia_mtime;
91 	if (ia_valid & ATTR_CTIME)
92 		attrs->ia_ctime = iattr->ia_ctime;
93 	if (ia_valid & ATTR_MODE)
94 		kn->mode = iattr->ia_mode;
95 	return 0;
96 }
97 
98 /**
99  * kernfs_setattr - set iattr on a node
100  * @kn: target node
101  * @iattr: iattr to set
102  *
103  * Returns 0 on success, -errno on failure.
104  */
105 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
106 {
107 	int ret;
108 
109 	mutex_lock(&kernfs_mutex);
110 	ret = __kernfs_setattr(kn, iattr);
111 	mutex_unlock(&kernfs_mutex);
112 	return ret;
113 }
114 
115 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
116 {
117 	struct inode *inode = d_inode(dentry);
118 	struct kernfs_node *kn = inode->i_private;
119 	int error;
120 
121 	if (!kn)
122 		return -EINVAL;
123 
124 	mutex_lock(&kernfs_mutex);
125 	error = setattr_prepare(dentry, iattr);
126 	if (error)
127 		goto out;
128 
129 	error = __kernfs_setattr(kn, iattr);
130 	if (error)
131 		goto out;
132 
133 	/* this ignores size changes */
134 	setattr_copy(inode, iattr);
135 
136 out:
137 	mutex_unlock(&kernfs_mutex);
138 	return error;
139 }
140 
141 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
142 {
143 	struct kernfs_node *kn = kernfs_dentry_node(dentry);
144 	struct kernfs_iattrs *attrs;
145 
146 	attrs = kernfs_iattrs(kn);
147 	if (!attrs)
148 		return -ENOMEM;
149 
150 	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
151 }
152 
153 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
154 {
155 	inode->i_mode = mode;
156 	inode->i_atime = inode->i_mtime =
157 		inode->i_ctime = current_time(inode);
158 }
159 
160 static inline void set_inode_attr(struct inode *inode,
161 				  struct kernfs_iattrs *attrs)
162 {
163 	inode->i_uid = attrs->ia_uid;
164 	inode->i_gid = attrs->ia_gid;
165 	inode->i_atime = attrs->ia_atime;
166 	inode->i_mtime = attrs->ia_mtime;
167 	inode->i_ctime = attrs->ia_ctime;
168 }
169 
170 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
171 {
172 	struct kernfs_iattrs *attrs = kn->iattr;
173 
174 	inode->i_mode = kn->mode;
175 	if (attrs)
176 		/*
177 		 * kernfs_node has non-default attributes get them from
178 		 * persistent copy in kernfs_node.
179 		 */
180 		set_inode_attr(inode, attrs);
181 
182 	if (kernfs_type(kn) == KERNFS_DIR)
183 		set_nlink(inode, kn->dir.subdirs + 2);
184 }
185 
186 int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
187 		       u32 request_mask, unsigned int query_flags)
188 {
189 	struct inode *inode = d_inode(path->dentry);
190 	struct kernfs_node *kn = inode->i_private;
191 
192 	mutex_lock(&kernfs_mutex);
193 	kernfs_refresh_inode(kn, inode);
194 	mutex_unlock(&kernfs_mutex);
195 
196 	generic_fillattr(inode, stat);
197 	return 0;
198 }
199 
200 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
201 {
202 	kernfs_get(kn);
203 	inode->i_private = kn;
204 	inode->i_mapping->a_ops = &kernfs_aops;
205 	inode->i_op = &kernfs_iops;
206 	inode->i_generation = kernfs_gen(kn);
207 
208 	set_default_inode_attr(inode, kn->mode);
209 	kernfs_refresh_inode(kn, inode);
210 
211 	/* initialize inode according to type */
212 	switch (kernfs_type(kn)) {
213 	case KERNFS_DIR:
214 		inode->i_op = &kernfs_dir_iops;
215 		inode->i_fop = &kernfs_dir_fops;
216 		if (kn->flags & KERNFS_EMPTY_DIR)
217 			make_empty_dir_inode(inode);
218 		break;
219 	case KERNFS_FILE:
220 		inode->i_size = kn->attr.size;
221 		inode->i_fop = &kernfs_file_fops;
222 		break;
223 	case KERNFS_LINK:
224 		inode->i_op = &kernfs_symlink_iops;
225 		break;
226 	default:
227 		BUG();
228 	}
229 
230 	unlock_new_inode(inode);
231 }
232 
233 /**
234  *	kernfs_get_inode - get inode for kernfs_node
235  *	@sb: super block
236  *	@kn: kernfs_node to allocate inode for
237  *
238  *	Get inode for @kn.  If such inode doesn't exist, a new inode is
239  *	allocated and basics are initialized.  New inode is returned
240  *	locked.
241  *
242  *	LOCKING:
243  *	Kernel thread context (may sleep).
244  *
245  *	RETURNS:
246  *	Pointer to allocated inode on success, NULL on failure.
247  */
248 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
249 {
250 	struct inode *inode;
251 
252 	inode = iget_locked(sb, kernfs_ino(kn));
253 	if (inode && (inode->i_state & I_NEW))
254 		kernfs_init_inode(kn, inode);
255 
256 	return inode;
257 }
258 
259 /*
260  * The kernfs_node serves as both an inode and a directory entry for
261  * kernfs.  To prevent the kernfs inode numbers from being freed
262  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
263  * super_operations.evict_inode() implementation is needed to drop that
264  * reference upon inode destruction.
265  */
266 void kernfs_evict_inode(struct inode *inode)
267 {
268 	struct kernfs_node *kn = inode->i_private;
269 
270 	truncate_inode_pages_final(&inode->i_data);
271 	clear_inode(inode);
272 	kernfs_put(kn);
273 }
274 
275 int kernfs_iop_permission(struct inode *inode, int mask)
276 {
277 	struct kernfs_node *kn;
278 
279 	if (mask & MAY_NOT_BLOCK)
280 		return -ECHILD;
281 
282 	kn = inode->i_private;
283 
284 	mutex_lock(&kernfs_mutex);
285 	kernfs_refresh_inode(kn, inode);
286 	mutex_unlock(&kernfs_mutex);
287 
288 	return generic_permission(inode, mask);
289 }
290 
291 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
292 		     void *value, size_t size)
293 {
294 	struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
295 	if (!attrs)
296 		return -ENODATA;
297 
298 	return simple_xattr_get(&attrs->xattrs, name, value, size);
299 }
300 
301 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
302 		     const void *value, size_t size, int flags)
303 {
304 	struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
305 	if (!attrs)
306 		return -ENOMEM;
307 
308 	return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL);
309 }
310 
311 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
312 				struct dentry *unused, struct inode *inode,
313 				const char *suffix, void *value, size_t size)
314 {
315 	const char *name = xattr_full_name(handler, suffix);
316 	struct kernfs_node *kn = inode->i_private;
317 
318 	return kernfs_xattr_get(kn, name, value, size);
319 }
320 
321 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
322 				struct dentry *unused, struct inode *inode,
323 				const char *suffix, const void *value,
324 				size_t size, int flags)
325 {
326 	const char *name = xattr_full_name(handler, suffix);
327 	struct kernfs_node *kn = inode->i_private;
328 
329 	return kernfs_xattr_set(kn, name, value, size, flags);
330 }
331 
332 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
333 				     const char *full_name,
334 				     struct simple_xattrs *xattrs,
335 				     const void *value, size_t size, int flags)
336 {
337 	atomic_t *sz = &kn->iattr->user_xattr_size;
338 	atomic_t *nr = &kn->iattr->nr_user_xattrs;
339 	ssize_t removed_size;
340 	int ret;
341 
342 	if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
343 		ret = -ENOSPC;
344 		goto dec_count_out;
345 	}
346 
347 	if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) {
348 		ret = -ENOSPC;
349 		goto dec_size_out;
350 	}
351 
352 	ret = simple_xattr_set(xattrs, full_name, value, size, flags,
353 			       &removed_size);
354 
355 	if (!ret && removed_size >= 0)
356 		size = removed_size;
357 	else if (!ret)
358 		return 0;
359 dec_size_out:
360 	atomic_sub(size, sz);
361 dec_count_out:
362 	atomic_dec(nr);
363 	return ret;
364 }
365 
366 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
367 				    const char *full_name,
368 				    struct simple_xattrs *xattrs,
369 				    const void *value, size_t size, int flags)
370 {
371 	atomic_t *sz = &kn->iattr->user_xattr_size;
372 	atomic_t *nr = &kn->iattr->nr_user_xattrs;
373 	ssize_t removed_size;
374 	int ret;
375 
376 	ret = simple_xattr_set(xattrs, full_name, value, size, flags,
377 			       &removed_size);
378 
379 	if (removed_size >= 0) {
380 		atomic_sub(removed_size, sz);
381 		atomic_dec(nr);
382 	}
383 
384 	return ret;
385 }
386 
387 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
388 				     struct dentry *unused, struct inode *inode,
389 				     const char *suffix, const void *value,
390 				     size_t size, int flags)
391 {
392 	const char *full_name = xattr_full_name(handler, suffix);
393 	struct kernfs_node *kn = inode->i_private;
394 	struct kernfs_iattrs *attrs;
395 
396 	if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
397 		return -EOPNOTSUPP;
398 
399 	attrs = kernfs_iattrs(kn);
400 	if (!attrs)
401 		return -ENOMEM;
402 
403 	if (value)
404 		return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs,
405 						 value, size, flags);
406 	else
407 		return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs,
408 						value, size, flags);
409 
410 }
411 
412 static const struct xattr_handler kernfs_trusted_xattr_handler = {
413 	.prefix = XATTR_TRUSTED_PREFIX,
414 	.get = kernfs_vfs_xattr_get,
415 	.set = kernfs_vfs_xattr_set,
416 };
417 
418 static const struct xattr_handler kernfs_security_xattr_handler = {
419 	.prefix = XATTR_SECURITY_PREFIX,
420 	.get = kernfs_vfs_xattr_get,
421 	.set = kernfs_vfs_xattr_set,
422 };
423 
424 static const struct xattr_handler kernfs_user_xattr_handler = {
425 	.prefix = XATTR_USER_PREFIX,
426 	.get = kernfs_vfs_xattr_get,
427 	.set = kernfs_vfs_user_xattr_set,
428 };
429 
430 const struct xattr_handler *kernfs_xattr_handlers[] = {
431 	&kernfs_trusted_xattr_handler,
432 	&kernfs_security_xattr_handler,
433 	&kernfs_user_xattr_handler,
434 	NULL
435 };
436