xref: /openbmc/linux/fs/kernfs/inode.c (revision b3d9fc14) 
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 user_namespace *mnt_userns, struct dentry *dentry,
116 		       struct iattr *iattr)
117 {
118 	struct inode *inode = d_inode(dentry);
119 	struct kernfs_node *kn = inode->i_private;
120 	int error;
121 
122 	if (!kn)
123 		return -EINVAL;
124 
125 	mutex_lock(&kernfs_mutex);
126 	error = setattr_prepare(&init_user_ns, dentry, iattr);
127 	if (error)
128 		goto out;
129 
130 	error = __kernfs_setattr(kn, iattr);
131 	if (error)
132 		goto out;
133 
134 	/* this ignores size changes */
135 	setattr_copy(&init_user_ns, inode, iattr);
136 
137 out:
138 	mutex_unlock(&kernfs_mutex);
139 	return error;
140 }
141 
142 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
143 {
144 	struct kernfs_node *kn = kernfs_dentry_node(dentry);
145 	struct kernfs_iattrs *attrs;
146 
147 	attrs = kernfs_iattrs(kn);
148 	if (!attrs)
149 		return -ENOMEM;
150 
151 	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
152 }
153 
154 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
155 {
156 	inode->i_mode = mode;
157 	inode->i_atime = inode->i_mtime =
158 		inode->i_ctime = current_time(inode);
159 }
160 
161 static inline void set_inode_attr(struct inode *inode,
162 				  struct kernfs_iattrs *attrs)
163 {
164 	inode->i_uid = attrs->ia_uid;
165 	inode->i_gid = attrs->ia_gid;
166 	inode->i_atime = attrs->ia_atime;
167 	inode->i_mtime = attrs->ia_mtime;
168 	inode->i_ctime = attrs->ia_ctime;
169 }
170 
171 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
172 {
173 	struct kernfs_iattrs *attrs = kn->iattr;
174 
175 	inode->i_mode = kn->mode;
176 	if (attrs)
177 		/*
178 		 * kernfs_node has non-default attributes get them from
179 		 * persistent copy in kernfs_node.
180 		 */
181 		set_inode_attr(inode, attrs);
182 
183 	if (kernfs_type(kn) == KERNFS_DIR)
184 		set_nlink(inode, kn->dir.subdirs + 2);
185 }
186 
187 int kernfs_iop_getattr(struct user_namespace *mnt_userns,
188 		       const struct path *path, struct kstat *stat,
189 		       u32 request_mask, unsigned int query_flags)
190 {
191 	struct inode *inode = d_inode(path->dentry);
192 	struct kernfs_node *kn = inode->i_private;
193 
194 	mutex_lock(&kernfs_mutex);
195 	kernfs_refresh_inode(kn, inode);
196 	mutex_unlock(&kernfs_mutex);
197 
198 	generic_fillattr(&init_user_ns, inode, stat);
199 	return 0;
200 }
201 
202 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
203 {
204 	kernfs_get(kn);
205 	inode->i_private = kn;
206 	inode->i_mapping->a_ops = &kernfs_aops;
207 	inode->i_op = &kernfs_iops;
208 	inode->i_generation = kernfs_gen(kn);
209 
210 	set_default_inode_attr(inode, kn->mode);
211 	kernfs_refresh_inode(kn, inode);
212 
213 	/* initialize inode according to type */
214 	switch (kernfs_type(kn)) {
215 	case KERNFS_DIR:
216 		inode->i_op = &kernfs_dir_iops;
217 		inode->i_fop = &kernfs_dir_fops;
218 		if (kn->flags & KERNFS_EMPTY_DIR)
219 			make_empty_dir_inode(inode);
220 		break;
221 	case KERNFS_FILE:
222 		inode->i_size = kn->attr.size;
223 		inode->i_fop = &kernfs_file_fops;
224 		break;
225 	case KERNFS_LINK:
226 		inode->i_op = &kernfs_symlink_iops;
227 		break;
228 	default:
229 		BUG();
230 	}
231 
232 	unlock_new_inode(inode);
233 }
234 
235 /**
236  *	kernfs_get_inode - get inode for kernfs_node
237  *	@sb: super block
238  *	@kn: kernfs_node to allocate inode for
239  *
240  *	Get inode for @kn.  If such inode doesn't exist, a new inode is
241  *	allocated and basics are initialized.  New inode is returned
242  *	locked.
243  *
244  *	LOCKING:
245  *	Kernel thread context (may sleep).
246  *
247  *	RETURNS:
248  *	Pointer to allocated inode on success, NULL on failure.
249  */
250 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
251 {
252 	struct inode *inode;
253 
254 	inode = iget_locked(sb, kernfs_ino(kn));
255 	if (inode && (inode->i_state & I_NEW))
256 		kernfs_init_inode(kn, inode);
257 
258 	return inode;
259 }
260 
261 /*
262  * The kernfs_node serves as both an inode and a directory entry for
263  * kernfs.  To prevent the kernfs inode numbers from being freed
264  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
265  * super_operations.evict_inode() implementation is needed to drop that
266  * reference upon inode destruction.
267  */
268 void kernfs_evict_inode(struct inode *inode)
269 {
270 	struct kernfs_node *kn = inode->i_private;
271 
272 	truncate_inode_pages_final(&inode->i_data);
273 	clear_inode(inode);
274 	kernfs_put(kn);
275 }
276 
277 int kernfs_iop_permission(struct user_namespace *mnt_userns,
278 			  struct inode *inode, int mask)
279 {
280 	struct kernfs_node *kn;
281 
282 	if (mask & MAY_NOT_BLOCK)
283 		return -ECHILD;
284 
285 	kn = inode->i_private;
286 
287 	mutex_lock(&kernfs_mutex);
288 	kernfs_refresh_inode(kn, inode);
289 	mutex_unlock(&kernfs_mutex);
290 
291 	return generic_permission(&init_user_ns, inode, mask);
292 }
293 
294 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
295 		     void *value, size_t size)
296 {
297 	struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
298 	if (!attrs)
299 		return -ENODATA;
300 
301 	return simple_xattr_get(&attrs->xattrs, name, value, size);
302 }
303 
304 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
305 		     const void *value, size_t size, int flags)
306 {
307 	struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
308 	if (!attrs)
309 		return -ENOMEM;
310 
311 	return simple_xattr_set(&attrs->xattrs, name, value, size, flags, NULL);
312 }
313 
314 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
315 				struct dentry *unused, struct inode *inode,
316 				const char *suffix, void *value, size_t size)
317 {
318 	const char *name = xattr_full_name(handler, suffix);
319 	struct kernfs_node *kn = inode->i_private;
320 
321 	return kernfs_xattr_get(kn, name, value, size);
322 }
323 
324 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
325 				struct user_namespace *mnt_userns,
326 				struct dentry *unused, struct inode *inode,
327 				const char *suffix, const void *value,
328 				size_t size, int flags)
329 {
330 	const char *name = xattr_full_name(handler, suffix);
331 	struct kernfs_node *kn = inode->i_private;
332 
333 	return kernfs_xattr_set(kn, name, value, size, flags);
334 }
335 
336 static int kernfs_vfs_user_xattr_add(struct kernfs_node *kn,
337 				     const char *full_name,
338 				     struct simple_xattrs *xattrs,
339 				     const void *value, size_t size, int flags)
340 {
341 	atomic_t *sz = &kn->iattr->user_xattr_size;
342 	atomic_t *nr = &kn->iattr->nr_user_xattrs;
343 	ssize_t removed_size;
344 	int ret;
345 
346 	if (atomic_inc_return(nr) > KERNFS_MAX_USER_XATTRS) {
347 		ret = -ENOSPC;
348 		goto dec_count_out;
349 	}
350 
351 	if (atomic_add_return(size, sz) > KERNFS_USER_XATTR_SIZE_LIMIT) {
352 		ret = -ENOSPC;
353 		goto dec_size_out;
354 	}
355 
356 	ret = simple_xattr_set(xattrs, full_name, value, size, flags,
357 			       &removed_size);
358 
359 	if (!ret && removed_size >= 0)
360 		size = removed_size;
361 	else if (!ret)
362 		return 0;
363 dec_size_out:
364 	atomic_sub(size, sz);
365 dec_count_out:
366 	atomic_dec(nr);
367 	return ret;
368 }
369 
370 static int kernfs_vfs_user_xattr_rm(struct kernfs_node *kn,
371 				    const char *full_name,
372 				    struct simple_xattrs *xattrs,
373 				    const void *value, size_t size, int flags)
374 {
375 	atomic_t *sz = &kn->iattr->user_xattr_size;
376 	atomic_t *nr = &kn->iattr->nr_user_xattrs;
377 	ssize_t removed_size;
378 	int ret;
379 
380 	ret = simple_xattr_set(xattrs, full_name, value, size, flags,
381 			       &removed_size);
382 
383 	if (removed_size >= 0) {
384 		atomic_sub(removed_size, sz);
385 		atomic_dec(nr);
386 	}
387 
388 	return ret;
389 }
390 
391 static int kernfs_vfs_user_xattr_set(const struct xattr_handler *handler,
392 				     struct user_namespace *mnt_userns,
393 				     struct dentry *unused, struct inode *inode,
394 				     const char *suffix, const void *value,
395 				     size_t size, int flags)
396 {
397 	const char *full_name = xattr_full_name(handler, suffix);
398 	struct kernfs_node *kn = inode->i_private;
399 	struct kernfs_iattrs *attrs;
400 
401 	if (!(kernfs_root(kn)->flags & KERNFS_ROOT_SUPPORT_USER_XATTR))
402 		return -EOPNOTSUPP;
403 
404 	attrs = kernfs_iattrs(kn);
405 	if (!attrs)
406 		return -ENOMEM;
407 
408 	if (value)
409 		return kernfs_vfs_user_xattr_add(kn, full_name, &attrs->xattrs,
410 						 value, size, flags);
411 	else
412 		return kernfs_vfs_user_xattr_rm(kn, full_name, &attrs->xattrs,
413 						value, size, flags);
414 
415 }
416 
417 static const struct xattr_handler kernfs_trusted_xattr_handler = {
418 	.prefix = XATTR_TRUSTED_PREFIX,
419 	.get = kernfs_vfs_xattr_get,
420 	.set = kernfs_vfs_xattr_set,
421 };
422 
423 static const struct xattr_handler kernfs_security_xattr_handler = {
424 	.prefix = XATTR_SECURITY_PREFIX,
425 	.get = kernfs_vfs_xattr_get,
426 	.set = kernfs_vfs_xattr_set,
427 };
428 
429 static const struct xattr_handler kernfs_user_xattr_handler = {
430 	.prefix = XATTR_USER_PREFIX,
431 	.get = kernfs_vfs_xattr_get,
432 	.set = kernfs_vfs_user_xattr_set,
433 };
434 
435 const struct xattr_handler *kernfs_xattr_handlers[] = {
436 	&kernfs_trusted_xattr_handler,
437 	&kernfs_security_xattr_handler,
438 	&kernfs_user_xattr_handler,
439 	NULL
440 };
441