xref: /openbmc/linux/fs/kernfs/inode.c (revision dc6a81c3) 
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 out_unlock:
57 	ret = kn->iattr;
58 	mutex_unlock(&iattr_mutex);
59 	return ret;
60 }
61 
62 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
63 {
64 	return __kernfs_iattrs(kn, 1);
65 }
66 
67 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
68 {
69 	return __kernfs_iattrs(kn, 0);
70 }
71 
72 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
73 {
74 	struct kernfs_iattrs *attrs;
75 	unsigned int ia_valid = iattr->ia_valid;
76 
77 	attrs = kernfs_iattrs(kn);
78 	if (!attrs)
79 		return -ENOMEM;
80 
81 	if (ia_valid & ATTR_UID)
82 		attrs->ia_uid = iattr->ia_uid;
83 	if (ia_valid & ATTR_GID)
84 		attrs->ia_gid = iattr->ia_gid;
85 	if (ia_valid & ATTR_ATIME)
86 		attrs->ia_atime = iattr->ia_atime;
87 	if (ia_valid & ATTR_MTIME)
88 		attrs->ia_mtime = iattr->ia_mtime;
89 	if (ia_valid & ATTR_CTIME)
90 		attrs->ia_ctime = iattr->ia_ctime;
91 	if (ia_valid & ATTR_MODE)
92 		kn->mode = iattr->ia_mode;
93 	return 0;
94 }
95 
96 /**
97  * kernfs_setattr - set iattr on a node
98  * @kn: target node
99  * @iattr: iattr to set
100  *
101  * Returns 0 on success, -errno on failure.
102  */
103 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
104 {
105 	int ret;
106 
107 	mutex_lock(&kernfs_mutex);
108 	ret = __kernfs_setattr(kn, iattr);
109 	mutex_unlock(&kernfs_mutex);
110 	return ret;
111 }
112 
113 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
114 {
115 	struct inode *inode = d_inode(dentry);
116 	struct kernfs_node *kn = inode->i_private;
117 	int error;
118 
119 	if (!kn)
120 		return -EINVAL;
121 
122 	mutex_lock(&kernfs_mutex);
123 	error = setattr_prepare(dentry, iattr);
124 	if (error)
125 		goto out;
126 
127 	error = __kernfs_setattr(kn, iattr);
128 	if (error)
129 		goto out;
130 
131 	/* this ignores size changes */
132 	setattr_copy(inode, iattr);
133 
134 out:
135 	mutex_unlock(&kernfs_mutex);
136 	return error;
137 }
138 
139 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
140 {
141 	struct kernfs_node *kn = kernfs_dentry_node(dentry);
142 	struct kernfs_iattrs *attrs;
143 
144 	attrs = kernfs_iattrs(kn);
145 	if (!attrs)
146 		return -ENOMEM;
147 
148 	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
149 }
150 
151 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
152 {
153 	inode->i_mode = mode;
154 	inode->i_atime = inode->i_mtime =
155 		inode->i_ctime = current_time(inode);
156 }
157 
158 static inline void set_inode_attr(struct inode *inode,
159 				  struct kernfs_iattrs *attrs)
160 {
161 	inode->i_uid = attrs->ia_uid;
162 	inode->i_gid = attrs->ia_gid;
163 	inode->i_atime = attrs->ia_atime;
164 	inode->i_mtime = attrs->ia_mtime;
165 	inode->i_ctime = attrs->ia_ctime;
166 }
167 
168 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
169 {
170 	struct kernfs_iattrs *attrs = kn->iattr;
171 
172 	inode->i_mode = kn->mode;
173 	if (attrs)
174 		/*
175 		 * kernfs_node has non-default attributes get them from
176 		 * persistent copy in kernfs_node.
177 		 */
178 		set_inode_attr(inode, attrs);
179 
180 	if (kernfs_type(kn) == KERNFS_DIR)
181 		set_nlink(inode, kn->dir.subdirs + 2);
182 }
183 
184 int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
185 		       u32 request_mask, unsigned int query_flags)
186 {
187 	struct inode *inode = d_inode(path->dentry);
188 	struct kernfs_node *kn = inode->i_private;
189 
190 	mutex_lock(&kernfs_mutex);
191 	kernfs_refresh_inode(kn, inode);
192 	mutex_unlock(&kernfs_mutex);
193 
194 	generic_fillattr(inode, stat);
195 	return 0;
196 }
197 
198 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
199 {
200 	kernfs_get(kn);
201 	inode->i_private = kn;
202 	inode->i_mapping->a_ops = &kernfs_aops;
203 	inode->i_op = &kernfs_iops;
204 	inode->i_generation = kernfs_gen(kn);
205 
206 	set_default_inode_attr(inode, kn->mode);
207 	kernfs_refresh_inode(kn, inode);
208 
209 	/* initialize inode according to type */
210 	switch (kernfs_type(kn)) {
211 	case KERNFS_DIR:
212 		inode->i_op = &kernfs_dir_iops;
213 		inode->i_fop = &kernfs_dir_fops;
214 		if (kn->flags & KERNFS_EMPTY_DIR)
215 			make_empty_dir_inode(inode);
216 		break;
217 	case KERNFS_FILE:
218 		inode->i_size = kn->attr.size;
219 		inode->i_fop = &kernfs_file_fops;
220 		break;
221 	case KERNFS_LINK:
222 		inode->i_op = &kernfs_symlink_iops;
223 		break;
224 	default:
225 		BUG();
226 	}
227 
228 	unlock_new_inode(inode);
229 }
230 
231 /**
232  *	kernfs_get_inode - get inode for kernfs_node
233  *	@sb: super block
234  *	@kn: kernfs_node to allocate inode for
235  *
236  *	Get inode for @kn.  If such inode doesn't exist, a new inode is
237  *	allocated and basics are initialized.  New inode is returned
238  *	locked.
239  *
240  *	LOCKING:
241  *	Kernel thread context (may sleep).
242  *
243  *	RETURNS:
244  *	Pointer to allocated inode on success, NULL on failure.
245  */
246 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
247 {
248 	struct inode *inode;
249 
250 	inode = iget_locked(sb, kernfs_ino(kn));
251 	if (inode && (inode->i_state & I_NEW))
252 		kernfs_init_inode(kn, inode);
253 
254 	return inode;
255 }
256 
257 /*
258  * The kernfs_node serves as both an inode and a directory entry for
259  * kernfs.  To prevent the kernfs inode numbers from being freed
260  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
261  * super_operations.evict_inode() implementation is needed to drop that
262  * reference upon inode destruction.
263  */
264 void kernfs_evict_inode(struct inode *inode)
265 {
266 	struct kernfs_node *kn = inode->i_private;
267 
268 	truncate_inode_pages_final(&inode->i_data);
269 	clear_inode(inode);
270 	kernfs_put(kn);
271 }
272 
273 int kernfs_iop_permission(struct inode *inode, int mask)
274 {
275 	struct kernfs_node *kn;
276 
277 	if (mask & MAY_NOT_BLOCK)
278 		return -ECHILD;
279 
280 	kn = inode->i_private;
281 
282 	mutex_lock(&kernfs_mutex);
283 	kernfs_refresh_inode(kn, inode);
284 	mutex_unlock(&kernfs_mutex);
285 
286 	return generic_permission(inode, mask);
287 }
288 
289 int kernfs_xattr_get(struct kernfs_node *kn, const char *name,
290 		     void *value, size_t size)
291 {
292 	struct kernfs_iattrs *attrs = kernfs_iattrs_noalloc(kn);
293 	if (!attrs)
294 		return -ENODATA;
295 
296 	return simple_xattr_get(&attrs->xattrs, name, value, size);
297 }
298 
299 int kernfs_xattr_set(struct kernfs_node *kn, const char *name,
300 		     const void *value, size_t size, int flags)
301 {
302 	struct kernfs_iattrs *attrs = kernfs_iattrs(kn);
303 	if (!attrs)
304 		return -ENOMEM;
305 
306 	return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
307 }
308 
309 static int kernfs_vfs_xattr_get(const struct xattr_handler *handler,
310 				struct dentry *unused, struct inode *inode,
311 				const char *suffix, void *value, size_t size)
312 {
313 	const char *name = xattr_full_name(handler, suffix);
314 	struct kernfs_node *kn = inode->i_private;
315 
316 	return kernfs_xattr_get(kn, name, value, size);
317 }
318 
319 static int kernfs_vfs_xattr_set(const struct xattr_handler *handler,
320 				struct dentry *unused, struct inode *inode,
321 				const char *suffix, const void *value,
322 				size_t size, int flags)
323 {
324 	const char *name = xattr_full_name(handler, suffix);
325 	struct kernfs_node *kn = inode->i_private;
326 
327 	return kernfs_xattr_set(kn, name, value, size, flags);
328 }
329 
330 static const struct xattr_handler kernfs_trusted_xattr_handler = {
331 	.prefix = XATTR_TRUSTED_PREFIX,
332 	.get = kernfs_vfs_xattr_get,
333 	.set = kernfs_vfs_xattr_set,
334 };
335 
336 static const struct xattr_handler kernfs_security_xattr_handler = {
337 	.prefix = XATTR_SECURITY_PREFIX,
338 	.get = kernfs_vfs_xattr_get,
339 	.set = kernfs_vfs_xattr_set,
340 };
341 
342 const struct xattr_handler *kernfs_xattr_handlers[] = {
343 	&kernfs_trusted_xattr_handler,
344 	&kernfs_security_xattr_handler,
345 	NULL
346 };
347