xref: /openbmc/linux/fs/kernfs/inode.c (revision 4a075bd4) 
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 	.listxattr	= kernfs_iop_listxattr,
32 };
33 
34 static struct kernfs_iattrs *__kernfs_iattrs(struct kernfs_node *kn, int alloc)
35 {
36 	static DEFINE_MUTEX(iattr_mutex);
37 	struct kernfs_iattrs *ret;
38 
39 	mutex_lock(&iattr_mutex);
40 
41 	if (kn->iattr || !alloc)
42 		goto out_unlock;
43 
44 	kn->iattr = kmem_cache_zalloc(kernfs_iattrs_cache, GFP_KERNEL);
45 	if (!kn->iattr)
46 		goto out_unlock;
47 
48 	/* assign default attributes */
49 	kn->iattr->ia_uid = GLOBAL_ROOT_UID;
50 	kn->iattr->ia_gid = GLOBAL_ROOT_GID;
51 
52 	ktime_get_real_ts64(&kn->iattr->ia_atime);
53 	kn->iattr->ia_mtime = kn->iattr->ia_atime;
54 	kn->iattr->ia_ctime = kn->iattr->ia_atime;
55 
56 	simple_xattrs_init(&kn->iattr->xattrs);
57 out_unlock:
58 	ret = kn->iattr;
59 	mutex_unlock(&iattr_mutex);
60 	return ret;
61 }
62 
63 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
64 {
65 	return __kernfs_iattrs(kn, 1);
66 }
67 
68 static struct kernfs_iattrs *kernfs_iattrs_noalloc(struct kernfs_node *kn)
69 {
70 	return __kernfs_iattrs(kn, 0);
71 }
72 
73 int __kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
74 {
75 	struct kernfs_iattrs *attrs;
76 	unsigned int ia_valid = iattr->ia_valid;
77 
78 	attrs = kernfs_iattrs(kn);
79 	if (!attrs)
80 		return -ENOMEM;
81 
82 	if (ia_valid & ATTR_UID)
83 		attrs->ia_uid = iattr->ia_uid;
84 	if (ia_valid & ATTR_GID)
85 		attrs->ia_gid = iattr->ia_gid;
86 	if (ia_valid & ATTR_ATIME)
87 		attrs->ia_atime = iattr->ia_atime;
88 	if (ia_valid & ATTR_MTIME)
89 		attrs->ia_mtime = iattr->ia_mtime;
90 	if (ia_valid & ATTR_CTIME)
91 		attrs->ia_ctime = iattr->ia_ctime;
92 	if (ia_valid & ATTR_MODE)
93 		kn->mode = iattr->ia_mode;
94 	return 0;
95 }
96 
97 /**
98  * kernfs_setattr - set iattr on a node
99  * @kn: target node
100  * @iattr: iattr to set
101  *
102  * Returns 0 on success, -errno on failure.
103  */
104 int kernfs_setattr(struct kernfs_node *kn, const struct iattr *iattr)
105 {
106 	int ret;
107 
108 	mutex_lock(&kernfs_mutex);
109 	ret = __kernfs_setattr(kn, iattr);
110 	mutex_unlock(&kernfs_mutex);
111 	return ret;
112 }
113 
114 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
115 {
116 	struct inode *inode = d_inode(dentry);
117 	struct kernfs_node *kn = inode->i_private;
118 	int error;
119 
120 	if (!kn)
121 		return -EINVAL;
122 
123 	mutex_lock(&kernfs_mutex);
124 	error = setattr_prepare(dentry, iattr);
125 	if (error)
126 		goto out;
127 
128 	error = __kernfs_setattr(kn, iattr);
129 	if (error)
130 		goto out;
131 
132 	/* this ignores size changes */
133 	setattr_copy(inode, iattr);
134 
135 out:
136 	mutex_unlock(&kernfs_mutex);
137 	return error;
138 }
139 
140 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
141 {
142 	struct kernfs_node *kn = kernfs_dentry_node(dentry);
143 	struct kernfs_iattrs *attrs;
144 
145 	attrs = kernfs_iattrs(kn);
146 	if (!attrs)
147 		return -ENOMEM;
148 
149 	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
150 }
151 
152 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
153 {
154 	inode->i_mode = mode;
155 	inode->i_atime = inode->i_mtime =
156 		inode->i_ctime = current_time(inode);
157 }
158 
159 static inline void set_inode_attr(struct inode *inode,
160 				  struct kernfs_iattrs *attrs)
161 {
162 	struct super_block *sb = inode->i_sb;
163 	inode->i_uid = attrs->ia_uid;
164 	inode->i_gid = attrs->ia_gid;
165 	inode->i_atime = timespec64_trunc(attrs->ia_atime, sb->s_time_gran);
166 	inode->i_mtime = timespec64_trunc(attrs->ia_mtime, sb->s_time_gran);
167 	inode->i_ctime = timespec64_trunc(attrs->ia_ctime, sb->s_time_gran);
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 = kn->id.generation;
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, kn->id.ino);
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);
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 const struct xattr_handler kernfs_trusted_xattr_handler = {
333 	.prefix = XATTR_TRUSTED_PREFIX,
334 	.get = kernfs_vfs_xattr_get,
335 	.set = kernfs_vfs_xattr_set,
336 };
337 
338 static const struct xattr_handler kernfs_security_xattr_handler = {
339 	.prefix = XATTR_SECURITY_PREFIX,
340 	.get = kernfs_vfs_xattr_get,
341 	.set = kernfs_vfs_xattr_set,
342 };
343 
344 const struct xattr_handler *kernfs_xattr_handlers[] = {
345 	&kernfs_trusted_xattr_handler,
346 	&kernfs_security_xattr_handler,
347 	NULL
348 };
349