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 
kernfs_iattrs(struct kernfs_node * kn)34 static struct kernfs_iattrs *kernfs_iattrs(struct kernfs_node *kn)
35 {
36 	static DEFINE_MUTEX(iattr_mutex);
37 	struct kernfs_iattrs *ret;
38 	struct iattr *iattrs;
39 
40 	mutex_lock(&iattr_mutex);
41 
42 	if (kn->iattr)
43 		goto out_unlock;
44 
45 	kn->iattr = kzalloc(sizeof(struct kernfs_iattrs), GFP_KERNEL);
46 	if (!kn->iattr)
47 		goto out_unlock;
48 	iattrs = &kn->iattr->ia_iattr;
49 
50 	/* assign default attributes */
51 	iattrs->ia_mode = kn->mode;
52 	iattrs->ia_uid = GLOBAL_ROOT_UID;
53 	iattrs->ia_gid = GLOBAL_ROOT_GID;
54 
55 	ktime_get_real_ts64(&iattrs->ia_atime);
56 	iattrs->ia_mtime = iattrs->ia_atime;
57 	iattrs->ia_ctime = iattrs->ia_atime;
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 
__kernfs_setattr(struct kernfs_node * kn,const struct iattr * iattr)66 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  */
kernfs_setattr(struct kernfs_node * kn,const struct iattr * iattr)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 
kernfs_iop_setattr(struct dentry * dentry,struct iattr * iattr)112 int kernfs_iop_setattr(struct dentry *dentry, struct iattr *iattr)
113 {
114 	struct inode *inode = d_inode(dentry);
115 	struct kernfs_node *kn = inode->i_private;
116 	int error;
117 
118 	if (!kn)
119 		return -EINVAL;
120 
121 	mutex_lock(&kernfs_mutex);
122 	error = setattr_prepare(dentry, 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 
kernfs_node_setsecdata(struct kernfs_iattrs * attrs,void ** secdata,u32 * secdata_len)138 static int kernfs_node_setsecdata(struct kernfs_iattrs *attrs, void **secdata,
139 				  u32 *secdata_len)
140 {
141 	void *old_secdata;
142 	size_t old_secdata_len;
143 
144 	old_secdata = attrs->ia_secdata;
145 	old_secdata_len = attrs->ia_secdata_len;
146 
147 	attrs->ia_secdata = *secdata;
148 	attrs->ia_secdata_len = *secdata_len;
149 
150 	*secdata = old_secdata;
151 	*secdata_len = old_secdata_len;
152 	return 0;
153 }
154 
kernfs_iop_listxattr(struct dentry * dentry,char * buf,size_t size)155 ssize_t kernfs_iop_listxattr(struct dentry *dentry, char *buf, size_t size)
156 {
157 	struct kernfs_node *kn = kernfs_dentry_node(dentry);
158 	struct kernfs_iattrs *attrs;
159 
160 	attrs = kernfs_iattrs(kn);
161 	if (!attrs)
162 		return -ENOMEM;
163 
164 	return simple_xattr_list(d_inode(dentry), &attrs->xattrs, buf, size);
165 }
166 
set_default_inode_attr(struct inode * inode,umode_t mode)167 static inline void set_default_inode_attr(struct inode *inode, umode_t mode)
168 {
169 	inode->i_mode = mode;
170 	inode->i_atime = inode->i_mtime =
171 		inode->i_ctime = current_time(inode);
172 }
173 
set_inode_attr(struct inode * inode,struct iattr * iattr)174 static inline void set_inode_attr(struct inode *inode, struct iattr *iattr)
175 {
176 	struct super_block *sb = inode->i_sb;
177 	inode->i_uid = iattr->ia_uid;
178 	inode->i_gid = iattr->ia_gid;
179 	inode->i_atime = timespec64_trunc(iattr->ia_atime, sb->s_time_gran);
180 	inode->i_mtime = timespec64_trunc(iattr->ia_mtime, sb->s_time_gran);
181 	inode->i_ctime = timespec64_trunc(iattr->ia_ctime, sb->s_time_gran);
182 }
183 
kernfs_refresh_inode(struct kernfs_node * kn,struct inode * inode)184 static void kernfs_refresh_inode(struct kernfs_node *kn, struct inode *inode)
185 {
186 	struct kernfs_iattrs *attrs = kn->iattr;
187 
188 	inode->i_mode = kn->mode;
189 	if (attrs) {
190 		/*
191 		 * kernfs_node has non-default attributes get them from
192 		 * persistent copy in kernfs_node.
193 		 */
194 		set_inode_attr(inode, &attrs->ia_iattr);
195 		security_inode_notifysecctx(inode, attrs->ia_secdata,
196 					    attrs->ia_secdata_len);
197 	}
198 
199 	if (kernfs_type(kn) == KERNFS_DIR)
200 		set_nlink(inode, kn->dir.subdirs + 2);
201 }
202 
kernfs_iop_getattr(const struct path * path,struct kstat * stat,u32 request_mask,unsigned int query_flags)203 int kernfs_iop_getattr(const struct path *path, struct kstat *stat,
204 		       u32 request_mask, unsigned int query_flags)
205 {
206 	struct inode *inode = d_inode(path->dentry);
207 	struct kernfs_node *kn = inode->i_private;
208 
209 	mutex_lock(&kernfs_mutex);
210 	kernfs_refresh_inode(kn, inode);
211 	mutex_unlock(&kernfs_mutex);
212 
213 	generic_fillattr(inode, stat);
214 	return 0;
215 }
216 
kernfs_init_inode(struct kernfs_node * kn,struct inode * inode)217 static void kernfs_init_inode(struct kernfs_node *kn, struct inode *inode)
218 {
219 	kernfs_get(kn);
220 	inode->i_private = kn;
221 	inode->i_mapping->a_ops = &kernfs_aops;
222 	inode->i_op = &kernfs_iops;
223 	inode->i_generation = kn->id.generation;
224 
225 	set_default_inode_attr(inode, kn->mode);
226 	kernfs_refresh_inode(kn, inode);
227 
228 	/* initialize inode according to type */
229 	switch (kernfs_type(kn)) {
230 	case KERNFS_DIR:
231 		inode->i_op = &kernfs_dir_iops;
232 		inode->i_fop = &kernfs_dir_fops;
233 		if (kn->flags & KERNFS_EMPTY_DIR)
234 			make_empty_dir_inode(inode);
235 		break;
236 	case KERNFS_FILE:
237 		inode->i_size = kn->attr.size;
238 		inode->i_fop = &kernfs_file_fops;
239 		break;
240 	case KERNFS_LINK:
241 		inode->i_op = &kernfs_symlink_iops;
242 		break;
243 	default:
244 		BUG();
245 	}
246 
247 	unlock_new_inode(inode);
248 }
249 
250 /**
251  *	kernfs_get_inode - get inode for kernfs_node
252  *	@sb: super block
253  *	@kn: kernfs_node to allocate inode for
254  *
255  *	Get inode for @kn.  If such inode doesn't exist, a new inode is
256  *	allocated and basics are initialized.  New inode is returned
257  *	locked.
258  *
259  *	LOCKING:
260  *	Kernel thread context (may sleep).
261  *
262  *	RETURNS:
263  *	Pointer to allocated inode on success, NULL on failure.
264  */
kernfs_get_inode(struct super_block * sb,struct kernfs_node * kn)265 struct inode *kernfs_get_inode(struct super_block *sb, struct kernfs_node *kn)
266 {
267 	struct inode *inode;
268 
269 	inode = iget_locked(sb, kn->id.ino);
270 	if (inode && (inode->i_state & I_NEW))
271 		kernfs_init_inode(kn, inode);
272 
273 	return inode;
274 }
275 
276 /*
277  * The kernfs_node serves as both an inode and a directory entry for
278  * kernfs.  To prevent the kernfs inode numbers from being freed
279  * prematurely we take a reference to kernfs_node from the kernfs inode.  A
280  * super_operations.evict_inode() implementation is needed to drop that
281  * reference upon inode destruction.
282  */
kernfs_evict_inode(struct inode * inode)283 void kernfs_evict_inode(struct inode *inode)
284 {
285 	struct kernfs_node *kn = inode->i_private;
286 
287 	truncate_inode_pages_final(&inode->i_data);
288 	clear_inode(inode);
289 	kernfs_put(kn);
290 }
291 
kernfs_iop_permission(struct inode * inode,int mask)292 int kernfs_iop_permission(struct inode *inode, int mask)
293 {
294 	struct kernfs_node *kn;
295 
296 	if (mask & MAY_NOT_BLOCK)
297 		return -ECHILD;
298 
299 	kn = inode->i_private;
300 
301 	mutex_lock(&kernfs_mutex);
302 	kernfs_refresh_inode(kn, inode);
303 	mutex_unlock(&kernfs_mutex);
304 
305 	return generic_permission(inode, mask);
306 }
307 
kernfs_xattr_get(const struct xattr_handler * handler,struct dentry * unused,struct inode * inode,const char * suffix,void * value,size_t size)308 static int kernfs_xattr_get(const struct xattr_handler *handler,
309 			    struct dentry *unused, struct inode *inode,
310 			    const char *suffix, void *value, size_t size)
311 {
312 	const char *name = xattr_full_name(handler, suffix);
313 	struct kernfs_node *kn = inode->i_private;
314 	struct kernfs_iattrs *attrs;
315 
316 	attrs = kernfs_iattrs(kn);
317 	if (!attrs)
318 		return -ENOMEM;
319 
320 	return simple_xattr_get(&attrs->xattrs, name, value, size);
321 }
322 
kernfs_xattr_set(const struct xattr_handler * handler,struct dentry * unused,struct inode * inode,const char * suffix,const void * value,size_t size,int flags)323 static int kernfs_xattr_set(const struct xattr_handler *handler,
324 			    struct dentry *unused, struct inode *inode,
325 			    const char *suffix, const void *value,
326 			    size_t size, int flags)
327 {
328 	const char *name = xattr_full_name(handler, suffix);
329 	struct kernfs_node *kn = inode->i_private;
330 	struct kernfs_iattrs *attrs;
331 
332 	attrs = kernfs_iattrs(kn);
333 	if (!attrs)
334 		return -ENOMEM;
335 
336 	return simple_xattr_set(&attrs->xattrs, name, value, size, flags);
337 }
338 
339 static const struct xattr_handler kernfs_trusted_xattr_handler = {
340 	.prefix = XATTR_TRUSTED_PREFIX,
341 	.get = kernfs_xattr_get,
342 	.set = kernfs_xattr_set,
343 };
344 
kernfs_security_xattr_set(const struct xattr_handler * handler,struct dentry * unused,struct inode * inode,const char * suffix,const void * value,size_t size,int flags)345 static int kernfs_security_xattr_set(const struct xattr_handler *handler,
346 				     struct dentry *unused, struct inode *inode,
347 				     const char *suffix, const void *value,
348 				     size_t size, int flags)
349 {
350 	struct kernfs_node *kn = inode->i_private;
351 	struct kernfs_iattrs *attrs;
352 	void *secdata;
353 	u32 secdata_len = 0;
354 	int error;
355 
356 	attrs = kernfs_iattrs(kn);
357 	if (!attrs)
358 		return -ENOMEM;
359 
360 	error = security_inode_setsecurity(inode, suffix, value, size, flags);
361 	if (error)
362 		return error;
363 	error = security_inode_getsecctx(inode, &secdata, &secdata_len);
364 	if (error)
365 		return error;
366 
367 	mutex_lock(&kernfs_mutex);
368 	error = kernfs_node_setsecdata(attrs, &secdata, &secdata_len);
369 	mutex_unlock(&kernfs_mutex);
370 
371 	if (secdata)
372 		security_release_secctx(secdata, secdata_len);
373 	return error;
374 }
375 
376 static const struct xattr_handler kernfs_security_xattr_handler = {
377 	.prefix = XATTR_SECURITY_PREFIX,
378 	.get = kernfs_xattr_get,
379 	.set = kernfs_security_xattr_set,
380 };
381 
382 const struct xattr_handler *kernfs_xattr_handlers[] = {
383 	&kernfs_trusted_xattr_handler,
384 	&kernfs_security_xattr_handler,
385 	NULL
386 };
387