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10#include <linux/fs.h>
11#include <linux/slab.h>
12#include <linux/xattr.h>
13#include "overlayfs.h"
14
15static int ovl_copy_up_truncate(struct dentry *dentry)
16{
17 int err;
18 struct dentry *parent;
19 struct kstat stat;
20 struct path lowerpath;
21
22 parent = dget_parent(dentry);
23 err = ovl_copy_up(parent);
24 if (err)
25 goto out_dput_parent;
26
27 ovl_path_lower(dentry, &lowerpath);
28 err = vfs_getattr(&lowerpath, &stat);
29 if (err)
30 goto out_dput_parent;
31
32 stat.size = 0;
33 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
34
35out_dput_parent:
36 dput(parent);
37 return err;
38}
39
40int ovl_setattr(struct dentry *dentry, struct iattr *attr)
41{
42 int err;
43 struct dentry *upperdentry;
44
45 err = ovl_want_write(dentry);
46 if (err)
47 goto out;
48
49 err = ovl_copy_up(dentry);
50 if (!err) {
51 upperdentry = ovl_dentry_upper(dentry);
52
53 mutex_lock(&upperdentry->d_inode->i_mutex);
54 err = notify_change(upperdentry, attr, NULL);
55 mutex_unlock(&upperdentry->d_inode->i_mutex);
56 }
57 ovl_drop_write(dentry);
58out:
59 return err;
60}
61
62static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
63 struct kstat *stat)
64{
65 struct path realpath;
66
67 ovl_path_real(dentry, &realpath);
68 return vfs_getattr(&realpath, stat);
69}
70
71int ovl_permission(struct inode *inode, int mask)
72{
73 struct ovl_entry *oe;
74 struct dentry *alias = NULL;
75 struct inode *realinode;
76 struct dentry *realdentry;
77 bool is_upper;
78 int err;
79
80 if (S_ISDIR(inode->i_mode)) {
81 oe = inode->i_private;
82 } else if (mask & MAY_NOT_BLOCK) {
83 return -ECHILD;
84 } else {
85
86
87
88
89 alias = d_find_any_alias(inode);
90 if (WARN_ON(!alias))
91 return -ENOENT;
92
93 oe = alias->d_fsdata;
94 }
95
96 realdentry = ovl_entry_real(oe, &is_upper);
97
98
99 realinode = ACCESS_ONCE(realdentry->d_inode);
100 if (!realinode) {
101 WARN_ON(!(mask & MAY_NOT_BLOCK));
102 err = -ENOENT;
103 goto out_dput;
104 }
105
106 if (mask & MAY_WRITE) {
107 umode_t mode = realinode->i_mode;
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122 err = -EROFS;
123 if (is_upper && !IS_RDONLY(inode) && IS_RDONLY(realinode) &&
124 (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode)))
125 goto out_dput;
126 }
127
128 err = __inode_permission(realinode, mask);
129out_dput:
130 dput(alias);
131 return err;
132}
133
134
135struct ovl_link_data {
136 struct dentry *realdentry;
137 void *cookie;
138};
139
140static const char *ovl_follow_link(struct dentry *dentry, void **cookie)
141{
142 struct dentry *realdentry;
143 struct inode *realinode;
144 struct ovl_link_data *data = NULL;
145 const char *ret;
146
147 realdentry = ovl_dentry_real(dentry);
148 realinode = realdentry->d_inode;
149
150 if (WARN_ON(!realinode->i_op->follow_link))
151 return ERR_PTR(-EPERM);
152
153 if (realinode->i_op->put_link) {
154 data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL);
155 if (!data)
156 return ERR_PTR(-ENOMEM);
157 data->realdentry = realdentry;
158 }
159
160 ret = realinode->i_op->follow_link(realdentry, cookie);
161 if (IS_ERR_OR_NULL(ret)) {
162 kfree(data);
163 return ret;
164 }
165
166 if (data)
167 data->cookie = *cookie;
168
169 *cookie = data;
170
171 return ret;
172}
173
174static void ovl_put_link(struct inode *unused, void *c)
175{
176 struct inode *realinode;
177 struct ovl_link_data *data = c;
178
179 if (!data)
180 return;
181
182 realinode = data->realdentry->d_inode;
183 realinode->i_op->put_link(realinode, data->cookie);
184 kfree(data);
185}
186
187static int ovl_readlink(struct dentry *dentry, char __user *buf, int bufsiz)
188{
189 struct path realpath;
190 struct inode *realinode;
191
192 ovl_path_real(dentry, &realpath);
193 realinode = realpath.dentry->d_inode;
194
195 if (!realinode->i_op->readlink)
196 return -EINVAL;
197
198 touch_atime(&realpath);
199
200 return realinode->i_op->readlink(realpath.dentry, buf, bufsiz);
201}
202
203
204static bool ovl_is_private_xattr(const char *name)
205{
206 return strncmp(name, OVL_XATTR_PRE_NAME, OVL_XATTR_PRE_LEN) == 0;
207}
208
209int ovl_setxattr(struct dentry *dentry, const char *name,
210 const void *value, size_t size, int flags)
211{
212 int err;
213 struct dentry *upperdentry;
214
215 err = ovl_want_write(dentry);
216 if (err)
217 goto out;
218
219 err = -EPERM;
220 if (ovl_is_private_xattr(name))
221 goto out_drop_write;
222
223 err = ovl_copy_up(dentry);
224 if (err)
225 goto out_drop_write;
226
227 upperdentry = ovl_dentry_upper(dentry);
228 err = vfs_setxattr(upperdentry, name, value, size, flags);
229
230out_drop_write:
231 ovl_drop_write(dentry);
232out:
233 return err;
234}
235
236static bool ovl_need_xattr_filter(struct dentry *dentry,
237 enum ovl_path_type type)
238{
239 if ((type & (__OVL_PATH_PURE | __OVL_PATH_UPPER)) == __OVL_PATH_UPPER)
240 return S_ISDIR(dentry->d_inode->i_mode);
241 else
242 return false;
243}
244
245ssize_t ovl_getxattr(struct dentry *dentry, const char *name,
246 void *value, size_t size)
247{
248 struct path realpath;
249 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
250
251 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
252 return -ENODATA;
253
254 return vfs_getxattr(realpath.dentry, name, value, size);
255}
256
257ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
258{
259 struct path realpath;
260 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
261 ssize_t res;
262 int off;
263
264 res = vfs_listxattr(realpath.dentry, list, size);
265 if (res <= 0 || size == 0)
266 return res;
267
268 if (!ovl_need_xattr_filter(dentry, type))
269 return res;
270
271
272 for (off = 0; off < res;) {
273 char *s = list + off;
274 size_t slen = strlen(s) + 1;
275
276 BUG_ON(off + slen > res);
277
278 if (ovl_is_private_xattr(s)) {
279 res -= slen;
280 memmove(s, s + slen, res - off);
281 } else {
282 off += slen;
283 }
284 }
285
286 return res;
287}
288
289int ovl_removexattr(struct dentry *dentry, const char *name)
290{
291 int err;
292 struct path realpath;
293 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
294
295 err = ovl_want_write(dentry);
296 if (err)
297 goto out;
298
299 err = -ENODATA;
300 if (ovl_need_xattr_filter(dentry, type) && ovl_is_private_xattr(name))
301 goto out_drop_write;
302
303 if (!OVL_TYPE_UPPER(type)) {
304 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
305 if (err < 0)
306 goto out_drop_write;
307
308 err = ovl_copy_up(dentry);
309 if (err)
310 goto out_drop_write;
311
312 ovl_path_upper(dentry, &realpath);
313 }
314
315 err = vfs_removexattr(realpath.dentry, name);
316out_drop_write:
317 ovl_drop_write(dentry);
318out:
319 return err;
320}
321
322static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
323 struct dentry *realdentry)
324{
325 if (OVL_TYPE_UPPER(type))
326 return false;
327
328 if (special_file(realdentry->d_inode->i_mode))
329 return false;
330
331 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
332 return false;
333
334 return true;
335}
336
337struct inode *ovl_d_select_inode(struct dentry *dentry, unsigned file_flags)
338{
339 int err;
340 struct path realpath;
341 enum ovl_path_type type;
342
343 if (d_is_dir(dentry))
344 return d_backing_inode(dentry);
345
346 type = ovl_path_real(dentry, &realpath);
347 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
348 err = ovl_want_write(dentry);
349 if (err)
350 return ERR_PTR(err);
351
352 if (file_flags & O_TRUNC)
353 err = ovl_copy_up_truncate(dentry);
354 else
355 err = ovl_copy_up(dentry);
356 ovl_drop_write(dentry);
357 if (err)
358 return ERR_PTR(err);
359
360 ovl_path_upper(dentry, &realpath);
361 }
362
363 if (realpath.dentry->d_flags & DCACHE_OP_SELECT_INODE)
364 return realpath.dentry->d_op->d_select_inode(realpath.dentry, file_flags);
365
366 return d_backing_inode(realpath.dentry);
367}
368
369static const struct inode_operations ovl_file_inode_operations = {
370 .setattr = ovl_setattr,
371 .permission = ovl_permission,
372 .getattr = ovl_getattr,
373 .setxattr = ovl_setxattr,
374 .getxattr = ovl_getxattr,
375 .listxattr = ovl_listxattr,
376 .removexattr = ovl_removexattr,
377};
378
379static const struct inode_operations ovl_symlink_inode_operations = {
380 .setattr = ovl_setattr,
381 .follow_link = ovl_follow_link,
382 .put_link = ovl_put_link,
383 .readlink = ovl_readlink,
384 .getattr = ovl_getattr,
385 .setxattr = ovl_setxattr,
386 .getxattr = ovl_getxattr,
387 .listxattr = ovl_listxattr,
388 .removexattr = ovl_removexattr,
389};
390
391struct inode *ovl_new_inode(struct super_block *sb, umode_t mode,
392 struct ovl_entry *oe)
393{
394 struct inode *inode;
395
396 inode = new_inode(sb);
397 if (!inode)
398 return NULL;
399
400 mode &= S_IFMT;
401
402 inode->i_ino = get_next_ino();
403 inode->i_mode = mode;
404 inode->i_flags |= S_NOATIME | S_NOCMTIME;
405
406 switch (mode) {
407 case S_IFDIR:
408 inode->i_private = oe;
409 inode->i_op = &ovl_dir_inode_operations;
410 inode->i_fop = &ovl_dir_operations;
411 break;
412
413 case S_IFLNK:
414 inode->i_op = &ovl_symlink_inode_operations;
415 break;
416
417 case S_IFREG:
418 case S_IFSOCK:
419 case S_IFBLK:
420 case S_IFCHR:
421 case S_IFIFO:
422 inode->i_op = &ovl_file_inode_operations;
423 break;
424
425 default:
426 WARN(1, "illegal file type: %i\n", mode);
427 iput(inode);
428 inode = NULL;
429 }
430
431 return inode;
432}
433
