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10#include <linux/fs.h>
11#include <linux/slab.h>
12#include <linux/xattr.h>
13#include <linux/posix_acl.h>
14#include "overlayfs.h"
15
16static int ovl_copy_up_truncate(struct dentry *dentry)
17{
18 int err;
19 struct dentry *parent;
20 struct kstat stat;
21 struct path lowerpath;
22 const struct cred *old_cred;
23
24 parent = dget_parent(dentry);
25 err = ovl_copy_up(parent);
26 if (err)
27 goto out_dput_parent;
28
29 ovl_path_lower(dentry, &lowerpath);
30
31 old_cred = ovl_override_creds(dentry->d_sb);
32 err = vfs_getattr(&lowerpath, &stat);
33 if (!err) {
34 stat.size = 0;
35 err = ovl_copy_up_one(parent, dentry, &lowerpath, &stat);
36 }
37 revert_creds(old_cred);
38
39out_dput_parent:
40 dput(parent);
41 return err;
42}
43
44int ovl_setattr(struct dentry *dentry, struct iattr *attr)
45{
46 int err;
47 struct dentry *upperdentry;
48 const struct cred *old_cred;
49
50
51
52
53
54
55
56
57
58
59 err = setattr_prepare(dentry, attr);
60 if (err)
61 return err;
62
63 err = ovl_want_write(dentry);
64 if (err)
65 goto out;
66
67 if (attr->ia_valid & ATTR_SIZE) {
68 struct inode *realinode = d_inode(ovl_dentry_real(dentry));
69
70 err = -ETXTBSY;
71 if (atomic_read(&realinode->i_writecount) < 0)
72 goto out_drop_write;
73 }
74
75 err = ovl_copy_up(dentry);
76 if (!err) {
77 struct inode *winode = NULL;
78
79 upperdentry = ovl_dentry_upper(dentry);
80
81 if (attr->ia_valid & ATTR_SIZE) {
82 winode = d_inode(upperdentry);
83 err = get_write_access(winode);
84 if (err)
85 goto out_drop_write;
86 }
87
88 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
89 attr->ia_valid &= ~ATTR_MODE;
90
91 inode_lock(upperdentry->d_inode);
92 old_cred = ovl_override_creds(dentry->d_sb);
93 err = notify_change(upperdentry, attr, NULL);
94 revert_creds(old_cred);
95 if (!err)
96 ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
97 inode_unlock(upperdentry->d_inode);
98
99 if (winode)
100 put_write_access(winode);
101 }
102out_drop_write:
103 ovl_drop_write(dentry);
104out:
105 return err;
106}
107
108static int ovl_getattr(struct vfsmount *mnt, struct dentry *dentry,
109 struct kstat *stat)
110{
111 struct path realpath;
112 const struct cred *old_cred;
113 int err;
114
115 ovl_path_real(dentry, &realpath);
116 old_cred = ovl_override_creds(dentry->d_sb);
117 err = vfs_getattr(&realpath, stat);
118 revert_creds(old_cred);
119 return err;
120}
121
122int ovl_permission(struct inode *inode, int mask)
123{
124 bool is_upper;
125 struct inode *realinode = ovl_inode_real(inode, &is_upper);
126 const struct cred *old_cred;
127 int err;
128
129
130 if (!realinode) {
131 WARN_ON(!(mask & MAY_NOT_BLOCK));
132 return -ECHILD;
133 }
134
135
136
137
138
139 err = generic_permission(inode, mask);
140 if (err)
141 return err;
142
143 old_cred = ovl_override_creds(inode->i_sb);
144 if (!is_upper && !special_file(realinode->i_mode) && mask & MAY_WRITE) {
145 mask &= ~(MAY_WRITE | MAY_APPEND);
146
147 mask |= MAY_READ;
148 }
149 err = inode_permission(realinode, mask);
150 revert_creds(old_cred);
151
152 return err;
153}
154
155static const char *ovl_get_link(struct dentry *dentry,
156 struct inode *inode,
157 struct delayed_call *done)
158{
159 const struct cred *old_cred;
160 const char *p;
161
162 if (!dentry)
163 return ERR_PTR(-ECHILD);
164
165 old_cred = ovl_override_creds(dentry->d_sb);
166 p = vfs_get_link(ovl_dentry_real(dentry), done);
167 revert_creds(old_cred);
168 return p;
169}
170
171bool ovl_is_private_xattr(const char *name)
172{
173 return strncmp(name, OVL_XATTR_PREFIX,
174 sizeof(OVL_XATTR_PREFIX) - 1) == 0;
175}
176
177int ovl_xattr_set(struct dentry *dentry, const char *name, const void *value,
178 size_t size, int flags)
179{
180 int err;
181 struct path realpath;
182 enum ovl_path_type type = ovl_path_real(dentry, &realpath);
183 const struct cred *old_cred;
184
185 err = ovl_want_write(dentry);
186 if (err)
187 goto out;
188
189 if (!value && !OVL_TYPE_UPPER(type)) {
190 err = vfs_getxattr(realpath.dentry, name, NULL, 0);
191 if (err < 0)
192 goto out_drop_write;
193 }
194
195 err = ovl_copy_up(dentry);
196 if (err)
197 goto out_drop_write;
198
199 if (!OVL_TYPE_UPPER(type))
200 ovl_path_upper(dentry, &realpath);
201
202 old_cred = ovl_override_creds(dentry->d_sb);
203 if (value)
204 err = vfs_setxattr(realpath.dentry, name, value, size, flags);
205 else {
206 WARN_ON(flags != XATTR_REPLACE);
207 err = vfs_removexattr(realpath.dentry, name);
208 }
209 revert_creds(old_cred);
210
211out_drop_write:
212 ovl_drop_write(dentry);
213out:
214 return err;
215}
216
217int ovl_xattr_get(struct dentry *dentry, const char *name,
218 void *value, size_t size)
219{
220 struct dentry *realdentry = ovl_dentry_real(dentry);
221 ssize_t res;
222 const struct cred *old_cred;
223
224 old_cred = ovl_override_creds(dentry->d_sb);
225 res = vfs_getxattr(realdentry, name, value, size);
226 revert_creds(old_cred);
227 return res;
228}
229
230ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
231{
232 struct dentry *realdentry = ovl_dentry_real(dentry);
233 ssize_t res;
234 size_t len;
235 char *s;
236 const struct cred *old_cred;
237
238 old_cred = ovl_override_creds(dentry->d_sb);
239 res = vfs_listxattr(realdentry, list, size);
240 revert_creds(old_cred);
241 if (res <= 0 || size == 0)
242 return res;
243
244
245 for (s = list, len = res; len;) {
246 size_t slen = strnlen(s, len) + 1;
247
248
249 if (WARN_ON(slen > len))
250 return -EIO;
251
252 len -= slen;
253 if (ovl_is_private_xattr(s)) {
254 res -= slen;
255 memmove(s, s + slen, len);
256 } else {
257 s += slen;
258 }
259 }
260
261 return res;
262}
263
264struct posix_acl *ovl_get_acl(struct inode *inode, int type)
265{
266 struct inode *realinode = ovl_inode_real(inode, NULL);
267 const struct cred *old_cred;
268 struct posix_acl *acl;
269
270 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
271 return NULL;
272
273 old_cred = ovl_override_creds(inode->i_sb);
274 acl = get_acl(realinode, type);
275 revert_creds(old_cred);
276
277 return acl;
278}
279
280static bool ovl_open_need_copy_up(int flags, enum ovl_path_type type,
281 struct dentry *realdentry)
282{
283 if (OVL_TYPE_UPPER(type))
284 return false;
285
286 if (special_file(realdentry->d_inode->i_mode))
287 return false;
288
289 if (!(OPEN_FMODE(flags) & FMODE_WRITE) && !(flags & O_TRUNC))
290 return false;
291
292 return true;
293}
294
295int ovl_open_maybe_copy_up(struct dentry *dentry, unsigned int file_flags)
296{
297 int err = 0;
298 struct path realpath;
299 enum ovl_path_type type;
300
301 type = ovl_path_real(dentry, &realpath);
302 if (ovl_open_need_copy_up(file_flags, type, realpath.dentry)) {
303 err = ovl_want_write(dentry);
304 if (!err) {
305 if (file_flags & O_TRUNC)
306 err = ovl_copy_up_truncate(dentry);
307 else
308 err = ovl_copy_up(dentry);
309 ovl_drop_write(dentry);
310 }
311 }
312
313 return err;
314}
315
316int ovl_update_time(struct inode *inode, struct timespec *ts, int flags)
317{
318 struct dentry *alias;
319 struct path upperpath;
320
321 if (!(flags & S_ATIME))
322 return 0;
323
324 alias = d_find_any_alias(inode);
325 if (!alias)
326 return 0;
327
328 ovl_path_upper(alias, &upperpath);
329 if (upperpath.dentry) {
330 touch_atime(&upperpath);
331 inode->i_atime = d_inode(upperpath.dentry)->i_atime;
332 }
333
334 dput(alias);
335
336 return 0;
337}
338
339static const struct inode_operations ovl_file_inode_operations = {
340 .setattr = ovl_setattr,
341 .permission = ovl_permission,
342 .getattr = ovl_getattr,
343 .listxattr = ovl_listxattr,
344 .get_acl = ovl_get_acl,
345 .update_time = ovl_update_time,
346};
347
348static const struct inode_operations ovl_symlink_inode_operations = {
349 .setattr = ovl_setattr,
350 .get_link = ovl_get_link,
351 .readlink = generic_readlink,
352 .getattr = ovl_getattr,
353 .listxattr = ovl_listxattr,
354 .update_time = ovl_update_time,
355};
356
357static void ovl_fill_inode(struct inode *inode, umode_t mode)
358{
359 inode->i_ino = get_next_ino();
360 inode->i_mode = mode;
361 inode->i_flags |= S_NOCMTIME;
362#ifdef CONFIG_FS_POSIX_ACL
363 inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
364#endif
365
366 mode &= S_IFMT;
367 switch (mode) {
368 case S_IFDIR:
369 inode->i_op = &ovl_dir_inode_operations;
370 inode->i_fop = &ovl_dir_operations;
371 break;
372
373 case S_IFLNK:
374 inode->i_op = &ovl_symlink_inode_operations;
375 break;
376
377 default:
378 WARN(1, "illegal file type: %i\n", mode);
379
380
381 case S_IFREG:
382 case S_IFSOCK:
383 case S_IFBLK:
384 case S_IFCHR:
385 case S_IFIFO:
386 inode->i_op = &ovl_file_inode_operations;
387 break;
388 }
389}
390
391struct inode *ovl_new_inode(struct super_block *sb, umode_t mode)
392{
393 struct inode *inode;
394
395 inode = new_inode(sb);
396 if (inode)
397 ovl_fill_inode(inode, mode);
398
399 return inode;
400}
401
402static int ovl_inode_test(struct inode *inode, void *data)
403{
404 return ovl_inode_real(inode, NULL) == data;
405}
406
407static int ovl_inode_set(struct inode *inode, void *data)
408{
409 inode->i_private = (void *) (((unsigned long) data) | OVL_ISUPPER_MASK);
410 return 0;
411}
412
413struct inode *ovl_get_inode(struct super_block *sb, struct inode *realinode)
414
415{
416 struct inode *inode;
417
418 inode = iget5_locked(sb, (unsigned long) realinode,
419 ovl_inode_test, ovl_inode_set, realinode);
420 if (inode && inode->i_state & I_NEW) {
421 ovl_fill_inode(inode, realinode->i_mode);
422 set_nlink(inode, realinode->i_nlink);
423 unlock_new_inode(inode);
424 }
425
426 return inode;
427}
428
