1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 *
4 * Copyright (C) 2011 Novell Inc.
5 */
6
7 #include <linux/fs.h>
8 #include <linux/slab.h>
9 #include <linux/cred.h>
10 #include <linux/xattr.h>
11 #include <linux/posix_acl.h>
12 #include <linux/ratelimit.h>
13 #include <linux/fiemap.h>
14 #include <linux/fileattr.h>
15 #include <linux/security.h>
16 #include <linux/namei.h>
17 #include "overlayfs.h"
18
19
ovl_setattr(struct user_namespace * mnt_userns,struct dentry * dentry,struct iattr * attr)20 int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
21 struct iattr *attr)
22 {
23 int err;
24 bool full_copy_up = false;
25 struct dentry *upperdentry;
26 const struct cred *old_cred;
27
28 err = setattr_prepare(&init_user_ns, dentry, attr);
29 if (err)
30 return err;
31
32 err = ovl_want_write(dentry);
33 if (err)
34 goto out;
35
36 if (attr->ia_valid & ATTR_SIZE) {
37 /* Truncate should trigger data copy up as well */
38 full_copy_up = true;
39 }
40
41 if (!full_copy_up)
42 err = ovl_copy_up(dentry);
43 else
44 err = ovl_copy_up_with_data(dentry);
45 if (!err) {
46 struct inode *winode = NULL;
47
48 upperdentry = ovl_dentry_upper(dentry);
49
50 if (attr->ia_valid & ATTR_SIZE) {
51 winode = d_inode(upperdentry);
52 err = get_write_access(winode);
53 if (err)
54 goto out_drop_write;
55 }
56
57 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
58 attr->ia_valid &= ~ATTR_MODE;
59
60 /*
61 * We might have to translate ovl file into real file object
62 * once use cases emerge. For now, simply don't let underlying
63 * filesystem rely on attr->ia_file
64 */
65 attr->ia_valid &= ~ATTR_FILE;
66
67 /*
68 * If open(O_TRUNC) is done, VFS calls ->setattr with ATTR_OPEN
69 * set. Overlayfs does not pass O_TRUNC flag to underlying
70 * filesystem during open -> do not pass ATTR_OPEN. This
71 * disables optimization in fuse which assumes open(O_TRUNC)
72 * already set file size to 0. But we never passed O_TRUNC to
73 * fuse. So by clearing ATTR_OPEN, fuse will be forced to send
74 * setattr request to server.
75 */
76 attr->ia_valid &= ~ATTR_OPEN;
77
78 inode_lock(upperdentry->d_inode);
79 old_cred = ovl_override_creds(dentry->d_sb);
80 err = notify_change(&init_user_ns, upperdentry, attr, NULL);
81 revert_creds(old_cred);
82 if (!err)
83 ovl_copyattr(upperdentry->d_inode, dentry->d_inode);
84 inode_unlock(upperdentry->d_inode);
85
86 if (winode)
87 put_write_access(winode);
88 }
89 out_drop_write:
90 ovl_drop_write(dentry);
91 out:
92 return err;
93 }
94
ovl_map_dev_ino(struct dentry * dentry,struct kstat * stat,int fsid)95 static void ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
96 {
97 bool samefs = ovl_same_fs(dentry->d_sb);
98 unsigned int xinobits = ovl_xino_bits(dentry->d_sb);
99 unsigned int xinoshift = 64 - xinobits;
100
101 if (samefs) {
102 /*
103 * When all layers are on the same fs, all real inode
104 * number are unique, so we use the overlay st_dev,
105 * which is friendly to du -x.
106 */
107 stat->dev = dentry->d_sb->s_dev;
108 return;
109 } else if (xinobits) {
110 /*
111 * All inode numbers of underlying fs should not be using the
112 * high xinobits, so we use high xinobits to partition the
113 * overlay st_ino address space. The high bits holds the fsid
114 * (upper fsid is 0). The lowest xinobit is reserved for mapping
115 * the non-persistent inode numbers range in case of overflow.
116 * This way all overlay inode numbers are unique and use the
117 * overlay st_dev.
118 */
119 if (likely(!(stat->ino >> xinoshift))) {
120 stat->ino |= ((u64)fsid) << (xinoshift + 1);
121 stat->dev = dentry->d_sb->s_dev;
122 return;
123 } else if (ovl_xino_warn(dentry->d_sb)) {
124 pr_warn_ratelimited("inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
125 dentry, stat->ino, xinobits);
126 }
127 }
128
129 /* The inode could not be mapped to a unified st_ino address space */
130 if (S_ISDIR(dentry->d_inode->i_mode)) {
131 /*
132 * Always use the overlay st_dev for directories, so 'find
133 * -xdev' will scan the entire overlay mount and won't cross the
134 * overlay mount boundaries.
135 *
136 * If not all layers are on the same fs the pair {real st_ino;
137 * overlay st_dev} is not unique, so use the non persistent
138 * overlay st_ino for directories.
139 */
140 stat->dev = dentry->d_sb->s_dev;
141 stat->ino = dentry->d_inode->i_ino;
142 } else {
143 /*
144 * For non-samefs setup, if we cannot map all layers st_ino
145 * to a unified address space, we need to make sure that st_dev
146 * is unique per underlying fs, so we use the unique anonymous
147 * bdev assigned to the underlying fs.
148 */
149 stat->dev = OVL_FS(dentry->d_sb)->fs[fsid].pseudo_dev;
150 }
151 }
152
ovl_getattr(struct user_namespace * mnt_userns,const struct path * path,struct kstat * stat,u32 request_mask,unsigned int flags)153 int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
154 struct kstat *stat, u32 request_mask, unsigned int flags)
155 {
156 struct dentry *dentry = path->dentry;
157 enum ovl_path_type type;
158 struct path realpath;
159 const struct cred *old_cred;
160 struct inode *inode = d_inode(dentry);
161 bool is_dir = S_ISDIR(inode->i_mode);
162 int fsid = 0;
163 int err;
164 bool metacopy_blocks = false;
165
166 metacopy_blocks = ovl_is_metacopy_dentry(dentry);
167
168 type = ovl_path_real(dentry, &realpath);
169 old_cred = ovl_override_creds(dentry->d_sb);
170 err = vfs_getattr(&realpath, stat, request_mask, flags);
171 if (err)
172 goto out;
173
174 /* Report the effective immutable/append-only STATX flags */
175 generic_fill_statx_attr(inode, stat);
176
177 /*
178 * For non-dir or same fs, we use st_ino of the copy up origin.
179 * This guaranties constant st_dev/st_ino across copy up.
180 * With xino feature and non-samefs, we use st_ino of the copy up
181 * origin masked with high bits that represent the layer id.
182 *
183 * If lower filesystem supports NFS file handles, this also guaranties
184 * persistent st_ino across mount cycle.
185 */
186 if (!is_dir || ovl_same_dev(dentry->d_sb)) {
187 if (!OVL_TYPE_UPPER(type)) {
188 fsid = ovl_layer_lower(dentry)->fsid;
189 } else if (OVL_TYPE_ORIGIN(type)) {
190 struct kstat lowerstat;
191 u32 lowermask = STATX_INO | STATX_BLOCKS |
192 (!is_dir ? STATX_NLINK : 0);
193
194 ovl_path_lower(dentry, &realpath);
195 err = vfs_getattr(&realpath, &lowerstat,
196 lowermask, flags);
197 if (err)
198 goto out;
199
200 /*
201 * Lower hardlinks may be broken on copy up to different
202 * upper files, so we cannot use the lower origin st_ino
203 * for those different files, even for the same fs case.
204 *
205 * Similarly, several redirected dirs can point to the
206 * same dir on a lower layer. With the "verify_lower"
207 * feature, we do not use the lower origin st_ino, if
208 * we haven't verified that this redirect is unique.
209 *
210 * With inodes index enabled, it is safe to use st_ino
211 * of an indexed origin. The index validates that the
212 * upper hardlink is not broken and that a redirected
213 * dir is the only redirect to that origin.
214 */
215 if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) ||
216 (!ovl_verify_lower(dentry->d_sb) &&
217 (is_dir || lowerstat.nlink == 1))) {
218 fsid = ovl_layer_lower(dentry)->fsid;
219 stat->ino = lowerstat.ino;
220 }
221
222 /*
223 * If we are querying a metacopy dentry and lower
224 * dentry is data dentry, then use the blocks we
225 * queried just now. We don't have to do additional
226 * vfs_getattr(). If lower itself is metacopy, then
227 * additional vfs_getattr() is unavoidable.
228 */
229 if (metacopy_blocks &&
230 realpath.dentry == ovl_dentry_lowerdata(dentry)) {
231 stat->blocks = lowerstat.blocks;
232 metacopy_blocks = false;
233 }
234 }
235
236 if (metacopy_blocks) {
237 /*
238 * If lower is not same as lowerdata or if there was
239 * no origin on upper, we can end up here.
240 */
241 struct kstat lowerdatastat;
242 u32 lowermask = STATX_BLOCKS;
243
244 ovl_path_lowerdata(dentry, &realpath);
245 err = vfs_getattr(&realpath, &lowerdatastat,
246 lowermask, flags);
247 if (err)
248 goto out;
249 stat->blocks = lowerdatastat.blocks;
250 }
251 }
252
253 ovl_map_dev_ino(dentry, stat, fsid);
254
255 /*
256 * It's probably not worth it to count subdirs to get the
257 * correct link count. nlink=1 seems to pacify 'find' and
258 * other utilities.
259 */
260 if (is_dir && OVL_TYPE_MERGE(type))
261 stat->nlink = 1;
262
263 /*
264 * Return the overlay inode nlinks for indexed upper inodes.
265 * Overlay inode nlink counts the union of the upper hardlinks
266 * and non-covered lower hardlinks. It does not include the upper
267 * index hardlink.
268 */
269 if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
270 stat->nlink = dentry->d_inode->i_nlink;
271
272 out:
273 revert_creds(old_cred);
274
275 return err;
276 }
277
ovl_permission(struct user_namespace * mnt_userns,struct inode * inode,int mask)278 int ovl_permission(struct user_namespace *mnt_userns,
279 struct inode *inode, int mask)
280 {
281 struct inode *upperinode = ovl_inode_upper(inode);
282 struct inode *realinode = upperinode ?: ovl_inode_lower(inode);
283 const struct cred *old_cred;
284 int err;
285
286 /* Careful in RCU walk mode */
287 if (!realinode) {
288 WARN_ON(!(mask & MAY_NOT_BLOCK));
289 return -ECHILD;
290 }
291
292 /*
293 * Check overlay inode with the creds of task and underlying inode
294 * with creds of mounter
295 */
296 err = generic_permission(&init_user_ns, inode, mask);
297 if (err)
298 return err;
299
300 old_cred = ovl_override_creds(inode->i_sb);
301 if (!upperinode &&
302 !special_file(realinode->i_mode) && mask & MAY_WRITE) {
303 mask &= ~(MAY_WRITE | MAY_APPEND);
304 /* Make sure mounter can read file for copy up later */
305 mask |= MAY_READ;
306 }
307 err = inode_permission(&init_user_ns, realinode, mask);
308 revert_creds(old_cred);
309
310 return err;
311 }
312
ovl_get_link(struct dentry * dentry,struct inode * inode,struct delayed_call * done)313 static const char *ovl_get_link(struct dentry *dentry,
314 struct inode *inode,
315 struct delayed_call *done)
316 {
317 const struct cred *old_cred;
318 const char *p;
319
320 if (!dentry)
321 return ERR_PTR(-ECHILD);
322
323 old_cred = ovl_override_creds(dentry->d_sb);
324 p = vfs_get_link(ovl_dentry_real(dentry), done);
325 revert_creds(old_cred);
326 return p;
327 }
328
ovl_is_private_xattr(struct super_block * sb,const char * name)329 bool ovl_is_private_xattr(struct super_block *sb, const char *name)
330 {
331 struct ovl_fs *ofs = sb->s_fs_info;
332
333 if (ofs->config.userxattr)
334 return strncmp(name, OVL_XATTR_USER_PREFIX,
335 sizeof(OVL_XATTR_USER_PREFIX) - 1) == 0;
336 else
337 return strncmp(name, OVL_XATTR_TRUSTED_PREFIX,
338 sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1) == 0;
339 }
340
ovl_xattr_set(struct dentry * dentry,struct inode * inode,const char * name,const void * value,size_t size,int flags)341 int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
342 const void *value, size_t size, int flags)
343 {
344 int err;
345 struct dentry *upperdentry = ovl_i_dentry_upper(inode);
346 struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
347 const struct cred *old_cred;
348
349 err = ovl_want_write(dentry);
350 if (err)
351 goto out;
352
353 if (!value && !upperdentry) {
354 old_cred = ovl_override_creds(dentry->d_sb);
355 err = vfs_getxattr(&init_user_ns, realdentry, name, NULL, 0);
356 revert_creds(old_cred);
357 if (err < 0)
358 goto out_drop_write;
359 }
360
361 if (!upperdentry) {
362 err = ovl_copy_up(dentry);
363 if (err)
364 goto out_drop_write;
365
366 realdentry = ovl_dentry_upper(dentry);
367 }
368
369 old_cred = ovl_override_creds(dentry->d_sb);
370 if (value)
371 err = vfs_setxattr(&init_user_ns, realdentry, name, value, size,
372 flags);
373 else {
374 WARN_ON(flags != XATTR_REPLACE);
375 err = vfs_removexattr(&init_user_ns, realdentry, name);
376 }
377 revert_creds(old_cred);
378
379 /* copy c/mtime */
380 ovl_copyattr(d_inode(realdentry), inode);
381
382 out_drop_write:
383 ovl_drop_write(dentry);
384 out:
385 return err;
386 }
387
ovl_xattr_get(struct dentry * dentry,struct inode * inode,const char * name,void * value,size_t size)388 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
389 void *value, size_t size)
390 {
391 ssize_t res;
392 const struct cred *old_cred;
393 struct dentry *realdentry =
394 ovl_i_dentry_upper(inode) ?: ovl_dentry_lower(dentry);
395
396 old_cred = ovl_override_creds(dentry->d_sb);
397 res = vfs_getxattr(&init_user_ns, realdentry, name, value, size);
398 revert_creds(old_cred);
399 return res;
400 }
401
ovl_can_list(struct super_block * sb,const char * s)402 static bool ovl_can_list(struct super_block *sb, const char *s)
403 {
404 /* Never list private (.overlay) */
405 if (ovl_is_private_xattr(sb, s))
406 return false;
407
408 /* List all non-trusted xattrs */
409 if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
410 return true;
411
412 /* list other trusted for superuser only */
413 return ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
414 }
415
ovl_listxattr(struct dentry * dentry,char * list,size_t size)416 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
417 {
418 struct dentry *realdentry = ovl_dentry_real(dentry);
419 ssize_t res;
420 size_t len;
421 char *s;
422 const struct cred *old_cred;
423
424 old_cred = ovl_override_creds(dentry->d_sb);
425 res = vfs_listxattr(realdentry, list, size);
426 revert_creds(old_cred);
427 if (res <= 0 || size == 0)
428 return res;
429
430 /* filter out private xattrs */
431 for (s = list, len = res; len;) {
432 size_t slen = strnlen(s, len) + 1;
433
434 /* underlying fs providing us with an broken xattr list? */
435 if (WARN_ON(slen > len))
436 return -EIO;
437
438 len -= slen;
439 if (!ovl_can_list(dentry->d_sb, s)) {
440 res -= slen;
441 memmove(s, s + slen, len);
442 } else {
443 s += slen;
444 }
445 }
446
447 return res;
448 }
449
ovl_get_acl(struct inode * inode,int type,bool rcu)450 struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
451 {
452 struct inode *realinode = ovl_inode_real(inode);
453 const struct cred *old_cred;
454 struct posix_acl *acl;
455
456 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
457 return NULL;
458
459 if (rcu)
460 return get_cached_acl_rcu(realinode, type);
461
462 old_cred = ovl_override_creds(inode->i_sb);
463 acl = get_acl(realinode, type);
464 revert_creds(old_cred);
465
466 return acl;
467 }
468
ovl_update_time(struct inode * inode,struct timespec64 * ts,int flags)469 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
470 {
471 if (flags & S_ATIME) {
472 struct ovl_fs *ofs = inode->i_sb->s_fs_info;
473 struct path upperpath = {
474 .mnt = ovl_upper_mnt(ofs),
475 .dentry = ovl_upperdentry_dereference(OVL_I(inode)),
476 };
477
478 if (upperpath.dentry) {
479 touch_atime(&upperpath);
480 inode->i_atime = d_inode(upperpath.dentry)->i_atime;
481 }
482 }
483 return 0;
484 }
485
ovl_fiemap(struct inode * inode,struct fiemap_extent_info * fieinfo,u64 start,u64 len)486 static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
487 u64 start, u64 len)
488 {
489 int err;
490 struct inode *realinode = ovl_inode_realdata(inode);
491 const struct cred *old_cred;
492
493 if (!realinode->i_op->fiemap)
494 return -EOPNOTSUPP;
495
496 old_cred = ovl_override_creds(inode->i_sb);
497 err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
498 revert_creds(old_cred);
499
500 return err;
501 }
502
503 /*
504 * Work around the fact that security_file_ioctl() takes a file argument.
505 * Introducing security_inode_fileattr_get/set() hooks would solve this issue
506 * properly.
507 */
ovl_security_fileattr(struct path * realpath,struct fileattr * fa,bool set)508 static int ovl_security_fileattr(struct path *realpath, struct fileattr *fa,
509 bool set)
510 {
511 struct file *file;
512 unsigned int cmd;
513 int err;
514
515 file = dentry_open(realpath, O_RDONLY, current_cred());
516 if (IS_ERR(file))
517 return PTR_ERR(file);
518
519 if (set)
520 cmd = fa->fsx_valid ? FS_IOC_FSSETXATTR : FS_IOC_SETFLAGS;
521 else
522 cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
523
524 err = security_file_ioctl(file, cmd, 0);
525 fput(file);
526
527 return err;
528 }
529
ovl_real_fileattr_set(struct path * realpath,struct fileattr * fa)530 int ovl_real_fileattr_set(struct path *realpath, struct fileattr *fa)
531 {
532 int err;
533
534 err = ovl_security_fileattr(realpath, fa, true);
535 if (err)
536 return err;
537
538 return vfs_fileattr_set(&init_user_ns, realpath->dentry, fa);
539 }
540
ovl_fileattr_set(struct user_namespace * mnt_userns,struct dentry * dentry,struct fileattr * fa)541 int ovl_fileattr_set(struct user_namespace *mnt_userns,
542 struct dentry *dentry, struct fileattr *fa)
543 {
544 struct inode *inode = d_inode(dentry);
545 struct path upperpath;
546 const struct cred *old_cred;
547 unsigned int flags;
548 int err;
549
550 err = ovl_want_write(dentry);
551 if (err)
552 goto out;
553
554 err = ovl_copy_up(dentry);
555 if (!err) {
556 ovl_path_real(dentry, &upperpath);
557
558 old_cred = ovl_override_creds(inode->i_sb);
559 /*
560 * Store immutable/append-only flags in xattr and clear them
561 * in upper fileattr (in case they were set by older kernel)
562 * so children of "ovl-immutable" directories lower aliases of
563 * "ovl-immutable" hardlinks could be copied up.
564 * Clear xattr when flags are cleared.
565 */
566 err = ovl_set_protattr(inode, upperpath.dentry, fa);
567 if (!err)
568 err = ovl_real_fileattr_set(&upperpath, fa);
569 revert_creds(old_cred);
570
571 /*
572 * Merge real inode flags with inode flags read from
573 * overlay.protattr xattr
574 */
575 flags = ovl_inode_real(inode)->i_flags & OVL_COPY_I_FLAGS_MASK;
576
577 BUILD_BUG_ON(OVL_PROT_I_FLAGS_MASK & ~OVL_COPY_I_FLAGS_MASK);
578 flags |= inode->i_flags & OVL_PROT_I_FLAGS_MASK;
579 inode_set_flags(inode, flags, OVL_COPY_I_FLAGS_MASK);
580
581 /* Update ctime */
582 ovl_copyattr(ovl_inode_real(inode), inode);
583 }
584 ovl_drop_write(dentry);
585 out:
586 return err;
587 }
588
589 /* Convert inode protection flags to fileattr flags */
ovl_fileattr_prot_flags(struct inode * inode,struct fileattr * fa)590 static void ovl_fileattr_prot_flags(struct inode *inode, struct fileattr *fa)
591 {
592 BUILD_BUG_ON(OVL_PROT_FS_FLAGS_MASK & ~FS_COMMON_FL);
593 BUILD_BUG_ON(OVL_PROT_FSX_FLAGS_MASK & ~FS_XFLAG_COMMON);
594
595 if (inode->i_flags & S_APPEND) {
596 fa->flags |= FS_APPEND_FL;
597 fa->fsx_xflags |= FS_XFLAG_APPEND;
598 }
599 if (inode->i_flags & S_IMMUTABLE) {
600 fa->flags |= FS_IMMUTABLE_FL;
601 fa->fsx_xflags |= FS_XFLAG_IMMUTABLE;
602 }
603 }
604
ovl_real_fileattr_get(struct path * realpath,struct fileattr * fa)605 int ovl_real_fileattr_get(struct path *realpath, struct fileattr *fa)
606 {
607 int err;
608
609 err = ovl_security_fileattr(realpath, fa, false);
610 if (err)
611 return err;
612
613 err = vfs_fileattr_get(realpath->dentry, fa);
614 if (err == -ENOIOCTLCMD)
615 err = -ENOTTY;
616 return err;
617 }
618
ovl_fileattr_get(struct dentry * dentry,struct fileattr * fa)619 int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa)
620 {
621 struct inode *inode = d_inode(dentry);
622 struct path realpath;
623 const struct cred *old_cred;
624 int err;
625
626 ovl_path_real(dentry, &realpath);
627
628 old_cred = ovl_override_creds(inode->i_sb);
629 err = ovl_real_fileattr_get(&realpath, fa);
630 ovl_fileattr_prot_flags(inode, fa);
631 revert_creds(old_cred);
632
633 return err;
634 }
635
636 static const struct inode_operations ovl_file_inode_operations = {
637 .setattr = ovl_setattr,
638 .permission = ovl_permission,
639 .getattr = ovl_getattr,
640 .listxattr = ovl_listxattr,
641 .get_acl = ovl_get_acl,
642 .update_time = ovl_update_time,
643 .fiemap = ovl_fiemap,
644 .fileattr_get = ovl_fileattr_get,
645 .fileattr_set = ovl_fileattr_set,
646 };
647
648 static const struct inode_operations ovl_symlink_inode_operations = {
649 .setattr = ovl_setattr,
650 .get_link = ovl_get_link,
651 .getattr = ovl_getattr,
652 .listxattr = ovl_listxattr,
653 .update_time = ovl_update_time,
654 };
655
656 static const struct inode_operations ovl_special_inode_operations = {
657 .setattr = ovl_setattr,
658 .permission = ovl_permission,
659 .getattr = ovl_getattr,
660 .listxattr = ovl_listxattr,
661 .get_acl = ovl_get_acl,
662 .update_time = ovl_update_time,
663 };
664
665 static const struct address_space_operations ovl_aops = {
666 /* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
667 .direct_IO = noop_direct_IO,
668 };
669
670 /*
671 * It is possible to stack overlayfs instance on top of another
672 * overlayfs instance as lower layer. We need to annotate the
673 * stackable i_mutex locks according to stack level of the super
674 * block instance. An overlayfs instance can never be in stack
675 * depth 0 (there is always a real fs below it). An overlayfs
676 * inode lock will use the lockdep annotation ovl_i_mutex_key[depth].
677 *
678 * For example, here is a snip from /proc/lockdep_chains after
679 * dir_iterate of nested overlayfs:
680 *
681 * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2)
682 * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
683 * [...] &type->i_mutex_dir_key (stack_depth=0)
684 *
685 * Locking order w.r.t ovl_want_write() is important for nested overlayfs.
686 *
687 * This chain is valid:
688 * - inode->i_rwsem (inode_lock[2])
689 * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0])
690 * - OVL_I(inode)->lock (ovl_inode_lock[2])
691 * - OVL_I(lowerinode)->lock (ovl_inode_lock[1])
692 *
693 * And this chain is valid:
694 * - inode->i_rwsem (inode_lock[2])
695 * - OVL_I(inode)->lock (ovl_inode_lock[2])
696 * - lowerinode->i_rwsem (inode_lock[1])
697 * - OVL_I(lowerinode)->lock (ovl_inode_lock[1])
698 *
699 * But lowerinode->i_rwsem SHOULD NOT be acquired while ovl_want_write() is
700 * held, because it is in reverse order of the non-nested case using the same
701 * upper fs:
702 * - inode->i_rwsem (inode_lock[1])
703 * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0])
704 * - OVL_I(inode)->lock (ovl_inode_lock[1])
705 */
706 #define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
707
ovl_lockdep_annotate_inode_mutex_key(struct inode * inode)708 static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
709 {
710 #ifdef CONFIG_LOCKDEP
711 static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING];
712 static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING];
713 static struct lock_class_key ovl_i_lock_key[OVL_MAX_NESTING];
714
715 int depth = inode->i_sb->s_stack_depth - 1;
716
717 if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING))
718 depth = 0;
719
720 if (S_ISDIR(inode->i_mode))
721 lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]);
722 else
723 lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]);
724
725 lockdep_set_class(&OVL_I(inode)->lock, &ovl_i_lock_key[depth]);
726 #endif
727 }
728
ovl_next_ino(struct inode * inode)729 static void ovl_next_ino(struct inode *inode)
730 {
731 struct ovl_fs *ofs = inode->i_sb->s_fs_info;
732
733 inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
734 if (unlikely(!inode->i_ino))
735 inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
736 }
737
ovl_map_ino(struct inode * inode,unsigned long ino,int fsid)738 static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
739 {
740 int xinobits = ovl_xino_bits(inode->i_sb);
741 unsigned int xinoshift = 64 - xinobits;
742
743 /*
744 * When d_ino is consistent with st_ino (samefs or i_ino has enough
745 * bits to encode layer), set the same value used for st_ino to i_ino,
746 * so inode number exposed via /proc/locks and a like will be
747 * consistent with d_ino and st_ino values. An i_ino value inconsistent
748 * with d_ino also causes nfsd readdirplus to fail.
749 */
750 inode->i_ino = ino;
751 if (ovl_same_fs(inode->i_sb)) {
752 return;
753 } else if (xinobits && likely(!(ino >> xinoshift))) {
754 inode->i_ino |= (unsigned long)fsid << (xinoshift + 1);
755 return;
756 }
757
758 /*
759 * For directory inodes on non-samefs with xino disabled or xino
760 * overflow, we allocate a non-persistent inode number, to be used for
761 * resolving st_ino collisions in ovl_map_dev_ino().
762 *
763 * To avoid ino collision with legitimate xino values from upper
764 * layer (fsid 0), use the lowest xinobit to map the non
765 * persistent inode numbers to the unified st_ino address space.
766 */
767 if (S_ISDIR(inode->i_mode)) {
768 ovl_next_ino(inode);
769 if (xinobits) {
770 inode->i_ino &= ~0UL >> xinobits;
771 inode->i_ino |= 1UL << xinoshift;
772 }
773 }
774 }
775
ovl_inode_init(struct inode * inode,struct ovl_inode_params * oip,unsigned long ino,int fsid)776 void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
777 unsigned long ino, int fsid)
778 {
779 struct inode *realinode;
780
781 if (oip->upperdentry)
782 OVL_I(inode)->__upperdentry = oip->upperdentry;
783 if (oip->lowerpath && oip->lowerpath->dentry)
784 OVL_I(inode)->lower = igrab(d_inode(oip->lowerpath->dentry));
785 if (oip->lowerdata)
786 OVL_I(inode)->lowerdata = igrab(d_inode(oip->lowerdata));
787
788 realinode = ovl_inode_real(inode);
789 ovl_copyattr(realinode, inode);
790 ovl_copyflags(realinode, inode);
791 ovl_map_ino(inode, ino, fsid);
792 }
793
ovl_fill_inode(struct inode * inode,umode_t mode,dev_t rdev)794 static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
795 {
796 inode->i_mode = mode;
797 inode->i_flags |= S_NOCMTIME;
798 #ifdef CONFIG_FS_POSIX_ACL
799 inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
800 #endif
801
802 ovl_lockdep_annotate_inode_mutex_key(inode);
803
804 switch (mode & S_IFMT) {
805 case S_IFREG:
806 inode->i_op = &ovl_file_inode_operations;
807 inode->i_fop = &ovl_file_operations;
808 inode->i_mapping->a_ops = &ovl_aops;
809 break;
810
811 case S_IFDIR:
812 inode->i_op = &ovl_dir_inode_operations;
813 inode->i_fop = &ovl_dir_operations;
814 break;
815
816 case S_IFLNK:
817 inode->i_op = &ovl_symlink_inode_operations;
818 break;
819
820 default:
821 inode->i_op = &ovl_special_inode_operations;
822 init_special_inode(inode, mode, rdev);
823 break;
824 }
825 }
826
827 /*
828 * With inodes index enabled, an overlay inode nlink counts the union of upper
829 * hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure
830 * upper inode, the following nlink modifying operations can happen:
831 *
832 * 1. Lower hardlink copy up
833 * 2. Upper hardlink created, unlinked or renamed over
834 * 3. Lower hardlink whiteout or renamed over
835 *
836 * For the first, copy up case, the union nlink does not change, whether the
837 * operation succeeds or fails, but the upper inode nlink may change.
838 * Therefore, before copy up, we store the union nlink value relative to the
839 * lower inode nlink in the index inode xattr .overlay.nlink.
840 *
841 * For the second, upper hardlink case, the union nlink should be incremented
842 * or decremented IFF the operation succeeds, aligned with nlink change of the
843 * upper inode. Therefore, before link/unlink/rename, we store the union nlink
844 * value relative to the upper inode nlink in the index inode.
845 *
846 * For the last, lower cover up case, we simplify things by preceding the
847 * whiteout or cover up with copy up. This makes sure that there is an index
848 * upper inode where the nlink xattr can be stored before the copied up upper
849 * entry is unlink.
850 */
851 #define OVL_NLINK_ADD_UPPER (1 << 0)
852
853 /*
854 * On-disk format for indexed nlink:
855 *
856 * nlink relative to the upper inode - "U[+-]NUM"
857 * nlink relative to the lower inode - "L[+-]NUM"
858 */
859
ovl_set_nlink_common(struct dentry * dentry,struct dentry * realdentry,const char * format)860 static int ovl_set_nlink_common(struct dentry *dentry,
861 struct dentry *realdentry, const char *format)
862 {
863 struct inode *inode = d_inode(dentry);
864 struct inode *realinode = d_inode(realdentry);
865 char buf[13];
866 int len;
867
868 len = snprintf(buf, sizeof(buf), format,
869 (int) (inode->i_nlink - realinode->i_nlink));
870
871 if (WARN_ON(len >= sizeof(buf)))
872 return -EIO;
873
874 return ovl_do_setxattr(OVL_FS(inode->i_sb), ovl_dentry_upper(dentry),
875 OVL_XATTR_NLINK, buf, len);
876 }
877
ovl_set_nlink_upper(struct dentry * dentry)878 int ovl_set_nlink_upper(struct dentry *dentry)
879 {
880 return ovl_set_nlink_common(dentry, ovl_dentry_upper(dentry), "U%+i");
881 }
882
ovl_set_nlink_lower(struct dentry * dentry)883 int ovl_set_nlink_lower(struct dentry *dentry)
884 {
885 return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i");
886 }
887
ovl_get_nlink(struct ovl_fs * ofs,struct dentry * lowerdentry,struct dentry * upperdentry,unsigned int fallback)888 unsigned int ovl_get_nlink(struct ovl_fs *ofs, struct dentry *lowerdentry,
889 struct dentry *upperdentry,
890 unsigned int fallback)
891 {
892 int nlink_diff;
893 int nlink;
894 char buf[13];
895 int err;
896
897 if (!lowerdentry || !upperdentry || d_inode(lowerdentry)->i_nlink == 1)
898 return fallback;
899
900 err = ovl_do_getxattr(ofs, upperdentry, OVL_XATTR_NLINK,
901 &buf, sizeof(buf) - 1);
902 if (err < 0)
903 goto fail;
904
905 buf[err] = '\0';
906 if ((buf[0] != 'L' && buf[0] != 'U') ||
907 (buf[1] != '+' && buf[1] != '-'))
908 goto fail;
909
910 err = kstrtoint(buf + 1, 10, &nlink_diff);
911 if (err < 0)
912 goto fail;
913
914 nlink = d_inode(buf[0] == 'L' ? lowerdentry : upperdentry)->i_nlink;
915 nlink += nlink_diff;
916
917 if (nlink <= 0)
918 goto fail;
919
920 return nlink;
921
922 fail:
923 pr_warn_ratelimited("failed to get index nlink (%pd2, err=%i)\n",
924 upperdentry, err);
925 return fallback;
926 }
927
ovl_new_inode(struct super_block * sb,umode_t mode,dev_t rdev)928 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
929 {
930 struct inode *inode;
931
932 inode = new_inode(sb);
933 if (inode)
934 ovl_fill_inode(inode, mode, rdev);
935
936 return inode;
937 }
938
ovl_inode_test(struct inode * inode,void * data)939 static int ovl_inode_test(struct inode *inode, void *data)
940 {
941 return inode->i_private == data;
942 }
943
ovl_inode_set(struct inode * inode,void * data)944 static int ovl_inode_set(struct inode *inode, void *data)
945 {
946 inode->i_private = data;
947 return 0;
948 }
949
ovl_verify_inode(struct inode * inode,struct dentry * lowerdentry,struct dentry * upperdentry,bool strict)950 static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
951 struct dentry *upperdentry, bool strict)
952 {
953 /*
954 * For directories, @strict verify from lookup path performs consistency
955 * checks, so NULL lower/upper in dentry must match NULL lower/upper in
956 * inode. Non @strict verify from NFS handle decode path passes NULL for
957 * 'unknown' lower/upper.
958 */
959 if (S_ISDIR(inode->i_mode) && strict) {
960 /* Real lower dir moved to upper layer under us? */
961 if (!lowerdentry && ovl_inode_lower(inode))
962 return false;
963
964 /* Lookup of an uncovered redirect origin? */
965 if (!upperdentry && ovl_inode_upper(inode))
966 return false;
967 }
968
969 /*
970 * Allow non-NULL lower inode in ovl_inode even if lowerdentry is NULL.
971 * This happens when finding a copied up overlay inode for a renamed
972 * or hardlinked overlay dentry and lower dentry cannot be followed
973 * by origin because lower fs does not support file handles.
974 */
975 if (lowerdentry && ovl_inode_lower(inode) != d_inode(lowerdentry))
976 return false;
977
978 /*
979 * Allow non-NULL __upperdentry in inode even if upperdentry is NULL.
980 * This happens when finding a lower alias for a copied up hard link.
981 */
982 if (upperdentry && ovl_inode_upper(inode) != d_inode(upperdentry))
983 return false;
984
985 return true;
986 }
987
ovl_lookup_inode(struct super_block * sb,struct dentry * real,bool is_upper)988 struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
989 bool is_upper)
990 {
991 struct inode *inode, *key = d_inode(real);
992
993 inode = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
994 if (!inode)
995 return NULL;
996
997 if (!ovl_verify_inode(inode, is_upper ? NULL : real,
998 is_upper ? real : NULL, false)) {
999 iput(inode);
1000 return ERR_PTR(-ESTALE);
1001 }
1002
1003 return inode;
1004 }
1005
ovl_lookup_trap_inode(struct super_block * sb,struct dentry * dir)1006 bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
1007 {
1008 struct inode *key = d_inode(dir);
1009 struct inode *trap;
1010 bool res;
1011
1012 trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
1013 if (!trap)
1014 return false;
1015
1016 res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
1017 !ovl_inode_lower(trap);
1018
1019 iput(trap);
1020 return res;
1021 }
1022
1023 /*
1024 * Create an inode cache entry for layer root dir, that will intentionally
1025 * fail ovl_verify_inode(), so any lookup that will find some layer root
1026 * will fail.
1027 */
ovl_get_trap_inode(struct super_block * sb,struct dentry * dir)1028 struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
1029 {
1030 struct inode *key = d_inode(dir);
1031 struct inode *trap;
1032
1033 if (!d_is_dir(dir))
1034 return ERR_PTR(-ENOTDIR);
1035
1036 trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
1037 ovl_inode_set, key);
1038 if (!trap)
1039 return ERR_PTR(-ENOMEM);
1040
1041 if (!(trap->i_state & I_NEW)) {
1042 /* Conflicting layer roots? */
1043 iput(trap);
1044 return ERR_PTR(-ELOOP);
1045 }
1046
1047 trap->i_mode = S_IFDIR;
1048 trap->i_flags = S_DEAD;
1049 unlock_new_inode(trap);
1050
1051 return trap;
1052 }
1053
1054 /*
1055 * Does overlay inode need to be hashed by lower inode?
1056 */
ovl_hash_bylower(struct super_block * sb,struct dentry * upper,struct dentry * lower,bool index)1057 static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
1058 struct dentry *lower, bool index)
1059 {
1060 struct ovl_fs *ofs = sb->s_fs_info;
1061
1062 /* No, if pure upper */
1063 if (!lower)
1064 return false;
1065
1066 /* Yes, if already indexed */
1067 if (index)
1068 return true;
1069
1070 /* Yes, if won't be copied up */
1071 if (!ovl_upper_mnt(ofs))
1072 return true;
1073
1074 /* No, if lower hardlink is or will be broken on copy up */
1075 if ((upper || !ovl_indexdir(sb)) &&
1076 !d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
1077 return false;
1078
1079 /* No, if non-indexed upper with NFS export */
1080 if (sb->s_export_op && upper)
1081 return false;
1082
1083 /* Otherwise, hash by lower inode for fsnotify */
1084 return true;
1085 }
1086
ovl_iget5(struct super_block * sb,struct inode * newinode,struct inode * key)1087 static struct inode *ovl_iget5(struct super_block *sb, struct inode *newinode,
1088 struct inode *key)
1089 {
1090 return newinode ? inode_insert5(newinode, (unsigned long) key,
1091 ovl_inode_test, ovl_inode_set, key) :
1092 iget5_locked(sb, (unsigned long) key,
1093 ovl_inode_test, ovl_inode_set, key);
1094 }
1095
ovl_get_inode(struct super_block * sb,struct ovl_inode_params * oip)1096 struct inode *ovl_get_inode(struct super_block *sb,
1097 struct ovl_inode_params *oip)
1098 {
1099 struct ovl_fs *ofs = OVL_FS(sb);
1100 struct dentry *upperdentry = oip->upperdentry;
1101 struct ovl_path *lowerpath = oip->lowerpath;
1102 struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
1103 struct inode *inode;
1104 struct dentry *lowerdentry = lowerpath ? lowerpath->dentry : NULL;
1105 bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry,
1106 oip->index);
1107 int fsid = bylower ? lowerpath->layer->fsid : 0;
1108 bool is_dir;
1109 unsigned long ino = 0;
1110 int err = oip->newinode ? -EEXIST : -ENOMEM;
1111
1112 if (!realinode)
1113 realinode = d_inode(lowerdentry);
1114
1115 /*
1116 * Copy up origin (lower) may exist for non-indexed upper, but we must
1117 * not use lower as hash key if this is a broken hardlink.
1118 */
1119 is_dir = S_ISDIR(realinode->i_mode);
1120 if (upperdentry || bylower) {
1121 struct inode *key = d_inode(bylower ? lowerdentry :
1122 upperdentry);
1123 unsigned int nlink = is_dir ? 1 : realinode->i_nlink;
1124
1125 inode = ovl_iget5(sb, oip->newinode, key);
1126 if (!inode)
1127 goto out_err;
1128 if (!(inode->i_state & I_NEW)) {
1129 /*
1130 * Verify that the underlying files stored in the inode
1131 * match those in the dentry.
1132 */
1133 if (!ovl_verify_inode(inode, lowerdentry, upperdentry,
1134 true)) {
1135 iput(inode);
1136 err = -ESTALE;
1137 goto out_err;
1138 }
1139
1140 dput(upperdentry);
1141 kfree(oip->redirect);
1142 goto out;
1143 }
1144
1145 /* Recalculate nlink for non-dir due to indexing */
1146 if (!is_dir)
1147 nlink = ovl_get_nlink(ofs, lowerdentry, upperdentry,
1148 nlink);
1149 set_nlink(inode, nlink);
1150 ino = key->i_ino;
1151 } else {
1152 /* Lower hardlink that will be broken on copy up */
1153 inode = new_inode(sb);
1154 if (!inode) {
1155 err = -ENOMEM;
1156 goto out_err;
1157 }
1158 ino = realinode->i_ino;
1159 fsid = lowerpath->layer->fsid;
1160 }
1161 ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
1162 ovl_inode_init(inode, oip, ino, fsid);
1163
1164 if (upperdentry && ovl_is_impuredir(sb, upperdentry))
1165 ovl_set_flag(OVL_IMPURE, inode);
1166
1167 if (oip->index)
1168 ovl_set_flag(OVL_INDEX, inode);
1169
1170 OVL_I(inode)->redirect = oip->redirect;
1171
1172 if (bylower)
1173 ovl_set_flag(OVL_CONST_INO, inode);
1174
1175 /* Check for non-merge dir that may have whiteouts */
1176 if (is_dir) {
1177 if (((upperdentry && lowerdentry) || oip->numlower > 1) ||
1178 ovl_check_origin_xattr(ofs, upperdentry ?: lowerdentry)) {
1179 ovl_set_flag(OVL_WHITEOUTS, inode);
1180 }
1181 }
1182
1183 /* Check for immutable/append-only inode flags in xattr */
1184 if (upperdentry)
1185 ovl_check_protattr(inode, upperdentry);
1186
1187 if (inode->i_state & I_NEW)
1188 unlock_new_inode(inode);
1189 out:
1190 return inode;
1191
1192 out_err:
1193 pr_warn_ratelimited("failed to get inode (%i)\n", err);
1194 inode = ERR_PTR(err);
1195 goto out;
1196 }
1197