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 struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
25 bool full_copy_up = false;
26 struct dentry *upperdentry;
27 const struct cred *old_cred;
28
29 err = setattr_prepare(&init_user_ns, dentry, attr);
30 if (err)
31 return err;
32
33 err = ovl_want_write(dentry);
34 if (err)
35 goto out;
36
37 if (attr->ia_valid & ATTR_SIZE) {
38 /* Truncate should trigger data copy up as well */
39 full_copy_up = true;
40 }
41
42 if (!full_copy_up)
43 err = ovl_copy_up(dentry);
44 else
45 err = ovl_copy_up_with_data(dentry);
46 if (!err) {
47 struct inode *winode = NULL;
48
49 upperdentry = ovl_dentry_upper(dentry);
50
51 if (attr->ia_valid & ATTR_SIZE) {
52 winode = d_inode(upperdentry);
53 err = get_write_access(winode);
54 if (err)
55 goto out_drop_write;
56 }
57
58 if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
59 attr->ia_valid &= ~ATTR_MODE;
60
61 /*
62 * We might have to translate ovl file into real file object
63 * once use cases emerge. For now, simply don't let underlying
64 * filesystem rely on attr->ia_file
65 */
66 attr->ia_valid &= ~ATTR_FILE;
67
68 /*
69 * If open(O_TRUNC) is done, VFS calls ->setattr with ATTR_OPEN
70 * set. Overlayfs does not pass O_TRUNC flag to underlying
71 * filesystem during open -> do not pass ATTR_OPEN. This
72 * disables optimization in fuse which assumes open(O_TRUNC)
73 * already set file size to 0. But we never passed O_TRUNC to
74 * fuse. So by clearing ATTR_OPEN, fuse will be forced to send
75 * setattr request to server.
76 */
77 attr->ia_valid &= ~ATTR_OPEN;
78
79 inode_lock(upperdentry->d_inode);
80 old_cred = ovl_override_creds(dentry->d_sb);
81 err = ovl_do_notify_change(ofs, upperdentry, attr);
82 revert_creds(old_cred);
83 if (!err)
84 ovl_copyattr(dentry->d_inode);
85 inode_unlock(upperdentry->d_inode);
86
87 if (winode)
88 put_write_access(winode);
89 }
90 out_drop_write:
91 ovl_drop_write(dentry);
92 out:
93 return err;
94 }
95
ovl_map_dev_ino(struct dentry * dentry,struct kstat * stat,int fsid)96 static void ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
97 {
98 bool samefs = ovl_same_fs(dentry->d_sb);
99 unsigned int xinobits = ovl_xino_bits(dentry->d_sb);
100 unsigned int xinoshift = 64 - xinobits;
101
102 if (samefs) {
103 /*
104 * When all layers are on the same fs, all real inode
105 * number are unique, so we use the overlay st_dev,
106 * which is friendly to du -x.
107 */
108 stat->dev = dentry->d_sb->s_dev;
109 return;
110 } else if (xinobits) {
111 /*
112 * All inode numbers of underlying fs should not be using the
113 * high xinobits, so we use high xinobits to partition the
114 * overlay st_ino address space. The high bits holds the fsid
115 * (upper fsid is 0). The lowest xinobit is reserved for mapping
116 * the non-persistent inode numbers range in case of overflow.
117 * This way all overlay inode numbers are unique and use the
118 * overlay st_dev.
119 */
120 if (likely(!(stat->ino >> xinoshift))) {
121 stat->ino |= ((u64)fsid) << (xinoshift + 1);
122 stat->dev = dentry->d_sb->s_dev;
123 return;
124 } else if (ovl_xino_warn(dentry->d_sb)) {
125 pr_warn_ratelimited("inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
126 dentry, stat->ino, xinobits);
127 }
128 }
129
130 /* The inode could not be mapped to a unified st_ino address space */
131 if (S_ISDIR(dentry->d_inode->i_mode)) {
132 /*
133 * Always use the overlay st_dev for directories, so 'find
134 * -xdev' will scan the entire overlay mount and won't cross the
135 * overlay mount boundaries.
136 *
137 * If not all layers are on the same fs the pair {real st_ino;
138 * overlay st_dev} is not unique, so use the non persistent
139 * overlay st_ino for directories.
140 */
141 stat->dev = dentry->d_sb->s_dev;
142 stat->ino = dentry->d_inode->i_ino;
143 } else {
144 /*
145 * For non-samefs setup, if we cannot map all layers st_ino
146 * to a unified address space, we need to make sure that st_dev
147 * is unique per underlying fs, so we use the unique anonymous
148 * bdev assigned to the underlying fs.
149 */
150 stat->dev = OVL_FS(dentry->d_sb)->fs[fsid].pseudo_dev;
151 }
152 }
153
ovl_getattr(struct user_namespace * mnt_userns,const struct path * path,struct kstat * stat,u32 request_mask,unsigned int flags)154 int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
155 struct kstat *stat, u32 request_mask, unsigned int flags)
156 {
157 struct dentry *dentry = path->dentry;
158 enum ovl_path_type type;
159 struct path realpath;
160 const struct cred *old_cred;
161 struct inode *inode = d_inode(dentry);
162 bool is_dir = S_ISDIR(inode->i_mode);
163 int fsid = 0;
164 int err;
165 bool metacopy_blocks = false;
166
167 metacopy_blocks = ovl_is_metacopy_dentry(dentry);
168
169 type = ovl_path_real(dentry, &realpath);
170 old_cred = ovl_override_creds(dentry->d_sb);
171 err = vfs_getattr(&realpath, stat, request_mask, flags);
172 if (err)
173 goto out;
174
175 /* Report the effective immutable/append-only STATX flags */
176 generic_fill_statx_attr(inode, stat);
177
178 /*
179 * For non-dir or same fs, we use st_ino of the copy up origin.
180 * This guaranties constant st_dev/st_ino across copy up.
181 * With xino feature and non-samefs, we use st_ino of the copy up
182 * origin masked with high bits that represent the layer id.
183 *
184 * If lower filesystem supports NFS file handles, this also guaranties
185 * persistent st_ino across mount cycle.
186 */
187 if (!is_dir || ovl_same_dev(dentry->d_sb)) {
188 if (!OVL_TYPE_UPPER(type)) {
189 fsid = ovl_layer_lower(dentry)->fsid;
190 } else if (OVL_TYPE_ORIGIN(type)) {
191 struct kstat lowerstat;
192 u32 lowermask = STATX_INO | STATX_BLOCKS |
193 (!is_dir ? STATX_NLINK : 0);
194
195 ovl_path_lower(dentry, &realpath);
196 err = vfs_getattr(&realpath, &lowerstat,
197 lowermask, flags);
198 if (err)
199 goto out;
200
201 /*
202 * Lower hardlinks may be broken on copy up to different
203 * upper files, so we cannot use the lower origin st_ino
204 * for those different files, even for the same fs case.
205 *
206 * Similarly, several redirected dirs can point to the
207 * same dir on a lower layer. With the "verify_lower"
208 * feature, we do not use the lower origin st_ino, if
209 * we haven't verified that this redirect is unique.
210 *
211 * With inodes index enabled, it is safe to use st_ino
212 * of an indexed origin. The index validates that the
213 * upper hardlink is not broken and that a redirected
214 * dir is the only redirect to that origin.
215 */
216 if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) ||
217 (!ovl_verify_lower(dentry->d_sb) &&
218 (is_dir || lowerstat.nlink == 1))) {
219 fsid = ovl_layer_lower(dentry)->fsid;
220 stat->ino = lowerstat.ino;
221 }
222
223 /*
224 * If we are querying a metacopy dentry and lower
225 * dentry is data dentry, then use the blocks we
226 * queried just now. We don't have to do additional
227 * vfs_getattr(). If lower itself is metacopy, then
228 * additional vfs_getattr() is unavoidable.
229 */
230 if (metacopy_blocks &&
231 realpath.dentry == ovl_dentry_lowerdata(dentry)) {
232 stat->blocks = lowerstat.blocks;
233 metacopy_blocks = false;
234 }
235 }
236
237 if (metacopy_blocks) {
238 /*
239 * If lower is not same as lowerdata or if there was
240 * no origin on upper, we can end up here.
241 */
242 struct kstat lowerdatastat;
243 u32 lowermask = STATX_BLOCKS;
244
245 ovl_path_lowerdata(dentry, &realpath);
246 err = vfs_getattr(&realpath, &lowerdatastat,
247 lowermask, flags);
248 if (err)
249 goto out;
250 stat->blocks = lowerdatastat.blocks;
251 }
252 }
253
254 ovl_map_dev_ino(dentry, stat, fsid);
255
256 /*
257 * It's probably not worth it to count subdirs to get the
258 * correct link count. nlink=1 seems to pacify 'find' and
259 * other utilities.
260 */
261 if (is_dir && OVL_TYPE_MERGE(type))
262 stat->nlink = 1;
263
264 /*
265 * Return the overlay inode nlinks for indexed upper inodes.
266 * Overlay inode nlink counts the union of the upper hardlinks
267 * and non-covered lower hardlinks. It does not include the upper
268 * index hardlink.
269 */
270 if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
271 stat->nlink = dentry->d_inode->i_nlink;
272
273 out:
274 revert_creds(old_cred);
275
276 return err;
277 }
278
ovl_permission(struct user_namespace * mnt_userns,struct inode * inode,int mask)279 int ovl_permission(struct user_namespace *mnt_userns,
280 struct inode *inode, int mask)
281 {
282 struct inode *upperinode = ovl_inode_upper(inode);
283 struct inode *realinode;
284 struct path realpath;
285 const struct cred *old_cred;
286 int err;
287
288 /* Careful in RCU walk mode */
289 ovl_i_path_real(inode, &realpath);
290 if (!realpath.dentry) {
291 WARN_ON(!(mask & MAY_NOT_BLOCK));
292 return -ECHILD;
293 }
294
295 /*
296 * Check overlay inode with the creds of task and underlying inode
297 * with creds of mounter
298 */
299 err = generic_permission(&init_user_ns, inode, mask);
300 if (err)
301 return err;
302
303 realinode = d_inode(realpath.dentry);
304 old_cred = ovl_override_creds(inode->i_sb);
305 if (!upperinode &&
306 !special_file(realinode->i_mode) && mask & MAY_WRITE) {
307 mask &= ~(MAY_WRITE | MAY_APPEND);
308 /* Make sure mounter can read file for copy up later */
309 mask |= MAY_READ;
310 }
311 err = inode_permission(mnt_user_ns(realpath.mnt), realinode, mask);
312 revert_creds(old_cred);
313
314 return err;
315 }
316
ovl_get_link(struct dentry * dentry,struct inode * inode,struct delayed_call * done)317 static const char *ovl_get_link(struct dentry *dentry,
318 struct inode *inode,
319 struct delayed_call *done)
320 {
321 const struct cred *old_cred;
322 const char *p;
323
324 if (!dentry)
325 return ERR_PTR(-ECHILD);
326
327 old_cred = ovl_override_creds(dentry->d_sb);
328 p = vfs_get_link(ovl_dentry_real(dentry), done);
329 revert_creds(old_cred);
330 return p;
331 }
332
ovl_is_private_xattr(struct super_block * sb,const char * name)333 bool ovl_is_private_xattr(struct super_block *sb, const char *name)
334 {
335 struct ovl_fs *ofs = sb->s_fs_info;
336
337 if (ofs->config.userxattr)
338 return strncmp(name, OVL_XATTR_USER_PREFIX,
339 sizeof(OVL_XATTR_USER_PREFIX) - 1) == 0;
340 else
341 return strncmp(name, OVL_XATTR_TRUSTED_PREFIX,
342 sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1) == 0;
343 }
344
ovl_xattr_set(struct dentry * dentry,struct inode * inode,const char * name,const void * value,size_t size,int flags)345 int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
346 const void *value, size_t size, int flags)
347 {
348 int err;
349 struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
350 struct dentry *upperdentry = ovl_i_dentry_upper(inode);
351 struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
352 struct path realpath;
353 const struct cred *old_cred;
354
355 err = ovl_want_write(dentry);
356 if (err)
357 goto out;
358
359 if (!value && !upperdentry) {
360 ovl_path_lower(dentry, &realpath);
361 old_cred = ovl_override_creds(dentry->d_sb);
362 err = vfs_getxattr(mnt_user_ns(realpath.mnt), realdentry, name, NULL, 0);
363 revert_creds(old_cred);
364 if (err < 0)
365 goto out_drop_write;
366 }
367
368 if (!upperdentry) {
369 err = ovl_copy_up(dentry);
370 if (err)
371 goto out_drop_write;
372
373 realdentry = ovl_dentry_upper(dentry);
374 }
375
376 old_cred = ovl_override_creds(dentry->d_sb);
377 if (value) {
378 err = ovl_do_setxattr(ofs, realdentry, name, value, size,
379 flags);
380 } else {
381 WARN_ON(flags != XATTR_REPLACE);
382 err = ovl_do_removexattr(ofs, realdentry, name);
383 }
384 revert_creds(old_cred);
385
386 /* copy c/mtime */
387 ovl_copyattr(inode);
388
389 out_drop_write:
390 ovl_drop_write(dentry);
391 out:
392 return err;
393 }
394
ovl_xattr_get(struct dentry * dentry,struct inode * inode,const char * name,void * value,size_t size)395 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
396 void *value, size_t size)
397 {
398 ssize_t res;
399 const struct cred *old_cred;
400 struct path realpath;
401
402 ovl_i_path_real(inode, &realpath);
403 old_cred = ovl_override_creds(dentry->d_sb);
404 res = vfs_getxattr(mnt_user_ns(realpath.mnt), realpath.dentry, name, value, size);
405 revert_creds(old_cred);
406 return res;
407 }
408
ovl_can_list(struct super_block * sb,const char * s)409 static bool ovl_can_list(struct super_block *sb, const char *s)
410 {
411 /* Never list private (.overlay) */
412 if (ovl_is_private_xattr(sb, s))
413 return false;
414
415 /* List all non-trusted xattrs */
416 if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
417 return true;
418
419 /* list other trusted for superuser only */
420 return ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
421 }
422
ovl_listxattr(struct dentry * dentry,char * list,size_t size)423 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
424 {
425 struct dentry *realdentry = ovl_dentry_real(dentry);
426 ssize_t res;
427 size_t len;
428 char *s;
429 const struct cred *old_cred;
430
431 old_cred = ovl_override_creds(dentry->d_sb);
432 res = vfs_listxattr(realdentry, list, size);
433 revert_creds(old_cred);
434 if (res <= 0 || size == 0)
435 return res;
436
437 /* filter out private xattrs */
438 for (s = list, len = res; len;) {
439 size_t slen = strnlen(s, len) + 1;
440
441 /* underlying fs providing us with an broken xattr list? */
442 if (WARN_ON(slen > len))
443 return -EIO;
444
445 len -= slen;
446 if (!ovl_can_list(dentry->d_sb, s)) {
447 res -= slen;
448 memmove(s, s + slen, len);
449 } else {
450 s += slen;
451 }
452 }
453
454 return res;
455 }
456
ovl_get_acl(struct inode * inode,int type,bool rcu)457 struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
458 {
459 struct inode *realinode = ovl_inode_real(inode);
460 const struct cred *old_cred;
461 struct posix_acl *acl;
462
463 if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !IS_POSIXACL(realinode))
464 return NULL;
465
466 if (rcu)
467 return get_cached_acl_rcu(realinode, type);
468
469 old_cred = ovl_override_creds(inode->i_sb);
470 acl = get_acl(realinode, type);
471 revert_creds(old_cred);
472
473 return acl;
474 }
475
ovl_update_time(struct inode * inode,struct timespec64 * ts,int flags)476 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
477 {
478 if (flags & S_ATIME) {
479 struct ovl_fs *ofs = inode->i_sb->s_fs_info;
480 struct path upperpath = {
481 .mnt = ovl_upper_mnt(ofs),
482 .dentry = ovl_upperdentry_dereference(OVL_I(inode)),
483 };
484
485 if (upperpath.dentry) {
486 touch_atime(&upperpath);
487 inode->i_atime = d_inode(upperpath.dentry)->i_atime;
488 }
489 }
490 return 0;
491 }
492
ovl_fiemap(struct inode * inode,struct fiemap_extent_info * fieinfo,u64 start,u64 len)493 static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
494 u64 start, u64 len)
495 {
496 int err;
497 struct inode *realinode = ovl_inode_realdata(inode);
498 const struct cred *old_cred;
499
500 if (!realinode->i_op->fiemap)
501 return -EOPNOTSUPP;
502
503 old_cred = ovl_override_creds(inode->i_sb);
504 err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
505 revert_creds(old_cred);
506
507 return err;
508 }
509
510 /*
511 * Work around the fact that security_file_ioctl() takes a file argument.
512 * Introducing security_inode_fileattr_get/set() hooks would solve this issue
513 * properly.
514 */
ovl_security_fileattr(struct path * realpath,struct fileattr * fa,bool set)515 static int ovl_security_fileattr(struct path *realpath, struct fileattr *fa,
516 bool set)
517 {
518 struct file *file;
519 unsigned int cmd;
520 int err;
521
522 file = dentry_open(realpath, O_RDONLY, current_cred());
523 if (IS_ERR(file))
524 return PTR_ERR(file);
525
526 if (set)
527 cmd = fa->fsx_valid ? FS_IOC_FSSETXATTR : FS_IOC_SETFLAGS;
528 else
529 cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
530
531 err = security_file_ioctl(file, cmd, 0);
532 fput(file);
533
534 return err;
535 }
536
ovl_real_fileattr_set(struct path * realpath,struct fileattr * fa)537 int ovl_real_fileattr_set(struct path *realpath, struct fileattr *fa)
538 {
539 int err;
540
541 err = ovl_security_fileattr(realpath, fa, true);
542 if (err)
543 return err;
544
545 return vfs_fileattr_set(mnt_user_ns(realpath->mnt), realpath->dentry, fa);
546 }
547
ovl_fileattr_set(struct user_namespace * mnt_userns,struct dentry * dentry,struct fileattr * fa)548 int ovl_fileattr_set(struct user_namespace *mnt_userns,
549 struct dentry *dentry, struct fileattr *fa)
550 {
551 struct inode *inode = d_inode(dentry);
552 struct path upperpath;
553 const struct cred *old_cred;
554 unsigned int flags;
555 int err;
556
557 err = ovl_want_write(dentry);
558 if (err)
559 goto out;
560
561 err = ovl_copy_up(dentry);
562 if (!err) {
563 ovl_path_real(dentry, &upperpath);
564
565 old_cred = ovl_override_creds(inode->i_sb);
566 /*
567 * Store immutable/append-only flags in xattr and clear them
568 * in upper fileattr (in case they were set by older kernel)
569 * so children of "ovl-immutable" directories lower aliases of
570 * "ovl-immutable" hardlinks could be copied up.
571 * Clear xattr when flags are cleared.
572 */
573 err = ovl_set_protattr(inode, upperpath.dentry, fa);
574 if (!err)
575 err = ovl_real_fileattr_set(&upperpath, fa);
576 revert_creds(old_cred);
577
578 /*
579 * Merge real inode flags with inode flags read from
580 * overlay.protattr xattr
581 */
582 flags = ovl_inode_real(inode)->i_flags & OVL_COPY_I_FLAGS_MASK;
583
584 BUILD_BUG_ON(OVL_PROT_I_FLAGS_MASK & ~OVL_COPY_I_FLAGS_MASK);
585 flags |= inode->i_flags & OVL_PROT_I_FLAGS_MASK;
586 inode_set_flags(inode, flags, OVL_COPY_I_FLAGS_MASK);
587
588 /* Update ctime */
589 ovl_copyattr(inode);
590 }
591 ovl_drop_write(dentry);
592 out:
593 return err;
594 }
595
596 /* Convert inode protection flags to fileattr flags */
ovl_fileattr_prot_flags(struct inode * inode,struct fileattr * fa)597 static void ovl_fileattr_prot_flags(struct inode *inode, struct fileattr *fa)
598 {
599 BUILD_BUG_ON(OVL_PROT_FS_FLAGS_MASK & ~FS_COMMON_FL);
600 BUILD_BUG_ON(OVL_PROT_FSX_FLAGS_MASK & ~FS_XFLAG_COMMON);
601
602 if (inode->i_flags & S_APPEND) {
603 fa->flags |= FS_APPEND_FL;
604 fa->fsx_xflags |= FS_XFLAG_APPEND;
605 }
606 if (inode->i_flags & S_IMMUTABLE) {
607 fa->flags |= FS_IMMUTABLE_FL;
608 fa->fsx_xflags |= FS_XFLAG_IMMUTABLE;
609 }
610 }
611
ovl_real_fileattr_get(struct path * realpath,struct fileattr * fa)612 int ovl_real_fileattr_get(struct path *realpath, struct fileattr *fa)
613 {
614 int err;
615
616 err = ovl_security_fileattr(realpath, fa, false);
617 if (err)
618 return err;
619
620 err = vfs_fileattr_get(realpath->dentry, fa);
621 if (err == -ENOIOCTLCMD)
622 err = -ENOTTY;
623 return err;
624 }
625
ovl_fileattr_get(struct dentry * dentry,struct fileattr * fa)626 int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa)
627 {
628 struct inode *inode = d_inode(dentry);
629 struct path realpath;
630 const struct cred *old_cred;
631 int err;
632
633 ovl_path_real(dentry, &realpath);
634
635 old_cred = ovl_override_creds(inode->i_sb);
636 err = ovl_real_fileattr_get(&realpath, fa);
637 ovl_fileattr_prot_flags(inode, fa);
638 revert_creds(old_cred);
639
640 return err;
641 }
642
643 static const struct inode_operations ovl_file_inode_operations = {
644 .setattr = ovl_setattr,
645 .permission = ovl_permission,
646 .getattr = ovl_getattr,
647 .listxattr = ovl_listxattr,
648 .get_acl = ovl_get_acl,
649 .update_time = ovl_update_time,
650 .fiemap = ovl_fiemap,
651 .fileattr_get = ovl_fileattr_get,
652 .fileattr_set = ovl_fileattr_set,
653 };
654
655 static const struct inode_operations ovl_symlink_inode_operations = {
656 .setattr = ovl_setattr,
657 .get_link = ovl_get_link,
658 .getattr = ovl_getattr,
659 .listxattr = ovl_listxattr,
660 .update_time = ovl_update_time,
661 };
662
663 static const struct inode_operations ovl_special_inode_operations = {
664 .setattr = ovl_setattr,
665 .permission = ovl_permission,
666 .getattr = ovl_getattr,
667 .listxattr = ovl_listxattr,
668 .get_acl = ovl_get_acl,
669 .update_time = ovl_update_time,
670 };
671
672 static const struct address_space_operations ovl_aops = {
673 /* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
674 .direct_IO = noop_direct_IO,
675 };
676
677 /*
678 * It is possible to stack overlayfs instance on top of another
679 * overlayfs instance as lower layer. We need to annotate the
680 * stackable i_mutex locks according to stack level of the super
681 * block instance. An overlayfs instance can never be in stack
682 * depth 0 (there is always a real fs below it). An overlayfs
683 * inode lock will use the lockdep annotation ovl_i_mutex_key[depth].
684 *
685 * For example, here is a snip from /proc/lockdep_chains after
686 * dir_iterate of nested overlayfs:
687 *
688 * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2)
689 * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
690 * [...] &type->i_mutex_dir_key (stack_depth=0)
691 *
692 * Locking order w.r.t ovl_want_write() is important for nested overlayfs.
693 *
694 * This chain is valid:
695 * - inode->i_rwsem (inode_lock[2])
696 * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0])
697 * - OVL_I(inode)->lock (ovl_inode_lock[2])
698 * - OVL_I(lowerinode)->lock (ovl_inode_lock[1])
699 *
700 * And this chain is valid:
701 * - inode->i_rwsem (inode_lock[2])
702 * - OVL_I(inode)->lock (ovl_inode_lock[2])
703 * - lowerinode->i_rwsem (inode_lock[1])
704 * - OVL_I(lowerinode)->lock (ovl_inode_lock[1])
705 *
706 * But lowerinode->i_rwsem SHOULD NOT be acquired while ovl_want_write() is
707 * held, because it is in reverse order of the non-nested case using the same
708 * upper fs:
709 * - inode->i_rwsem (inode_lock[1])
710 * - upper_mnt->mnt_sb->s_writers (ovl_want_write[0])
711 * - OVL_I(inode)->lock (ovl_inode_lock[1])
712 */
713 #define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
714
ovl_lockdep_annotate_inode_mutex_key(struct inode * inode)715 static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
716 {
717 #ifdef CONFIG_LOCKDEP
718 static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING];
719 static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING];
720 static struct lock_class_key ovl_i_lock_key[OVL_MAX_NESTING];
721
722 int depth = inode->i_sb->s_stack_depth - 1;
723
724 if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING))
725 depth = 0;
726
727 if (S_ISDIR(inode->i_mode))
728 lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]);
729 else
730 lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]);
731
732 lockdep_set_class(&OVL_I(inode)->lock, &ovl_i_lock_key[depth]);
733 #endif
734 }
735
ovl_next_ino(struct inode * inode)736 static void ovl_next_ino(struct inode *inode)
737 {
738 struct ovl_fs *ofs = inode->i_sb->s_fs_info;
739
740 inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
741 if (unlikely(!inode->i_ino))
742 inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
743 }
744
ovl_map_ino(struct inode * inode,unsigned long ino,int fsid)745 static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
746 {
747 int xinobits = ovl_xino_bits(inode->i_sb);
748 unsigned int xinoshift = 64 - xinobits;
749
750 /*
751 * When d_ino is consistent with st_ino (samefs or i_ino has enough
752 * bits to encode layer), set the same value used for st_ino to i_ino,
753 * so inode number exposed via /proc/locks and a like will be
754 * consistent with d_ino and st_ino values. An i_ino value inconsistent
755 * with d_ino also causes nfsd readdirplus to fail.
756 */
757 inode->i_ino = ino;
758 if (ovl_same_fs(inode->i_sb)) {
759 return;
760 } else if (xinobits && likely(!(ino >> xinoshift))) {
761 inode->i_ino |= (unsigned long)fsid << (xinoshift + 1);
762 return;
763 }
764
765 /*
766 * For directory inodes on non-samefs with xino disabled or xino
767 * overflow, we allocate a non-persistent inode number, to be used for
768 * resolving st_ino collisions in ovl_map_dev_ino().
769 *
770 * To avoid ino collision with legitimate xino values from upper
771 * layer (fsid 0), use the lowest xinobit to map the non
772 * persistent inode numbers to the unified st_ino address space.
773 */
774 if (S_ISDIR(inode->i_mode)) {
775 ovl_next_ino(inode);
776 if (xinobits) {
777 inode->i_ino &= ~0UL >> xinobits;
778 inode->i_ino |= 1UL << xinoshift;
779 }
780 }
781 }
782
ovl_inode_init(struct inode * inode,struct ovl_inode_params * oip,unsigned long ino,int fsid)783 void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
784 unsigned long ino, int fsid)
785 {
786 struct inode *realinode;
787 struct ovl_inode *oi = OVL_I(inode);
788
789 if (oip->upperdentry)
790 oi->__upperdentry = oip->upperdentry;
791 if (oip->lowerpath && oip->lowerpath->dentry) {
792 oi->lowerpath.dentry = dget(oip->lowerpath->dentry);
793 oi->lowerpath.layer = oip->lowerpath->layer;
794 }
795 if (oip->lowerdata)
796 oi->lowerdata = igrab(d_inode(oip->lowerdata));
797
798 realinode = ovl_inode_real(inode);
799 ovl_copyattr(inode);
800 ovl_copyflags(realinode, inode);
801 ovl_map_ino(inode, ino, fsid);
802 }
803
ovl_fill_inode(struct inode * inode,umode_t mode,dev_t rdev)804 static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
805 {
806 inode->i_mode = mode;
807 inode->i_flags |= S_NOCMTIME;
808 #ifdef CONFIG_FS_POSIX_ACL
809 inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
810 #endif
811
812 ovl_lockdep_annotate_inode_mutex_key(inode);
813
814 switch (mode & S_IFMT) {
815 case S_IFREG:
816 inode->i_op = &ovl_file_inode_operations;
817 inode->i_fop = &ovl_file_operations;
818 inode->i_mapping->a_ops = &ovl_aops;
819 break;
820
821 case S_IFDIR:
822 inode->i_op = &ovl_dir_inode_operations;
823 inode->i_fop = &ovl_dir_operations;
824 break;
825
826 case S_IFLNK:
827 inode->i_op = &ovl_symlink_inode_operations;
828 break;
829
830 default:
831 inode->i_op = &ovl_special_inode_operations;
832 init_special_inode(inode, mode, rdev);
833 break;
834 }
835 }
836
837 /*
838 * With inodes index enabled, an overlay inode nlink counts the union of upper
839 * hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure
840 * upper inode, the following nlink modifying operations can happen:
841 *
842 * 1. Lower hardlink copy up
843 * 2. Upper hardlink created, unlinked or renamed over
844 * 3. Lower hardlink whiteout or renamed over
845 *
846 * For the first, copy up case, the union nlink does not change, whether the
847 * operation succeeds or fails, but the upper inode nlink may change.
848 * Therefore, before copy up, we store the union nlink value relative to the
849 * lower inode nlink in the index inode xattr .overlay.nlink.
850 *
851 * For the second, upper hardlink case, the union nlink should be incremented
852 * or decremented IFF the operation succeeds, aligned with nlink change of the
853 * upper inode. Therefore, before link/unlink/rename, we store the union nlink
854 * value relative to the upper inode nlink in the index inode.
855 *
856 * For the last, lower cover up case, we simplify things by preceding the
857 * whiteout or cover up with copy up. This makes sure that there is an index
858 * upper inode where the nlink xattr can be stored before the copied up upper
859 * entry is unlink.
860 */
861 #define OVL_NLINK_ADD_UPPER (1 << 0)
862
863 /*
864 * On-disk format for indexed nlink:
865 *
866 * nlink relative to the upper inode - "U[+-]NUM"
867 * nlink relative to the lower inode - "L[+-]NUM"
868 */
869
ovl_set_nlink_common(struct dentry * dentry,struct dentry * realdentry,const char * format)870 static int ovl_set_nlink_common(struct dentry *dentry,
871 struct dentry *realdentry, const char *format)
872 {
873 struct inode *inode = d_inode(dentry);
874 struct inode *realinode = d_inode(realdentry);
875 char buf[13];
876 int len;
877
878 len = snprintf(buf, sizeof(buf), format,
879 (int) (inode->i_nlink - realinode->i_nlink));
880
881 if (WARN_ON(len >= sizeof(buf)))
882 return -EIO;
883
884 return ovl_setxattr(OVL_FS(inode->i_sb), ovl_dentry_upper(dentry),
885 OVL_XATTR_NLINK, buf, len);
886 }
887
ovl_set_nlink_upper(struct dentry * dentry)888 int ovl_set_nlink_upper(struct dentry *dentry)
889 {
890 return ovl_set_nlink_common(dentry, ovl_dentry_upper(dentry), "U%+i");
891 }
892
ovl_set_nlink_lower(struct dentry * dentry)893 int ovl_set_nlink_lower(struct dentry *dentry)
894 {
895 return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i");
896 }
897
ovl_get_nlink(struct ovl_fs * ofs,struct dentry * lowerdentry,struct dentry * upperdentry,unsigned int fallback)898 unsigned int ovl_get_nlink(struct ovl_fs *ofs, struct dentry *lowerdentry,
899 struct dentry *upperdentry,
900 unsigned int fallback)
901 {
902 int nlink_diff;
903 int nlink;
904 char buf[13];
905 int err;
906
907 if (!lowerdentry || !upperdentry || d_inode(lowerdentry)->i_nlink == 1)
908 return fallback;
909
910 err = ovl_getxattr_upper(ofs, upperdentry, OVL_XATTR_NLINK,
911 &buf, sizeof(buf) - 1);
912 if (err < 0)
913 goto fail;
914
915 buf[err] = '\0';
916 if ((buf[0] != 'L' && buf[0] != 'U') ||
917 (buf[1] != '+' && buf[1] != '-'))
918 goto fail;
919
920 err = kstrtoint(buf + 1, 10, &nlink_diff);
921 if (err < 0)
922 goto fail;
923
924 nlink = d_inode(buf[0] == 'L' ? lowerdentry : upperdentry)->i_nlink;
925 nlink += nlink_diff;
926
927 if (nlink <= 0)
928 goto fail;
929
930 return nlink;
931
932 fail:
933 pr_warn_ratelimited("failed to get index nlink (%pd2, err=%i)\n",
934 upperdentry, err);
935 return fallback;
936 }
937
ovl_new_inode(struct super_block * sb,umode_t mode,dev_t rdev)938 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
939 {
940 struct inode *inode;
941
942 inode = new_inode(sb);
943 if (inode)
944 ovl_fill_inode(inode, mode, rdev);
945
946 return inode;
947 }
948
ovl_inode_test(struct inode * inode,void * data)949 static int ovl_inode_test(struct inode *inode, void *data)
950 {
951 return inode->i_private == data;
952 }
953
ovl_inode_set(struct inode * inode,void * data)954 static int ovl_inode_set(struct inode *inode, void *data)
955 {
956 inode->i_private = data;
957 return 0;
958 }
959
ovl_verify_inode(struct inode * inode,struct dentry * lowerdentry,struct dentry * upperdentry,bool strict)960 static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
961 struct dentry *upperdentry, bool strict)
962 {
963 /*
964 * For directories, @strict verify from lookup path performs consistency
965 * checks, so NULL lower/upper in dentry must match NULL lower/upper in
966 * inode. Non @strict verify from NFS handle decode path passes NULL for
967 * 'unknown' lower/upper.
968 */
969 if (S_ISDIR(inode->i_mode) && strict) {
970 /* Real lower dir moved to upper layer under us? */
971 if (!lowerdentry && ovl_inode_lower(inode))
972 return false;
973
974 /* Lookup of an uncovered redirect origin? */
975 if (!upperdentry && ovl_inode_upper(inode))
976 return false;
977 }
978
979 /*
980 * Allow non-NULL lower inode in ovl_inode even if lowerdentry is NULL.
981 * This happens when finding a copied up overlay inode for a renamed
982 * or hardlinked overlay dentry and lower dentry cannot be followed
983 * by origin because lower fs does not support file handles.
984 */
985 if (lowerdentry && ovl_inode_lower(inode) != d_inode(lowerdentry))
986 return false;
987
988 /*
989 * Allow non-NULL __upperdentry in inode even if upperdentry is NULL.
990 * This happens when finding a lower alias for a copied up hard link.
991 */
992 if (upperdentry && ovl_inode_upper(inode) != d_inode(upperdentry))
993 return false;
994
995 return true;
996 }
997
ovl_lookup_inode(struct super_block * sb,struct dentry * real,bool is_upper)998 struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
999 bool is_upper)
1000 {
1001 struct inode *inode, *key = d_inode(real);
1002
1003 inode = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
1004 if (!inode)
1005 return NULL;
1006
1007 if (!ovl_verify_inode(inode, is_upper ? NULL : real,
1008 is_upper ? real : NULL, false)) {
1009 iput(inode);
1010 return ERR_PTR(-ESTALE);
1011 }
1012
1013 return inode;
1014 }
1015
ovl_lookup_trap_inode(struct super_block * sb,struct dentry * dir)1016 bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
1017 {
1018 struct inode *key = d_inode(dir);
1019 struct inode *trap;
1020 bool res;
1021
1022 trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
1023 if (!trap)
1024 return false;
1025
1026 res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
1027 !ovl_inode_lower(trap);
1028
1029 iput(trap);
1030 return res;
1031 }
1032
1033 /*
1034 * Create an inode cache entry for layer root dir, that will intentionally
1035 * fail ovl_verify_inode(), so any lookup that will find some layer root
1036 * will fail.
1037 */
ovl_get_trap_inode(struct super_block * sb,struct dentry * dir)1038 struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
1039 {
1040 struct inode *key = d_inode(dir);
1041 struct inode *trap;
1042
1043 if (!d_is_dir(dir))
1044 return ERR_PTR(-ENOTDIR);
1045
1046 trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
1047 ovl_inode_set, key);
1048 if (!trap)
1049 return ERR_PTR(-ENOMEM);
1050
1051 if (!(trap->i_state & I_NEW)) {
1052 /* Conflicting layer roots? */
1053 iput(trap);
1054 return ERR_PTR(-ELOOP);
1055 }
1056
1057 trap->i_mode = S_IFDIR;
1058 trap->i_flags = S_DEAD;
1059 unlock_new_inode(trap);
1060
1061 return trap;
1062 }
1063
1064 /*
1065 * Does overlay inode need to be hashed by lower inode?
1066 */
ovl_hash_bylower(struct super_block * sb,struct dentry * upper,struct dentry * lower,bool index)1067 static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
1068 struct dentry *lower, bool index)
1069 {
1070 struct ovl_fs *ofs = sb->s_fs_info;
1071
1072 /* No, if pure upper */
1073 if (!lower)
1074 return false;
1075
1076 /* Yes, if already indexed */
1077 if (index)
1078 return true;
1079
1080 /* Yes, if won't be copied up */
1081 if (!ovl_upper_mnt(ofs))
1082 return true;
1083
1084 /* No, if lower hardlink is or will be broken on copy up */
1085 if ((upper || !ovl_indexdir(sb)) &&
1086 !d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
1087 return false;
1088
1089 /* No, if non-indexed upper with NFS export */
1090 if (sb->s_export_op && upper)
1091 return false;
1092
1093 /* Otherwise, hash by lower inode for fsnotify */
1094 return true;
1095 }
1096
ovl_iget5(struct super_block * sb,struct inode * newinode,struct inode * key)1097 static struct inode *ovl_iget5(struct super_block *sb, struct inode *newinode,
1098 struct inode *key)
1099 {
1100 return newinode ? inode_insert5(newinode, (unsigned long) key,
1101 ovl_inode_test, ovl_inode_set, key) :
1102 iget5_locked(sb, (unsigned long) key,
1103 ovl_inode_test, ovl_inode_set, key);
1104 }
1105
ovl_get_inode(struct super_block * sb,struct ovl_inode_params * oip)1106 struct inode *ovl_get_inode(struct super_block *sb,
1107 struct ovl_inode_params *oip)
1108 {
1109 struct ovl_fs *ofs = OVL_FS(sb);
1110 struct dentry *upperdentry = oip->upperdentry;
1111 struct ovl_path *lowerpath = oip->lowerpath;
1112 struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
1113 struct inode *inode;
1114 struct dentry *lowerdentry = lowerpath ? lowerpath->dentry : NULL;
1115 struct path realpath = {
1116 .dentry = upperdentry ?: lowerdentry,
1117 .mnt = upperdentry ? ovl_upper_mnt(ofs) : lowerpath->layer->mnt,
1118 };
1119 bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry,
1120 oip->index);
1121 int fsid = bylower ? lowerpath->layer->fsid : 0;
1122 bool is_dir;
1123 unsigned long ino = 0;
1124 int err = oip->newinode ? -EEXIST : -ENOMEM;
1125
1126 if (!realinode)
1127 realinode = d_inode(lowerdentry);
1128
1129 /*
1130 * Copy up origin (lower) may exist for non-indexed upper, but we must
1131 * not use lower as hash key if this is a broken hardlink.
1132 */
1133 is_dir = S_ISDIR(realinode->i_mode);
1134 if (upperdentry || bylower) {
1135 struct inode *key = d_inode(bylower ? lowerdentry :
1136 upperdentry);
1137 unsigned int nlink = is_dir ? 1 : realinode->i_nlink;
1138
1139 inode = ovl_iget5(sb, oip->newinode, key);
1140 if (!inode)
1141 goto out_err;
1142 if (!(inode->i_state & I_NEW)) {
1143 /*
1144 * Verify that the underlying files stored in the inode
1145 * match those in the dentry.
1146 */
1147 if (!ovl_verify_inode(inode, lowerdentry, upperdentry,
1148 true)) {
1149 iput(inode);
1150 err = -ESTALE;
1151 goto out_err;
1152 }
1153
1154 dput(upperdentry);
1155 kfree(oip->redirect);
1156 goto out;
1157 }
1158
1159 /* Recalculate nlink for non-dir due to indexing */
1160 if (!is_dir)
1161 nlink = ovl_get_nlink(ofs, lowerdentry, upperdentry,
1162 nlink);
1163 set_nlink(inode, nlink);
1164 ino = key->i_ino;
1165 } else {
1166 /* Lower hardlink that will be broken on copy up */
1167 inode = new_inode(sb);
1168 if (!inode) {
1169 err = -ENOMEM;
1170 goto out_err;
1171 }
1172 ino = realinode->i_ino;
1173 fsid = lowerpath->layer->fsid;
1174 }
1175 ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
1176 ovl_inode_init(inode, oip, ino, fsid);
1177
1178 if (upperdentry && ovl_is_impuredir(sb, upperdentry))
1179 ovl_set_flag(OVL_IMPURE, inode);
1180
1181 if (oip->index)
1182 ovl_set_flag(OVL_INDEX, inode);
1183
1184 OVL_I(inode)->redirect = oip->redirect;
1185
1186 if (bylower)
1187 ovl_set_flag(OVL_CONST_INO, inode);
1188
1189 /* Check for non-merge dir that may have whiteouts */
1190 if (is_dir) {
1191 if (((upperdentry && lowerdentry) || oip->numlower > 1) ||
1192 ovl_path_check_origin_xattr(ofs, &realpath)) {
1193 ovl_set_flag(OVL_WHITEOUTS, inode);
1194 }
1195 }
1196
1197 /* Check for immutable/append-only inode flags in xattr */
1198 if (upperdentry)
1199 ovl_check_protattr(inode, upperdentry);
1200
1201 if (inode->i_state & I_NEW)
1202 unlock_new_inode(inode);
1203 out:
1204 return inode;
1205
1206 out_err:
1207 pr_warn_ratelimited("failed to get inode (%i)\n", err);
1208 inode = ERR_PTR(err);
1209 goto out;
1210 }
1211