1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 *
4 * Copyright (C) 2011 Novell Inc.
5 */
6
7 #include <uapi/linux/magic.h>
8 #include <linux/fs.h>
9 #include <linux/namei.h>
10 #include <linux/xattr.h>
11 #include <linux/mount.h>
12 #include <linux/parser.h>
13 #include <linux/module.h>
14 #include <linux/statfs.h>
15 #include <linux/seq_file.h>
16 #include <linux/posix_acl_xattr.h>
17 #include <linux/exportfs.h>
18 #include <linux/file.h>
19 #include <linux/fs_context.h>
20 #include <linux/fs_parser.h>
21 #include "overlayfs.h"
22 #include "params.h"
23
24 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
25 MODULE_DESCRIPTION("Overlay filesystem");
26 MODULE_LICENSE("GPL");
27
28
29 struct ovl_dir_cache;
30
31 static struct dentry *ovl_d_real(struct dentry *dentry, enum d_real_type type)
32 {
33 struct dentry *upper, *lower;
34 int err;
35
36 switch (type) {
37 case D_REAL_DATA:
38 case D_REAL_METADATA:
39 break;
40 default:
41 goto bug;
42 }
43
44 if (!d_is_reg(dentry)) {
45 /* d_real_inode() is only relevant for regular files */
46 return dentry;
47 }
48
49 upper = ovl_dentry_upper(dentry);
50 if (upper && (type == D_REAL_METADATA ||
51 ovl_has_upperdata(d_inode(dentry))))
52 return upper;
53
54 if (type == D_REAL_METADATA) {
55 lower = ovl_dentry_lower(dentry);
56 goto real_lower;
57 }
58
59 /*
60 * Best effort lazy lookup of lowerdata for D_REAL_DATA case to return
61 * the real lowerdata dentry. The only current caller of d_real() with
62 * D_REAL_DATA is d_real_inode() from trace_uprobe and this caller is
63 * likely going to be followed reading from the file, before placing
64 * uprobes on offset within the file, so lowerdata should be available
65 * when setting the uprobe.
66 */
67 err = ovl_verify_lowerdata(dentry);
68 if (err)
69 goto bug;
70 lower = ovl_dentry_lowerdata(dentry);
71 if (!lower)
72 goto bug;
73
74 real_lower:
75 /* Handle recursion into stacked lower fs */
76 return d_real(lower, type);
77
78 bug:
79 WARN(1, "%s(%pd4, %d): real dentry not found\n", __func__, dentry, type);
80 return dentry;
81 }
82
83 static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak)
84 {
85 int ret = 1;
86
87 if (!d)
88 return 1;
89
90 if (weak) {
91 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE)
92 ret = d->d_op->d_weak_revalidate(d, flags);
93 } else if (d->d_flags & DCACHE_OP_REVALIDATE) {
94 ret = d->d_op->d_revalidate(d, flags);
95 if (!ret) {
96 if (!(flags & LOOKUP_RCU))
97 d_invalidate(d);
98 ret = -ESTALE;
99 }
100 }
101 return ret;
102 }
103
104 static int ovl_dentry_revalidate_common(struct dentry *dentry,
105 unsigned int flags, bool weak)
106 {
107 struct ovl_entry *oe;
108 struct ovl_path *lowerstack;
109 struct inode *inode = d_inode_rcu(dentry);
110 struct dentry *upper;
111 unsigned int i;
112 int ret = 1;
113
114 /* Careful in RCU mode */
115 if (!inode)
116 return -ECHILD;
117
118 oe = OVL_I_E(inode);
119 lowerstack = ovl_lowerstack(oe);
120 upper = ovl_i_dentry_upper(inode);
121 if (upper)
122 ret = ovl_revalidate_real(upper, flags, weak);
123
124 for (i = 0; ret > 0 && i < ovl_numlower(oe); i++)
125 ret = ovl_revalidate_real(lowerstack[i].dentry, flags, weak);
126
127 return ret;
128 }
129
130 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
131 {
132 return ovl_dentry_revalidate_common(dentry, flags, false);
133 }
134
135 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
136 {
137 return ovl_dentry_revalidate_common(dentry, flags, true);
138 }
139
140 static const struct dentry_operations ovl_dentry_operations = {
141 .d_real = ovl_d_real,
142 .d_revalidate = ovl_dentry_revalidate,
143 .d_weak_revalidate = ovl_dentry_weak_revalidate,
144 };
145
146 static struct kmem_cache *ovl_inode_cachep;
147
148 static struct inode *ovl_alloc_inode(struct super_block *sb)
149 {
150 struct ovl_inode *oi = alloc_inode_sb(sb, ovl_inode_cachep, GFP_KERNEL);
151
152 if (!oi)
153 return NULL;
154
155 oi->cache = NULL;
156 oi->redirect = NULL;
157 oi->version = 0;
158 oi->flags = 0;
159 oi->__upperdentry = NULL;
160 oi->lowerdata_redirect = NULL;
161 oi->oe = NULL;
162 mutex_init(&oi->lock);
163
164 return &oi->vfs_inode;
165 }
166
167 static void ovl_free_inode(struct inode *inode)
168 {
169 struct ovl_inode *oi = OVL_I(inode);
170
171 kfree(oi->redirect);
172 kfree(oi->oe);
173 mutex_destroy(&oi->lock);
174 kmem_cache_free(ovl_inode_cachep, oi);
175 }
176
177 static void ovl_destroy_inode(struct inode *inode)
178 {
179 struct ovl_inode *oi = OVL_I(inode);
180
181 dput(oi->__upperdentry);
182 ovl_stack_put(ovl_lowerstack(oi->oe), ovl_numlower(oi->oe));
183 if (S_ISDIR(inode->i_mode))
184 ovl_dir_cache_free(inode);
185 else
186 kfree(oi->lowerdata_redirect);
187 }
188
189 static void ovl_put_super(struct super_block *sb)
190 {
191 struct ovl_fs *ofs = OVL_FS(sb);
192
193 if (ofs)
194 ovl_free_fs(ofs);
195 }
196
197 /* Sync real dirty inodes in upper filesystem (if it exists) */
198 static int ovl_sync_fs(struct super_block *sb, int wait)
199 {
200 struct ovl_fs *ofs = OVL_FS(sb);
201 struct super_block *upper_sb;
202 int ret;
203
204 ret = ovl_sync_status(ofs);
205 /*
206 * We have to always set the err, because the return value isn't
207 * checked in syncfs, and instead indirectly return an error via
208 * the sb's writeback errseq, which VFS inspects after this call.
209 */
210 if (ret < 0) {
211 errseq_set(&sb->s_wb_err, -EIO);
212 return -EIO;
213 }
214
215 if (!ret)
216 return ret;
217
218 /*
219 * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
220 * All the super blocks will be iterated, including upper_sb.
221 *
222 * If this is a syncfs(2) call, then we do need to call
223 * sync_filesystem() on upper_sb, but enough if we do it when being
224 * called with wait == 1.
225 */
226 if (!wait)
227 return 0;
228
229 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
230
231 down_read(&upper_sb->s_umount);
232 ret = sync_filesystem(upper_sb);
233 up_read(&upper_sb->s_umount);
234
235 return ret;
236 }
237
238 /**
239 * ovl_statfs
240 * @dentry: The dentry to query
241 * @buf: The struct kstatfs to fill in with stats
242 *
243 * Get the filesystem statistics. As writes always target the upper layer
244 * filesystem pass the statfs to the upper filesystem (if it exists)
245 */
246 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
247 {
248 struct super_block *sb = dentry->d_sb;
249 struct ovl_fs *ofs = OVL_FS(sb);
250 struct dentry *root_dentry = sb->s_root;
251 struct path path;
252 int err;
253
254 ovl_path_real(root_dentry, &path);
255
256 err = vfs_statfs(&path, buf);
257 if (!err) {
258 buf->f_namelen = ofs->namelen;
259 buf->f_type = OVERLAYFS_SUPER_MAGIC;
260 if (ovl_has_fsid(ofs))
261 buf->f_fsid = uuid_to_fsid(sb->s_uuid.b);
262 }
263
264 return err;
265 }
266
267 static const struct super_operations ovl_super_operations = {
268 .alloc_inode = ovl_alloc_inode,
269 .free_inode = ovl_free_inode,
270 .destroy_inode = ovl_destroy_inode,
271 .drop_inode = generic_delete_inode,
272 .put_super = ovl_put_super,
273 .sync_fs = ovl_sync_fs,
274 .statfs = ovl_statfs,
275 .show_options = ovl_show_options,
276 };
277
278 #define OVL_WORKDIR_NAME "work"
279 #define OVL_INDEXDIR_NAME "index"
280
281 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
282 const char *name, bool persist)
283 {
284 struct inode *dir = ofs->workbasedir->d_inode;
285 struct vfsmount *mnt = ovl_upper_mnt(ofs);
286 struct dentry *work;
287 int err;
288 bool retried = false;
289
290 inode_lock_nested(dir, I_MUTEX_PARENT);
291 retry:
292 work = ovl_lookup_upper(ofs, name, ofs->workbasedir, strlen(name));
293
294 if (!IS_ERR(work)) {
295 struct iattr attr = {
296 .ia_valid = ATTR_MODE,
297 .ia_mode = S_IFDIR | 0,
298 };
299
300 if (work->d_inode) {
301 err = -EEXIST;
302 if (retried)
303 goto out_dput;
304
305 if (persist)
306 goto out_unlock;
307
308 retried = true;
309 err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0);
310 dput(work);
311 if (err == -EINVAL) {
312 work = ERR_PTR(err);
313 goto out_unlock;
314 }
315 goto retry;
316 }
317
318 err = ovl_mkdir_real(ofs, dir, &work, attr.ia_mode);
319 if (err)
320 goto out_dput;
321
322 /* Weird filesystem returning with hashed negative (kernfs)? */
323 err = -EINVAL;
324 if (d_really_is_negative(work))
325 goto out_dput;
326
327 /*
328 * Try to remove POSIX ACL xattrs from workdir. We are good if:
329 *
330 * a) success (there was a POSIX ACL xattr and was removed)
331 * b) -ENODATA (there was no POSIX ACL xattr)
332 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
333 *
334 * There are various other error values that could effectively
335 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
336 * if the xattr name is too long), but the set of filesystems
337 * allowed as upper are limited to "normal" ones, where checking
338 * for the above two errors is sufficient.
339 */
340 err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_DEFAULT);
341 if (err && err != -ENODATA && err != -EOPNOTSUPP)
342 goto out_dput;
343
344 err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_ACCESS);
345 if (err && err != -ENODATA && err != -EOPNOTSUPP)
346 goto out_dput;
347
348 /* Clear any inherited mode bits */
349 inode_lock(work->d_inode);
350 err = ovl_do_notify_change(ofs, work, &attr);
351 inode_unlock(work->d_inode);
352 if (err)
353 goto out_dput;
354 } else {
355 err = PTR_ERR(work);
356 goto out_err;
357 }
358 out_unlock:
359 inode_unlock(dir);
360 return work;
361
362 out_dput:
363 dput(work);
364 out_err:
365 pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
366 ofs->config.workdir, name, -err);
367 work = NULL;
368 goto out_unlock;
369 }
370
371 static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs,
372 const char *name)
373 {
374 struct kstatfs statfs;
375 int err = vfs_statfs(path, &statfs);
376
377 if (err)
378 pr_err("statfs failed on '%s'\n", name);
379 else
380 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
381
382 return err;
383 }
384
385 static int ovl_lower_dir(const char *name, struct path *path,
386 struct ovl_fs *ofs, int *stack_depth)
387 {
388 int fh_type;
389 int err;
390
391 err = ovl_check_namelen(path, ofs, name);
392 if (err)
393 return err;
394
395 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
396
397 /*
398 * The inodes index feature and NFS export need to encode and decode
399 * file handles, so they require that all layers support them.
400 */
401 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
402 if ((ofs->config.nfs_export ||
403 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
404 ofs->config.index = false;
405 ofs->config.nfs_export = false;
406 pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
407 name);
408 }
409 ofs->nofh |= !fh_type;
410 /*
411 * Decoding origin file handle is required for persistent st_ino.
412 * Without persistent st_ino, xino=auto falls back to xino=off.
413 */
414 if (ofs->config.xino == OVL_XINO_AUTO &&
415 ofs->config.upperdir && !fh_type) {
416 ofs->config.xino = OVL_XINO_OFF;
417 pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n",
418 name);
419 }
420
421 /* Check if lower fs has 32bit inode numbers */
422 if (fh_type != FILEID_INO32_GEN)
423 ofs->xino_mode = -1;
424
425 return 0;
426 }
427
428 /* Workdir should not be subdir of upperdir and vice versa */
429 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
430 {
431 bool ok = false;
432
433 if (workdir != upperdir) {
434 struct dentry *trap = lock_rename(workdir, upperdir);
435 if (!IS_ERR(trap))
436 unlock_rename(workdir, upperdir);
437 ok = (trap == NULL);
438 }
439 return ok;
440 }
441
442 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
443 struct inode **ptrap, const char *name)
444 {
445 struct inode *trap;
446 int err;
447
448 trap = ovl_get_trap_inode(sb, dir);
449 err = PTR_ERR_OR_ZERO(trap);
450 if (err) {
451 if (err == -ELOOP)
452 pr_err("conflicting %s path\n", name);
453 return err;
454 }
455
456 *ptrap = trap;
457 return 0;
458 }
459
460 /*
461 * Determine how we treat concurrent use of upperdir/workdir based on the
462 * index feature. This is papering over mount leaks of container runtimes,
463 * for example, an old overlay mount is leaked and now its upperdir is
464 * attempted to be used as a lower layer in a new overlay mount.
465 */
466 static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
467 {
468 if (ofs->config.index) {
469 pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
470 name);
471 return -EBUSY;
472 } else {
473 pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
474 name);
475 return 0;
476 }
477 }
478
479 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
480 struct ovl_layer *upper_layer,
481 const struct path *upperpath)
482 {
483 struct vfsmount *upper_mnt;
484 int err;
485
486 /* Upperdir path should not be r/o */
487 if (__mnt_is_readonly(upperpath->mnt)) {
488 pr_err("upper fs is r/o, try multi-lower layers mount\n");
489 err = -EINVAL;
490 goto out;
491 }
492
493 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
494 if (err)
495 goto out;
496
497 err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap,
498 "upperdir");
499 if (err)
500 goto out;
501
502 upper_mnt = clone_private_mount(upperpath);
503 err = PTR_ERR(upper_mnt);
504 if (IS_ERR(upper_mnt)) {
505 pr_err("failed to clone upperpath\n");
506 goto out;
507 }
508
509 /* Don't inherit atime flags */
510 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
511 upper_layer->mnt = upper_mnt;
512 upper_layer->idx = 0;
513 upper_layer->fsid = 0;
514
515 /*
516 * Inherit SB_NOSEC flag from upperdir.
517 *
518 * This optimization changes behavior when a security related attribute
519 * (suid/sgid/security.*) is changed on an underlying layer. This is
520 * okay because we don't yet have guarantees in that case, but it will
521 * need careful treatment once we want to honour changes to underlying
522 * filesystems.
523 */
524 if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
525 sb->s_flags |= SB_NOSEC;
526
527 if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
528 ofs->upperdir_locked = true;
529 } else {
530 err = ovl_report_in_use(ofs, "upperdir");
531 if (err)
532 goto out;
533 }
534
535 err = 0;
536 out:
537 return err;
538 }
539
540 /*
541 * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
542 * negative values if error is encountered.
543 */
544 static int ovl_check_rename_whiteout(struct ovl_fs *ofs)
545 {
546 struct dentry *workdir = ofs->workdir;
547 struct inode *dir = d_inode(workdir);
548 struct dentry *temp;
549 struct dentry *dest;
550 struct dentry *whiteout;
551 struct name_snapshot name;
552 int err;
553
554 inode_lock_nested(dir, I_MUTEX_PARENT);
555
556 temp = ovl_create_temp(ofs, workdir, OVL_CATTR(S_IFREG | 0));
557 err = PTR_ERR(temp);
558 if (IS_ERR(temp))
559 goto out_unlock;
560
561 dest = ovl_lookup_temp(ofs, workdir);
562 err = PTR_ERR(dest);
563 if (IS_ERR(dest)) {
564 dput(temp);
565 goto out_unlock;
566 }
567
568 /* Name is inline and stable - using snapshot as a copy helper */
569 take_dentry_name_snapshot(&name, temp);
570 err = ovl_do_rename(ofs, dir, temp, dir, dest, RENAME_WHITEOUT);
571 if (err) {
572 if (err == -EINVAL)
573 err = 0;
574 goto cleanup_temp;
575 }
576
577 whiteout = ovl_lookup_upper(ofs, name.name.name, workdir, name.name.len);
578 err = PTR_ERR(whiteout);
579 if (IS_ERR(whiteout))
580 goto cleanup_temp;
581
582 err = ovl_upper_is_whiteout(ofs, whiteout);
583
584 /* Best effort cleanup of whiteout and temp file */
585 if (err)
586 ovl_cleanup(ofs, dir, whiteout);
587 dput(whiteout);
588
589 cleanup_temp:
590 ovl_cleanup(ofs, dir, temp);
591 release_dentry_name_snapshot(&name);
592 dput(temp);
593 dput(dest);
594
595 out_unlock:
596 inode_unlock(dir);
597
598 return err;
599 }
600
601 static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs,
602 struct dentry *parent,
603 const char *name, umode_t mode)
604 {
605 size_t len = strlen(name);
606 struct dentry *child;
607
608 inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
609 child = ovl_lookup_upper(ofs, name, parent, len);
610 if (!IS_ERR(child) && !child->d_inode)
611 child = ovl_create_real(ofs, parent->d_inode, child,
612 OVL_CATTR(mode));
613 inode_unlock(parent->d_inode);
614 dput(parent);
615
616 return child;
617 }
618
619 /*
620 * Creates $workdir/work/incompat/volatile/dirty file if it is not already
621 * present.
622 */
623 static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
624 {
625 unsigned int ctr;
626 struct dentry *d = dget(ofs->workbasedir);
627 static const char *const volatile_path[] = {
628 OVL_WORKDIR_NAME, "incompat", "volatile", "dirty"
629 };
630 const char *const *name = volatile_path;
631
632 for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) {
633 d = ovl_lookup_or_create(ofs, d, *name, ctr > 1 ? S_IFDIR : S_IFREG);
634 if (IS_ERR(d))
635 return PTR_ERR(d);
636 }
637 dput(d);
638 return 0;
639 }
640
641 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
642 const struct path *workpath)
643 {
644 struct vfsmount *mnt = ovl_upper_mnt(ofs);
645 struct dentry *workdir;
646 struct file *tmpfile;
647 bool rename_whiteout;
648 bool d_type;
649 int fh_type;
650 int err;
651
652 err = mnt_want_write(mnt);
653 if (err)
654 return err;
655
656 workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
657 err = PTR_ERR(workdir);
658 if (IS_ERR_OR_NULL(workdir))
659 goto out;
660
661 ofs->workdir = workdir;
662
663 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
664 if (err)
665 goto out;
666
667 /*
668 * Upper should support d_type, else whiteouts are visible. Given
669 * workdir and upper are on same fs, we can do iterate_dir() on
670 * workdir. This check requires successful creation of workdir in
671 * previous step.
672 */
673 err = ovl_check_d_type_supported(workpath);
674 if (err < 0)
675 goto out;
676
677 d_type = err;
678 if (!d_type)
679 pr_warn("upper fs needs to support d_type.\n");
680
681 /* Check if upper/work fs supports O_TMPFILE */
682 tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0);
683 ofs->tmpfile = !IS_ERR(tmpfile);
684 if (ofs->tmpfile)
685 fput(tmpfile);
686 else
687 pr_warn("upper fs does not support tmpfile.\n");
688
689
690 /* Check if upper/work fs supports RENAME_WHITEOUT */
691 err = ovl_check_rename_whiteout(ofs);
692 if (err < 0)
693 goto out;
694
695 rename_whiteout = err;
696 if (!rename_whiteout)
697 pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
698
699 /*
700 * Check if upper/work fs supports (trusted|user).overlay.* xattr
701 */
702 err = ovl_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "", 1);
703 if (err) {
704 pr_warn("failed to set xattr on upper\n");
705 ofs->noxattr = true;
706 if (ovl_redirect_follow(ofs)) {
707 ofs->config.redirect_mode = OVL_REDIRECT_NOFOLLOW;
708 pr_warn("...falling back to redirect_dir=nofollow.\n");
709 }
710 if (ofs->config.metacopy) {
711 ofs->config.metacopy = false;
712 pr_warn("...falling back to metacopy=off.\n");
713 }
714 if (ofs->config.index) {
715 ofs->config.index = false;
716 pr_warn("...falling back to index=off.\n");
717 }
718 if (ovl_has_fsid(ofs)) {
719 ofs->config.uuid = OVL_UUID_NULL;
720 pr_warn("...falling back to uuid=null.\n");
721 }
722 /*
723 * xattr support is required for persistent st_ino.
724 * Without persistent st_ino, xino=auto falls back to xino=off.
725 */
726 if (ofs->config.xino == OVL_XINO_AUTO) {
727 ofs->config.xino = OVL_XINO_OFF;
728 pr_warn("...falling back to xino=off.\n");
729 }
730 if (err == -EPERM && !ofs->config.userxattr)
731 pr_info("try mounting with 'userxattr' option\n");
732 err = 0;
733 } else {
734 ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
735 }
736
737 /*
738 * We allowed sub-optimal upper fs configuration and don't want to break
739 * users over kernel upgrade, but we never allowed remote upper fs, so
740 * we can enforce strict requirements for remote upper fs.
741 */
742 if (ovl_dentry_remote(ofs->workdir) &&
743 (!d_type || !rename_whiteout || ofs->noxattr)) {
744 pr_err("upper fs missing required features.\n");
745 err = -EINVAL;
746 goto out;
747 }
748
749 /*
750 * For volatile mount, create a incompat/volatile/dirty file to keep
751 * track of it.
752 */
753 if (ofs->config.ovl_volatile) {
754 err = ovl_create_volatile_dirty(ofs);
755 if (err < 0) {
756 pr_err("Failed to create volatile/dirty file.\n");
757 goto out;
758 }
759 }
760
761 /* Check if upper/work fs supports file handles */
762 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
763 if (ofs->config.index && !fh_type) {
764 ofs->config.index = false;
765 pr_warn("upper fs does not support file handles, falling back to index=off.\n");
766 }
767 ofs->nofh |= !fh_type;
768
769 /* Check if upper fs has 32bit inode numbers */
770 if (fh_type != FILEID_INO32_GEN)
771 ofs->xino_mode = -1;
772
773 /* NFS export of r/w mount depends on index */
774 if (ofs->config.nfs_export && !ofs->config.index) {
775 pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
776 ofs->config.nfs_export = false;
777 }
778 out:
779 mnt_drop_write(mnt);
780 return err;
781 }
782
783 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
784 const struct path *upperpath,
785 const struct path *workpath)
786 {
787 int err;
788
789 err = -EINVAL;
790 if (upperpath->mnt != workpath->mnt) {
791 pr_err("workdir and upperdir must reside under the same mount\n");
792 return err;
793 }
794 if (!ovl_workdir_ok(workpath->dentry, upperpath->dentry)) {
795 pr_err("workdir and upperdir must be separate subtrees\n");
796 return err;
797 }
798
799 ofs->workbasedir = dget(workpath->dentry);
800
801 if (ovl_inuse_trylock(ofs->workbasedir)) {
802 ofs->workdir_locked = true;
803 } else {
804 err = ovl_report_in_use(ofs, "workdir");
805 if (err)
806 return err;
807 }
808
809 err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
810 "workdir");
811 if (err)
812 return err;
813
814 return ovl_make_workdir(sb, ofs, workpath);
815 }
816
817 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
818 struct ovl_entry *oe, const struct path *upperpath)
819 {
820 struct vfsmount *mnt = ovl_upper_mnt(ofs);
821 struct dentry *indexdir;
822 struct dentry *origin = ovl_lowerstack(oe)->dentry;
823 const struct ovl_fh *fh;
824 int err;
825
826 fh = ovl_get_origin_fh(ofs, origin);
827 if (IS_ERR(fh))
828 return PTR_ERR(fh);
829
830 err = mnt_want_write(mnt);
831 if (err)
832 goto out_free_fh;
833
834 /* Verify lower root is upper root origin */
835 err = ovl_verify_origin_fh(ofs, upperpath->dentry, fh, true);
836 if (err) {
837 pr_err("failed to verify upper root origin\n");
838 goto out;
839 }
840
841 /* index dir will act also as workdir */
842 iput(ofs->workdir_trap);
843 ofs->workdir_trap = NULL;
844 dput(ofs->workdir);
845 ofs->workdir = NULL;
846 indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
847 if (IS_ERR(indexdir)) {
848 err = PTR_ERR(indexdir);
849 } else if (indexdir) {
850 ofs->workdir = indexdir;
851 err = ovl_setup_trap(sb, indexdir, &ofs->workdir_trap,
852 "indexdir");
853 if (err)
854 goto out;
855
856 /*
857 * Verify upper root is exclusively associated with index dir.
858 * Older kernels stored upper fh in ".overlay.origin"
859 * xattr. If that xattr exists, verify that it is a match to
860 * upper dir file handle. In any case, verify or set xattr
861 * ".overlay.upper" to indicate that index may have
862 * directory entries.
863 */
864 if (ovl_check_origin_xattr(ofs, indexdir)) {
865 err = ovl_verify_origin_xattr(ofs, indexdir,
866 OVL_XATTR_ORIGIN,
867 upperpath->dentry, true,
868 false);
869 if (err)
870 pr_err("failed to verify index dir 'origin' xattr\n");
871 }
872 err = ovl_verify_upper(ofs, indexdir, upperpath->dentry, true);
873 if (err)
874 pr_err("failed to verify index dir 'upper' xattr\n");
875
876 /* Cleanup bad/stale/orphan index entries */
877 if (!err)
878 err = ovl_indexdir_cleanup(ofs);
879 }
880 if (err || !indexdir)
881 pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
882
883 out:
884 mnt_drop_write(mnt);
885 out_free_fh:
886 kfree(fh);
887 return err;
888 }
889
890 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
891 {
892 unsigned int i;
893
894 if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
895 return true;
896
897 /*
898 * We allow using single lower with null uuid for index and nfs_export
899 * for example to support those features with single lower squashfs.
900 * To avoid regressions in setups of overlay with re-formatted lower
901 * squashfs, do not allow decoding origin with lower null uuid unless
902 * user opted-in to one of the new features that require following the
903 * lower inode of non-dir upper.
904 */
905 if (ovl_allow_offline_changes(ofs) && uuid_is_null(uuid))
906 return false;
907
908 for (i = 0; i < ofs->numfs; i++) {
909 /*
910 * We use uuid to associate an overlay lower file handle with a
911 * lower layer, so we can accept lower fs with null uuid as long
912 * as all lower layers with null uuid are on the same fs.
913 * if we detect multiple lower fs with the same uuid, we
914 * disable lower file handle decoding on all of them.
915 */
916 if (ofs->fs[i].is_lower &&
917 uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
918 ofs->fs[i].bad_uuid = true;
919 return false;
920 }
921 }
922 return true;
923 }
924
925 /* Get a unique fsid for the layer */
926 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
927 {
928 struct super_block *sb = path->mnt->mnt_sb;
929 unsigned int i;
930 dev_t dev;
931 int err;
932 bool bad_uuid = false;
933 bool warn = false;
934
935 for (i = 0; i < ofs->numfs; i++) {
936 if (ofs->fs[i].sb == sb)
937 return i;
938 }
939
940 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
941 bad_uuid = true;
942 if (ofs->config.xino == OVL_XINO_AUTO) {
943 ofs->config.xino = OVL_XINO_OFF;
944 warn = true;
945 }
946 if (ofs->config.index || ofs->config.nfs_export) {
947 ofs->config.index = false;
948 ofs->config.nfs_export = false;
949 warn = true;
950 }
951 if (warn) {
952 pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n",
953 uuid_is_null(&sb->s_uuid) ? "null" :
954 "conflicting",
955 path->dentry, ovl_xino_mode(&ofs->config));
956 }
957 }
958
959 err = get_anon_bdev(&dev);
960 if (err) {
961 pr_err("failed to get anonymous bdev for lowerpath\n");
962 return err;
963 }
964
965 ofs->fs[ofs->numfs].sb = sb;
966 ofs->fs[ofs->numfs].pseudo_dev = dev;
967 ofs->fs[ofs->numfs].bad_uuid = bad_uuid;
968
969 return ofs->numfs++;
970 }
971
972 /*
973 * The fsid after the last lower fsid is used for the data layers.
974 * It is a "null fs" with a null sb, null uuid, and no pseudo dev.
975 */
976 static int ovl_get_data_fsid(struct ovl_fs *ofs)
977 {
978 return ofs->numfs;
979 }
980
981
982 static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
983 struct ovl_fs_context *ctx, struct ovl_layer *layers)
984 {
985 int err;
986 unsigned int i;
987 size_t nr_merged_lower;
988
989 ofs->fs = kcalloc(ctx->nr + 2, sizeof(struct ovl_sb), GFP_KERNEL);
990 if (ofs->fs == NULL)
991 return -ENOMEM;
992
993 /*
994 * idx/fsid 0 are reserved for upper fs even with lower only overlay
995 * and the last fsid is reserved for "null fs" of the data layers.
996 */
997 ofs->numfs++;
998
999 /*
1000 * All lower layers that share the same fs as upper layer, use the same
1001 * pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower
1002 * only overlay to simplify ovl_fs_free().
1003 * is_lower will be set if upper fs is shared with a lower layer.
1004 */
1005 err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
1006 if (err) {
1007 pr_err("failed to get anonymous bdev for upper fs\n");
1008 return err;
1009 }
1010
1011 if (ovl_upper_mnt(ofs)) {
1012 ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
1013 ofs->fs[0].is_lower = false;
1014 }
1015
1016 nr_merged_lower = ctx->nr - ctx->nr_data;
1017 for (i = 0; i < ctx->nr; i++) {
1018 struct ovl_fs_context_layer *l = &ctx->lower[i];
1019 struct vfsmount *mnt;
1020 struct inode *trap;
1021 int fsid;
1022
1023 if (i < nr_merged_lower)
1024 fsid = ovl_get_fsid(ofs, &l->path);
1025 else
1026 fsid = ovl_get_data_fsid(ofs);
1027 if (fsid < 0)
1028 return fsid;
1029
1030 /*
1031 * Check if lower root conflicts with this overlay layers before
1032 * checking if it is in-use as upperdir/workdir of "another"
1033 * mount, because we do not bother to check in ovl_is_inuse() if
1034 * the upperdir/workdir is in fact in-use by our
1035 * upperdir/workdir.
1036 */
1037 err = ovl_setup_trap(sb, l->path.dentry, &trap, "lowerdir");
1038 if (err)
1039 return err;
1040
1041 if (ovl_is_inuse(l->path.dentry)) {
1042 err = ovl_report_in_use(ofs, "lowerdir");
1043 if (err) {
1044 iput(trap);
1045 return err;
1046 }
1047 }
1048
1049 mnt = clone_private_mount(&l->path);
1050 err = PTR_ERR(mnt);
1051 if (IS_ERR(mnt)) {
1052 pr_err("failed to clone lowerpath\n");
1053 iput(trap);
1054 return err;
1055 }
1056
1057 /*
1058 * Make lower layers R/O. That way fchmod/fchown on lower file
1059 * will fail instead of modifying lower fs.
1060 */
1061 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1062
1063 layers[ofs->numlayer].trap = trap;
1064 layers[ofs->numlayer].mnt = mnt;
1065 layers[ofs->numlayer].idx = ofs->numlayer;
1066 layers[ofs->numlayer].fsid = fsid;
1067 layers[ofs->numlayer].fs = &ofs->fs[fsid];
1068 /* Store for printing lowerdir=... in ovl_show_options() */
1069 ofs->config.lowerdirs[ofs->numlayer] = l->name;
1070 l->name = NULL;
1071 ofs->numlayer++;
1072 ofs->fs[fsid].is_lower = true;
1073 }
1074
1075 /*
1076 * When all layers on same fs, overlay can use real inode numbers.
1077 * With mount option "xino=<on|auto>", mounter declares that there are
1078 * enough free high bits in underlying fs to hold the unique fsid.
1079 * If overlayfs does encounter underlying inodes using the high xino
1080 * bits reserved for fsid, it emits a warning and uses the original
1081 * inode number or a non persistent inode number allocated from a
1082 * dedicated range.
1083 */
1084 if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) {
1085 if (ofs->config.xino == OVL_XINO_ON)
1086 pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
1087 ofs->xino_mode = 0;
1088 } else if (ofs->config.xino == OVL_XINO_OFF) {
1089 ofs->xino_mode = -1;
1090 } else if (ofs->xino_mode < 0) {
1091 /*
1092 * This is a roundup of number of bits needed for encoding
1093 * fsid, where fsid 0 is reserved for upper fs (even with
1094 * lower only overlay) +1 extra bit is reserved for the non
1095 * persistent inode number range that is used for resolving
1096 * xino lower bits overflow.
1097 */
1098 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
1099 ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
1100 }
1101
1102 if (ofs->xino_mode > 0) {
1103 pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
1104 ofs->xino_mode);
1105 }
1106
1107 return 0;
1108 }
1109
1110 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1111 struct ovl_fs_context *ctx,
1112 struct ovl_fs *ofs,
1113 struct ovl_layer *layers)
1114 {
1115 int err;
1116 unsigned int i;
1117 size_t nr_merged_lower;
1118 struct ovl_entry *oe;
1119 struct ovl_path *lowerstack;
1120
1121 struct ovl_fs_context_layer *l;
1122
1123 if (!ofs->config.upperdir && ctx->nr == 1) {
1124 pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
1125 return ERR_PTR(-EINVAL);
1126 }
1127
1128 err = -EINVAL;
1129 for (i = 0; i < ctx->nr; i++) {
1130 l = &ctx->lower[i];
1131
1132 err = ovl_lower_dir(l->name, &l->path, ofs, &sb->s_stack_depth);
1133 if (err)
1134 return ERR_PTR(err);
1135 }
1136
1137 err = -EINVAL;
1138 sb->s_stack_depth++;
1139 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1140 pr_err("maximum fs stacking depth exceeded\n");
1141 return ERR_PTR(err);
1142 }
1143
1144 err = ovl_get_layers(sb, ofs, ctx, layers);
1145 if (err)
1146 return ERR_PTR(err);
1147
1148 err = -ENOMEM;
1149 /* Data-only layers are not merged in root directory */
1150 nr_merged_lower = ctx->nr - ctx->nr_data;
1151 oe = ovl_alloc_entry(nr_merged_lower);
1152 if (!oe)
1153 return ERR_PTR(err);
1154
1155 lowerstack = ovl_lowerstack(oe);
1156 for (i = 0; i < nr_merged_lower; i++) {
1157 l = &ctx->lower[i];
1158 lowerstack[i].dentry = dget(l->path.dentry);
1159 lowerstack[i].layer = &ofs->layers[i + 1];
1160 }
1161 ofs->numdatalayer = ctx->nr_data;
1162
1163 return oe;
1164 }
1165
1166 /*
1167 * Check if this layer root is a descendant of:
1168 * - another layer of this overlayfs instance
1169 * - upper/work dir of any overlayfs instance
1170 */
1171 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
1172 struct dentry *dentry, const char *name,
1173 bool is_lower)
1174 {
1175 struct dentry *next = dentry, *parent;
1176 int err = 0;
1177
1178 if (!dentry)
1179 return 0;
1180
1181 parent = dget_parent(next);
1182
1183 /* Walk back ancestors to root (inclusive) looking for traps */
1184 while (!err && parent != next) {
1185 if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
1186 err = -ELOOP;
1187 pr_err("overlapping %s path\n", name);
1188 } else if (ovl_is_inuse(parent)) {
1189 err = ovl_report_in_use(ofs, name);
1190 }
1191 next = parent;
1192 parent = dget_parent(next);
1193 dput(next);
1194 }
1195
1196 dput(parent);
1197
1198 return err;
1199 }
1200
1201 /*
1202 * Check if any of the layers or work dirs overlap.
1203 */
1204 static int ovl_check_overlapping_layers(struct super_block *sb,
1205 struct ovl_fs *ofs)
1206 {
1207 int i, err;
1208
1209 if (ovl_upper_mnt(ofs)) {
1210 err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
1211 "upperdir", false);
1212 if (err)
1213 return err;
1214
1215 /*
1216 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1217 * this instance and covers overlapping work and index dirs,
1218 * unless work or index dir have been moved since created inside
1219 * workbasedir. In that case, we already have their traps in
1220 * inode cache and we will catch that case on lookup.
1221 */
1222 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
1223 false);
1224 if (err)
1225 return err;
1226 }
1227
1228 for (i = 1; i < ofs->numlayer; i++) {
1229 err = ovl_check_layer(sb, ofs,
1230 ofs->layers[i].mnt->mnt_root,
1231 "lowerdir", true);
1232 if (err)
1233 return err;
1234 }
1235
1236 return 0;
1237 }
1238
1239 static struct dentry *ovl_get_root(struct super_block *sb,
1240 struct dentry *upperdentry,
1241 struct ovl_entry *oe)
1242 {
1243 struct dentry *root;
1244 struct ovl_fs *ofs = OVL_FS(sb);
1245 struct ovl_path *lowerpath = ovl_lowerstack(oe);
1246 unsigned long ino = d_inode(lowerpath->dentry)->i_ino;
1247 int fsid = lowerpath->layer->fsid;
1248 struct ovl_inode_params oip = {
1249 .upperdentry = upperdentry,
1250 .oe = oe,
1251 };
1252
1253 root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1254 if (!root)
1255 return NULL;
1256
1257 if (upperdentry) {
1258 /* Root inode uses upper st_ino/i_ino */
1259 ino = d_inode(upperdentry)->i_ino;
1260 fsid = 0;
1261 ovl_dentry_set_upper_alias(root);
1262 if (ovl_is_impuredir(sb, upperdentry))
1263 ovl_set_flag(OVL_IMPURE, d_inode(root));
1264 }
1265
1266 /* Look for xwhiteouts marker except in the lowermost layer */
1267 for (int i = 0; i < ovl_numlower(oe) - 1; i++, lowerpath++) {
1268 struct path path = {
1269 .mnt = lowerpath->layer->mnt,
1270 .dentry = lowerpath->dentry,
1271 };
1272
1273 /* overlay.opaque=x means xwhiteouts directory */
1274 if (ovl_get_opaquedir_val(ofs, &path) == 'x') {
1275 ovl_layer_set_xwhiteouts(ofs, lowerpath->layer);
1276 ovl_dentry_set_xwhiteouts(root);
1277 }
1278 }
1279
1280 /* Root is always merge -> can have whiteouts */
1281 ovl_set_flag(OVL_WHITEOUTS, d_inode(root));
1282 ovl_dentry_set_flag(OVL_E_CONNECTED, root);
1283 ovl_set_upperdata(d_inode(root));
1284 ovl_inode_init(d_inode(root), &oip, ino, fsid);
1285 ovl_dentry_init_flags(root, upperdentry, oe, DCACHE_OP_WEAK_REVALIDATE);
1286 /* root keeps a reference of upperdentry */
1287 dget(upperdentry);
1288
1289 return root;
1290 }
1291
1292 int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
1293 {
1294 struct ovl_fs *ofs = sb->s_fs_info;
1295 struct ovl_fs_context *ctx = fc->fs_private;
1296 struct dentry *root_dentry;
1297 struct ovl_entry *oe;
1298 struct ovl_layer *layers;
1299 struct cred *cred;
1300 int err;
1301
1302 err = -EIO;
1303 if (WARN_ON(fc->user_ns != current_user_ns()))
1304 goto out_err;
1305
1306 sb->s_d_op = &ovl_dentry_operations;
1307
1308 err = -ENOMEM;
1309 ofs->creator_cred = cred = prepare_creds();
1310 if (!cred)
1311 goto out_err;
1312
1313 err = ovl_fs_params_verify(ctx, &ofs->config);
1314 if (err)
1315 goto out_err;
1316
1317 err = -EINVAL;
1318 if (ctx->nr == 0) {
1319 if (!(fc->sb_flags & SB_SILENT))
1320 pr_err("missing 'lowerdir'\n");
1321 goto out_err;
1322 }
1323
1324 err = -ENOMEM;
1325 layers = kcalloc(ctx->nr + 1, sizeof(struct ovl_layer), GFP_KERNEL);
1326 if (!layers)
1327 goto out_err;
1328
1329 ofs->config.lowerdirs = kcalloc(ctx->nr + 1, sizeof(char *), GFP_KERNEL);
1330 if (!ofs->config.lowerdirs) {
1331 kfree(layers);
1332 goto out_err;
1333 }
1334 ofs->layers = layers;
1335 /*
1336 * Layer 0 is reserved for upper even if there's no upper.
1337 * config.lowerdirs[0] is used for storing the user provided colon
1338 * separated lowerdir string.
1339 */
1340 ofs->config.lowerdirs[0] = ctx->lowerdir_all;
1341 ctx->lowerdir_all = NULL;
1342 ofs->numlayer = 1;
1343
1344 sb->s_stack_depth = 0;
1345 sb->s_maxbytes = MAX_LFS_FILESIZE;
1346 atomic_long_set(&ofs->last_ino, 1);
1347 /* Assume underlying fs uses 32bit inodes unless proven otherwise */
1348 if (ofs->config.xino != OVL_XINO_OFF) {
1349 ofs->xino_mode = BITS_PER_LONG - 32;
1350 if (!ofs->xino_mode) {
1351 pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
1352 ofs->config.xino = OVL_XINO_OFF;
1353 }
1354 }
1355
1356 /* alloc/destroy_inode needed for setting up traps in inode cache */
1357 sb->s_op = &ovl_super_operations;
1358
1359 if (ofs->config.upperdir) {
1360 struct super_block *upper_sb;
1361
1362 err = -EINVAL;
1363 if (!ofs->config.workdir) {
1364 pr_err("missing 'workdir'\n");
1365 goto out_err;
1366 }
1367
1368 err = ovl_get_upper(sb, ofs, &layers[0], &ctx->upper);
1369 if (err)
1370 goto out_err;
1371
1372 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
1373 if (!ovl_should_sync(ofs)) {
1374 ofs->errseq = errseq_sample(&upper_sb->s_wb_err);
1375 if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) {
1376 err = -EIO;
1377 pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n");
1378 goto out_err;
1379 }
1380 }
1381
1382 err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work);
1383 if (err)
1384 goto out_err;
1385
1386 if (!ofs->workdir)
1387 sb->s_flags |= SB_RDONLY;
1388
1389 sb->s_stack_depth = upper_sb->s_stack_depth;
1390 sb->s_time_gran = upper_sb->s_time_gran;
1391 }
1392 oe = ovl_get_lowerstack(sb, ctx, ofs, layers);
1393 err = PTR_ERR(oe);
1394 if (IS_ERR(oe))
1395 goto out_err;
1396
1397 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1398 if (!ovl_upper_mnt(ofs))
1399 sb->s_flags |= SB_RDONLY;
1400
1401 if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) {
1402 pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n");
1403 ofs->config.uuid = OVL_UUID_NULL;
1404 } else if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) {
1405 /* Use per instance persistent uuid/fsid */
1406 ovl_init_uuid_xattr(sb, ofs, &ctx->upper);
1407 }
1408
1409 if (!ovl_force_readonly(ofs) && ofs->config.index) {
1410 err = ovl_get_indexdir(sb, ofs, oe, &ctx->upper);
1411 if (err)
1412 goto out_free_oe;
1413
1414 /* Force r/o mount with no index dir */
1415 if (!ofs->workdir)
1416 sb->s_flags |= SB_RDONLY;
1417 }
1418
1419 err = ovl_check_overlapping_layers(sb, ofs);
1420 if (err)
1421 goto out_free_oe;
1422
1423 /* Show index=off in /proc/mounts for forced r/o mount */
1424 if (!ofs->workdir) {
1425 ofs->config.index = false;
1426 if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
1427 pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
1428 ofs->config.nfs_export = false;
1429 }
1430 }
1431
1432 if (ofs->config.metacopy && ofs->config.nfs_export) {
1433 pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1434 ofs->config.nfs_export = false;
1435 }
1436
1437 /*
1438 * Support encoding decodable file handles with nfs_export=on
1439 * and encoding non-decodable file handles with nfs_export=off
1440 * if all layers support file handles.
1441 */
1442 if (ofs->config.nfs_export)
1443 sb->s_export_op = &ovl_export_operations;
1444 else if (!ofs->nofh)
1445 sb->s_export_op = &ovl_export_fid_operations;
1446
1447 /* Never override disk quota limits or use reserved space */
1448 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1449
1450 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1451 sb->s_xattr = ovl_xattr_handlers(ofs);
1452 sb->s_fs_info = ofs;
1453 #ifdef CONFIG_FS_POSIX_ACL
1454 sb->s_flags |= SB_POSIXACL;
1455 #endif
1456 sb->s_iflags |= SB_I_SKIP_SYNC;
1457 /*
1458 * Ensure that umask handling is done by the filesystems used
1459 * for the the upper layer instead of overlayfs as that would
1460 * lead to unexpected results.
1461 */
1462 sb->s_iflags |= SB_I_NOUMASK;
1463 sb->s_iflags |= SB_I_EVM_HMAC_UNSUPPORTED;
1464
1465 err = -ENOMEM;
1466 root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe);
1467 if (!root_dentry)
1468 goto out_free_oe;
1469
1470 sb->s_root = root_dentry;
1471
1472 return 0;
1473
1474 out_free_oe:
1475 ovl_free_entry(oe);
1476 out_err:
1477 ovl_free_fs(ofs);
1478 sb->s_fs_info = NULL;
1479 return err;
1480 }
1481
1482 struct file_system_type ovl_fs_type = {
1483 .owner = THIS_MODULE,
1484 .name = "overlay",
1485 .init_fs_context = ovl_init_fs_context,
1486 .parameters = ovl_parameter_spec,
1487 .fs_flags = FS_USERNS_MOUNT,
1488 .kill_sb = kill_anon_super,
1489 };
1490 MODULE_ALIAS_FS("overlay");
1491
1492 static void ovl_inode_init_once(void *foo)
1493 {
1494 struct ovl_inode *oi = foo;
1495
1496 inode_init_once(&oi->vfs_inode);
1497 }
1498
1499 static int __init ovl_init(void)
1500 {
1501 int err;
1502
1503 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1504 sizeof(struct ovl_inode), 0,
1505 (SLAB_RECLAIM_ACCOUNT|
1506 SLAB_ACCOUNT),
1507 ovl_inode_init_once);
1508 if (ovl_inode_cachep == NULL)
1509 return -ENOMEM;
1510
1511 err = register_filesystem(&ovl_fs_type);
1512 if (!err)
1513 return 0;
1514
1515 kmem_cache_destroy(ovl_inode_cachep);
1516
1517 return err;
1518 }
1519
1520 static void __exit ovl_exit(void)
1521 {
1522 unregister_filesystem(&ovl_fs_type);
1523
1524 /*
1525 * Make sure all delayed rcu free inodes are flushed before we
1526 * destroy cache.
1527 */
1528 rcu_barrier();
1529 kmem_cache_destroy(ovl_inode_cachep);
1530 }
1531
1532 module_init(ovl_init);
1533 module_exit(ovl_exit);
1534
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