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
ovl_d_real(struct dentry * dentry,enum d_real_type type)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
ovl_revalidate_real(struct dentry * d,unsigned int flags,bool weak)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 struct dentry *parent;
95 struct inode *dir;
96 struct name_snapshot n;
97
98 if (flags & LOOKUP_RCU) {
99 parent = READ_ONCE(d->d_parent);
100 dir = d_inode_rcu(parent);
101 if (!dir)
102 return -ECHILD;
103 } else {
104 parent = dget_parent(d);
105 dir = d_inode(parent);
106 }
107 take_dentry_name_snapshot(&n, d);
108 ret = d->d_op->d_revalidate(dir, &n.name, d, flags);
109 release_dentry_name_snapshot(&n);
110 if (!(flags & LOOKUP_RCU))
111 dput(parent);
112 if (!ret) {
113 if (!(flags & LOOKUP_RCU))
114 d_invalidate(d);
115 ret = -ESTALE;
116 }
117 }
118 return ret;
119 }
120
ovl_dentry_revalidate_common(struct dentry * dentry,unsigned int flags,bool weak)121 static int ovl_dentry_revalidate_common(struct dentry *dentry,
122 unsigned int flags, bool weak)
123 {
124 struct ovl_entry *oe;
125 struct ovl_path *lowerstack;
126 struct inode *inode = d_inode_rcu(dentry);
127 struct dentry *upper;
128 unsigned int i;
129 int ret = 1;
130
131 /* Careful in RCU mode */
132 if (!inode)
133 return -ECHILD;
134
135 oe = OVL_I_E(inode);
136 lowerstack = ovl_lowerstack(oe);
137 upper = ovl_i_dentry_upper(inode);
138 if (upper)
139 ret = ovl_revalidate_real(upper, flags, weak);
140
141 for (i = 0; ret > 0 && i < ovl_numlower(oe); i++)
142 ret = ovl_revalidate_real(lowerstack[i].dentry, flags, weak);
143
144 return ret;
145 }
146
ovl_dentry_revalidate(struct inode * dir,const struct qstr * name,struct dentry * dentry,unsigned int flags)147 static int ovl_dentry_revalidate(struct inode *dir, const struct qstr *name,
148 struct dentry *dentry, unsigned int flags)
149 {
150 return ovl_dentry_revalidate_common(dentry, flags, false);
151 }
152
ovl_dentry_weak_revalidate(struct dentry * dentry,unsigned int flags)153 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
154 {
155 return ovl_dentry_revalidate_common(dentry, flags, true);
156 }
157
158 static const struct dentry_operations ovl_dentry_operations = {
159 .d_real = ovl_d_real,
160 .d_revalidate = ovl_dentry_revalidate,
161 .d_weak_revalidate = ovl_dentry_weak_revalidate,
162 };
163
164 #if IS_ENABLED(CONFIG_UNICODE)
165 static const struct dentry_operations ovl_dentry_ci_operations = {
166 .d_real = ovl_d_real,
167 .d_revalidate = ovl_dentry_revalidate,
168 .d_weak_revalidate = ovl_dentry_weak_revalidate,
169 .d_hash = generic_ci_d_hash,
170 .d_compare = generic_ci_d_compare,
171 };
172 #endif
173
174 static struct kmem_cache *ovl_inode_cachep;
175
ovl_alloc_inode(struct super_block * sb)176 static struct inode *ovl_alloc_inode(struct super_block *sb)
177 {
178 struct ovl_inode *oi = alloc_inode_sb(sb, ovl_inode_cachep, GFP_KERNEL);
179
180 if (!oi)
181 return NULL;
182
183 oi->cache = NULL;
184 oi->redirect = NULL;
185 oi->version = 0;
186 oi->flags = 0;
187 oi->__upperdentry = NULL;
188 oi->lowerdata_redirect = NULL;
189 oi->oe = NULL;
190 mutex_init(&oi->lock);
191
192 return &oi->vfs_inode;
193 }
194
ovl_free_inode(struct inode * inode)195 static void ovl_free_inode(struct inode *inode)
196 {
197 struct ovl_inode *oi = OVL_I(inode);
198
199 kfree(oi->redirect);
200 kfree(oi->oe);
201 mutex_destroy(&oi->lock);
202 kmem_cache_free(ovl_inode_cachep, oi);
203 }
204
ovl_destroy_inode(struct inode * inode)205 static void ovl_destroy_inode(struct inode *inode)
206 {
207 struct ovl_inode *oi = OVL_I(inode);
208
209 dput(oi->__upperdentry);
210 ovl_stack_put(ovl_lowerstack(oi->oe), ovl_numlower(oi->oe));
211 if (S_ISDIR(inode->i_mode))
212 ovl_dir_cache_free(inode);
213 else
214 kfree(oi->lowerdata_redirect);
215 }
216
ovl_put_super(struct super_block * sb)217 static void ovl_put_super(struct super_block *sb)
218 {
219 struct ovl_fs *ofs = OVL_FS(sb);
220
221 if (ofs)
222 ovl_free_fs(ofs);
223 }
224
225 /* Sync real dirty inodes in upper filesystem (if it exists) */
ovl_sync_fs(struct super_block * sb,int wait)226 static int ovl_sync_fs(struct super_block *sb, int wait)
227 {
228 struct ovl_fs *ofs = OVL_FS(sb);
229 struct super_block *upper_sb;
230 int ret;
231
232 ret = ovl_sync_status(ofs);
233
234 if (ret < 0)
235 return -EIO;
236
237 if (!ret)
238 return ret;
239
240 /*
241 * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
242 * All the super blocks will be iterated, including upper_sb.
243 *
244 * If this is a syncfs(2) call, then we do need to call
245 * sync_filesystem() on upper_sb, but enough if we do it when being
246 * called with wait == 1.
247 */
248 if (!wait)
249 return 0;
250
251 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
252
253 down_read(&upper_sb->s_umount);
254 ret = sync_filesystem(upper_sb);
255 up_read(&upper_sb->s_umount);
256
257 return ret;
258 }
259
260 /**
261 * ovl_statfs
262 * @dentry: The dentry to query
263 * @buf: The struct kstatfs to fill in with stats
264 *
265 * Get the filesystem statistics. As writes always target the upper layer
266 * filesystem pass the statfs to the upper filesystem (if it exists)
267 */
ovl_statfs(struct dentry * dentry,struct kstatfs * buf)268 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
269 {
270 struct super_block *sb = dentry->d_sb;
271 struct ovl_fs *ofs = OVL_FS(sb);
272 struct dentry *root_dentry = sb->s_root;
273 struct path path;
274 int err;
275
276 ovl_path_real(root_dentry, &path);
277
278 err = vfs_statfs(&path, buf);
279 if (!err) {
280 buf->f_namelen = ofs->namelen;
281 buf->f_type = OVERLAYFS_SUPER_MAGIC;
282 if (ovl_has_fsid(ofs))
283 buf->f_fsid = uuid_to_fsid(sb->s_uuid.b);
284 }
285
286 return err;
287 }
288
289 static const struct super_operations ovl_super_operations = {
290 .alloc_inode = ovl_alloc_inode,
291 .free_inode = ovl_free_inode,
292 .destroy_inode = ovl_destroy_inode,
293 .drop_inode = inode_just_drop,
294 .put_super = ovl_put_super,
295 .sync_fs = ovl_sync_fs,
296 .statfs = ovl_statfs,
297 .show_options = ovl_show_options,
298 };
299
300 #define OVL_WORKDIR_NAME "work"
301 #define OVL_INDEXDIR_NAME "index"
302
ovl_workdir_create(struct ovl_fs * ofs,const char * name,bool persist)303 static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
304 const char *name, bool persist)
305 {
306 struct inode *dir = ofs->workbasedir->d_inode;
307 struct vfsmount *mnt = ovl_upper_mnt(ofs);
308 struct dentry *work;
309 int err;
310 bool retried = false;
311
312 retry:
313 inode_lock_nested(dir, I_MUTEX_PARENT);
314 work = ovl_lookup_upper(ofs, name, ofs->workbasedir, strlen(name));
315
316 if (!IS_ERR(work)) {
317 struct iattr attr = {
318 .ia_valid = ATTR_MODE,
319 .ia_mode = S_IFDIR | 0,
320 };
321
322 if (work->d_inode) {
323 err = -EEXIST;
324 inode_unlock(dir);
325 if (retried)
326 goto out_dput;
327
328 if (persist)
329 return work;
330
331 retried = true;
332 err = ovl_workdir_cleanup(ofs, ofs->workbasedir, mnt, work, 0);
333 dput(work);
334 if (err == -EINVAL)
335 return ERR_PTR(err);
336
337 goto retry;
338 }
339
340 work = ovl_do_mkdir(ofs, dir, work, attr.ia_mode);
341 inode_unlock(dir);
342 err = PTR_ERR(work);
343 if (IS_ERR(work))
344 goto out_err;
345
346 /* Weird filesystem returning with hashed negative (kernfs)? */
347 err = -EINVAL;
348 if (d_really_is_negative(work))
349 goto out_dput;
350
351 /*
352 * Try to remove POSIX ACL xattrs from workdir. We are good if:
353 *
354 * a) success (there was a POSIX ACL xattr and was removed)
355 * b) -ENODATA (there was no POSIX ACL xattr)
356 * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
357 *
358 * There are various other error values that could effectively
359 * mean that the xattr doesn't exist (e.g. -ERANGE is returned
360 * if the xattr name is too long), but the set of filesystems
361 * allowed as upper are limited to "normal" ones, where checking
362 * for the above two errors is sufficient.
363 */
364 err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_DEFAULT);
365 if (err && err != -ENODATA && err != -EOPNOTSUPP)
366 goto out_dput;
367
368 err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_ACCESS);
369 if (err && err != -ENODATA && err != -EOPNOTSUPP)
370 goto out_dput;
371
372 /* Clear any inherited mode bits */
373 inode_lock(work->d_inode);
374 err = ovl_do_notify_change(ofs, work, &attr);
375 inode_unlock(work->d_inode);
376 if (err)
377 goto out_dput;
378 } else {
379 inode_unlock(dir);
380 err = PTR_ERR(work);
381 goto out_err;
382 }
383 return work;
384
385 out_dput:
386 dput(work);
387 out_err:
388 pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
389 ofs->config.workdir, name, -err);
390 return NULL;
391 }
392
ovl_check_namelen(const struct path * path,struct ovl_fs * ofs,const char * name)393 static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs,
394 const char *name)
395 {
396 struct kstatfs statfs;
397 int err = vfs_statfs(path, &statfs);
398
399 if (err)
400 pr_err("statfs failed on '%s'\n", name);
401 else
402 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
403
404 return err;
405 }
406
ovl_lower_dir(const char * name,const struct path * path,struct ovl_fs * ofs,int * stack_depth)407 static int ovl_lower_dir(const char *name, const struct path *path,
408 struct ovl_fs *ofs, int *stack_depth)
409 {
410 int fh_type;
411 int err;
412
413 err = ovl_check_namelen(path, ofs, name);
414 if (err)
415 return err;
416
417 *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
418
419 /*
420 * The inodes index feature and NFS export need to encode and decode
421 * file handles, so they require that all layers support them.
422 */
423 fh_type = ovl_can_decode_fh(path->dentry->d_sb);
424 if ((ofs->config.nfs_export ||
425 (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
426 ofs->config.index = false;
427 ofs->config.nfs_export = false;
428 pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
429 name);
430 }
431 ofs->nofh |= !fh_type;
432 /*
433 * Decoding origin file handle is required for persistent st_ino.
434 * Without persistent st_ino, xino=auto falls back to xino=off.
435 */
436 if (ofs->config.xino == OVL_XINO_AUTO &&
437 ofs->config.upperdir && !fh_type) {
438 ofs->config.xino = OVL_XINO_OFF;
439 pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n",
440 name);
441 }
442
443 /* Check if lower fs has 32bit inode numbers */
444 if (fh_type != FILEID_INO32_GEN)
445 ofs->xino_mode = -1;
446
447 return 0;
448 }
449
450 /* Workdir should not be subdir of upperdir and vice versa */
ovl_workdir_ok(struct dentry * workdir,struct dentry * upperdir)451 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
452 {
453 bool ok = false;
454
455 if (workdir != upperdir) {
456 struct dentry *trap = lock_rename(workdir, upperdir);
457 if (!IS_ERR(trap))
458 unlock_rename(workdir, upperdir);
459 ok = (trap == NULL);
460 }
461 return ok;
462 }
463
ovl_setup_trap(struct super_block * sb,struct dentry * dir,struct inode ** ptrap,const char * name)464 static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
465 struct inode **ptrap, const char *name)
466 {
467 struct inode *trap;
468 int err;
469
470 trap = ovl_get_trap_inode(sb, dir);
471 err = PTR_ERR_OR_ZERO(trap);
472 if (err) {
473 if (err == -ELOOP)
474 pr_err("conflicting %s path\n", name);
475 return err;
476 }
477
478 *ptrap = trap;
479 return 0;
480 }
481
482 /*
483 * Determine how we treat concurrent use of upperdir/workdir based on the
484 * index feature. This is papering over mount leaks of container runtimes,
485 * for example, an old overlay mount is leaked and now its upperdir is
486 * attempted to be used as a lower layer in a new overlay mount.
487 */
ovl_report_in_use(struct ovl_fs * ofs,const char * name)488 static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
489 {
490 if (ofs->config.index) {
491 pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
492 name);
493 return -EBUSY;
494 } else {
495 pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
496 name);
497 return 0;
498 }
499 }
500
ovl_get_upper(struct super_block * sb,struct ovl_fs * ofs,struct ovl_layer * upper_layer,const struct path * upperpath)501 static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
502 struct ovl_layer *upper_layer,
503 const struct path *upperpath)
504 {
505 struct vfsmount *upper_mnt;
506 int err;
507
508 /* Upperdir path should not be r/o */
509 if (__mnt_is_readonly(upperpath->mnt)) {
510 pr_err("upper fs is r/o, try multi-lower layers mount\n");
511 err = -EINVAL;
512 goto out;
513 }
514
515 err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
516 if (err)
517 goto out;
518
519 err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap,
520 "upperdir");
521 if (err)
522 goto out;
523
524 upper_mnt = clone_private_mount(upperpath);
525 err = PTR_ERR(upper_mnt);
526 if (IS_ERR(upper_mnt)) {
527 pr_err("failed to clone upperpath\n");
528 goto out;
529 }
530
531 /* Don't inherit atime flags */
532 upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
533 upper_layer->mnt = upper_mnt;
534 upper_layer->idx = 0;
535 upper_layer->fsid = 0;
536
537 /*
538 * Inherit SB_NOSEC flag from upperdir.
539 *
540 * This optimization changes behavior when a security related attribute
541 * (suid/sgid/security.*) is changed on an underlying layer. This is
542 * okay because we don't yet have guarantees in that case, but it will
543 * need careful treatment once we want to honour changes to underlying
544 * filesystems.
545 */
546 if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
547 sb->s_flags |= SB_NOSEC;
548
549 if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
550 ofs->upperdir_locked = true;
551 } else {
552 err = ovl_report_in_use(ofs, "upperdir");
553 if (err)
554 goto out;
555 }
556
557 err = 0;
558 out:
559 return err;
560 }
561
562 /*
563 * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
564 * negative values if error is encountered.
565 */
ovl_check_rename_whiteout(struct ovl_fs * ofs)566 static int ovl_check_rename_whiteout(struct ovl_fs *ofs)
567 {
568 struct dentry *workdir = ofs->workdir;
569 struct dentry *temp;
570 struct dentry *dest;
571 struct dentry *whiteout;
572 struct name_snapshot name;
573 int err;
574
575 temp = ovl_create_temp(ofs, workdir, OVL_CATTR(S_IFREG | 0));
576 err = PTR_ERR(temp);
577 if (IS_ERR(temp))
578 return err;
579
580 err = ovl_parent_lock(workdir, temp);
581 if (err) {
582 dput(temp);
583 return err;
584 }
585 dest = ovl_lookup_temp(ofs, workdir);
586 err = PTR_ERR(dest);
587 if (IS_ERR(dest)) {
588 dput(temp);
589 ovl_parent_unlock(workdir);
590 return err;
591 }
592
593 /* Name is inline and stable - using snapshot as a copy helper */
594 take_dentry_name_snapshot(&name, temp);
595 err = ovl_do_rename(ofs, workdir, temp, workdir, dest, RENAME_WHITEOUT);
596 ovl_parent_unlock(workdir);
597 if (err) {
598 if (err == -EINVAL)
599 err = 0;
600 goto cleanup_temp;
601 }
602
603 whiteout = ovl_lookup_upper_unlocked(ofs, name.name.name,
604 workdir, name.name.len);
605 err = PTR_ERR(whiteout);
606 if (IS_ERR(whiteout))
607 goto cleanup_temp;
608
609 err = ovl_upper_is_whiteout(ofs, whiteout);
610
611 /* Best effort cleanup of whiteout and temp file */
612 if (err)
613 ovl_cleanup(ofs, workdir, whiteout);
614 dput(whiteout);
615
616 cleanup_temp:
617 ovl_cleanup(ofs, workdir, temp);
618 release_dentry_name_snapshot(&name);
619 dput(temp);
620 dput(dest);
621
622 return err;
623 }
624
ovl_lookup_or_create(struct ovl_fs * ofs,struct dentry * parent,const char * name,umode_t mode)625 static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs,
626 struct dentry *parent,
627 const char *name, umode_t mode)
628 {
629 size_t len = strlen(name);
630 struct dentry *child;
631
632 inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
633 child = ovl_lookup_upper(ofs, name, parent, len);
634 if (!IS_ERR(child) && !child->d_inode)
635 child = ovl_create_real(ofs, parent, child, OVL_CATTR(mode));
636 inode_unlock(parent->d_inode);
637 dput(parent);
638
639 return child;
640 }
641
642 /*
643 * Creates $workdir/work/incompat/volatile/dirty file if it is not already
644 * present.
645 */
ovl_create_volatile_dirty(struct ovl_fs * ofs)646 static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
647 {
648 unsigned int ctr;
649 struct dentry *d = dget(ofs->workbasedir);
650 static const char *const volatile_path[] = {
651 OVL_WORKDIR_NAME, "incompat", "volatile", "dirty"
652 };
653 const char *const *name = volatile_path;
654
655 for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) {
656 d = ovl_lookup_or_create(ofs, d, *name, ctr > 1 ? S_IFDIR : S_IFREG);
657 if (IS_ERR(d))
658 return PTR_ERR(d);
659 }
660 dput(d);
661 return 0;
662 }
663
ovl_make_workdir(struct super_block * sb,struct ovl_fs * ofs,const struct path * workpath)664 static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
665 const struct path *workpath)
666 {
667 struct vfsmount *mnt = ovl_upper_mnt(ofs);
668 struct dentry *workdir;
669 struct file *tmpfile;
670 bool rename_whiteout;
671 bool d_type;
672 int fh_type;
673 int err;
674
675 err = mnt_want_write(mnt);
676 if (err)
677 return err;
678
679 workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
680 err = PTR_ERR(workdir);
681 if (IS_ERR_OR_NULL(workdir))
682 goto out;
683
684 ofs->workdir = workdir;
685
686 err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
687 if (err)
688 goto out;
689
690 /*
691 * Upper should support d_type, else whiteouts are visible. Given
692 * workdir and upper are on same fs, we can do iterate_dir() on
693 * workdir. This check requires successful creation of workdir in
694 * previous step.
695 */
696 err = ovl_check_d_type_supported(workpath);
697 if (err < 0)
698 goto out;
699
700 d_type = err;
701 if (!d_type)
702 pr_warn("upper fs needs to support d_type.\n");
703
704 /* Check if upper/work fs supports O_TMPFILE */
705 tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0);
706 ofs->tmpfile = !IS_ERR(tmpfile);
707 if (ofs->tmpfile)
708 fput(tmpfile);
709 else
710 pr_warn("upper fs does not support tmpfile.\n");
711
712
713 /* Check if upper/work fs supports RENAME_WHITEOUT */
714 err = ovl_check_rename_whiteout(ofs);
715 if (err < 0)
716 goto out;
717
718 rename_whiteout = err;
719 if (!rename_whiteout)
720 pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
721
722 /*
723 * Check if upper/work fs supports (trusted|user).overlay.* xattr
724 */
725 err = ovl_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1);
726 if (err) {
727 pr_warn("failed to set xattr on upper\n");
728 ofs->noxattr = true;
729 if (ovl_redirect_follow(ofs)) {
730 ofs->config.redirect_mode = OVL_REDIRECT_NOFOLLOW;
731 pr_warn("...falling back to redirect_dir=nofollow.\n");
732 }
733 if (ofs->config.metacopy) {
734 ofs->config.metacopy = false;
735 pr_warn("...falling back to metacopy=off.\n");
736 }
737 if (ofs->config.index) {
738 ofs->config.index = false;
739 pr_warn("...falling back to index=off.\n");
740 }
741 if (ovl_has_fsid(ofs)) {
742 ofs->config.uuid = OVL_UUID_NULL;
743 pr_warn("...falling back to uuid=null.\n");
744 }
745 /*
746 * xattr support is required for persistent st_ino.
747 * Without persistent st_ino, xino=auto falls back to xino=off.
748 */
749 if (ofs->config.xino == OVL_XINO_AUTO) {
750 ofs->config.xino = OVL_XINO_OFF;
751 pr_warn("...falling back to xino=off.\n");
752 }
753 if (err == -EPERM && !ofs->config.userxattr)
754 pr_info("try mounting with 'userxattr' option\n");
755 err = 0;
756 } else {
757 ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
758 }
759
760 /*
761 * We allowed sub-optimal upper fs configuration and don't want to break
762 * users over kernel upgrade, but we never allowed remote upper fs, so
763 * we can enforce strict requirements for remote upper fs.
764 */
765 if (ovl_dentry_remote(ofs->workdir) &&
766 (!d_type || !rename_whiteout || ofs->noxattr)) {
767 pr_err("upper fs missing required features.\n");
768 err = -EINVAL;
769 goto out;
770 }
771
772 /*
773 * For volatile mount, create a incompat/volatile/dirty file to keep
774 * track of it.
775 */
776 if (ofs->config.ovl_volatile) {
777 err = ovl_create_volatile_dirty(ofs);
778 if (err < 0) {
779 pr_err("Failed to create volatile/dirty file.\n");
780 goto out;
781 }
782 }
783
784 /* Check if upper/work fs supports file handles */
785 fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
786 if (ofs->config.index && !fh_type) {
787 ofs->config.index = false;
788 pr_warn("upper fs does not support file handles, falling back to index=off.\n");
789 }
790 ofs->nofh |= !fh_type;
791
792 /* Check if upper fs has 32bit inode numbers */
793 if (fh_type != FILEID_INO32_GEN)
794 ofs->xino_mode = -1;
795
796 /* NFS export of r/w mount depends on index */
797 if (ofs->config.nfs_export && !ofs->config.index) {
798 pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
799 ofs->config.nfs_export = false;
800 }
801 out:
802 mnt_drop_write(mnt);
803 return err;
804 }
805
ovl_get_workdir(struct super_block * sb,struct ovl_fs * ofs,const struct path * upperpath,const struct path * workpath)806 static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
807 const struct path *upperpath,
808 const struct path *workpath)
809 {
810 int err;
811
812 err = -EINVAL;
813 if (upperpath->mnt != workpath->mnt) {
814 pr_err("workdir and upperdir must reside under the same mount\n");
815 return err;
816 }
817 if (!ovl_workdir_ok(workpath->dentry, upperpath->dentry)) {
818 pr_err("workdir and upperdir must be separate subtrees\n");
819 return err;
820 }
821
822 ofs->workbasedir = dget(workpath->dentry);
823
824 if (ovl_inuse_trylock(ofs->workbasedir)) {
825 ofs->workdir_locked = true;
826 } else {
827 err = ovl_report_in_use(ofs, "workdir");
828 if (err)
829 return err;
830 }
831
832 err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
833 "workdir");
834 if (err)
835 return err;
836
837 return ovl_make_workdir(sb, ofs, workpath);
838 }
839
ovl_get_indexdir(struct super_block * sb,struct ovl_fs * ofs,struct ovl_entry * oe,const struct path * upperpath)840 static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
841 struct ovl_entry *oe, const struct path *upperpath)
842 {
843 struct vfsmount *mnt = ovl_upper_mnt(ofs);
844 struct dentry *indexdir;
845 struct dentry *origin = ovl_lowerstack(oe)->dentry;
846 const struct ovl_fh *fh;
847 int err;
848
849 fh = ovl_get_origin_fh(ofs, origin);
850 if (IS_ERR(fh))
851 return PTR_ERR(fh);
852
853 err = mnt_want_write(mnt);
854 if (err)
855 goto out_free_fh;
856
857 /* Verify lower root is upper root origin */
858 err = ovl_verify_origin_fh(ofs, upperpath->dentry, fh, true);
859 if (err) {
860 pr_err("failed to verify upper root origin\n");
861 goto out;
862 }
863
864 /* index dir will act also as workdir */
865 iput(ofs->workdir_trap);
866 ofs->workdir_trap = NULL;
867 dput(ofs->workdir);
868 ofs->workdir = NULL;
869 indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
870 if (IS_ERR(indexdir)) {
871 err = PTR_ERR(indexdir);
872 } else if (indexdir) {
873 ofs->workdir = indexdir;
874 err = ovl_setup_trap(sb, indexdir, &ofs->workdir_trap,
875 "indexdir");
876 if (err)
877 goto out;
878
879 /*
880 * Verify upper root is exclusively associated with index dir.
881 * Older kernels stored upper fh in ".overlay.origin"
882 * xattr. If that xattr exists, verify that it is a match to
883 * upper dir file handle. In any case, verify or set xattr
884 * ".overlay.upper" to indicate that index may have
885 * directory entries.
886 */
887 if (ovl_check_origin_xattr(ofs, indexdir)) {
888 err = ovl_verify_origin_xattr(ofs, indexdir,
889 OVL_XATTR_ORIGIN,
890 upperpath->dentry, true,
891 false);
892 if (err)
893 pr_err("failed to verify index dir 'origin' xattr\n");
894 }
895 err = ovl_verify_upper(ofs, indexdir, upperpath->dentry, true);
896 if (err)
897 pr_err("failed to verify index dir 'upper' xattr\n");
898
899 /* Cleanup bad/stale/orphan index entries */
900 if (!err)
901 err = ovl_indexdir_cleanup(ofs);
902 }
903 if (err || !indexdir)
904 pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
905
906 out:
907 mnt_drop_write(mnt);
908 out_free_fh:
909 kfree(fh);
910 return err;
911 }
912
ovl_lower_uuid_ok(struct ovl_fs * ofs,const uuid_t * uuid)913 static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
914 {
915 unsigned int i;
916
917 if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
918 return true;
919
920 /*
921 * We allow using single lower with null uuid for index and nfs_export
922 * for example to support those features with single lower squashfs.
923 * To avoid regressions in setups of overlay with re-formatted lower
924 * squashfs, do not allow decoding origin with lower null uuid unless
925 * user opted-in to one of the new features that require following the
926 * lower inode of non-dir upper.
927 */
928 if (ovl_allow_offline_changes(ofs) && uuid_is_null(uuid))
929 return false;
930
931 for (i = 0; i < ofs->numfs; i++) {
932 /*
933 * We use uuid to associate an overlay lower file handle with a
934 * lower layer, so we can accept lower fs with null uuid as long
935 * as all lower layers with null uuid are on the same fs.
936 * if we detect multiple lower fs with the same uuid, we
937 * disable lower file handle decoding on all of them.
938 */
939 if (ofs->fs[i].is_lower &&
940 uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
941 ofs->fs[i].bad_uuid = true;
942 return false;
943 }
944 }
945 return true;
946 }
947
948 /* Get a unique fsid for the layer */
ovl_get_fsid(struct ovl_fs * ofs,const struct path * path)949 static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
950 {
951 struct super_block *sb = path->mnt->mnt_sb;
952 unsigned int i;
953 dev_t dev;
954 int err;
955 bool bad_uuid = false;
956 bool warn = false;
957
958 for (i = 0; i < ofs->numfs; i++) {
959 if (ofs->fs[i].sb == sb)
960 return i;
961 }
962
963 if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
964 bad_uuid = true;
965 if (ofs->config.xino == OVL_XINO_AUTO) {
966 ofs->config.xino = OVL_XINO_OFF;
967 warn = true;
968 }
969 if (ofs->config.index || ofs->config.nfs_export) {
970 ofs->config.index = false;
971 ofs->config.nfs_export = false;
972 warn = true;
973 }
974 if (warn) {
975 pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n",
976 uuid_is_null(&sb->s_uuid) ? "null" :
977 "conflicting",
978 path->dentry, ovl_xino_mode(&ofs->config));
979 }
980 }
981
982 err = get_anon_bdev(&dev);
983 if (err) {
984 pr_err("failed to get anonymous bdev for lowerpath\n");
985 return err;
986 }
987
988 ofs->fs[ofs->numfs].sb = sb;
989 ofs->fs[ofs->numfs].pseudo_dev = dev;
990 ofs->fs[ofs->numfs].bad_uuid = bad_uuid;
991
992 return ofs->numfs++;
993 }
994
995 /*
996 * The fsid after the last lower fsid is used for the data layers.
997 * It is a "null fs" with a null sb, null uuid, and no pseudo dev.
998 */
ovl_get_data_fsid(struct ovl_fs * ofs)999 static int ovl_get_data_fsid(struct ovl_fs *ofs)
1000 {
1001 return ofs->numfs;
1002 }
1003
1004 /*
1005 * Set the ovl sb encoding as the same one used by the first layer
1006 */
ovl_set_encoding(struct super_block * sb,struct super_block * fs_sb)1007 static int ovl_set_encoding(struct super_block *sb, struct super_block *fs_sb)
1008 {
1009 if (!sb_has_encoding(fs_sb))
1010 return 0;
1011
1012 #if IS_ENABLED(CONFIG_UNICODE)
1013 if (sb_has_strict_encoding(fs_sb)) {
1014 pr_err("strict encoding not supported\n");
1015 return -EINVAL;
1016 }
1017
1018 sb->s_encoding = fs_sb->s_encoding;
1019 sb->s_encoding_flags = fs_sb->s_encoding_flags;
1020 #endif
1021 return 0;
1022 }
1023
ovl_get_layers(struct super_block * sb,struct ovl_fs * ofs,struct ovl_fs_context * ctx,struct ovl_layer * layers)1024 static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
1025 struct ovl_fs_context *ctx, struct ovl_layer *layers)
1026 {
1027 int err;
1028 unsigned int i;
1029 size_t nr_merged_lower;
1030
1031 ofs->fs = kcalloc(ctx->nr + 2, sizeof(struct ovl_sb), GFP_KERNEL);
1032 if (ofs->fs == NULL)
1033 return -ENOMEM;
1034
1035 /*
1036 * idx/fsid 0 are reserved for upper fs even with lower only overlay
1037 * and the last fsid is reserved for "null fs" of the data layers.
1038 */
1039 ofs->numfs++;
1040
1041 /*
1042 * All lower layers that share the same fs as upper layer, use the same
1043 * pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower
1044 * only overlay to simplify ovl_fs_free().
1045 * is_lower will be set if upper fs is shared with a lower layer.
1046 */
1047 err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
1048 if (err) {
1049 pr_err("failed to get anonymous bdev for upper fs\n");
1050 return err;
1051 }
1052
1053 if (ovl_upper_mnt(ofs)) {
1054 ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
1055 ofs->fs[0].is_lower = false;
1056
1057 if (ofs->casefold) {
1058 err = ovl_set_encoding(sb, ofs->fs[0].sb);
1059 if (err)
1060 return err;
1061 }
1062 }
1063
1064 nr_merged_lower = ctx->nr - ctx->nr_data;
1065 for (i = 0; i < ctx->nr; i++) {
1066 struct ovl_fs_context_layer *l = &ctx->lower[i];
1067 struct vfsmount *mnt;
1068 struct inode *trap;
1069 int fsid;
1070
1071 if (i < nr_merged_lower)
1072 fsid = ovl_get_fsid(ofs, &l->path);
1073 else
1074 fsid = ovl_get_data_fsid(ofs);
1075 if (fsid < 0)
1076 return fsid;
1077
1078 /*
1079 * Check if lower root conflicts with this overlay layers before
1080 * checking if it is in-use as upperdir/workdir of "another"
1081 * mount, because we do not bother to check in ovl_is_inuse() if
1082 * the upperdir/workdir is in fact in-use by our
1083 * upperdir/workdir.
1084 */
1085 err = ovl_setup_trap(sb, l->path.dentry, &trap, "lowerdir");
1086 if (err)
1087 return err;
1088
1089 if (ovl_is_inuse(l->path.dentry)) {
1090 err = ovl_report_in_use(ofs, "lowerdir");
1091 if (err) {
1092 iput(trap);
1093 return err;
1094 }
1095 }
1096
1097 mnt = clone_private_mount(&l->path);
1098 err = PTR_ERR(mnt);
1099 if (IS_ERR(mnt)) {
1100 pr_err("failed to clone lowerpath\n");
1101 iput(trap);
1102 return err;
1103 }
1104
1105 /*
1106 * Make lower layers R/O. That way fchmod/fchown on lower file
1107 * will fail instead of modifying lower fs.
1108 */
1109 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
1110
1111 layers[ofs->numlayer].trap = trap;
1112 layers[ofs->numlayer].mnt = mnt;
1113 layers[ofs->numlayer].idx = ofs->numlayer;
1114 layers[ofs->numlayer].fsid = fsid;
1115 layers[ofs->numlayer].fs = &ofs->fs[fsid];
1116 /* Store for printing lowerdir=... in ovl_show_options() */
1117 ofs->config.lowerdirs[ofs->numlayer] = l->name;
1118 l->name = NULL;
1119 ofs->numlayer++;
1120 ofs->fs[fsid].is_lower = true;
1121
1122 if (ofs->casefold) {
1123 if (!ovl_upper_mnt(ofs) && !sb_has_encoding(sb)) {
1124 err = ovl_set_encoding(sb, ofs->fs[fsid].sb);
1125 if (err)
1126 return err;
1127 }
1128
1129 if (!sb_same_encoding(sb, mnt->mnt_sb)) {
1130 pr_err("all layers must have the same encoding\n");
1131 return -EINVAL;
1132 }
1133 }
1134 }
1135
1136 /*
1137 * When all layers on same fs, overlay can use real inode numbers.
1138 * With mount option "xino=<on|auto>", mounter declares that there are
1139 * enough free high bits in underlying fs to hold the unique fsid.
1140 * If overlayfs does encounter underlying inodes using the high xino
1141 * bits reserved for fsid, it emits a warning and uses the original
1142 * inode number or a non persistent inode number allocated from a
1143 * dedicated range.
1144 */
1145 if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) {
1146 if (ofs->config.xino == OVL_XINO_ON)
1147 pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
1148 ofs->xino_mode = 0;
1149 } else if (ofs->config.xino == OVL_XINO_OFF) {
1150 ofs->xino_mode = -1;
1151 } else if (ofs->xino_mode < 0) {
1152 /*
1153 * This is a roundup of number of bits needed for encoding
1154 * fsid, where fsid 0 is reserved for upper fs (even with
1155 * lower only overlay) +1 extra bit is reserved for the non
1156 * persistent inode number range that is used for resolving
1157 * xino lower bits overflow.
1158 */
1159 BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
1160 ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
1161 }
1162
1163 if (ofs->xino_mode > 0) {
1164 pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
1165 ofs->xino_mode);
1166 }
1167
1168 return 0;
1169 }
1170
ovl_get_lowerstack(struct super_block * sb,struct ovl_fs_context * ctx,struct ovl_fs * ofs,struct ovl_layer * layers)1171 static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
1172 struct ovl_fs_context *ctx,
1173 struct ovl_fs *ofs,
1174 struct ovl_layer *layers)
1175 {
1176 int err;
1177 unsigned int i;
1178 size_t nr_merged_lower;
1179 struct ovl_entry *oe;
1180 struct ovl_path *lowerstack;
1181
1182 struct ovl_fs_context_layer *l;
1183
1184 if (!ofs->config.upperdir && ctx->nr == 1) {
1185 pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
1186 return ERR_PTR(-EINVAL);
1187 }
1188
1189 if (ctx->nr == ctx->nr_data) {
1190 pr_err("at least one non-data lowerdir is required\n");
1191 return ERR_PTR(-EINVAL);
1192 }
1193
1194 err = -EINVAL;
1195 for (i = 0; i < ctx->nr; i++) {
1196 l = &ctx->lower[i];
1197
1198 err = ovl_lower_dir(l->name, &l->path, ofs, &sb->s_stack_depth);
1199 if (err)
1200 return ERR_PTR(err);
1201 }
1202
1203 err = -EINVAL;
1204 sb->s_stack_depth++;
1205 if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
1206 pr_err("maximum fs stacking depth exceeded\n");
1207 return ERR_PTR(err);
1208 }
1209
1210 err = ovl_get_layers(sb, ofs, ctx, layers);
1211 if (err)
1212 return ERR_PTR(err);
1213
1214 err = -ENOMEM;
1215 /* Data-only layers are not merged in root directory */
1216 nr_merged_lower = ctx->nr - ctx->nr_data;
1217 oe = ovl_alloc_entry(nr_merged_lower);
1218 if (!oe)
1219 return ERR_PTR(err);
1220
1221 lowerstack = ovl_lowerstack(oe);
1222 for (i = 0; i < nr_merged_lower; i++) {
1223 l = &ctx->lower[i];
1224 lowerstack[i].dentry = dget(l->path.dentry);
1225 lowerstack[i].layer = &ofs->layers[i + 1];
1226 }
1227 ofs->numdatalayer = ctx->nr_data;
1228
1229 return oe;
1230 }
1231
1232 /*
1233 * Check if this layer root is a descendant of:
1234 * - another layer of this overlayfs instance
1235 * - upper/work dir of any overlayfs instance
1236 */
ovl_check_layer(struct super_block * sb,struct ovl_fs * ofs,struct dentry * dentry,const char * name,bool is_lower)1237 static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
1238 struct dentry *dentry, const char *name,
1239 bool is_lower)
1240 {
1241 struct dentry *next = dentry, *parent;
1242 int err = 0;
1243
1244 if (!dentry)
1245 return 0;
1246
1247 parent = dget_parent(next);
1248
1249 /* Walk back ancestors to root (inclusive) looking for traps */
1250 while (!err && parent != next) {
1251 if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
1252 err = -ELOOP;
1253 pr_err("overlapping %s path\n", name);
1254 } else if (ovl_is_inuse(parent)) {
1255 err = ovl_report_in_use(ofs, name);
1256 }
1257 next = parent;
1258 parent = dget_parent(next);
1259 dput(next);
1260 }
1261
1262 dput(parent);
1263
1264 return err;
1265 }
1266
1267 /*
1268 * Check if any of the layers or work dirs overlap.
1269 */
ovl_check_overlapping_layers(struct super_block * sb,struct ovl_fs * ofs)1270 static int ovl_check_overlapping_layers(struct super_block *sb,
1271 struct ovl_fs *ofs)
1272 {
1273 int i, err;
1274
1275 if (ovl_upper_mnt(ofs)) {
1276 err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
1277 "upperdir", false);
1278 if (err)
1279 return err;
1280
1281 /*
1282 * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
1283 * this instance and covers overlapping work and index dirs,
1284 * unless work or index dir have been moved since created inside
1285 * workbasedir. In that case, we already have their traps in
1286 * inode cache and we will catch that case on lookup.
1287 */
1288 err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
1289 false);
1290 if (err)
1291 return err;
1292 }
1293
1294 for (i = 1; i < ofs->numlayer; i++) {
1295 err = ovl_check_layer(sb, ofs,
1296 ofs->layers[i].mnt->mnt_root,
1297 "lowerdir", true);
1298 if (err)
1299 return err;
1300 }
1301
1302 return 0;
1303 }
1304
ovl_get_root(struct super_block * sb,struct dentry * upperdentry,struct ovl_entry * oe)1305 static struct dentry *ovl_get_root(struct super_block *sb,
1306 struct dentry *upperdentry,
1307 struct ovl_entry *oe)
1308 {
1309 struct dentry *root;
1310 struct ovl_fs *ofs = OVL_FS(sb);
1311 struct ovl_path *lowerpath = ovl_lowerstack(oe);
1312 unsigned long ino = d_inode(lowerpath->dentry)->i_ino;
1313 int fsid = lowerpath->layer->fsid;
1314 struct ovl_inode_params oip = {
1315 .upperdentry = upperdentry,
1316 .oe = oe,
1317 };
1318
1319 root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
1320 if (!root)
1321 return NULL;
1322
1323 if (upperdentry) {
1324 /* Root inode uses upper st_ino/i_ino */
1325 ino = d_inode(upperdentry)->i_ino;
1326 fsid = 0;
1327 ovl_dentry_set_upper_alias(root);
1328 if (ovl_is_impuredir(sb, upperdentry))
1329 ovl_set_flag(OVL_IMPURE, d_inode(root));
1330 }
1331
1332 /* Look for xwhiteouts marker except in the lowermost layer */
1333 for (int i = 0; i < ovl_numlower(oe) - 1; i++, lowerpath++) {
1334 struct path path = {
1335 .mnt = lowerpath->layer->mnt,
1336 .dentry = lowerpath->dentry,
1337 };
1338
1339 /* overlay.opaque=x means xwhiteouts directory */
1340 if (ovl_get_opaquedir_val(ofs, &path) == 'x') {
1341 ovl_layer_set_xwhiteouts(ofs, lowerpath->layer);
1342 ovl_dentry_set_xwhiteouts(root);
1343 }
1344 }
1345
1346 /* Root is always merge -> can have whiteouts */
1347 ovl_set_flag(OVL_WHITEOUTS, d_inode(root));
1348 ovl_dentry_set_flag(OVL_E_CONNECTED, root);
1349 ovl_set_upperdata(d_inode(root));
1350 ovl_inode_init(d_inode(root), &oip, ino, fsid);
1351 WARN_ON(!!IS_CASEFOLDED(d_inode(root)) != ofs->casefold);
1352 ovl_dentry_init_flags(root, upperdentry, oe, DCACHE_OP_WEAK_REVALIDATE);
1353 /* root keeps a reference of upperdentry */
1354 dget(upperdentry);
1355
1356 return root;
1357 }
1358
ovl_set_d_op(struct super_block * sb)1359 static void ovl_set_d_op(struct super_block *sb)
1360 {
1361 #if IS_ENABLED(CONFIG_UNICODE)
1362 struct ovl_fs *ofs = sb->s_fs_info;
1363
1364 if (ofs->casefold) {
1365 set_default_d_op(sb, &ovl_dentry_ci_operations);
1366 return;
1367 }
1368 #endif
1369 set_default_d_op(sb, &ovl_dentry_operations);
1370 }
1371
ovl_fill_super(struct super_block * sb,struct fs_context * fc)1372 int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
1373 {
1374 struct ovl_fs *ofs = sb->s_fs_info;
1375 struct ovl_fs_context *ctx = fc->fs_private;
1376 const struct cred *old_cred = NULL;
1377 struct dentry *root_dentry;
1378 struct ovl_entry *oe;
1379 struct ovl_layer *layers;
1380 struct cred *cred;
1381 int err;
1382
1383 err = -EIO;
1384 if (WARN_ON(fc->user_ns != current_user_ns()))
1385 goto out_err;
1386
1387 ovl_set_d_op(sb);
1388
1389 err = -ENOMEM;
1390 if (!ofs->creator_cred)
1391 ofs->creator_cred = cred = prepare_creds();
1392 else
1393 cred = (struct cred *)ofs->creator_cred;
1394 if (!cred)
1395 goto out_err;
1396
1397 old_cred = ovl_override_creds(sb);
1398
1399 err = ovl_fs_params_verify(ctx, &ofs->config);
1400 if (err)
1401 goto out_err;
1402
1403 err = -EINVAL;
1404 if (ctx->nr == 0) {
1405 if (!(fc->sb_flags & SB_SILENT))
1406 pr_err("missing 'lowerdir'\n");
1407 goto out_err;
1408 }
1409
1410 err = -ENOMEM;
1411 layers = kcalloc(ctx->nr + 1, sizeof(struct ovl_layer), GFP_KERNEL);
1412 if (!layers)
1413 goto out_err;
1414
1415 ofs->config.lowerdirs = kcalloc(ctx->nr + 1, sizeof(char *), GFP_KERNEL);
1416 if (!ofs->config.lowerdirs) {
1417 kfree(layers);
1418 goto out_err;
1419 }
1420 ofs->layers = layers;
1421 /*
1422 * Layer 0 is reserved for upper even if there's no upper.
1423 * config.lowerdirs[0] is used for storing the user provided colon
1424 * separated lowerdir string.
1425 */
1426 ofs->config.lowerdirs[0] = ctx->lowerdir_all;
1427 ctx->lowerdir_all = NULL;
1428 ofs->numlayer = 1;
1429
1430 sb->s_stack_depth = 0;
1431 sb->s_maxbytes = MAX_LFS_FILESIZE;
1432 atomic_long_set(&ofs->last_ino, 1);
1433 /* Assume underlying fs uses 32bit inodes unless proven otherwise */
1434 if (ofs->config.xino != OVL_XINO_OFF) {
1435 ofs->xino_mode = BITS_PER_LONG - 32;
1436 if (!ofs->xino_mode) {
1437 pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
1438 ofs->config.xino = OVL_XINO_OFF;
1439 }
1440 }
1441
1442 /* alloc/destroy_inode needed for setting up traps in inode cache */
1443 sb->s_op = &ovl_super_operations;
1444
1445 if (ofs->config.upperdir) {
1446 struct super_block *upper_sb;
1447
1448 err = -EINVAL;
1449 if (!ofs->config.workdir) {
1450 pr_err("missing 'workdir'\n");
1451 goto out_err;
1452 }
1453
1454 err = ovl_get_upper(sb, ofs, &layers[0], &ctx->upper);
1455 if (err)
1456 goto out_err;
1457
1458 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
1459 if (!ovl_should_sync(ofs)) {
1460 ofs->errseq = errseq_sample(&upper_sb->s_wb_err);
1461 if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) {
1462 err = -EIO;
1463 pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n");
1464 goto out_err;
1465 }
1466 }
1467
1468 err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work);
1469 if (err)
1470 goto out_err;
1471
1472 if (!ofs->workdir)
1473 sb->s_flags |= SB_RDONLY;
1474
1475 sb->s_stack_depth = upper_sb->s_stack_depth;
1476 sb->s_time_gran = upper_sb->s_time_gran;
1477 }
1478 oe = ovl_get_lowerstack(sb, ctx, ofs, layers);
1479 err = PTR_ERR(oe);
1480 if (IS_ERR(oe))
1481 goto out_err;
1482
1483 /* If the upper fs is nonexistent, we mark overlayfs r/o too */
1484 if (!ovl_upper_mnt(ofs))
1485 sb->s_flags |= SB_RDONLY;
1486
1487 if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) {
1488 pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n");
1489 ofs->config.uuid = OVL_UUID_NULL;
1490 } else if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) {
1491 /* Use per instance persistent uuid/fsid */
1492 ovl_init_uuid_xattr(sb, ofs, &ctx->upper);
1493 }
1494
1495 if (!ovl_force_readonly(ofs) && ofs->config.index) {
1496 err = ovl_get_indexdir(sb, ofs, oe, &ctx->upper);
1497 if (err)
1498 goto out_free_oe;
1499
1500 /* Force r/o mount with no index dir */
1501 if (!ofs->workdir)
1502 sb->s_flags |= SB_RDONLY;
1503 }
1504
1505 err = ovl_check_overlapping_layers(sb, ofs);
1506 if (err)
1507 goto out_free_oe;
1508
1509 /* Show index=off in /proc/mounts for forced r/o mount */
1510 if (!ofs->workdir) {
1511 ofs->config.index = false;
1512 if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
1513 pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
1514 ofs->config.nfs_export = false;
1515 }
1516 }
1517
1518 if (ofs->config.metacopy && ofs->config.nfs_export) {
1519 pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
1520 ofs->config.nfs_export = false;
1521 }
1522
1523 /*
1524 * Support encoding decodable file handles with nfs_export=on
1525 * and encoding non-decodable file handles with nfs_export=off
1526 * if all layers support file handles.
1527 */
1528 if (ofs->config.nfs_export)
1529 sb->s_export_op = &ovl_export_operations;
1530 else if (!ofs->nofh)
1531 sb->s_export_op = &ovl_export_fid_operations;
1532
1533 /* Never override disk quota limits or use reserved space */
1534 cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
1535
1536 sb->s_magic = OVERLAYFS_SUPER_MAGIC;
1537 sb->s_xattr = ovl_xattr_handlers(ofs);
1538 sb->s_fs_info = ofs;
1539 #ifdef CONFIG_FS_POSIX_ACL
1540 sb->s_flags |= SB_POSIXACL;
1541 #endif
1542 sb->s_iflags |= SB_I_SKIP_SYNC;
1543 /*
1544 * Ensure that umask handling is done by the filesystems used
1545 * for the the upper layer instead of overlayfs as that would
1546 * lead to unexpected results.
1547 */
1548 sb->s_iflags |= SB_I_NOUMASK;
1549 sb->s_iflags |= SB_I_EVM_HMAC_UNSUPPORTED;
1550
1551 err = -ENOMEM;
1552 root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe);
1553 if (!root_dentry)
1554 goto out_free_oe;
1555
1556 sb->s_root = root_dentry;
1557
1558 ovl_revert_creds(old_cred);
1559 return 0;
1560
1561 out_free_oe:
1562 ovl_free_entry(oe);
1563 out_err:
1564 /*
1565 * Revert creds before calling ovl_free_fs() which will call
1566 * put_cred() and put_cred() requires that the cred's that are
1567 * put are not the caller's creds, i.e., current->cred.
1568 */
1569 if (old_cred)
1570 ovl_revert_creds(old_cred);
1571 ovl_free_fs(ofs);
1572 sb->s_fs_info = NULL;
1573 return err;
1574 }
1575
1576 struct file_system_type ovl_fs_type = {
1577 .owner = THIS_MODULE,
1578 .name = "overlay",
1579 .init_fs_context = ovl_init_fs_context,
1580 .parameters = ovl_parameter_spec,
1581 .fs_flags = FS_USERNS_MOUNT,
1582 .kill_sb = kill_anon_super,
1583 };
1584 MODULE_ALIAS_FS("overlay");
1585
ovl_inode_init_once(void * foo)1586 static void ovl_inode_init_once(void *foo)
1587 {
1588 struct ovl_inode *oi = foo;
1589
1590 inode_init_once(&oi->vfs_inode);
1591 }
1592
ovl_init(void)1593 static int __init ovl_init(void)
1594 {
1595 int err;
1596
1597 ovl_inode_cachep = kmem_cache_create("ovl_inode",
1598 sizeof(struct ovl_inode), 0,
1599 (SLAB_RECLAIM_ACCOUNT|
1600 SLAB_ACCOUNT),
1601 ovl_inode_init_once);
1602 if (ovl_inode_cachep == NULL)
1603 return -ENOMEM;
1604
1605 err = register_filesystem(&ovl_fs_type);
1606 if (!err)
1607 return 0;
1608
1609 kmem_cache_destroy(ovl_inode_cachep);
1610
1611 return err;
1612 }
1613
ovl_exit(void)1614 static void __exit ovl_exit(void)
1615 {
1616 unregister_filesystem(&ovl_fs_type);
1617
1618 /*
1619 * Make sure all delayed rcu free inodes are flushed before we
1620 * destroy cache.
1621 */
1622 rcu_barrier();
1623 kmem_cache_destroy(ovl_inode_cachep);
1624 }
1625
1626 module_init(ovl_init);
1627 module_exit(ovl_exit);
1628