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(inode: 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(dentry: 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(d: upper, flags, weak); |
123 | |
124 | for (i = 0; ret > 0 && i < ovl_numlower(oe); i++) |
125 | ret = ovl_revalidate_real(d: 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, weak: 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, weak: 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, cache: 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(objp: oi->redirect); |
172 | kfree(objp: oi->oe); |
173 | mutex_destroy(lock: &oi->lock); |
174 | kmem_cache_free(s: ovl_inode_cachep, objp: 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(stack: ovl_lowerstack(oe: oi->oe), n: ovl_numlower(oe: oi->oe)); |
183 | if (S_ISDIR(inode->i_mode)) |
184 | ovl_dir_cache_free(inode); |
185 | else |
186 | kfree(objp: 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(eseq: &sb->s_wb_err, 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(sem: &upper_sb->s_umount); |
232 | ret = sync_filesystem(upper_sb); |
233 | up_read(sem: &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(dentry: root_dentry, path: &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(uuid: 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(inode: dir, subclass: I_MUTEX_PARENT); |
291 | retry: |
292 | work = ovl_lookup_upper(ofs, name, base: ofs->workbasedir, strlen(name)); |
293 | |
294 | if (!IS_ERR(ptr: 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, dentry: work, level: 0); |
310 | dput(work); |
311 | if (err == -EINVAL) { |
312 | work = ERR_PTR(error: err); |
313 | goto out_unlock; |
314 | } |
315 | goto retry; |
316 | } |
317 | |
318 | err = ovl_mkdir_real(ofs, dir, newdentry: &work, mode: 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(dentry: 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, dentry: 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, dentry: 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(inode: work->d_inode); |
350 | err = ovl_do_notify_change(ofs, upperdentry: work, attr: &attr); |
351 | inode_unlock(inode: work->d_inode); |
352 | if (err) |
353 | goto out_dput; |
354 | } else { |
355 | err = PTR_ERR(ptr: work); |
356 | goto out_err; |
357 | } |
358 | out_unlock: |
359 | inode_unlock(inode: 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(sb: 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(ptr: 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(ptr: 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(mnt: 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(path: upperpath, ofs, name: ofs->config.upperdir); |
494 | if (err) |
495 | goto out; |
496 | |
497 | err = ovl_setup_trap(sb, dir: upperpath->dentry, ptrap: &upper_layer->trap, |
498 | name: "upperdir" ); |
499 | if (err) |
500 | goto out; |
501 | |
502 | upper_mnt = clone_private_mount(path: upperpath); |
503 | err = PTR_ERR(ptr: upper_mnt); |
504 | if (IS_ERR(ptr: 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(dentry: ovl_upper_mnt(ofs)->mnt_root)) { |
528 | ofs->upperdir_locked = true; |
529 | } else { |
530 | err = ovl_report_in_use(ofs, name: "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(dentry: 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(inode: dir, subclass: I_MUTEX_PARENT); |
555 | |
556 | temp = ovl_create_temp(ofs, workdir, OVL_CATTR(S_IFREG | 0)); |
557 | err = PTR_ERR(ptr: temp); |
558 | if (IS_ERR(ptr: temp)) |
559 | goto out_unlock; |
560 | |
561 | dest = ovl_lookup_temp(ofs, workdir); |
562 | err = PTR_ERR(ptr: dest); |
563 | if (IS_ERR(ptr: 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, olddir: dir, olddentry: temp, newdir: dir, newdentry: 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.name, base: workdir, len: name.name.len); |
578 | err = PTR_ERR(ptr: whiteout); |
579 | if (IS_ERR(ptr: whiteout)) |
580 | goto cleanup_temp; |
581 | |
582 | err = ovl_upper_is_whiteout(ofs, upperdentry: whiteout); |
583 | |
584 | /* Best effort cleanup of whiteout and temp file */ |
585 | if (err) |
586 | ovl_cleanup(ofs, dir, dentry: whiteout); |
587 | dput(whiteout); |
588 | |
589 | cleanup_temp: |
590 | ovl_cleanup(ofs, dir, dentry: temp); |
591 | release_dentry_name_snapshot(&name); |
592 | dput(temp); |
593 | dput(dest); |
594 | |
595 | out_unlock: |
596 | inode_unlock(inode: 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(inode: parent->d_inode, subclass: I_MUTEX_PARENT); |
609 | child = ovl_lookup_upper(ofs, name, base: parent, len); |
610 | if (!IS_ERR(ptr: child) && !child->d_inode) |
611 | child = ovl_create_real(ofs, dir: parent->d_inode, newdentry: child, |
612 | OVL_CATTR(mode)); |
613 | inode_unlock(inode: 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(dentry: 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, parent: d, name: *name, mode: ctr > 1 ? S_IFDIR : S_IFREG); |
634 | if (IS_ERR(ptr: d)) |
635 | return PTR_ERR(ptr: 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, persist: false); |
657 | err = PTR_ERR(ptr: workdir); |
658 | if (IS_ERR_OR_NULL(ptr: workdir)) |
659 | goto out; |
660 | |
661 | ofs->workdir = workdir; |
662 | |
663 | err = ovl_setup_trap(sb, dir: ofs->workdir, ptrap: &ofs->workdir_trap, name: "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(realpath: 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, dentry: ofs->workdir, S_IFREG | 0); |
683 | ofs->tmpfile = !IS_ERR(ptr: 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, dentry: ofs->workdir, ox: OVL_XATTR_OPAQUE, value: "0" , size: 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, dentry: ofs->workdir, ox: 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(dentry: 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(sb: 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(workdir: workpath->dentry, upperdir: upperpath->dentry)) { |
795 | pr_err("workdir and upperdir must be separate subtrees\n" ); |
796 | return err; |
797 | } |
798 | |
799 | ofs->workbasedir = dget(dentry: workpath->dentry); |
800 | |
801 | if (ovl_inuse_trylock(dentry: ofs->workbasedir)) { |
802 | ofs->workdir_locked = true; |
803 | } else { |
804 | err = ovl_report_in_use(ofs, name: "workdir" ); |
805 | if (err) |
806 | return err; |
807 | } |
808 | |
809 | err = ovl_setup_trap(sb, dir: ofs->workbasedir, ptrap: &ofs->workbasedir_trap, |
810 | name: "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(ptr: fh)) |
828 | return PTR_ERR(ptr: 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, upper: upperpath->dentry, fh, set: 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, persist: true); |
847 | if (IS_ERR(ptr: indexdir)) { |
848 | err = PTR_ERR(ptr: indexdir); |
849 | } else if (indexdir) { |
850 | ofs->workdir = indexdir; |
851 | err = ovl_setup_trap(sb, dir: indexdir, ptrap: &ofs->workdir_trap, |
852 | name: "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, upperdentry: indexdir)) { |
865 | err = ovl_verify_origin_xattr(ofs, dentry: indexdir, |
866 | ox: OVL_XATTR_ORIGIN, |
867 | real: upperpath->dentry, is_upper: true, |
868 | set: false); |
869 | if (err) |
870 | pr_err("failed to verify index dir 'origin' xattr\n" ); |
871 | } |
872 | err = ovl_verify_upper(ofs, index: indexdir, upper: upperpath->dentry, set: 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(objp: 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(u1: &ofs->fs[i].sb->s_uuid, u2: 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, uuid: &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(n: ctx->nr + 2, size: 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, path: &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, dir: l->path.dentry, ptrap: &trap, name: "lowerdir" ); |
1038 | if (err) |
1039 | return err; |
1040 | |
1041 | if (ovl_is_inuse(dentry: l->path.dentry)) { |
1042 | err = ovl_report_in_use(ofs, name: "lowerdir" ); |
1043 | if (err) { |
1044 | iput(trap); |
1045 | return err; |
1046 | } |
1047 | } |
1048 | |
1049 | mnt = clone_private_mount(path: &l->path); |
1050 | err = PTR_ERR(ptr: mnt); |
1051 | if (IS_ERR(ptr: 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(error: -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(name: l->name, path: &l->path, ofs, stack_depth: &sb->s_stack_depth); |
1133 | if (err) |
1134 | return ERR_PTR(error: 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(error: err); |
1142 | } |
1143 | |
1144 | err = ovl_get_layers(sb, ofs, ctx, layers); |
1145 | if (err) |
1146 | return ERR_PTR(error: 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(numlower: nr_merged_lower); |
1152 | if (!oe) |
1153 | return ERR_PTR(error: 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(dentry: 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(dentry: 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, dir: parent)) { |
1186 | err = -ELOOP; |
1187 | pr_err("overlapping %s path\n" , name); |
1188 | } else if (ovl_is_inuse(dentry: parent)) { |
1189 | err = ovl_report_in_use(ofs, name); |
1190 | } |
1191 | next = parent; |
1192 | parent = dget_parent(dentry: 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, dentry: ovl_upper_mnt(ofs)->mnt_root, |
1211 | name: "upperdir" , is_lower: 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, dentry: ofs->workbasedir, name: "workdir" , |
1223 | is_lower: 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 | dentry: ofs->layers[i].mnt->mnt_root, |
1231 | name: "lowerdir" , is_lower: 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(dentry: 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, rdev: 0)); |
1254 | if (!root) |
1255 | return NULL; |
1256 | |
1257 | if (upperdentry) { |
1258 | /* Root inode uses upper st_ino/i_ino */ |
1259 | ino = d_inode(dentry: upperdentry)->i_ino; |
1260 | fsid = 0; |
1261 | ovl_dentry_set_upper_alias(dentry: root); |
1262 | if (ovl_is_impuredir(sb, upperdentry)) |
1263 | ovl_set_flag(flag: OVL_IMPURE, inode: d_inode(dentry: 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: &path) == 'x') { |
1275 | ovl_layer_set_xwhiteouts(ofs, layer: lowerpath->layer); |
1276 | ovl_dentry_set_xwhiteouts(dentry: root); |
1277 | } |
1278 | } |
1279 | |
1280 | /* Root is always merge -> can have whiteouts */ |
1281 | ovl_set_flag(flag: OVL_WHITEOUTS, inode: d_inode(dentry: root)); |
1282 | ovl_dentry_set_flag(flag: OVL_E_CONNECTED, dentry: root); |
1283 | ovl_set_upperdata(inode: d_inode(dentry: root)); |
1284 | ovl_inode_init(inode: d_inode(dentry: root), oip: &oip, ino, fsid); |
1285 | ovl_dentry_init_flags(dentry: root, upperdentry, oe, DCACHE_OP_WEAK_REVALIDATE); |
1286 | /* root keeps a reference of upperdentry */ |
1287 | dget(dentry: 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, config: &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(n: ctx->nr + 1, size: sizeof(struct ovl_layer), GFP_KERNEL); |
1326 | if (!layers) |
1327 | goto out_err; |
1328 | |
1329 | ofs->config.lowerdirs = kcalloc(n: ctx->nr + 1, size: sizeof(char *), GFP_KERNEL); |
1330 | if (!ofs->config.lowerdirs) { |
1331 | kfree(objp: 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(v: &ofs->last_ino, i: 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, upper_layer: &layers[0], upperpath: &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(eseq: &upper_sb->s_wb_err); |
1375 | if (errseq_check(eseq: &upper_sb->s_wb_err, since: 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, upperpath: &ctx->upper, workpath: &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(ptr: oe); |
1394 | if (IS_ERR(ptr: 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, upperpath: &ctx->upper); |
1407 | } |
1408 | |
1409 | if (!ovl_force_readonly(ofs) && ofs->config.index) { |
1410 | err = ovl_get_indexdir(sb, ofs, oe, upperpath: &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_UNSUPPORTED; |
1464 | |
1465 | err = -ENOMEM; |
1466 | root_dentry = ovl_get_root(sb, upperdentry: 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(name: "ovl_inode" , |
1504 | size: sizeof(struct ovl_inode), align: 0, |
1505 | flags: (SLAB_RECLAIM_ACCOUNT| |
1506 | SLAB_ACCOUNT), |
1507 | ctor: 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(s: 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(s: ovl_inode_cachep); |
1530 | } |
1531 | |
1532 | module_init(ovl_init); |
1533 | module_exit(ovl_exit); |
1534 | |