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1 /*
2  *
3  * Copyright (C) 2011 Novell Inc.
4  *
5  * This program is free software; you can redistribute it and/or modify it
6  * under the terms of the GNU General Public License version 2 as published by
7  * the Free Software Foundation.
8  */
9 
10 #include <linux/fs.h>
11 #include <linux/namei.h>
12 #include <linux/xattr.h>
13 #include <linux/security.h>
14 #include <linux/cred.h>
15 #include <linux/module.h>
16 #include <linux/posix_acl.h>
17 #include <linux/posix_acl_xattr.h>
18 #include <linux/atomic.h>
19 #include <linux/ratelimit.h>
20 #include "overlayfs.h"
21 
22 static unsigned short ovl_redirect_max = 256;
23 module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
24 MODULE_PARM_DESC(ovl_redirect_max,
25 		 "Maximum length of absolute redirect xattr value");
26 
ovl_cleanup(struct inode * wdir,struct dentry * wdentry)27 int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
28 {
29 	int err;
30 
31 	dget(wdentry);
32 	if (d_is_dir(wdentry))
33 		err = ovl_do_rmdir(wdir, wdentry);
34 	else
35 		err = ovl_do_unlink(wdir, wdentry);
36 	dput(wdentry);
37 
38 	if (err) {
39 		pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
40 		       wdentry, err);
41 	}
42 
43 	return err;
44 }
45 
ovl_lookup_temp(struct dentry * workdir)46 struct dentry *ovl_lookup_temp(struct dentry *workdir)
47 {
48 	struct dentry *temp;
49 	char name[20];
50 	static atomic_t temp_id = ATOMIC_INIT(0);
51 
52 	/* counter is allowed to wrap, since temp dentries are ephemeral */
53 	snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
54 
55 	temp = lookup_one_len(name, workdir, strlen(name));
56 	if (!IS_ERR(temp) && temp->d_inode) {
57 		pr_err("overlayfs: workdir/%s already exists\n", name);
58 		dput(temp);
59 		temp = ERR_PTR(-EIO);
60 	}
61 
62 	return temp;
63 }
64 
65 /* caller holds i_mutex on workdir */
ovl_whiteout(struct dentry * workdir,struct dentry * dentry)66 static struct dentry *ovl_whiteout(struct dentry *workdir,
67 				   struct dentry *dentry)
68 {
69 	int err;
70 	struct dentry *whiteout;
71 	struct inode *wdir = workdir->d_inode;
72 
73 	whiteout = ovl_lookup_temp(workdir);
74 	if (IS_ERR(whiteout))
75 		return whiteout;
76 
77 	err = ovl_do_whiteout(wdir, whiteout);
78 	if (err) {
79 		dput(whiteout);
80 		whiteout = ERR_PTR(err);
81 	}
82 
83 	return whiteout;
84 }
85 
ovl_create_real(struct inode * dir,struct dentry * newdentry,struct cattr * attr,struct dentry * hardlink,bool debug)86 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
87 		    struct cattr *attr, struct dentry *hardlink, bool debug)
88 {
89 	int err;
90 
91 	if (newdentry->d_inode)
92 		return -ESTALE;
93 
94 	if (hardlink) {
95 		err = ovl_do_link(hardlink, dir, newdentry, debug);
96 	} else {
97 		switch (attr->mode & S_IFMT) {
98 		case S_IFREG:
99 			err = ovl_do_create(dir, newdentry, attr->mode, debug);
100 			break;
101 
102 		case S_IFDIR:
103 			err = ovl_do_mkdir(dir, newdentry, attr->mode, debug);
104 			break;
105 
106 		case S_IFCHR:
107 		case S_IFBLK:
108 		case S_IFIFO:
109 		case S_IFSOCK:
110 			err = ovl_do_mknod(dir, newdentry,
111 					   attr->mode, attr->rdev, debug);
112 			break;
113 
114 		case S_IFLNK:
115 			err = ovl_do_symlink(dir, newdentry, attr->link, debug);
116 			break;
117 
118 		default:
119 			err = -EPERM;
120 		}
121 	}
122 	if (!err && WARN_ON(!newdentry->d_inode)) {
123 		/*
124 		 * Not quite sure if non-instantiated dentry is legal or not.
125 		 * VFS doesn't seem to care so check and warn here.
126 		 */
127 		err = -ENOENT;
128 	}
129 	return err;
130 }
131 
ovl_set_opaque_xerr(struct dentry * dentry,struct dentry * upper,int xerr)132 static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
133 			       int xerr)
134 {
135 	int err;
136 
137 	err = ovl_check_setxattr(dentry, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
138 	if (!err)
139 		ovl_dentry_set_opaque(dentry);
140 
141 	return err;
142 }
143 
ovl_set_opaque(struct dentry * dentry,struct dentry * upperdentry)144 static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
145 {
146 	/*
147 	 * Fail with -EIO when trying to create opaque dir and upper doesn't
148 	 * support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
149 	 * return a specific error for noxattr case.
150 	 */
151 	return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
152 }
153 
154 /* Common operations required to be done after creation of file on upper */
ovl_instantiate(struct dentry * dentry,struct inode * inode,struct dentry * newdentry,bool hardlink)155 static void ovl_instantiate(struct dentry *dentry, struct inode *inode,
156 			    struct dentry *newdentry, bool hardlink)
157 {
158 	ovl_dentry_version_inc(dentry->d_parent, false);
159 	ovl_dentry_set_upper_alias(dentry);
160 	if (!hardlink) {
161 		ovl_inode_update(inode, newdentry);
162 		ovl_copyattr(newdentry->d_inode, inode);
163 	} else {
164 		WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
165 		dput(newdentry);
166 		inc_nlink(inode);
167 	}
168 	d_instantiate(dentry, inode);
169 	/* Force lookup of new upper hardlink to find its lower */
170 	if (hardlink)
171 		d_drop(dentry);
172 }
173 
ovl_type_merge(struct dentry * dentry)174 static bool ovl_type_merge(struct dentry *dentry)
175 {
176 	return OVL_TYPE_MERGE(ovl_path_type(dentry));
177 }
178 
ovl_type_origin(struct dentry * dentry)179 static bool ovl_type_origin(struct dentry *dentry)
180 {
181 	return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
182 }
183 
ovl_create_upper(struct dentry * dentry,struct inode * inode,struct cattr * attr,struct dentry * hardlink)184 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
185 			    struct cattr *attr, struct dentry *hardlink)
186 {
187 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
188 	struct inode *udir = upperdir->d_inode;
189 	struct dentry *newdentry;
190 	int err;
191 
192 	if (!hardlink && !IS_POSIXACL(udir))
193 		attr->mode &= ~current_umask();
194 
195 	inode_lock_nested(udir, I_MUTEX_PARENT);
196 	newdentry = lookup_one_len(dentry->d_name.name, upperdir,
197 				   dentry->d_name.len);
198 	err = PTR_ERR(newdentry);
199 	if (IS_ERR(newdentry))
200 		goto out_unlock;
201 	err = ovl_create_real(udir, newdentry, attr, hardlink, false);
202 	if (err)
203 		goto out_dput;
204 
205 	if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
206 		/* Setting opaque here is just an optimization, allow to fail */
207 		ovl_set_opaque(dentry, newdentry);
208 	}
209 
210 	ovl_instantiate(dentry, inode, newdentry, !!hardlink);
211 	newdentry = NULL;
212 out_dput:
213 	dput(newdentry);
214 out_unlock:
215 	inode_unlock(udir);
216 	return err;
217 }
218 
ovl_clear_empty(struct dentry * dentry,struct list_head * list)219 static struct dentry *ovl_clear_empty(struct dentry *dentry,
220 				      struct list_head *list)
221 {
222 	struct dentry *workdir = ovl_workdir(dentry);
223 	struct inode *wdir = workdir->d_inode;
224 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
225 	struct inode *udir = upperdir->d_inode;
226 	struct path upperpath;
227 	struct dentry *upper;
228 	struct dentry *opaquedir;
229 	struct kstat stat;
230 	int err;
231 
232 	if (WARN_ON(!workdir))
233 		return ERR_PTR(-EROFS);
234 
235 	err = ovl_lock_rename_workdir(workdir, upperdir);
236 	if (err)
237 		goto out;
238 
239 	ovl_path_upper(dentry, &upperpath);
240 	err = vfs_getattr(&upperpath, &stat,
241 			  STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
242 	if (err)
243 		goto out_unlock;
244 
245 	err = -ESTALE;
246 	if (!S_ISDIR(stat.mode))
247 		goto out_unlock;
248 	upper = upperpath.dentry;
249 	if (upper->d_parent->d_inode != udir)
250 		goto out_unlock;
251 
252 	opaquedir = ovl_lookup_temp(workdir);
253 	err = PTR_ERR(opaquedir);
254 	if (IS_ERR(opaquedir))
255 		goto out_unlock;
256 
257 	err = ovl_create_real(wdir, opaquedir,
258 			      &(struct cattr){.mode = stat.mode}, NULL, true);
259 	if (err)
260 		goto out_dput;
261 
262 	err = ovl_copy_xattr(upper, opaquedir);
263 	if (err)
264 		goto out_cleanup;
265 
266 	err = ovl_set_opaque(dentry, opaquedir);
267 	if (err)
268 		goto out_cleanup;
269 
270 	inode_lock(opaquedir->d_inode);
271 	err = ovl_set_attr(opaquedir, &stat);
272 	inode_unlock(opaquedir->d_inode);
273 	if (err)
274 		goto out_cleanup;
275 
276 	err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
277 	if (err)
278 		goto out_cleanup;
279 
280 	ovl_cleanup_whiteouts(upper, list);
281 	ovl_cleanup(wdir, upper);
282 	unlock_rename(workdir, upperdir);
283 
284 	/* dentry's upper doesn't match now, get rid of it */
285 	d_drop(dentry);
286 
287 	return opaquedir;
288 
289 out_cleanup:
290 	ovl_cleanup(wdir, opaquedir);
291 out_dput:
292 	dput(opaquedir);
293 out_unlock:
294 	unlock_rename(workdir, upperdir);
295 out:
296 	return ERR_PTR(err);
297 }
298 
ovl_check_empty_and_clear(struct dentry * dentry)299 static struct dentry *ovl_check_empty_and_clear(struct dentry *dentry)
300 {
301 	int err;
302 	struct dentry *ret = NULL;
303 	enum ovl_path_type type = ovl_path_type(dentry);
304 	LIST_HEAD(list);
305 
306 	err = ovl_check_empty_dir(dentry, &list);
307 	if (err) {
308 		ret = ERR_PTR(err);
309 		goto out_free;
310 	}
311 
312 	/*
313 	 * When removing an empty opaque directory, then it makes no sense to
314 	 * replace it with an exact replica of itself.
315 	 *
316 	 * If no upperdentry then skip clearing whiteouts.
317 	 *
318 	 * Can race with copy-up, since we don't hold the upperdir mutex.
319 	 * Doesn't matter, since copy-up can't create a non-empty directory
320 	 * from an empty one.
321 	 */
322 	if (OVL_TYPE_UPPER(type) && OVL_TYPE_MERGE(type))
323 		ret = ovl_clear_empty(dentry, &list);
324 
325 out_free:
326 	ovl_cache_free(&list);
327 
328 	return ret;
329 }
330 
ovl_set_upper_acl(struct dentry * upperdentry,const char * name,const struct posix_acl * acl)331 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
332 			     const struct posix_acl *acl)
333 {
334 	void *buffer;
335 	size_t size;
336 	int err;
337 
338 	if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
339 		return 0;
340 
341 	size = posix_acl_to_xattr(NULL, acl, NULL, 0);
342 	buffer = kmalloc(size, GFP_KERNEL);
343 	if (!buffer)
344 		return -ENOMEM;
345 
346 	size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
347 	err = size;
348 	if (err < 0)
349 		goto out_free;
350 
351 	err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
352 out_free:
353 	kfree(buffer);
354 	return err;
355 }
356 
ovl_create_over_whiteout(struct dentry * dentry,struct inode * inode,struct cattr * cattr,struct dentry * hardlink)357 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
358 				    struct cattr *cattr,
359 				    struct dentry *hardlink)
360 {
361 	struct dentry *workdir = ovl_workdir(dentry);
362 	struct inode *wdir = workdir->d_inode;
363 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
364 	struct inode *udir = upperdir->d_inode;
365 	struct dentry *upper;
366 	struct dentry *newdentry;
367 	int err;
368 	struct posix_acl *acl, *default_acl;
369 
370 	if (WARN_ON(!workdir))
371 		return -EROFS;
372 
373 	if (!hardlink) {
374 		err = posix_acl_create(dentry->d_parent->d_inode,
375 				       &cattr->mode, &default_acl, &acl);
376 		if (err)
377 			return err;
378 	}
379 
380 	err = ovl_lock_rename_workdir(workdir, upperdir);
381 	if (err)
382 		goto out;
383 
384 	newdentry = ovl_lookup_temp(workdir);
385 	err = PTR_ERR(newdentry);
386 	if (IS_ERR(newdentry))
387 		goto out_unlock;
388 
389 	upper = lookup_one_len(dentry->d_name.name, upperdir,
390 			       dentry->d_name.len);
391 	err = PTR_ERR(upper);
392 	if (IS_ERR(upper))
393 		goto out_dput;
394 
395 	err = -ESTALE;
396 	if (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper)))
397 		goto out_dput2;
398 
399 	err = ovl_create_real(wdir, newdentry, cattr, hardlink, true);
400 	if (err)
401 		goto out_dput2;
402 
403 	/*
404 	 * mode could have been mutilated due to umask (e.g. sgid directory)
405 	 */
406 	if (!hardlink &&
407 	    !S_ISLNK(cattr->mode) &&
408 	    newdentry->d_inode->i_mode != cattr->mode) {
409 		struct iattr attr = {
410 			.ia_valid = ATTR_MODE,
411 			.ia_mode = cattr->mode,
412 		};
413 		inode_lock(newdentry->d_inode);
414 		err = notify_change(newdentry, &attr, NULL);
415 		inode_unlock(newdentry->d_inode);
416 		if (err)
417 			goto out_cleanup;
418 	}
419 	if (!hardlink) {
420 		err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
421 					acl);
422 		if (err)
423 			goto out_cleanup;
424 
425 		err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
426 					default_acl);
427 		if (err)
428 			goto out_cleanup;
429 	}
430 
431 	if (!hardlink && S_ISDIR(cattr->mode)) {
432 		err = ovl_set_opaque(dentry, newdentry);
433 		if (err)
434 			goto out_cleanup;
435 
436 		err = ovl_do_rename(wdir, newdentry, udir, upper,
437 				    RENAME_EXCHANGE);
438 		if (err)
439 			goto out_cleanup;
440 
441 		ovl_cleanup(wdir, upper);
442 	} else {
443 		err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
444 		if (err)
445 			goto out_cleanup;
446 	}
447 	ovl_instantiate(dentry, inode, newdentry, !!hardlink);
448 	newdentry = NULL;
449 out_dput2:
450 	dput(upper);
451 out_dput:
452 	dput(newdentry);
453 out_unlock:
454 	unlock_rename(workdir, upperdir);
455 out:
456 	if (!hardlink) {
457 		posix_acl_release(acl);
458 		posix_acl_release(default_acl);
459 	}
460 	return err;
461 
462 out_cleanup:
463 	ovl_cleanup(wdir, newdentry);
464 	goto out_dput2;
465 }
466 
ovl_create_or_link(struct dentry * dentry,struct inode * inode,struct cattr * attr,struct dentry * hardlink,bool origin)467 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
468 			      struct cattr *attr, struct dentry *hardlink,
469 			      bool origin)
470 {
471 	int err;
472 	const struct cred *old_cred, *hold_cred = NULL;
473 	struct cred *override_cred;
474 	struct dentry *parent = dentry->d_parent;
475 
476 	err = ovl_copy_up(parent);
477 	if (err)
478 		return err;
479 
480 	old_cred = ovl_override_creds(dentry->d_sb);
481 
482 	/*
483 	 * When linking a file with copy up origin into a new parent, mark the
484 	 * new parent dir "impure".
485 	 */
486 	if (origin) {
487 		err = ovl_set_impure(parent, ovl_dentry_upper(parent));
488 		if (err)
489 			goto out_revert_creds;
490 	}
491 
492 	err = -ENOMEM;
493 	override_cred = prepare_creds();
494 	if (override_cred) {
495 		override_cred->fsuid = inode->i_uid;
496 		override_cred->fsgid = inode->i_gid;
497 		if (!hardlink) {
498 			err = security_dentry_create_files_as(dentry,
499 					attr->mode, &dentry->d_name,
500 					old_cred ? old_cred : current_cred(),
501 					override_cred);
502 			if (err) {
503 				put_cred(override_cred);
504 				goto out_revert_creds;
505 			}
506 		}
507 		hold_cred = override_creds(override_cred);
508 		put_cred(override_cred);
509 
510 		if (!ovl_dentry_is_whiteout(dentry))
511 			err = ovl_create_upper(dentry, inode, attr,
512 						hardlink);
513 		else
514 			err = ovl_create_over_whiteout(dentry, inode, attr,
515 							hardlink);
516 	}
517 out_revert_creds:
518 	ovl_revert_creds(old_cred ?: hold_cred);
519 	if (old_cred && hold_cred)
520 		put_cred(hold_cred);
521 	if (!err) {
522 		struct inode *realinode = d_inode(ovl_dentry_upper(dentry));
523 
524 		WARN_ON(inode->i_mode != realinode->i_mode);
525 		WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
526 		WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
527 	}
528 	return err;
529 }
530 
ovl_create_object(struct dentry * dentry,int mode,dev_t rdev,const char * link)531 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
532 			     const char *link)
533 {
534 	int err;
535 	struct inode *inode;
536 	struct cattr attr = {
537 		.rdev = rdev,
538 		.link = link,
539 	};
540 
541 	err = ovl_want_write(dentry);
542 	if (err)
543 		goto out;
544 
545 	err = -ENOMEM;
546 	inode = ovl_new_inode(dentry->d_sb, mode, rdev);
547 	if (!inode)
548 		goto out_drop_write;
549 
550 	inode_init_owner(inode, dentry->d_parent->d_inode, mode);
551 	attr.mode = inode->i_mode;
552 
553 	err = ovl_create_or_link(dentry, inode, &attr, NULL, false);
554 	if (err)
555 		iput(inode);
556 
557 out_drop_write:
558 	ovl_drop_write(dentry);
559 out:
560 	return err;
561 }
562 
ovl_create(struct inode * dir,struct dentry * dentry,umode_t mode,bool excl)563 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
564 		      bool excl)
565 {
566 	return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
567 }
568 
ovl_mkdir(struct inode * dir,struct dentry * dentry,umode_t mode)569 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
570 {
571 	return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
572 }
573 
ovl_mknod(struct inode * dir,struct dentry * dentry,umode_t mode,dev_t rdev)574 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
575 		     dev_t rdev)
576 {
577 	/* Don't allow creation of "whiteout" on overlay */
578 	if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
579 		return -EPERM;
580 
581 	return ovl_create_object(dentry, mode, rdev, NULL);
582 }
583 
ovl_symlink(struct inode * dir,struct dentry * dentry,const char * link)584 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
585 		       const char *link)
586 {
587 	return ovl_create_object(dentry, S_IFLNK, 0, link);
588 }
589 
ovl_link(struct dentry * old,struct inode * newdir,struct dentry * new)590 static int ovl_link(struct dentry *old, struct inode *newdir,
591 		    struct dentry *new)
592 {
593 	int err;
594 	bool locked = false;
595 	struct inode *inode;
596 
597 	err = ovl_want_write(old);
598 	if (err)
599 		goto out;
600 
601 	err = ovl_copy_up(old);
602 	if (err)
603 		goto out_drop_write;
604 
605 	err = ovl_copy_up(new->d_parent);
606 	if (err)
607 		goto out_drop_write;
608 
609 
610 	err = ovl_nlink_start(old, &locked);
611 	if (err)
612 		goto out_drop_write;
613 
614 	inode = d_inode(old);
615 	ihold(inode);
616 
617 	err = ovl_create_or_link(new, inode, NULL, ovl_dentry_upper(old),
618 				 ovl_type_origin(old));
619 	if (err)
620 		iput(inode);
621 
622 	ovl_nlink_end(old, locked);
623 out_drop_write:
624 	ovl_drop_write(old);
625 out:
626 	return err;
627 }
628 
ovl_matches_upper(struct dentry * dentry,struct dentry * upper)629 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
630 {
631 	return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
632 }
633 
ovl_remove_and_whiteout(struct dentry * dentry,bool is_dir)634 static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
635 {
636 	struct dentry *workdir = ovl_workdir(dentry);
637 	struct inode *wdir = workdir->d_inode;
638 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
639 	struct inode *udir = upperdir->d_inode;
640 	struct dentry *whiteout;
641 	struct dentry *upper;
642 	struct dentry *opaquedir = NULL;
643 	int err;
644 	int flags = 0;
645 
646 	if (WARN_ON(!workdir))
647 		return -EROFS;
648 
649 	if (is_dir) {
650 		opaquedir = ovl_check_empty_and_clear(dentry);
651 		err = PTR_ERR(opaquedir);
652 		if (IS_ERR(opaquedir))
653 			goto out;
654 	}
655 
656 	err = ovl_lock_rename_workdir(workdir, upperdir);
657 	if (err)
658 		goto out_dput;
659 
660 	upper = lookup_one_len(dentry->d_name.name, upperdir,
661 			       dentry->d_name.len);
662 	err = PTR_ERR(upper);
663 	if (IS_ERR(upper))
664 		goto out_unlock;
665 
666 	err = -ESTALE;
667 	if ((opaquedir && upper != opaquedir) ||
668 	    (!opaquedir && ovl_dentry_upper(dentry) &&
669 	     !ovl_matches_upper(dentry, upper))) {
670 		goto out_dput_upper;
671 	}
672 
673 	whiteout = ovl_whiteout(workdir, dentry);
674 	err = PTR_ERR(whiteout);
675 	if (IS_ERR(whiteout))
676 		goto out_dput_upper;
677 
678 	if (d_is_dir(upper))
679 		flags = RENAME_EXCHANGE;
680 
681 	err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
682 	if (err)
683 		goto kill_whiteout;
684 	if (flags)
685 		ovl_cleanup(wdir, upper);
686 
687 	ovl_dentry_version_inc(dentry->d_parent, true);
688 out_d_drop:
689 	d_drop(dentry);
690 	dput(whiteout);
691 out_dput_upper:
692 	dput(upper);
693 out_unlock:
694 	unlock_rename(workdir, upperdir);
695 out_dput:
696 	dput(opaquedir);
697 out:
698 	return err;
699 
700 kill_whiteout:
701 	ovl_cleanup(wdir, whiteout);
702 	goto out_d_drop;
703 }
704 
ovl_remove_upper(struct dentry * dentry,bool is_dir)705 static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
706 {
707 	struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
708 	struct inode *dir = upperdir->d_inode;
709 	struct dentry *upper;
710 	struct dentry *opaquedir = NULL;
711 	int err;
712 
713 	/* Redirect dir can be !ovl_lower_positive && OVL_TYPE_MERGE */
714 	if (is_dir && ovl_dentry_get_redirect(dentry)) {
715 		opaquedir = ovl_check_empty_and_clear(dentry);
716 		err = PTR_ERR(opaquedir);
717 		if (IS_ERR(opaquedir))
718 			goto out;
719 	}
720 
721 	inode_lock_nested(dir, I_MUTEX_PARENT);
722 	upper = lookup_one_len(dentry->d_name.name, upperdir,
723 			       dentry->d_name.len);
724 	err = PTR_ERR(upper);
725 	if (IS_ERR(upper))
726 		goto out_unlock;
727 
728 	err = -ESTALE;
729 	if ((opaquedir && upper != opaquedir) ||
730 	    (!opaquedir && !ovl_matches_upper(dentry, upper)))
731 		goto out_dput_upper;
732 
733 	if (is_dir)
734 		err = vfs_rmdir(dir, upper);
735 	else
736 		err = vfs_unlink(dir, upper, NULL);
737 	ovl_dentry_version_inc(dentry->d_parent, ovl_type_origin(dentry));
738 
739 	/*
740 	 * Keeping this dentry hashed would mean having to release
741 	 * upperpath/lowerpath, which could only be done if we are the
742 	 * sole user of this dentry.  Too tricky...  Just unhash for
743 	 * now.
744 	 */
745 	if (!err)
746 		d_drop(dentry);
747 out_dput_upper:
748 	dput(upper);
749 out_unlock:
750 	inode_unlock(dir);
751 	dput(opaquedir);
752 out:
753 	return err;
754 }
755 
ovl_do_remove(struct dentry * dentry,bool is_dir)756 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
757 {
758 	int err;
759 	bool locked = false;
760 	const struct cred *old_cred;
761 
762 	err = ovl_want_write(dentry);
763 	if (err)
764 		goto out;
765 
766 	err = ovl_copy_up(dentry->d_parent);
767 	if (err)
768 		goto out_drop_write;
769 
770 	err = ovl_nlink_start(dentry, &locked);
771 	if (err)
772 		goto out_drop_write;
773 
774 	old_cred = ovl_override_creds(dentry->d_sb);
775 	if (!ovl_lower_positive(dentry))
776 		err = ovl_remove_upper(dentry, is_dir);
777 	else
778 		err = ovl_remove_and_whiteout(dentry, is_dir);
779 	ovl_revert_creds(old_cred);
780 	if (!err) {
781 		if (is_dir)
782 			clear_nlink(dentry->d_inode);
783 		else
784 			drop_nlink(dentry->d_inode);
785 	}
786 	ovl_nlink_end(dentry, locked);
787 out_drop_write:
788 	ovl_drop_write(dentry);
789 out:
790 	return err;
791 }
792 
ovl_unlink(struct inode * dir,struct dentry * dentry)793 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
794 {
795 	return ovl_do_remove(dentry, false);
796 }
797 
ovl_rmdir(struct inode * dir,struct dentry * dentry)798 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
799 {
800 	return ovl_do_remove(dentry, true);
801 }
802 
ovl_type_merge_or_lower(struct dentry * dentry)803 static bool ovl_type_merge_or_lower(struct dentry *dentry)
804 {
805 	enum ovl_path_type type = ovl_path_type(dentry);
806 
807 	return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
808 }
809 
ovl_can_move(struct dentry * dentry)810 static bool ovl_can_move(struct dentry *dentry)
811 {
812 	return ovl_redirect_dir(dentry->d_sb) ||
813 		!d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
814 }
815 
ovl_get_redirect(struct dentry * dentry,bool samedir)816 static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
817 {
818 	char *buf, *ret;
819 	struct dentry *d, *tmp;
820 	int buflen = ovl_redirect_max + 1;
821 
822 	if (samedir) {
823 		ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
824 			       GFP_KERNEL);
825 		goto out;
826 	}
827 
828 	buf = ret = kmalloc(buflen, GFP_KERNEL);
829 	if (!buf)
830 		goto out;
831 
832 	buflen--;
833 	buf[buflen] = '\0';
834 	for (d = dget(dentry); !IS_ROOT(d);) {
835 		const char *name;
836 		int thislen;
837 
838 		spin_lock(&d->d_lock);
839 		name = ovl_dentry_get_redirect(d);
840 		if (name) {
841 			thislen = strlen(name);
842 		} else {
843 			name = d->d_name.name;
844 			thislen = d->d_name.len;
845 		}
846 
847 		/* If path is too long, fall back to userspace move */
848 		if (thislen + (name[0] != '/') > buflen) {
849 			ret = ERR_PTR(-EXDEV);
850 			spin_unlock(&d->d_lock);
851 			goto out_put;
852 		}
853 
854 		buflen -= thislen;
855 		memcpy(&buf[buflen], name, thislen);
856 		tmp = dget_dlock(d->d_parent);
857 		spin_unlock(&d->d_lock);
858 
859 		dput(d);
860 		d = tmp;
861 
862 		/* Absolute redirect: finished */
863 		if (buf[buflen] == '/')
864 			break;
865 		buflen--;
866 		buf[buflen] = '/';
867 	}
868 	ret = kstrdup(&buf[buflen], GFP_KERNEL);
869 out_put:
870 	dput(d);
871 	kfree(buf);
872 out:
873 	return ret ? ret : ERR_PTR(-ENOMEM);
874 }
875 
ovl_set_redirect(struct dentry * dentry,bool samedir)876 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
877 {
878 	int err;
879 	const char *redirect = ovl_dentry_get_redirect(dentry);
880 
881 	if (redirect && (samedir || redirect[0] == '/'))
882 		return 0;
883 
884 	redirect = ovl_get_redirect(dentry, samedir);
885 	if (IS_ERR(redirect))
886 		return PTR_ERR(redirect);
887 
888 	err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
889 				 OVL_XATTR_REDIRECT,
890 				 redirect, strlen(redirect), -EXDEV);
891 	if (!err) {
892 		spin_lock(&dentry->d_lock);
893 		ovl_dentry_set_redirect(dentry, redirect);
894 		spin_unlock(&dentry->d_lock);
895 	} else {
896 		kfree(redirect);
897 		pr_warn_ratelimited("overlay: failed to set redirect (%i)\n", err);
898 		/* Fall back to userspace copy-up */
899 		err = -EXDEV;
900 	}
901 	return err;
902 }
903 
ovl_rename(struct inode * olddir,struct dentry * old,struct inode * newdir,struct dentry * new,unsigned int flags)904 static int ovl_rename(struct inode *olddir, struct dentry *old,
905 		      struct inode *newdir, struct dentry *new,
906 		      unsigned int flags)
907 {
908 	int err;
909 	bool locked = false;
910 	struct dentry *old_upperdir;
911 	struct dentry *new_upperdir;
912 	struct dentry *olddentry;
913 	struct dentry *newdentry;
914 	struct dentry *trap;
915 	bool old_opaque;
916 	bool new_opaque;
917 	bool cleanup_whiteout = false;
918 	bool overwrite = !(flags & RENAME_EXCHANGE);
919 	bool is_dir = d_is_dir(old);
920 	bool new_is_dir = d_is_dir(new);
921 	bool samedir = olddir == newdir;
922 	struct dentry *opaquedir = NULL;
923 	const struct cred *old_cred = NULL;
924 
925 	err = -EINVAL;
926 	if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
927 		goto out;
928 
929 	flags &= ~RENAME_NOREPLACE;
930 
931 	/* Don't copy up directory trees */
932 	err = -EXDEV;
933 	if (!ovl_can_move(old))
934 		goto out;
935 	if (!overwrite && !ovl_can_move(new))
936 		goto out;
937 
938 	err = ovl_want_write(old);
939 	if (err)
940 		goto out;
941 
942 	err = ovl_copy_up(old);
943 	if (err)
944 		goto out_drop_write;
945 
946 	err = ovl_copy_up(new->d_parent);
947 	if (err)
948 		goto out_drop_write;
949 	if (!overwrite) {
950 		err = ovl_copy_up(new);
951 		if (err)
952 			goto out_drop_write;
953 	} else {
954 		err = ovl_nlink_start(new, &locked);
955 		if (err)
956 			goto out_drop_write;
957 	}
958 
959 	old_cred = ovl_override_creds(old->d_sb);
960 
961 	if (overwrite && new_is_dir && ovl_type_merge_or_lower(new)) {
962 		opaquedir = ovl_check_empty_and_clear(new);
963 		err = PTR_ERR(opaquedir);
964 		if (IS_ERR(opaquedir)) {
965 			opaquedir = NULL;
966 			goto out_revert_creds;
967 		}
968 	}
969 
970 	if (overwrite) {
971 		if (ovl_lower_positive(old)) {
972 			if (!ovl_dentry_is_whiteout(new)) {
973 				/* Whiteout source */
974 				flags |= RENAME_WHITEOUT;
975 			} else {
976 				/* Switch whiteouts */
977 				flags |= RENAME_EXCHANGE;
978 			}
979 		} else if (is_dir && ovl_dentry_is_whiteout(new)) {
980 			flags |= RENAME_EXCHANGE;
981 			cleanup_whiteout = true;
982 		}
983 	}
984 
985 	old_upperdir = ovl_dentry_upper(old->d_parent);
986 	new_upperdir = ovl_dentry_upper(new->d_parent);
987 
988 	if (!samedir) {
989 		/*
990 		 * When moving a merge dir or non-dir with copy up origin into
991 		 * a new parent, we are marking the new parent dir "impure".
992 		 * When ovl_iterate() iterates an "impure" upper dir, it will
993 		 * lookup the origin inodes of the entries to fill d_ino.
994 		 */
995 		if (ovl_type_origin(old)) {
996 			err = ovl_set_impure(new->d_parent, new_upperdir);
997 			if (err)
998 				goto out_revert_creds;
999 		}
1000 		if (!overwrite && ovl_type_origin(new)) {
1001 			err = ovl_set_impure(old->d_parent, old_upperdir);
1002 			if (err)
1003 				goto out_revert_creds;
1004 		}
1005 	}
1006 
1007 	trap = lock_rename(new_upperdir, old_upperdir);
1008 
1009 	olddentry = lookup_one_len(old->d_name.name, old_upperdir,
1010 				   old->d_name.len);
1011 	err = PTR_ERR(olddentry);
1012 	if (IS_ERR(olddentry))
1013 		goto out_unlock;
1014 
1015 	err = -ESTALE;
1016 	if (!ovl_matches_upper(old, olddentry))
1017 		goto out_dput_old;
1018 
1019 	newdentry = lookup_one_len(new->d_name.name, new_upperdir,
1020 				   new->d_name.len);
1021 	err = PTR_ERR(newdentry);
1022 	if (IS_ERR(newdentry))
1023 		goto out_dput_old;
1024 
1025 	old_opaque = ovl_dentry_is_opaque(old);
1026 	new_opaque = ovl_dentry_is_opaque(new);
1027 
1028 	err = -ESTALE;
1029 	if (d_inode(new) && ovl_dentry_upper(new)) {
1030 		if (opaquedir) {
1031 			if (newdentry != opaquedir)
1032 				goto out_dput;
1033 		} else {
1034 			if (!ovl_matches_upper(new, newdentry))
1035 				goto out_dput;
1036 		}
1037 	} else {
1038 		if (!d_is_negative(newdentry) &&
1039 		    (!new_opaque || !ovl_is_whiteout(newdentry)))
1040 			goto out_dput;
1041 	}
1042 
1043 	if (olddentry == trap)
1044 		goto out_dput;
1045 	if (newdentry == trap)
1046 		goto out_dput;
1047 
1048 	if (olddentry->d_inode == newdentry->d_inode)
1049 		goto out_dput;
1050 
1051 	err = 0;
1052 	if (is_dir) {
1053 		if (ovl_type_merge_or_lower(old))
1054 			err = ovl_set_redirect(old, samedir);
1055 		else if (!old_opaque && ovl_type_merge(new->d_parent))
1056 			err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1057 		if (err)
1058 			goto out_dput;
1059 	}
1060 	if (!overwrite && new_is_dir) {
1061 		if (ovl_type_merge_or_lower(new))
1062 			err = ovl_set_redirect(new, samedir);
1063 		else if (!new_opaque && ovl_type_merge(old->d_parent))
1064 			err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1065 		if (err)
1066 			goto out_dput;
1067 	}
1068 
1069 	err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1070 			    new_upperdir->d_inode, newdentry, flags);
1071 	if (err)
1072 		goto out_dput;
1073 
1074 	if (cleanup_whiteout)
1075 		ovl_cleanup(old_upperdir->d_inode, newdentry);
1076 
1077 	if (overwrite && d_inode(new)) {
1078 		if (new_is_dir)
1079 			clear_nlink(d_inode(new));
1080 		else
1081 			drop_nlink(d_inode(new));
1082 	}
1083 
1084 	ovl_dentry_version_inc(old->d_parent,
1085 			       !overwrite && ovl_type_origin(new));
1086 	ovl_dentry_version_inc(new->d_parent, ovl_type_origin(old));
1087 
1088 out_dput:
1089 	dput(newdentry);
1090 out_dput_old:
1091 	dput(olddentry);
1092 out_unlock:
1093 	unlock_rename(new_upperdir, old_upperdir);
1094 out_revert_creds:
1095 	ovl_revert_creds(old_cred);
1096 	ovl_nlink_end(new, locked);
1097 out_drop_write:
1098 	ovl_drop_write(old);
1099 out:
1100 	dput(opaquedir);
1101 	return err;
1102 }
1103 
1104 const struct inode_operations ovl_dir_inode_operations = {
1105 	.lookup		= ovl_lookup,
1106 	.mkdir		= ovl_mkdir,
1107 	.symlink	= ovl_symlink,
1108 	.unlink		= ovl_unlink,
1109 	.rmdir		= ovl_rmdir,
1110 	.rename		= ovl_rename,
1111 	.link		= ovl_link,
1112 	.setattr	= ovl_setattr,
1113 	.create		= ovl_create,
1114 	.mknod		= ovl_mknod,
1115 	.permission	= ovl_permission,
1116 	.getattr	= ovl_getattr,
1117 	.listxattr	= ovl_listxattr,
1118 	.get_acl	= ovl_get_acl,
1119 	.update_time	= ovl_update_time,
1120 };
1121