1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3  *
4  * Copyright (C) 2011 Novell Inc.
5  */
6 
7 #include <linux/fs.h>
8 #include <linux/slab.h>
9 #include <linux/cred.h>
10 #include <linux/xattr.h>
11 #include <linux/posix_acl.h>
12 #include <linux/ratelimit.h>
13 #include <linux/fiemap.h>
14 #include <linux/fileattr.h>
15 #include <linux/security.h>
16 #include <linux/namei.h>
17 #include "overlayfs.h"
18 
19 
ovl_setattr(struct user_namespace * mnt_userns,struct dentry * dentry,struct iattr * attr)20 int ovl_setattr(struct user_namespace *mnt_userns, struct dentry *dentry,
21 		struct iattr *attr)
22 {
23 	int err;
24 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
25 	bool full_copy_up = false;
26 	struct dentry *upperdentry;
27 	const struct cred *old_cred;
28 
29 	err = setattr_prepare(&init_user_ns, dentry, attr);
30 	if (err)
31 		return err;
32 
33 	err = ovl_want_write(dentry);
34 	if (err)
35 		goto out;
36 
37 	if (attr->ia_valid & ATTR_SIZE) {
38 		/* Truncate should trigger data copy up as well */
39 		full_copy_up = true;
40 	}
41 
42 	if (!full_copy_up)
43 		err = ovl_copy_up(dentry);
44 	else
45 		err = ovl_copy_up_with_data(dentry);
46 	if (!err) {
47 		struct inode *winode = NULL;
48 
49 		upperdentry = ovl_dentry_upper(dentry);
50 
51 		if (attr->ia_valid & ATTR_SIZE) {
52 			winode = d_inode(upperdentry);
53 			err = get_write_access(winode);
54 			if (err)
55 				goto out_drop_write;
56 		}
57 
58 		if (attr->ia_valid & (ATTR_KILL_SUID|ATTR_KILL_SGID))
59 			attr->ia_valid &= ~ATTR_MODE;
60 
61 		/*
62 		 * We might have to translate ovl file into real file object
63 		 * once use cases emerge.  For now, simply don't let underlying
64 		 * filesystem rely on attr->ia_file
65 		 */
66 		attr->ia_valid &= ~ATTR_FILE;
67 
68 		/*
69 		 * If open(O_TRUNC) is done, VFS calls ->setattr with ATTR_OPEN
70 		 * set.  Overlayfs does not pass O_TRUNC flag to underlying
71 		 * filesystem during open -> do not pass ATTR_OPEN.  This
72 		 * disables optimization in fuse which assumes open(O_TRUNC)
73 		 * already set file size to 0.  But we never passed O_TRUNC to
74 		 * fuse.  So by clearing ATTR_OPEN, fuse will be forced to send
75 		 * setattr request to server.
76 		 */
77 		attr->ia_valid &= ~ATTR_OPEN;
78 
79 		inode_lock(upperdentry->d_inode);
80 		old_cred = ovl_override_creds(dentry->d_sb);
81 		err = ovl_do_notify_change(ofs, upperdentry, attr);
82 		revert_creds(old_cred);
83 		if (!err)
84 			ovl_copyattr(dentry->d_inode);
85 		inode_unlock(upperdentry->d_inode);
86 
87 		if (winode)
88 			put_write_access(winode);
89 	}
90 out_drop_write:
91 	ovl_drop_write(dentry);
92 out:
93 	return err;
94 }
95 
ovl_map_dev_ino(struct dentry * dentry,struct kstat * stat,int fsid)96 static void ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid)
97 {
98 	bool samefs = ovl_same_fs(dentry->d_sb);
99 	unsigned int xinobits = ovl_xino_bits(dentry->d_sb);
100 	unsigned int xinoshift = 64 - xinobits;
101 
102 	if (samefs) {
103 		/*
104 		 * When all layers are on the same fs, all real inode
105 		 * number are unique, so we use the overlay st_dev,
106 		 * which is friendly to du -x.
107 		 */
108 		stat->dev = dentry->d_sb->s_dev;
109 		return;
110 	} else if (xinobits) {
111 		/*
112 		 * All inode numbers of underlying fs should not be using the
113 		 * high xinobits, so we use high xinobits to partition the
114 		 * overlay st_ino address space. The high bits holds the fsid
115 		 * (upper fsid is 0). The lowest xinobit is reserved for mapping
116 		 * the non-persistent inode numbers range in case of overflow.
117 		 * This way all overlay inode numbers are unique and use the
118 		 * overlay st_dev.
119 		 */
120 		if (likely(!(stat->ino >> xinoshift))) {
121 			stat->ino |= ((u64)fsid) << (xinoshift + 1);
122 			stat->dev = dentry->d_sb->s_dev;
123 			return;
124 		} else if (ovl_xino_warn(dentry->d_sb)) {
125 			pr_warn_ratelimited("inode number too big (%pd2, ino=%llu, xinobits=%d)\n",
126 					    dentry, stat->ino, xinobits);
127 		}
128 	}
129 
130 	/* The inode could not be mapped to a unified st_ino address space */
131 	if (S_ISDIR(dentry->d_inode->i_mode)) {
132 		/*
133 		 * Always use the overlay st_dev for directories, so 'find
134 		 * -xdev' will scan the entire overlay mount and won't cross the
135 		 * overlay mount boundaries.
136 		 *
137 		 * If not all layers are on the same fs the pair {real st_ino;
138 		 * overlay st_dev} is not unique, so use the non persistent
139 		 * overlay st_ino for directories.
140 		 */
141 		stat->dev = dentry->d_sb->s_dev;
142 		stat->ino = dentry->d_inode->i_ino;
143 	} else {
144 		/*
145 		 * For non-samefs setup, if we cannot map all layers st_ino
146 		 * to a unified address space, we need to make sure that st_dev
147 		 * is unique per underlying fs, so we use the unique anonymous
148 		 * bdev assigned to the underlying fs.
149 		 */
150 		stat->dev = OVL_FS(dentry->d_sb)->fs[fsid].pseudo_dev;
151 	}
152 }
153 
ovl_getattr(struct user_namespace * mnt_userns,const struct path * path,struct kstat * stat,u32 request_mask,unsigned int flags)154 int ovl_getattr(struct user_namespace *mnt_userns, const struct path *path,
155 		struct kstat *stat, u32 request_mask, unsigned int flags)
156 {
157 	struct dentry *dentry = path->dentry;
158 	enum ovl_path_type type;
159 	struct path realpath;
160 	const struct cred *old_cred;
161 	struct inode *inode = d_inode(dentry);
162 	bool is_dir = S_ISDIR(inode->i_mode);
163 	int fsid = 0;
164 	int err;
165 	bool metacopy_blocks = false;
166 
167 	metacopy_blocks = ovl_is_metacopy_dentry(dentry);
168 
169 	type = ovl_path_real(dentry, &realpath);
170 	old_cred = ovl_override_creds(dentry->d_sb);
171 	err = vfs_getattr(&realpath, stat, request_mask, flags);
172 	if (err)
173 		goto out;
174 
175 	/* Report the effective immutable/append-only STATX flags */
176 	generic_fill_statx_attr(inode, stat);
177 
178 	/*
179 	 * For non-dir or same fs, we use st_ino of the copy up origin.
180 	 * This guaranties constant st_dev/st_ino across copy up.
181 	 * With xino feature and non-samefs, we use st_ino of the copy up
182 	 * origin masked with high bits that represent the layer id.
183 	 *
184 	 * If lower filesystem supports NFS file handles, this also guaranties
185 	 * persistent st_ino across mount cycle.
186 	 */
187 	if (!is_dir || ovl_same_dev(dentry->d_sb)) {
188 		if (!OVL_TYPE_UPPER(type)) {
189 			fsid = ovl_layer_lower(dentry)->fsid;
190 		} else if (OVL_TYPE_ORIGIN(type)) {
191 			struct kstat lowerstat;
192 			u32 lowermask = STATX_INO | STATX_BLOCKS |
193 					(!is_dir ? STATX_NLINK : 0);
194 
195 			ovl_path_lower(dentry, &realpath);
196 			err = vfs_getattr(&realpath, &lowerstat,
197 					  lowermask, flags);
198 			if (err)
199 				goto out;
200 
201 			/*
202 			 * Lower hardlinks may be broken on copy up to different
203 			 * upper files, so we cannot use the lower origin st_ino
204 			 * for those different files, even for the same fs case.
205 			 *
206 			 * Similarly, several redirected dirs can point to the
207 			 * same dir on a lower layer. With the "verify_lower"
208 			 * feature, we do not use the lower origin st_ino, if
209 			 * we haven't verified that this redirect is unique.
210 			 *
211 			 * With inodes index enabled, it is safe to use st_ino
212 			 * of an indexed origin. The index validates that the
213 			 * upper hardlink is not broken and that a redirected
214 			 * dir is the only redirect to that origin.
215 			 */
216 			if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) ||
217 			    (!ovl_verify_lower(dentry->d_sb) &&
218 			     (is_dir || lowerstat.nlink == 1))) {
219 				fsid = ovl_layer_lower(dentry)->fsid;
220 				stat->ino = lowerstat.ino;
221 			}
222 
223 			/*
224 			 * If we are querying a metacopy dentry and lower
225 			 * dentry is data dentry, then use the blocks we
226 			 * queried just now. We don't have to do additional
227 			 * vfs_getattr(). If lower itself is metacopy, then
228 			 * additional vfs_getattr() is unavoidable.
229 			 */
230 			if (metacopy_blocks &&
231 			    realpath.dentry == ovl_dentry_lowerdata(dentry)) {
232 				stat->blocks = lowerstat.blocks;
233 				metacopy_blocks = false;
234 			}
235 		}
236 
237 		if (metacopy_blocks) {
238 			/*
239 			 * If lower is not same as lowerdata or if there was
240 			 * no origin on upper, we can end up here.
241 			 */
242 			struct kstat lowerdatastat;
243 			u32 lowermask = STATX_BLOCKS;
244 
245 			ovl_path_lowerdata(dentry, &realpath);
246 			err = vfs_getattr(&realpath, &lowerdatastat,
247 					  lowermask, flags);
248 			if (err)
249 				goto out;
250 			stat->blocks = lowerdatastat.blocks;
251 		}
252 	}
253 
254 	ovl_map_dev_ino(dentry, stat, fsid);
255 
256 	/*
257 	 * It's probably not worth it to count subdirs to get the
258 	 * correct link count.  nlink=1 seems to pacify 'find' and
259 	 * other utilities.
260 	 */
261 	if (is_dir && OVL_TYPE_MERGE(type))
262 		stat->nlink = 1;
263 
264 	/*
265 	 * Return the overlay inode nlinks for indexed upper inodes.
266 	 * Overlay inode nlink counts the union of the upper hardlinks
267 	 * and non-covered lower hardlinks. It does not include the upper
268 	 * index hardlink.
269 	 */
270 	if (!is_dir && ovl_test_flag(OVL_INDEX, d_inode(dentry)))
271 		stat->nlink = dentry->d_inode->i_nlink;
272 
273 out:
274 	revert_creds(old_cred);
275 
276 	return err;
277 }
278 
ovl_permission(struct user_namespace * mnt_userns,struct inode * inode,int mask)279 int ovl_permission(struct user_namespace *mnt_userns,
280 		   struct inode *inode, int mask)
281 {
282 	struct inode *upperinode = ovl_inode_upper(inode);
283 	struct inode *realinode;
284 	struct path realpath;
285 	const struct cred *old_cred;
286 	int err;
287 
288 	/* Careful in RCU walk mode */
289 	ovl_i_path_real(inode, &realpath);
290 	if (!realpath.dentry) {
291 		WARN_ON(!(mask & MAY_NOT_BLOCK));
292 		return -ECHILD;
293 	}
294 
295 	/*
296 	 * Check overlay inode with the creds of task and underlying inode
297 	 * with creds of mounter
298 	 */
299 	err = generic_permission(&init_user_ns, inode, mask);
300 	if (err)
301 		return err;
302 
303 	realinode = d_inode(realpath.dentry);
304 	old_cred = ovl_override_creds(inode->i_sb);
305 	if (!upperinode &&
306 	    !special_file(realinode->i_mode) && mask & MAY_WRITE) {
307 		mask &= ~(MAY_WRITE | MAY_APPEND);
308 		/* Make sure mounter can read file for copy up later */
309 		mask |= MAY_READ;
310 	}
311 	err = inode_permission(mnt_user_ns(realpath.mnt), realinode, mask);
312 	revert_creds(old_cred);
313 
314 	return err;
315 }
316 
ovl_get_link(struct dentry * dentry,struct inode * inode,struct delayed_call * done)317 static const char *ovl_get_link(struct dentry *dentry,
318 				struct inode *inode,
319 				struct delayed_call *done)
320 {
321 	const struct cred *old_cred;
322 	const char *p;
323 
324 	if (!dentry)
325 		return ERR_PTR(-ECHILD);
326 
327 	old_cred = ovl_override_creds(dentry->d_sb);
328 	p = vfs_get_link(ovl_dentry_real(dentry), done);
329 	revert_creds(old_cred);
330 	return p;
331 }
332 
ovl_is_private_xattr(struct super_block * sb,const char * name)333 bool ovl_is_private_xattr(struct super_block *sb, const char *name)
334 {
335 	struct ovl_fs *ofs = sb->s_fs_info;
336 
337 	if (ofs->config.userxattr)
338 		return strncmp(name, OVL_XATTR_USER_PREFIX,
339 			       sizeof(OVL_XATTR_USER_PREFIX) - 1) == 0;
340 	else
341 		return strncmp(name, OVL_XATTR_TRUSTED_PREFIX,
342 			       sizeof(OVL_XATTR_TRUSTED_PREFIX) - 1) == 0;
343 }
344 
ovl_xattr_set(struct dentry * dentry,struct inode * inode,const char * name,const void * value,size_t size,int flags)345 int ovl_xattr_set(struct dentry *dentry, struct inode *inode, const char *name,
346 		  const void *value, size_t size, int flags)
347 {
348 	int err;
349 	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
350 	struct dentry *upperdentry = ovl_i_dentry_upper(inode);
351 	struct dentry *realdentry = upperdentry ?: ovl_dentry_lower(dentry);
352 	struct path realpath;
353 	const struct cred *old_cred;
354 
355 	err = ovl_want_write(dentry);
356 	if (err)
357 		goto out;
358 
359 	if (!value && !upperdentry) {
360 		ovl_path_lower(dentry, &realpath);
361 		old_cred = ovl_override_creds(dentry->d_sb);
362 		err = vfs_getxattr(mnt_user_ns(realpath.mnt), realdentry, name, NULL, 0);
363 		revert_creds(old_cred);
364 		if (err < 0)
365 			goto out_drop_write;
366 	}
367 
368 	if (!upperdentry) {
369 		err = ovl_copy_up(dentry);
370 		if (err)
371 			goto out_drop_write;
372 
373 		realdentry = ovl_dentry_upper(dentry);
374 	}
375 
376 	old_cred = ovl_override_creds(dentry->d_sb);
377 	if (value) {
378 		err = ovl_do_setxattr(ofs, realdentry, name, value, size,
379 				      flags);
380 	} else {
381 		WARN_ON(flags != XATTR_REPLACE);
382 		err = ovl_do_removexattr(ofs, realdentry, name);
383 	}
384 	revert_creds(old_cred);
385 
386 	/* copy c/mtime */
387 	ovl_copyattr(inode);
388 
389 out_drop_write:
390 	ovl_drop_write(dentry);
391 out:
392 	return err;
393 }
394 
ovl_xattr_get(struct dentry * dentry,struct inode * inode,const char * name,void * value,size_t size)395 int ovl_xattr_get(struct dentry *dentry, struct inode *inode, const char *name,
396 		  void *value, size_t size)
397 {
398 	ssize_t res;
399 	const struct cred *old_cred;
400 	struct path realpath;
401 
402 	ovl_i_path_real(inode, &realpath);
403 	old_cred = ovl_override_creds(dentry->d_sb);
404 	res = vfs_getxattr(mnt_user_ns(realpath.mnt), realpath.dentry, name, value, size);
405 	revert_creds(old_cred);
406 	return res;
407 }
408 
ovl_can_list(struct super_block * sb,const char * s)409 static bool ovl_can_list(struct super_block *sb, const char *s)
410 {
411 	/* Never list private (.overlay) */
412 	if (ovl_is_private_xattr(sb, s))
413 		return false;
414 
415 	/* List all non-trusted xattrs */
416 	if (strncmp(s, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) != 0)
417 		return true;
418 
419 	/* list other trusted for superuser only */
420 	return ns_capable_noaudit(&init_user_ns, CAP_SYS_ADMIN);
421 }
422 
ovl_listxattr(struct dentry * dentry,char * list,size_t size)423 ssize_t ovl_listxattr(struct dentry *dentry, char *list, size_t size)
424 {
425 	struct dentry *realdentry = ovl_dentry_real(dentry);
426 	ssize_t res;
427 	size_t len;
428 	char *s;
429 	const struct cred *old_cred;
430 
431 	old_cred = ovl_override_creds(dentry->d_sb);
432 	res = vfs_listxattr(realdentry, list, size);
433 	revert_creds(old_cred);
434 	if (res <= 0 || size == 0)
435 		return res;
436 
437 	/* filter out private xattrs */
438 	for (s = list, len = res; len;) {
439 		size_t slen = strnlen(s, len) + 1;
440 
441 		/* underlying fs providing us with an broken xattr list? */
442 		if (WARN_ON(slen > len))
443 			return -EIO;
444 
445 		len -= slen;
446 		if (!ovl_can_list(dentry->d_sb, s)) {
447 			res -= slen;
448 			memmove(s, s + slen, len);
449 		} else {
450 			s += slen;
451 		}
452 	}
453 
454 	return res;
455 }
456 
457 #ifdef CONFIG_FS_POSIX_ACL
458 /*
459  * Apply the idmapping of the layer to POSIX ACLs. The caller must pass a clone
460  * of the POSIX ACLs retrieved from the lower layer to this function to not
461  * alter the POSIX ACLs for the underlying filesystem.
462  */
ovl_idmap_posix_acl(struct inode * realinode,struct user_namespace * mnt_userns,struct posix_acl * acl)463 static void ovl_idmap_posix_acl(struct inode *realinode,
464 				struct user_namespace *mnt_userns,
465 				struct posix_acl *acl)
466 {
467 	struct user_namespace *fs_userns = i_user_ns(realinode);
468 
469 	for (unsigned int i = 0; i < acl->a_count; i++) {
470 		vfsuid_t vfsuid;
471 		vfsgid_t vfsgid;
472 
473 		struct posix_acl_entry *e = &acl->a_entries[i];
474 		switch (e->e_tag) {
475 		case ACL_USER:
476 			vfsuid = make_vfsuid(mnt_userns, fs_userns, e->e_uid);
477 			e->e_uid = vfsuid_into_kuid(vfsuid);
478 			break;
479 		case ACL_GROUP:
480 			vfsgid = make_vfsgid(mnt_userns, fs_userns, e->e_gid);
481 			e->e_gid = vfsgid_into_kgid(vfsgid);
482 			break;
483 		}
484 	}
485 }
486 
487 /*
488  * When the relevant layer is an idmapped mount we need to take the idmapping
489  * of the layer into account and translate any ACL_{GROUP,USER} values
490  * according to the idmapped mount.
491  *
492  * We cannot alter the ACLs returned from the relevant layer as that would
493  * alter the cached values filesystem wide for the lower filesystem. Instead we
494  * can clone the ACLs and then apply the relevant idmapping of the layer.
495  *
496  * This is obviously only relevant when idmapped layers are used.
497  */
ovl_get_acl(struct inode * inode,int type,bool rcu)498 struct posix_acl *ovl_get_acl(struct inode *inode, int type, bool rcu)
499 {
500 	struct inode *realinode = ovl_inode_real(inode);
501 	struct posix_acl *acl, *clone;
502 	struct path realpath;
503 
504 	if (!IS_POSIXACL(realinode))
505 		return NULL;
506 
507 	/* Careful in RCU walk mode */
508 	ovl_i_path_real(inode, &realpath);
509 	if (!realpath.dentry) {
510 		WARN_ON(!rcu);
511 		return ERR_PTR(-ECHILD);
512 	}
513 
514 	if (rcu) {
515 		acl = get_cached_acl_rcu(realinode, type);
516 	} else {
517 		const struct cred *old_cred;
518 
519 		old_cred = ovl_override_creds(inode->i_sb);
520 		acl = get_acl(realinode, type);
521 		revert_creds(old_cred);
522 	}
523 	/*
524 	 * If there are no POSIX ACLs, or we encountered an error,
525 	 * or the layer isn't idmapped we don't need to do anything.
526 	 */
527 	if (!is_idmapped_mnt(realpath.mnt) || IS_ERR_OR_NULL(acl))
528 		return acl;
529 
530 	/*
531 	 * We only get here if the layer is idmapped. So drop out of RCU path
532 	 * walk so we can clone the ACLs. There's no need to release the ACLs
533 	 * since get_cached_acl_rcu() doesn't take a reference on the ACLs.
534 	 */
535 	if (rcu)
536 		return ERR_PTR(-ECHILD);
537 
538 	clone = posix_acl_clone(acl, GFP_KERNEL);
539 	if (!clone)
540 		clone = ERR_PTR(-ENOMEM);
541 	else
542 		ovl_idmap_posix_acl(realinode, mnt_user_ns(realpath.mnt), clone);
543 	/*
544 	 * Since we're not in RCU path walk we always need to release the
545 	 * original ACLs.
546 	 */
547 	posix_acl_release(acl);
548 	return clone;
549 }
550 #endif
551 
ovl_update_time(struct inode * inode,struct timespec64 * ts,int flags)552 int ovl_update_time(struct inode *inode, struct timespec64 *ts, int flags)
553 {
554 	if (flags & S_ATIME) {
555 		struct ovl_fs *ofs = inode->i_sb->s_fs_info;
556 		struct path upperpath = {
557 			.mnt = ovl_upper_mnt(ofs),
558 			.dentry = ovl_upperdentry_dereference(OVL_I(inode)),
559 		};
560 
561 		if (upperpath.dentry) {
562 			touch_atime(&upperpath);
563 			inode->i_atime = d_inode(upperpath.dentry)->i_atime;
564 		}
565 	}
566 	return 0;
567 }
568 
ovl_fiemap(struct inode * inode,struct fiemap_extent_info * fieinfo,u64 start,u64 len)569 static int ovl_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
570 		      u64 start, u64 len)
571 {
572 	int err;
573 	struct inode *realinode = ovl_inode_realdata(inode);
574 	const struct cred *old_cred;
575 
576 	if (!realinode->i_op->fiemap)
577 		return -EOPNOTSUPP;
578 
579 	old_cred = ovl_override_creds(inode->i_sb);
580 	err = realinode->i_op->fiemap(realinode, fieinfo, start, len);
581 	revert_creds(old_cred);
582 
583 	return err;
584 }
585 
586 /*
587  * Work around the fact that security_file_ioctl() takes a file argument.
588  * Introducing security_inode_fileattr_get/set() hooks would solve this issue
589  * properly.
590  */
ovl_security_fileattr(const struct path * realpath,struct fileattr * fa,bool set)591 static int ovl_security_fileattr(const struct path *realpath, struct fileattr *fa,
592 				 bool set)
593 {
594 	struct file *file;
595 	unsigned int cmd;
596 	int err;
597 
598 	file = dentry_open(realpath, O_RDONLY, current_cred());
599 	if (IS_ERR(file))
600 		return PTR_ERR(file);
601 
602 	if (set)
603 		cmd = fa->fsx_valid ? FS_IOC_FSSETXATTR : FS_IOC_SETFLAGS;
604 	else
605 		cmd = fa->fsx_valid ? FS_IOC_FSGETXATTR : FS_IOC_GETFLAGS;
606 
607 	err = security_file_ioctl(file, cmd, 0);
608 	fput(file);
609 
610 	return err;
611 }
612 
ovl_real_fileattr_set(const struct path * realpath,struct fileattr * fa)613 int ovl_real_fileattr_set(const struct path *realpath, struct fileattr *fa)
614 {
615 	int err;
616 
617 	err = ovl_security_fileattr(realpath, fa, true);
618 	if (err)
619 		return err;
620 
621 	return vfs_fileattr_set(mnt_user_ns(realpath->mnt), realpath->dentry, fa);
622 }
623 
ovl_fileattr_set(struct user_namespace * mnt_userns,struct dentry * dentry,struct fileattr * fa)624 int ovl_fileattr_set(struct user_namespace *mnt_userns,
625 		     struct dentry *dentry, struct fileattr *fa)
626 {
627 	struct inode *inode = d_inode(dentry);
628 	struct path upperpath;
629 	const struct cred *old_cred;
630 	unsigned int flags;
631 	int err;
632 
633 	err = ovl_want_write(dentry);
634 	if (err)
635 		goto out;
636 
637 	err = ovl_copy_up(dentry);
638 	if (!err) {
639 		ovl_path_real(dentry, &upperpath);
640 
641 		old_cred = ovl_override_creds(inode->i_sb);
642 		/*
643 		 * Store immutable/append-only flags in xattr and clear them
644 		 * in upper fileattr (in case they were set by older kernel)
645 		 * so children of "ovl-immutable" directories lower aliases of
646 		 * "ovl-immutable" hardlinks could be copied up.
647 		 * Clear xattr when flags are cleared.
648 		 */
649 		err = ovl_set_protattr(inode, upperpath.dentry, fa);
650 		if (!err)
651 			err = ovl_real_fileattr_set(&upperpath, fa);
652 		revert_creds(old_cred);
653 
654 		/*
655 		 * Merge real inode flags with inode flags read from
656 		 * overlay.protattr xattr
657 		 */
658 		flags = ovl_inode_real(inode)->i_flags & OVL_COPY_I_FLAGS_MASK;
659 
660 		BUILD_BUG_ON(OVL_PROT_I_FLAGS_MASK & ~OVL_COPY_I_FLAGS_MASK);
661 		flags |= inode->i_flags & OVL_PROT_I_FLAGS_MASK;
662 		inode_set_flags(inode, flags, OVL_COPY_I_FLAGS_MASK);
663 
664 		/* Update ctime */
665 		ovl_copyattr(inode);
666 	}
667 	ovl_drop_write(dentry);
668 out:
669 	return err;
670 }
671 
672 /* Convert inode protection flags to fileattr flags */
ovl_fileattr_prot_flags(struct inode * inode,struct fileattr * fa)673 static void ovl_fileattr_prot_flags(struct inode *inode, struct fileattr *fa)
674 {
675 	BUILD_BUG_ON(OVL_PROT_FS_FLAGS_MASK & ~FS_COMMON_FL);
676 	BUILD_BUG_ON(OVL_PROT_FSX_FLAGS_MASK & ~FS_XFLAG_COMMON);
677 
678 	if (inode->i_flags & S_APPEND) {
679 		fa->flags |= FS_APPEND_FL;
680 		fa->fsx_xflags |= FS_XFLAG_APPEND;
681 	}
682 	if (inode->i_flags & S_IMMUTABLE) {
683 		fa->flags |= FS_IMMUTABLE_FL;
684 		fa->fsx_xflags |= FS_XFLAG_IMMUTABLE;
685 	}
686 }
687 
ovl_real_fileattr_get(const struct path * realpath,struct fileattr * fa)688 int ovl_real_fileattr_get(const struct path *realpath, struct fileattr *fa)
689 {
690 	int err;
691 
692 	err = ovl_security_fileattr(realpath, fa, false);
693 	if (err)
694 		return err;
695 
696 	err = vfs_fileattr_get(realpath->dentry, fa);
697 	if (err == -ENOIOCTLCMD)
698 		err = -ENOTTY;
699 	return err;
700 }
701 
ovl_fileattr_get(struct dentry * dentry,struct fileattr * fa)702 int ovl_fileattr_get(struct dentry *dentry, struct fileattr *fa)
703 {
704 	struct inode *inode = d_inode(dentry);
705 	struct path realpath;
706 	const struct cred *old_cred;
707 	int err;
708 
709 	ovl_path_real(dentry, &realpath);
710 
711 	old_cred = ovl_override_creds(inode->i_sb);
712 	err = ovl_real_fileattr_get(&realpath, fa);
713 	ovl_fileattr_prot_flags(inode, fa);
714 	revert_creds(old_cred);
715 
716 	return err;
717 }
718 
719 static const struct inode_operations ovl_file_inode_operations = {
720 	.setattr	= ovl_setattr,
721 	.permission	= ovl_permission,
722 	.getattr	= ovl_getattr,
723 	.listxattr	= ovl_listxattr,
724 	.get_acl	= ovl_get_acl,
725 	.update_time	= ovl_update_time,
726 	.fiemap		= ovl_fiemap,
727 	.fileattr_get	= ovl_fileattr_get,
728 	.fileattr_set	= ovl_fileattr_set,
729 };
730 
731 static const struct inode_operations ovl_symlink_inode_operations = {
732 	.setattr	= ovl_setattr,
733 	.get_link	= ovl_get_link,
734 	.getattr	= ovl_getattr,
735 	.listxattr	= ovl_listxattr,
736 	.update_time	= ovl_update_time,
737 };
738 
739 static const struct inode_operations ovl_special_inode_operations = {
740 	.setattr	= ovl_setattr,
741 	.permission	= ovl_permission,
742 	.getattr	= ovl_getattr,
743 	.listxattr	= ovl_listxattr,
744 	.get_acl	= ovl_get_acl,
745 	.update_time	= ovl_update_time,
746 };
747 
748 static const struct address_space_operations ovl_aops = {
749 	/* For O_DIRECT dentry_open() checks f_mapping->a_ops->direct_IO */
750 	.direct_IO		= noop_direct_IO,
751 };
752 
753 /*
754  * It is possible to stack overlayfs instance on top of another
755  * overlayfs instance as lower layer. We need to annotate the
756  * stackable i_mutex locks according to stack level of the super
757  * block instance. An overlayfs instance can never be in stack
758  * depth 0 (there is always a real fs below it).  An overlayfs
759  * inode lock will use the lockdep annotation ovl_i_mutex_key[depth].
760  *
761  * For example, here is a snip from /proc/lockdep_chains after
762  * dir_iterate of nested overlayfs:
763  *
764  * [...] &ovl_i_mutex_dir_key[depth]   (stack_depth=2)
765  * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
766  * [...] &type->i_mutex_dir_key        (stack_depth=0)
767  *
768  * Locking order w.r.t ovl_want_write() is important for nested overlayfs.
769  *
770  * This chain is valid:
771  * - inode->i_rwsem			(inode_lock[2])
772  * - upper_mnt->mnt_sb->s_writers	(ovl_want_write[0])
773  * - OVL_I(inode)->lock			(ovl_inode_lock[2])
774  * - OVL_I(lowerinode)->lock		(ovl_inode_lock[1])
775  *
776  * And this chain is valid:
777  * - inode->i_rwsem			(inode_lock[2])
778  * - OVL_I(inode)->lock			(ovl_inode_lock[2])
779  * - lowerinode->i_rwsem		(inode_lock[1])
780  * - OVL_I(lowerinode)->lock		(ovl_inode_lock[1])
781  *
782  * But lowerinode->i_rwsem SHOULD NOT be acquired while ovl_want_write() is
783  * held, because it is in reverse order of the non-nested case using the same
784  * upper fs:
785  * - inode->i_rwsem			(inode_lock[1])
786  * - upper_mnt->mnt_sb->s_writers	(ovl_want_write[0])
787  * - OVL_I(inode)->lock			(ovl_inode_lock[1])
788  */
789 #define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
790 
ovl_lockdep_annotate_inode_mutex_key(struct inode * inode)791 static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
792 {
793 #ifdef CONFIG_LOCKDEP
794 	static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING];
795 	static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING];
796 	static struct lock_class_key ovl_i_lock_key[OVL_MAX_NESTING];
797 
798 	int depth = inode->i_sb->s_stack_depth - 1;
799 
800 	if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING))
801 		depth = 0;
802 
803 	if (S_ISDIR(inode->i_mode))
804 		lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]);
805 	else
806 		lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]);
807 
808 	lockdep_set_class(&OVL_I(inode)->lock, &ovl_i_lock_key[depth]);
809 #endif
810 }
811 
ovl_next_ino(struct inode * inode)812 static void ovl_next_ino(struct inode *inode)
813 {
814 	struct ovl_fs *ofs = inode->i_sb->s_fs_info;
815 
816 	inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
817 	if (unlikely(!inode->i_ino))
818 		inode->i_ino = atomic_long_inc_return(&ofs->last_ino);
819 }
820 
ovl_map_ino(struct inode * inode,unsigned long ino,int fsid)821 static void ovl_map_ino(struct inode *inode, unsigned long ino, int fsid)
822 {
823 	int xinobits = ovl_xino_bits(inode->i_sb);
824 	unsigned int xinoshift = 64 - xinobits;
825 
826 	/*
827 	 * When d_ino is consistent with st_ino (samefs or i_ino has enough
828 	 * bits to encode layer), set the same value used for st_ino to i_ino,
829 	 * so inode number exposed via /proc/locks and a like will be
830 	 * consistent with d_ino and st_ino values. An i_ino value inconsistent
831 	 * with d_ino also causes nfsd readdirplus to fail.
832 	 */
833 	inode->i_ino = ino;
834 	if (ovl_same_fs(inode->i_sb)) {
835 		return;
836 	} else if (xinobits && likely(!(ino >> xinoshift))) {
837 		inode->i_ino |= (unsigned long)fsid << (xinoshift + 1);
838 		return;
839 	}
840 
841 	/*
842 	 * For directory inodes on non-samefs with xino disabled or xino
843 	 * overflow, we allocate a non-persistent inode number, to be used for
844 	 * resolving st_ino collisions in ovl_map_dev_ino().
845 	 *
846 	 * To avoid ino collision with legitimate xino values from upper
847 	 * layer (fsid 0), use the lowest xinobit to map the non
848 	 * persistent inode numbers to the unified st_ino address space.
849 	 */
850 	if (S_ISDIR(inode->i_mode)) {
851 		ovl_next_ino(inode);
852 		if (xinobits) {
853 			inode->i_ino &= ~0UL >> xinobits;
854 			inode->i_ino |= 1UL << xinoshift;
855 		}
856 	}
857 }
858 
ovl_inode_init(struct inode * inode,struct ovl_inode_params * oip,unsigned long ino,int fsid)859 void ovl_inode_init(struct inode *inode, struct ovl_inode_params *oip,
860 		    unsigned long ino, int fsid)
861 {
862 	struct inode *realinode;
863 	struct ovl_inode *oi = OVL_I(inode);
864 
865 	if (oip->upperdentry)
866 		oi->__upperdentry = oip->upperdentry;
867 	if (oip->lowerpath && oip->lowerpath->dentry) {
868 		oi->lowerpath.dentry = dget(oip->lowerpath->dentry);
869 		oi->lowerpath.layer = oip->lowerpath->layer;
870 	}
871 	if (oip->lowerdata)
872 		oi->lowerdata = igrab(d_inode(oip->lowerdata));
873 
874 	realinode = ovl_inode_real(inode);
875 	ovl_copyattr(inode);
876 	ovl_copyflags(realinode, inode);
877 	ovl_map_ino(inode, ino, fsid);
878 }
879 
ovl_fill_inode(struct inode * inode,umode_t mode,dev_t rdev)880 static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
881 {
882 	inode->i_mode = mode;
883 	inode->i_flags |= S_NOCMTIME;
884 #ifdef CONFIG_FS_POSIX_ACL
885 	inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
886 #endif
887 
888 	ovl_lockdep_annotate_inode_mutex_key(inode);
889 
890 	switch (mode & S_IFMT) {
891 	case S_IFREG:
892 		inode->i_op = &ovl_file_inode_operations;
893 		inode->i_fop = &ovl_file_operations;
894 		inode->i_mapping->a_ops = &ovl_aops;
895 		break;
896 
897 	case S_IFDIR:
898 		inode->i_op = &ovl_dir_inode_operations;
899 		inode->i_fop = &ovl_dir_operations;
900 		break;
901 
902 	case S_IFLNK:
903 		inode->i_op = &ovl_symlink_inode_operations;
904 		break;
905 
906 	default:
907 		inode->i_op = &ovl_special_inode_operations;
908 		init_special_inode(inode, mode, rdev);
909 		break;
910 	}
911 }
912 
913 /*
914  * With inodes index enabled, an overlay inode nlink counts the union of upper
915  * hardlinks and non-covered lower hardlinks. During the lifetime of a non-pure
916  * upper inode, the following nlink modifying operations can happen:
917  *
918  * 1. Lower hardlink copy up
919  * 2. Upper hardlink created, unlinked or renamed over
920  * 3. Lower hardlink whiteout or renamed over
921  *
922  * For the first, copy up case, the union nlink does not change, whether the
923  * operation succeeds or fails, but the upper inode nlink may change.
924  * Therefore, before copy up, we store the union nlink value relative to the
925  * lower inode nlink in the index inode xattr .overlay.nlink.
926  *
927  * For the second, upper hardlink case, the union nlink should be incremented
928  * or decremented IFF the operation succeeds, aligned with nlink change of the
929  * upper inode. Therefore, before link/unlink/rename, we store the union nlink
930  * value relative to the upper inode nlink in the index inode.
931  *
932  * For the last, lower cover up case, we simplify things by preceding the
933  * whiteout or cover up with copy up. This makes sure that there is an index
934  * upper inode where the nlink xattr can be stored before the copied up upper
935  * entry is unlink.
936  */
937 #define OVL_NLINK_ADD_UPPER	(1 << 0)
938 
939 /*
940  * On-disk format for indexed nlink:
941  *
942  * nlink relative to the upper inode - "U[+-]NUM"
943  * nlink relative to the lower inode - "L[+-]NUM"
944  */
945 
ovl_set_nlink_common(struct dentry * dentry,struct dentry * realdentry,const char * format)946 static int ovl_set_nlink_common(struct dentry *dentry,
947 				struct dentry *realdentry, const char *format)
948 {
949 	struct inode *inode = d_inode(dentry);
950 	struct inode *realinode = d_inode(realdentry);
951 	char buf[13];
952 	int len;
953 
954 	len = snprintf(buf, sizeof(buf), format,
955 		       (int) (inode->i_nlink - realinode->i_nlink));
956 
957 	if (WARN_ON(len >= sizeof(buf)))
958 		return -EIO;
959 
960 	return ovl_setxattr(OVL_FS(inode->i_sb), ovl_dentry_upper(dentry),
961 			    OVL_XATTR_NLINK, buf, len);
962 }
963 
ovl_set_nlink_upper(struct dentry * dentry)964 int ovl_set_nlink_upper(struct dentry *dentry)
965 {
966 	return ovl_set_nlink_common(dentry, ovl_dentry_upper(dentry), "U%+i");
967 }
968 
ovl_set_nlink_lower(struct dentry * dentry)969 int ovl_set_nlink_lower(struct dentry *dentry)
970 {
971 	return ovl_set_nlink_common(dentry, ovl_dentry_lower(dentry), "L%+i");
972 }
973 
ovl_get_nlink(struct ovl_fs * ofs,struct dentry * lowerdentry,struct dentry * upperdentry,unsigned int fallback)974 unsigned int ovl_get_nlink(struct ovl_fs *ofs, struct dentry *lowerdentry,
975 			   struct dentry *upperdentry,
976 			   unsigned int fallback)
977 {
978 	int nlink_diff;
979 	int nlink;
980 	char buf[13];
981 	int err;
982 
983 	if (!lowerdentry || !upperdentry || d_inode(lowerdentry)->i_nlink == 1)
984 		return fallback;
985 
986 	err = ovl_getxattr_upper(ofs, upperdentry, OVL_XATTR_NLINK,
987 				 &buf, sizeof(buf) - 1);
988 	if (err < 0)
989 		goto fail;
990 
991 	buf[err] = '\0';
992 	if ((buf[0] != 'L' && buf[0] != 'U') ||
993 	    (buf[1] != '+' && buf[1] != '-'))
994 		goto fail;
995 
996 	err = kstrtoint(buf + 1, 10, &nlink_diff);
997 	if (err < 0)
998 		goto fail;
999 
1000 	nlink = d_inode(buf[0] == 'L' ? lowerdentry : upperdentry)->i_nlink;
1001 	nlink += nlink_diff;
1002 
1003 	if (nlink <= 0)
1004 		goto fail;
1005 
1006 	return nlink;
1007 
1008 fail:
1009 	pr_warn_ratelimited("failed to get index nlink (%pd2, err=%i)\n",
1010 			    upperdentry, err);
1011 	return fallback;
1012 }
1013 
ovl_new_inode(struct super_block * sb,umode_t mode,dev_t rdev)1014 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev)
1015 {
1016 	struct inode *inode;
1017 
1018 	inode = new_inode(sb);
1019 	if (inode)
1020 		ovl_fill_inode(inode, mode, rdev);
1021 
1022 	return inode;
1023 }
1024 
ovl_inode_test(struct inode * inode,void * data)1025 static int ovl_inode_test(struct inode *inode, void *data)
1026 {
1027 	return inode->i_private == data;
1028 }
1029 
ovl_inode_set(struct inode * inode,void * data)1030 static int ovl_inode_set(struct inode *inode, void *data)
1031 {
1032 	inode->i_private = data;
1033 	return 0;
1034 }
1035 
ovl_verify_inode(struct inode * inode,struct dentry * lowerdentry,struct dentry * upperdentry,bool strict)1036 static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
1037 			     struct dentry *upperdentry, bool strict)
1038 {
1039 	/*
1040 	 * For directories, @strict verify from lookup path performs consistency
1041 	 * checks, so NULL lower/upper in dentry must match NULL lower/upper in
1042 	 * inode. Non @strict verify from NFS handle decode path passes NULL for
1043 	 * 'unknown' lower/upper.
1044 	 */
1045 	if (S_ISDIR(inode->i_mode) && strict) {
1046 		/* Real lower dir moved to upper layer under us? */
1047 		if (!lowerdentry && ovl_inode_lower(inode))
1048 			return false;
1049 
1050 		/* Lookup of an uncovered redirect origin? */
1051 		if (!upperdentry && ovl_inode_upper(inode))
1052 			return false;
1053 	}
1054 
1055 	/*
1056 	 * Allow non-NULL lower inode in ovl_inode even if lowerdentry is NULL.
1057 	 * This happens when finding a copied up overlay inode for a renamed
1058 	 * or hardlinked overlay dentry and lower dentry cannot be followed
1059 	 * by origin because lower fs does not support file handles.
1060 	 */
1061 	if (lowerdentry && ovl_inode_lower(inode) != d_inode(lowerdentry))
1062 		return false;
1063 
1064 	/*
1065 	 * Allow non-NULL __upperdentry in inode even if upperdentry is NULL.
1066 	 * This happens when finding a lower alias for a copied up hard link.
1067 	 */
1068 	if (upperdentry && ovl_inode_upper(inode) != d_inode(upperdentry))
1069 		return false;
1070 
1071 	return true;
1072 }
1073 
ovl_lookup_inode(struct super_block * sb,struct dentry * real,bool is_upper)1074 struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
1075 			       bool is_upper)
1076 {
1077 	struct inode *inode, *key = d_inode(real);
1078 
1079 	inode = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
1080 	if (!inode)
1081 		return NULL;
1082 
1083 	if (!ovl_verify_inode(inode, is_upper ? NULL : real,
1084 			      is_upper ? real : NULL, false)) {
1085 		iput(inode);
1086 		return ERR_PTR(-ESTALE);
1087 	}
1088 
1089 	return inode;
1090 }
1091 
ovl_lookup_trap_inode(struct super_block * sb,struct dentry * dir)1092 bool ovl_lookup_trap_inode(struct super_block *sb, struct dentry *dir)
1093 {
1094 	struct inode *key = d_inode(dir);
1095 	struct inode *trap;
1096 	bool res;
1097 
1098 	trap = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
1099 	if (!trap)
1100 		return false;
1101 
1102 	res = IS_DEADDIR(trap) && !ovl_inode_upper(trap) &&
1103 				  !ovl_inode_lower(trap);
1104 
1105 	iput(trap);
1106 	return res;
1107 }
1108 
1109 /*
1110  * Create an inode cache entry for layer root dir, that will intentionally
1111  * fail ovl_verify_inode(), so any lookup that will find some layer root
1112  * will fail.
1113  */
ovl_get_trap_inode(struct super_block * sb,struct dentry * dir)1114 struct inode *ovl_get_trap_inode(struct super_block *sb, struct dentry *dir)
1115 {
1116 	struct inode *key = d_inode(dir);
1117 	struct inode *trap;
1118 
1119 	if (!d_is_dir(dir))
1120 		return ERR_PTR(-ENOTDIR);
1121 
1122 	trap = iget5_locked(sb, (unsigned long) key, ovl_inode_test,
1123 			    ovl_inode_set, key);
1124 	if (!trap)
1125 		return ERR_PTR(-ENOMEM);
1126 
1127 	if (!(trap->i_state & I_NEW)) {
1128 		/* Conflicting layer roots? */
1129 		iput(trap);
1130 		return ERR_PTR(-ELOOP);
1131 	}
1132 
1133 	trap->i_mode = S_IFDIR;
1134 	trap->i_flags = S_DEAD;
1135 	unlock_new_inode(trap);
1136 
1137 	return trap;
1138 }
1139 
1140 /*
1141  * Does overlay inode need to be hashed by lower inode?
1142  */
ovl_hash_bylower(struct super_block * sb,struct dentry * upper,struct dentry * lower,bool index)1143 static bool ovl_hash_bylower(struct super_block *sb, struct dentry *upper,
1144 			     struct dentry *lower, bool index)
1145 {
1146 	struct ovl_fs *ofs = sb->s_fs_info;
1147 
1148 	/* No, if pure upper */
1149 	if (!lower)
1150 		return false;
1151 
1152 	/* Yes, if already indexed */
1153 	if (index)
1154 		return true;
1155 
1156 	/* Yes, if won't be copied up */
1157 	if (!ovl_upper_mnt(ofs))
1158 		return true;
1159 
1160 	/* No, if lower hardlink is or will be broken on copy up */
1161 	if ((upper || !ovl_indexdir(sb)) &&
1162 	    !d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
1163 		return false;
1164 
1165 	/* No, if non-indexed upper with NFS export */
1166 	if (sb->s_export_op && upper)
1167 		return false;
1168 
1169 	/* Otherwise, hash by lower inode for fsnotify */
1170 	return true;
1171 }
1172 
ovl_iget5(struct super_block * sb,struct inode * newinode,struct inode * key)1173 static struct inode *ovl_iget5(struct super_block *sb, struct inode *newinode,
1174 			       struct inode *key)
1175 {
1176 	return newinode ? inode_insert5(newinode, (unsigned long) key,
1177 					 ovl_inode_test, ovl_inode_set, key) :
1178 			  iget5_locked(sb, (unsigned long) key,
1179 				       ovl_inode_test, ovl_inode_set, key);
1180 }
1181 
ovl_get_inode(struct super_block * sb,struct ovl_inode_params * oip)1182 struct inode *ovl_get_inode(struct super_block *sb,
1183 			    struct ovl_inode_params *oip)
1184 {
1185 	struct ovl_fs *ofs = OVL_FS(sb);
1186 	struct dentry *upperdentry = oip->upperdentry;
1187 	struct ovl_path *lowerpath = oip->lowerpath;
1188 	struct inode *realinode = upperdentry ? d_inode(upperdentry) : NULL;
1189 	struct inode *inode;
1190 	struct dentry *lowerdentry = lowerpath ? lowerpath->dentry : NULL;
1191 	struct path realpath = {
1192 		.dentry = upperdentry ?: lowerdentry,
1193 		.mnt = upperdentry ? ovl_upper_mnt(ofs) : lowerpath->layer->mnt,
1194 	};
1195 	bool bylower = ovl_hash_bylower(sb, upperdentry, lowerdentry,
1196 					oip->index);
1197 	int fsid = bylower ? lowerpath->layer->fsid : 0;
1198 	bool is_dir;
1199 	unsigned long ino = 0;
1200 	int err = oip->newinode ? -EEXIST : -ENOMEM;
1201 
1202 	if (!realinode)
1203 		realinode = d_inode(lowerdentry);
1204 
1205 	/*
1206 	 * Copy up origin (lower) may exist for non-indexed upper, but we must
1207 	 * not use lower as hash key if this is a broken hardlink.
1208 	 */
1209 	is_dir = S_ISDIR(realinode->i_mode);
1210 	if (upperdentry || bylower) {
1211 		struct inode *key = d_inode(bylower ? lowerdentry :
1212 						      upperdentry);
1213 		unsigned int nlink = is_dir ? 1 : realinode->i_nlink;
1214 
1215 		inode = ovl_iget5(sb, oip->newinode, key);
1216 		if (!inode)
1217 			goto out_err;
1218 		if (!(inode->i_state & I_NEW)) {
1219 			/*
1220 			 * Verify that the underlying files stored in the inode
1221 			 * match those in the dentry.
1222 			 */
1223 			if (!ovl_verify_inode(inode, lowerdentry, upperdentry,
1224 					      true)) {
1225 				iput(inode);
1226 				err = -ESTALE;
1227 				goto out_err;
1228 			}
1229 
1230 			dput(upperdentry);
1231 			kfree(oip->redirect);
1232 			goto out;
1233 		}
1234 
1235 		/* Recalculate nlink for non-dir due to indexing */
1236 		if (!is_dir)
1237 			nlink = ovl_get_nlink(ofs, lowerdentry, upperdentry,
1238 					      nlink);
1239 		set_nlink(inode, nlink);
1240 		ino = key->i_ino;
1241 	} else {
1242 		/* Lower hardlink that will be broken on copy up */
1243 		inode = new_inode(sb);
1244 		if (!inode) {
1245 			err = -ENOMEM;
1246 			goto out_err;
1247 		}
1248 		ino = realinode->i_ino;
1249 		fsid = lowerpath->layer->fsid;
1250 	}
1251 	ovl_fill_inode(inode, realinode->i_mode, realinode->i_rdev);
1252 	ovl_inode_init(inode, oip, ino, fsid);
1253 
1254 	if (upperdentry && ovl_is_impuredir(sb, upperdentry))
1255 		ovl_set_flag(OVL_IMPURE, inode);
1256 
1257 	if (oip->index)
1258 		ovl_set_flag(OVL_INDEX, inode);
1259 
1260 	OVL_I(inode)->redirect = oip->redirect;
1261 
1262 	if (bylower)
1263 		ovl_set_flag(OVL_CONST_INO, inode);
1264 
1265 	/* Check for non-merge dir that may have whiteouts */
1266 	if (is_dir) {
1267 		if (((upperdentry && lowerdentry) || oip->numlower > 1) ||
1268 		    ovl_path_check_origin_xattr(ofs, &realpath)) {
1269 			ovl_set_flag(OVL_WHITEOUTS, inode);
1270 		}
1271 	}
1272 
1273 	/* Check for immutable/append-only inode flags in xattr */
1274 	if (upperdentry)
1275 		ovl_check_protattr(inode, upperdentry);
1276 
1277 	if (inode->i_state & I_NEW)
1278 		unlock_new_inode(inode);
1279 out:
1280 	return inode;
1281 
1282 out_err:
1283 	pr_warn_ratelimited("failed to get inode (%i)\n", err);
1284 	inode = ERR_PTR(err);
1285 	goto out;
1286 }
1287