kernel/fs/overlayfs/dir.c

   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/atomic.h>
  16 #include "overlayfs.h"
  17
  18 void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
  19 {
  20         int err;
  21
  22         dget(wdentry);
  23         if (d_is_dir(wdentry))
  24                 err = ovl_do_rmdir(wdir, wdentry);
  25         else
  26                 err = ovl_do_unlink(wdir, wdentry);
  27         dput(wdentry);
  28
  29         if (err) {
  30                 pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
  31                        wdentry, err);
  32         }
  33 }
  34
  35 struct dentry *ovl_lookup_temp(struct dentry *workdir, struct dentry *dentry)
  36 {
  37         struct dentry *temp;
  38         char name[20];
  39         static atomic_t temp_id = ATOMIC_INIT(0);
  40
  41         /* counter is allowed to wrap, since temp dentries are ephemeral */
  42         snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
  43
  44         temp = lookup_one_len(name, workdir, strlen(name));
  45         if (!IS_ERR(temp) && temp->d_inode) {
  46                 pr_err("overlayfs: workdir/%s already exists\n", name);
  47                 dput(temp);
  48                 temp = ERR_PTR(-EIO);
  49         }
  50
  51         return temp;
  52 }
  53
  54 /* caller holds i_mutex on workdir */
  55 static struct dentry *ovl_whiteout(struct dentry *workdir,
  56                                    struct dentry *dentry)
  57 {
  58         int err;
  59         struct dentry *whiteout;
  60         struct inode *wdir = workdir->d_inode;
  61
  62         whiteout = ovl_lookup_temp(workdir, dentry);
  63         if (IS_ERR(whiteout))
  64                 return whiteout;
  65
  66         err = ovl_do_whiteout(wdir, whiteout);
  67         if (err) {
  68                 dput(whiteout);
  69                 whiteout = ERR_PTR(err);
  70         }
  71
  72         return whiteout;
  73 }
  74
  75 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
  76                     struct kstat *stat, const char *link,
  77                     struct dentry *hardlink, bool debug)
  78 {
  79         int err;
  80
  81         if (newdentry->d_inode)
  82                 return -ESTALE;
  83
  84         if (hardlink) {
  85                 err = ovl_do_link(hardlink, dir, newdentry, debug);
  86         } else {
  87                 switch (stat->mode & S_IFMT) {
  88                 case S_IFREG:
  89                         err = ovl_do_create(dir, newdentry, stat->mode, debug);
  90                         break;
  91
  92                 case S_IFDIR:
  93                         err = ovl_do_mkdir(dir, newdentry, stat->mode, debug);
  94                         break;
  95
  96                 case S_IFCHR:
  97                 case S_IFBLK:
  98                 case S_IFIFO:
  99                 case S_IFSOCK:
 100                         err = ovl_do_mknod(dir, newdentry,
 101                                            stat->mode, stat->rdev, debug);
 102                         break;
 103
 104                 case S_IFLNK:
 105                         err = ovl_do_symlink(dir, newdentry, link, debug);
 106                         break;
 107
 108                 default:
 109                         err = -EPERM;
 110                 }
 111         }
 112         if (!err && WARN_ON(!newdentry->d_inode)) {
 113                 /*
 114                  * Not quite sure if non-instantiated dentry is legal or not.
 115                  * VFS doesn't seem to care so check and warn here.
 116                  */
 117                 err = -ENOENT;
 118         }
 119         return err;
 120 }
 121
 122 static int ovl_set_opaque(struct dentry *upperdentry)
 123 {
 124         return ovl_do_setxattr(upperdentry, OVL_XATTR_OPAQUE, "y", 1, 0);
 125 }
 126
 127 static void ovl_remove_opaque(struct dentry *upperdentry)
 128 {
 129         int err;
 130
 131         err = ovl_do_removexattr(upperdentry, OVL_XATTR_OPAQUE);
 132         if (err) {
 133                 pr_warn("overlayfs: failed to remove opaque from '%s' (%i)\n",
 134                         upperdentry->d_name.name, err);
 135         }
 136 }
 137
 138 static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
 139                          struct kstat *stat)
 140 {
 141         int err;
 142         enum ovl_path_type type;
 143         struct path realpath;
 144
 145         type = ovl_path_real(dentry, &realpath);
 146         err = vfs_getattr(&realpath, stat);
 147         if (err)
 148                 return err;
 149
 150         stat->dev = dentry->d_sb->s_dev;
 151         stat->ino = dentry->d_inode->i_ino;
 152
 153         /*
 154          * It's probably not worth it to count subdirs to get the
 155          * correct link count.  nlink=1 seems to pacify 'find' and
 156          * other utilities.
 157          */
 158         if (OVL_TYPE_MERGE(type))
 159                 stat->nlink = 1;
 160
 161         return 0;
 162 }
 163
 164 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 165                             struct kstat *stat, const char *link,
 166                             struct dentry *hardlink)
 167 {
 168         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 169         struct inode *udir = upperdir->d_inode;
 170         struct dentry *newdentry;
 171         int err;
 172
 173         mutex_lock_nested(&udir->i_mutex, I_MUTEX_PARENT);
 174         newdentry = lookup_one_len(dentry->d_name.name, upperdir,
 175                                    dentry->d_name.len);
 176         err = PTR_ERR(newdentry);
 177         if (IS_ERR(newdentry))
 178                 goto out_unlock;
 179         err = ovl_create_real(udir, newdentry, stat, link, hardlink, false);
 180         if (err)
 181                 goto out_dput;
 182
 183         ovl_dentry_version_inc(dentry->d_parent);
 184         ovl_dentry_update(dentry, newdentry);
 185         ovl_copyattr(newdentry->d_inode, inode);
 186         d_instantiate(dentry, inode);
 187         newdentry = NULL;
 188 out_dput:
 189         dput(newdentry);
 190 out_unlock:
 191         mutex_unlock(&udir->i_mutex);
 192         return err;
 193 }
 194
 195 static int ovl_lock_rename_workdir(struct dentry *workdir,
 196                                    struct dentry *upperdir)
 197 {
 198         /* Workdir should not be the same as upperdir */
 199         if (workdir == upperdir)
 200                 goto err;
 201
 202         /* Workdir should not be subdir of upperdir and vice versa */
 203         if (lock_rename(workdir, upperdir) != NULL)
 204                 goto err_unlock;
 205
 206         return 0;
 207
 208 err_unlock:
 209         unlock_rename(workdir, upperdir);
 210 err:
 211         pr_err("overlayfs: failed to lock workdir+upperdir\n");
 212         return -EIO;
 213 }
 214
 215 static struct dentry *ovl_clear_empty(struct dentry *dentry,
 216                                       struct list_head *list)
 217 {
 218         struct dentry *workdir = ovl_workdir(dentry);
 219         struct inode *wdir = workdir->d_inode;
 220         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 221         struct inode *udir = upperdir->d_inode;
 222         struct path upperpath;
 223         struct dentry *upper;
 224         struct dentry *opaquedir;
 225         struct kstat stat;
 226         int err;
 227
 228         if (WARN_ON(!workdir))
 229                 return ERR_PTR(-EROFS);
 230
 231         err = ovl_lock_rename_workdir(workdir, upperdir);
 232         if (err)
 233                 goto out;
 234
 235         ovl_path_upper(dentry, &upperpath);
 236         err = vfs_getattr(&upperpath, &stat);
 237         if (err)
 238                 goto out_unlock;
 239
 240         err = -ESTALE;
 241         if (!S_ISDIR(stat.mode))
 242                 goto out_unlock;
 243         upper = upperpath.dentry;
 244         if (upper->d_parent->d_inode != udir)
 245                 goto out_unlock;
 246
 247         opaquedir = ovl_lookup_temp(workdir, dentry);
 248         err = PTR_ERR(opaquedir);
 249         if (IS_ERR(opaquedir))
 250                 goto out_unlock;
 251
 252         err = ovl_create_real(wdir, opaquedir, &stat, NULL, NULL, true);
 253         if (err)
 254                 goto out_dput;
 255
 256         err = ovl_copy_xattr(upper, opaquedir);
 257         if (err)
 258                 goto out_cleanup;
 259
 260         err = ovl_set_opaque(opaquedir);
 261         if (err)
 262                 goto out_cleanup;
 263
 264         mutex_lock(&opaquedir->d_inode->i_mutex);
 265         err = ovl_set_attr(opaquedir, &stat);
 266         mutex_unlock(&opaquedir->d_inode->i_mutex);
 267         if (err)
 268                 goto out_cleanup;
 269
 270         err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
 271         if (err)
 272                 goto out_cleanup;
 273
 274         ovl_cleanup_whiteouts(upper, list);
 275         ovl_cleanup(wdir, upper);
 276         unlock_rename(workdir, upperdir);
 277
 278         /* dentry's upper doesn't match now, get rid of it */
 279         d_drop(dentry);
 280
 281         return opaquedir;
 282
 283 out_cleanup:
 284         ovl_cleanup(wdir, opaquedir);
 285 out_dput:
 286         dput(opaquedir);
 287 out_unlock:
 288         unlock_rename(workdir, upperdir);
 289 out:
 290         return ERR_PTR(err);
 291 }
 292
 293 static struct dentry *ovl_check_empty_and_clear(struct dentry *dentry)
 294 {
 295         int err;
 296         struct dentry *ret = NULL;
 297         LIST_HEAD(list);
 298
 299         err = ovl_check_empty_dir(dentry, &list);
 300         if (err)
 301                 ret = ERR_PTR(err);
 302         else {
 303                 /*
 304                  * If no upperdentry then skip clearing whiteouts.
 305                  *
 306                  * Can race with copy-up, since we don't hold the upperdir
 307                  * mutex.  Doesn't matter, since copy-up can't create a
 308                  * non-empty directory from an empty one.
 309                  */
 310                 if (ovl_dentry_upper(dentry))
 311                         ret = ovl_clear_empty(dentry, &list);
 312         }
 313
 314         ovl_cache_free(&list);
 315
 316         return ret;
 317 }
 318
 319 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 320                                     struct kstat *stat, const char *link,
 321                                     struct dentry *hardlink)
 322 {
 323         struct dentry *workdir = ovl_workdir(dentry);
 324         struct inode *wdir = workdir->d_inode;
 325         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 326         struct inode *udir = upperdir->d_inode;
 327         struct dentry *upper;
 328         struct dentry *newdentry;
 329         int err;
 330
 331         if (WARN_ON(!workdir))
 332                 return -EROFS;
 333
 334         err = ovl_lock_rename_workdir(workdir, upperdir);
 335         if (err)
 336                 goto out;
 337
 338         newdentry = ovl_lookup_temp(workdir, dentry);
 339         err = PTR_ERR(newdentry);
 340         if (IS_ERR(newdentry))
 341                 goto out_unlock;
 342
 343         upper = lookup_one_len(dentry->d_name.name, upperdir,
 344                                dentry->d_name.len);
 345         err = PTR_ERR(upper);
 346         if (IS_ERR(upper))
 347                 goto out_dput;
 348
 349         err = ovl_create_real(wdir, newdentry, stat, link, hardlink, true);
 350         if (err)
 351                 goto out_dput2;
 352
 353         if (S_ISDIR(stat->mode)) {
 354                 err = ovl_set_opaque(newdentry);
 355                 if (err)
 356                         goto out_cleanup;
 357
 358                 err = ovl_do_rename(wdir, newdentry, udir, upper,
 359                                     RENAME_EXCHANGE);
 360                 if (err)
 361                         goto out_cleanup;
 362
 363                 ovl_cleanup(wdir, upper);
 364         } else {
 365                 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
 366                 if (err)
 367                         goto out_cleanup;
 368         }
 369         ovl_dentry_version_inc(dentry->d_parent);
 370         ovl_dentry_update(dentry, newdentry);
 371         ovl_copyattr(newdentry->d_inode, inode);
 372         d_instantiate(dentry, inode);
 373         newdentry = NULL;
 374 out_dput2:
 375         dput(upper);
 376 out_dput:
 377         dput(newdentry);
 378 out_unlock:
 379         unlock_rename(workdir, upperdir);
 380 out:
 381         return err;
 382
 383 out_cleanup:
 384         ovl_cleanup(wdir, newdentry);
 385         goto out_dput2;
 386 }
 387
 388 static int ovl_create_or_link(struct dentry *dentry, int mode, dev_t rdev,
 389                               const char *link, struct dentry *hardlink)
 390 {
 391         int err;
 392         struct inode *inode;
 393         struct kstat stat = {
 394                 .mode = mode,
 395                 .rdev = rdev,
 396         };
 397
 398         err = -ENOMEM;
 399         inode = ovl_new_inode(dentry->d_sb, mode, dentry->d_fsdata);
 400         if (!inode)
 401                 goto out;
 402
 403         err = ovl_copy_up(dentry->d_parent);
 404         if (err)
 405                 goto out_iput;
 406
 407         if (!ovl_dentry_is_opaque(dentry)) {
 408                 err = ovl_create_upper(dentry, inode, &stat, link, hardlink);
 409         } else {
 410                 const struct cred *old_cred;
 411                 struct cred *override_cred;
 412
 413                 err = -ENOMEM;
 414                 override_cred = prepare_creds();
 415                 if (!override_cred)
 416                         goto out_iput;
 417
 418                 /*
 419                  * CAP_SYS_ADMIN for setting opaque xattr
 420                  * CAP_DAC_OVERRIDE for create in workdir, rename
 421                  * CAP_FOWNER for removing whiteout from sticky dir
 422                  */
 423                 cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 424                 cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 425                 cap_raise(override_cred->cap_effective, CAP_FOWNER);
 426                 old_cred = override_creds(override_cred);
 427
 428                 err = ovl_create_over_whiteout(dentry, inode, &stat, link,
 429                                                hardlink);
 430
 431                 revert_creds(old_cred);
 432                 put_cred(override_cred);
 433         }
 434
 435         if (!err)
 436                 inode = NULL;
 437 out_iput:
 438         iput(inode);
 439 out:
 440         return err;
 441 }
 442
 443 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 444                              const char *link)
 445 {
 446         int err;
 447
 448         err = ovl_want_write(dentry);
 449         if (!err) {
 450                 err = ovl_create_or_link(dentry, mode, rdev, link, NULL);
 451                 ovl_drop_write(dentry);
 452         }
 453
 454         return err;
 455 }
 456
 457 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 458                       bool excl)
 459 {
 460         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 461 }
 462
 463 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 464 {
 465         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 466 }
 467
 468 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 469                      dev_t rdev)
 470 {
 471         /* Don't allow creation of "whiteout" on overlay */
 472         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
 473                 return -EPERM;
 474
 475         return ovl_create_object(dentry, mode, rdev, NULL);
 476 }
 477
 478 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
 479                        const char *link)
 480 {
 481         return ovl_create_object(dentry, S_IFLNK, 0, link);
 482 }
 483
 484 static int ovl_link(struct dentry *old, struct inode *newdir,
 485                     struct dentry *new)
 486 {
 487         int err;
 488         struct dentry *upper;
 489
 490         err = ovl_want_write(old);
 491         if (err)
 492                 goto out;
 493
 494         err = ovl_copy_up(old);
 495         if (err)
 496                 goto out_drop_write;
 497
 498         upper = ovl_dentry_upper(old);
 499         err = ovl_create_or_link(new, upper->d_inode->i_mode, 0, NULL, upper);
 500
 501 out_drop_write:
 502         ovl_drop_write(old);
 503 out:
 504         return err;
 505 }
 506
 507 static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
 508 {
 509         struct dentry *workdir = ovl_workdir(dentry);
 510         struct inode *wdir = workdir->d_inode;
 511         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 512         struct inode *udir = upperdir->d_inode;
 513         struct dentry *whiteout;
 514         struct dentry *upper;
 515         struct dentry *opaquedir = NULL;
 516         int err;
 517         int flags = 0;
 518
 519         if (WARN_ON(!workdir))
 520                 return -EROFS;
 521
 522         if (is_dir) {
 523                 if (OVL_TYPE_MERGE_OR_LOWER(ovl_path_type(dentry))) {
 524                         opaquedir = ovl_check_empty_and_clear(dentry);
 525                         err = PTR_ERR(opaquedir);
 526                         if (IS_ERR(opaquedir))
 527                                 goto out;
 528                 } else {
 529                         LIST_HEAD(list);
 530
 531                         /*
 532                          * When removing an empty opaque directory, then it
 533                          * makes no sense to replace it with an exact replica of
 534                          * itself.  But emptiness still needs to be checked.
 535                          */
 536                         err = ovl_check_empty_dir(dentry, &list);
 537                         ovl_cache_free(&list);
 538                         if (err)
 539                                 goto out;
 540                 }
 541         }
 542
 543         err = ovl_lock_rename_workdir(workdir, upperdir);
 544         if (err)
 545                 goto out_dput;
 546
 547         upper = lookup_one_len(dentry->d_name.name, upperdir,
 548                                dentry->d_name.len);
 549         err = PTR_ERR(upper);
 550         if (IS_ERR(upper))
 551                 goto out_unlock;
 552
 553         err = -ESTALE;
 554         if ((opaquedir && upper != opaquedir) ||
 555             (!opaquedir && ovl_dentry_upper(dentry) &&
 556              upper != ovl_dentry_upper(dentry))) {
 557                 goto out_dput_upper;
 558         }
 559
 560         whiteout = ovl_whiteout(workdir, dentry);
 561         err = PTR_ERR(whiteout);
 562         if (IS_ERR(whiteout))
 563                 goto out_dput_upper;
 564
 565         if (d_is_dir(upper))
 566                 flags = RENAME_EXCHANGE;
 567
 568         err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
 569         if (err)
 570                 goto kill_whiteout;
 571         if (flags)
 572                 ovl_cleanup(wdir, upper);
 573
 574         ovl_dentry_version_inc(dentry->d_parent);
 575 out_d_drop:
 576         d_drop(dentry);
 577         dput(whiteout);
 578 out_dput_upper:
 579         dput(upper);
 580 out_unlock:
 581         unlock_rename(workdir, upperdir);
 582 out_dput:
 583         dput(opaquedir);
 584 out:
 585         return err;
 586
 587 kill_whiteout:
 588         ovl_cleanup(wdir, whiteout);
 589         goto out_d_drop;
 590 }
 591
 592 static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 593 {
 594         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 595         struct inode *dir = upperdir->d_inode;
 596         struct dentry *upper;
 597         int err;
 598
 599         mutex_lock_nested(&dir->i_mutex, I_MUTEX_PARENT);
 600         upper = lookup_one_len(dentry->d_name.name, upperdir,
 601                                dentry->d_name.len);
 602         err = PTR_ERR(upper);
 603         if (IS_ERR(upper))
 604                 goto out_unlock;
 605
 606         err = -ESTALE;
 607         if (upper == ovl_dentry_upper(dentry)) {
 608                 if (is_dir)
 609                         err = vfs_rmdir(dir, upper);
 610                 else
 611                         err = vfs_unlink(dir, upper, NULL);
 612                 ovl_dentry_version_inc(dentry->d_parent);
 613         }
 614         dput(upper);
 615
 616         /*
 617          * Keeping this dentry hashed would mean having to release
 618          * upperpath/lowerpath, which could only be done if we are the
 619          * sole user of this dentry.  Too tricky...  Just unhash for
 620          * now.
 621          */
 622         if (!err)
 623                 d_drop(dentry);
 624 out_unlock:
 625         mutex_unlock(&dir->i_mutex);
 626
 627         return err;
 628 }
 629
 630 static inline int ovl_check_sticky(struct dentry *dentry)
 631 {
 632         struct inode *dir = ovl_dentry_real(dentry->d_parent)->d_inode;
 633         struct inode *inode = ovl_dentry_real(dentry)->d_inode;
 634
 635         if (check_sticky(dir, inode))
 636                 return -EPERM;
 637
 638         return 0;
 639 }
 640
 641 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 642 {
 643         enum ovl_path_type type;
 644         int err;
 645
 646         err = ovl_check_sticky(dentry);
 647         if (err)
 648                 goto out;
 649
 650         err = ovl_want_write(dentry);
 651         if (err)
 652                 goto out;
 653
 654         err = ovl_copy_up(dentry->d_parent);
 655         if (err)
 656                 goto out_drop_write;
 657
 658         type = ovl_path_type(dentry);
 659         if (OVL_TYPE_PURE_UPPER(type)) {
 660                 err = ovl_remove_upper(dentry, is_dir);
 661         } else {
 662                 const struct cred *old_cred;
 663                 struct cred *override_cred;
 664
 665                 err = -ENOMEM;
 666                 override_cred = prepare_creds();
 667                 if (!override_cred)
 668                         goto out_drop_write;
 669
 670                 /*
 671                  * CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
 672                  * CAP_DAC_OVERRIDE for create in workdir, rename
 673                  * CAP_FOWNER for removing whiteout from sticky dir
 674                  * CAP_FSETID for chmod of opaque dir
 675                  * CAP_CHOWN for chown of opaque dir
 676                  */
 677                 cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 678                 cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 679                 cap_raise(override_cred->cap_effective, CAP_FOWNER);
 680                 cap_raise(override_cred->cap_effective, CAP_FSETID);
 681                 cap_raise(override_cred->cap_effective, CAP_CHOWN);
 682                 old_cred = override_creds(override_cred);
 683
 684                 err = ovl_remove_and_whiteout(dentry, is_dir);
 685
 686                 revert_creds(old_cred);
 687                 put_cred(override_cred);
 688         }
 689 out_drop_write:
 690         ovl_drop_write(dentry);
 691 out:
 692         return err;
 693 }
 694
 695 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
 696 {
 697         return ovl_do_remove(dentry, false);
 698 }
 699
 700 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
 701 {
 702         return ovl_do_remove(dentry, true);
 703 }
 704
 705 static int ovl_rename2(struct inode *olddir, struct dentry *old,
 706                        struct inode *newdir, struct dentry *new,
 707                        unsigned int flags)
 708 {
 709         int err;
 710         enum ovl_path_type old_type;
 711         enum ovl_path_type new_type;
 712         struct dentry *old_upperdir;
 713         struct dentry *new_upperdir;
 714         struct dentry *olddentry;
 715         struct dentry *newdentry;
 716         struct dentry *trap;
 717         bool old_opaque;
 718         bool new_opaque;
 719         bool new_create = false;
 720         bool cleanup_whiteout = false;
 721         bool overwrite = !(flags & RENAME_EXCHANGE);
 722         bool is_dir = d_is_dir(old);
 723         bool new_is_dir = false;
 724         struct dentry *opaquedir = NULL;
 725         const struct cred *old_cred = NULL;
 726         struct cred *override_cred = NULL;
 727
 728         err = -EINVAL;
 729         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
 730                 goto out;
 731
 732         flags &= ~RENAME_NOREPLACE;
 733
 734         err = ovl_check_sticky(old);
 735         if (err)
 736                 goto out;
 737
 738         /* Don't copy up directory trees */
 739         old_type = ovl_path_type(old);
 740         err = -EXDEV;
 741         if (OVL_TYPE_MERGE_OR_LOWER(old_type) && is_dir)
 742                 goto out;
 743
 744         if (new->d_inode) {
 745                 err = ovl_check_sticky(new);
 746                 if (err)
 747                         goto out;
 748
 749                 if (d_is_dir(new))
 750                         new_is_dir = true;
 751
 752                 new_type = ovl_path_type(new);
 753                 err = -EXDEV;
 754                 if (!overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir)
 755                         goto out;
 756
 757                 err = 0;
 758                 if (!OVL_TYPE_UPPER(new_type) && !OVL_TYPE_UPPER(old_type)) {
 759                         if (ovl_dentry_lower(old)->d_inode ==
 760                             ovl_dentry_lower(new)->d_inode)
 761                                 goto out;
 762                 }
 763                 if (OVL_TYPE_UPPER(new_type) && OVL_TYPE_UPPER(old_type)) {
 764                         if (ovl_dentry_upper(old)->d_inode ==
 765                             ovl_dentry_upper(new)->d_inode)
 766                                 goto out;
 767                 }
 768         } else {
 769                 if (ovl_dentry_is_opaque(new))
 770                         new_type = __OVL_PATH_UPPER;
 771                 else
 772                         new_type = __OVL_PATH_UPPER | __OVL_PATH_PURE;
 773         }
 774
 775         err = ovl_want_write(old);
 776         if (err)
 777                 goto out;
 778
 779         err = ovl_copy_up(old);
 780         if (err)
 781                 goto out_drop_write;
 782
 783         err = ovl_copy_up(new->d_parent);
 784         if (err)
 785                 goto out_drop_write;
 786         if (!overwrite) {
 787                 err = ovl_copy_up(new);
 788                 if (err)
 789                         goto out_drop_write;
 790         }
 791
 792         old_opaque = !OVL_TYPE_PURE_UPPER(old_type);
 793         new_opaque = !OVL_TYPE_PURE_UPPER(new_type);
 794
 795         if (old_opaque || new_opaque) {
 796                 err = -ENOMEM;
 797                 override_cred = prepare_creds();
 798                 if (!override_cred)
 799                         goto out_drop_write;
 800
 801                 /*
 802                  * CAP_SYS_ADMIN for setting xattr on whiteout, opaque dir
 803                  * CAP_DAC_OVERRIDE for create in workdir
 804                  * CAP_FOWNER for removing whiteout from sticky dir
 805                  * CAP_FSETID for chmod of opaque dir
 806                  * CAP_CHOWN for chown of opaque dir
 807                  */
 808                 cap_raise(override_cred->cap_effective, CAP_SYS_ADMIN);
 809                 cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
 810                 cap_raise(override_cred->cap_effective, CAP_FOWNER);
 811                 cap_raise(override_cred->cap_effective, CAP_FSETID);
 812                 cap_raise(override_cred->cap_effective, CAP_CHOWN);
 813                 old_cred = override_creds(override_cred);
 814         }
 815
 816         if (overwrite && OVL_TYPE_MERGE_OR_LOWER(new_type) && new_is_dir) {
 817                 opaquedir = ovl_check_empty_and_clear(new);
 818                 err = PTR_ERR(opaquedir);
 819                 if (IS_ERR(opaquedir)) {
 820                         opaquedir = NULL;
 821                         goto out_revert_creds;
 822                 }
 823         }
 824
 825         if (overwrite) {
 826                 if (old_opaque) {
 827                         if (new->d_inode || !new_opaque) {
 828                                 /* Whiteout source */
 829                                 flags |= RENAME_WHITEOUT;
 830                         } else {
 831                                 /* Switch whiteouts */
 832                                 flags |= RENAME_EXCHANGE;
 833                         }
 834                 } else if (is_dir && !new->d_inode && new_opaque) {
 835                         flags |= RENAME_EXCHANGE;
 836                         cleanup_whiteout = true;
 837                 }
 838         }
 839
 840         old_upperdir = ovl_dentry_upper(old->d_parent);
 841         new_upperdir = ovl_dentry_upper(new->d_parent);
 842
 843         trap = lock_rename(new_upperdir, old_upperdir);
 844
 845
 846         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
 847                                    old->d_name.len);
 848         err = PTR_ERR(olddentry);
 849         if (IS_ERR(olddentry))
 850                 goto out_unlock;
 851
 852         err = -ESTALE;
 853         if (olddentry != ovl_dentry_upper(old))
 854                 goto out_dput_old;
 855
 856         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
 857                                    new->d_name.len);
 858         err = PTR_ERR(newdentry);
 859         if (IS_ERR(newdentry))
 860                 goto out_dput_old;
 861
 862         err = -ESTALE;
 863         if (ovl_dentry_upper(new)) {
 864                 if (opaquedir) {
 865                         if (newdentry != opaquedir)
 866                                 goto out_dput;
 867                 } else {
 868                         if (newdentry != ovl_dentry_upper(new))
 869                                 goto out_dput;
 870                 }
 871         } else {
 872                 new_create = true;
 873                 if (!d_is_negative(newdentry) &&
 874                     (!new_opaque || !ovl_is_whiteout(newdentry)))
 875                         goto out_dput;
 876         }
 877
 878         if (olddentry == trap)
 879                 goto out_dput;
 880         if (newdentry == trap)
 881                 goto out_dput;
 882
 883         if (is_dir && !old_opaque && new_opaque) {
 884                 err = ovl_set_opaque(olddentry);
 885                 if (err)
 886                         goto out_dput;
 887         }
 888         if (!overwrite && new_is_dir && old_opaque && !new_opaque) {
 889                 err = ovl_set_opaque(newdentry);
 890                 if (err)
 891                         goto out_dput;
 892         }
 893
 894         if (old_opaque || new_opaque) {
 895                 err = ovl_do_rename(old_upperdir->d_inode, olddentry,
 896                                     new_upperdir->d_inode, newdentry,
 897                                     flags);
 898         } else {
 899                 /* No debug for the plain case */
 900                 BUG_ON(flags & ~RENAME_EXCHANGE);
 901                 err = vfs_rename(old_upperdir->d_inode, olddentry,
 902                                  new_upperdir->d_inode, newdentry,
 903                                  NULL, flags);
 904         }
 905
 906         if (err) {
 907                 if (is_dir && !old_opaque && new_opaque)
 908                         ovl_remove_opaque(olddentry);
 909                 if (!overwrite && new_is_dir && old_opaque && !new_opaque)
 910                         ovl_remove_opaque(newdentry);
 911                 goto out_dput;
 912         }
 913
 914         if (is_dir && old_opaque && !new_opaque)
 915                 ovl_remove_opaque(olddentry);
 916         if (!overwrite && new_is_dir && !old_opaque && new_opaque)
 917                 ovl_remove_opaque(newdentry);
 918
 919         /*
 920          * Old dentry now lives in different location. Dentries in
 921          * lowerstack are stale. We cannot drop them here because
 922          * access to them is lockless. This could be only pure upper
 923          * or opaque directory - numlower is zero. Or upper non-dir
 924          * entry - its pureness is tracked by flag opaque.
 925          */
 926         if (old_opaque != new_opaque) {
 927                 ovl_dentry_set_opaque(old, new_opaque);
 928                 if (!overwrite)
 929                         ovl_dentry_set_opaque(new, old_opaque);
 930         }
 931
 932         if (cleanup_whiteout)
 933                 ovl_cleanup(old_upperdir->d_inode, newdentry);
 934
 935         ovl_dentry_version_inc(old->d_parent);
 936         ovl_dentry_version_inc(new->d_parent);
 937
 938 out_dput:
 939         dput(newdentry);
 940 out_dput_old:
 941         dput(olddentry);
 942 out_unlock:
 943         unlock_rename(new_upperdir, old_upperdir);
 944 out_revert_creds:
 945         if (old_opaque || new_opaque) {
 946                 revert_creds(old_cred);
 947                 put_cred(override_cred);
 948         }
 949 out_drop_write:
 950         ovl_drop_write(old);
 951 out:
 952         dput(opaquedir);
 953         return err;
 954 }
 955
 956 const struct inode_operations ovl_dir_inode_operations = {
 957         .lookup         = ovl_lookup,
 958         .mkdir          = ovl_mkdir,
 959         .symlink        = ovl_symlink,
 960         .unlink         = ovl_unlink,
 961         .rmdir          = ovl_rmdir,
 962         .rename2        = ovl_rename2,
 963         .link           = ovl_link,
 964         .setattr        = ovl_setattr,
 965         .create         = ovl_create,
 966         .mknod          = ovl_mknod,
 967         .permission     = ovl_permission,
 968         .getattr        = ovl_dir_getattr,
 969         .setxattr       = ovl_setxattr,
 970         .getxattr       = ovl_getxattr,
 971         .listxattr      = ovl_listxattr,
 972         .removexattr    = ovl_removexattr,
 973 };