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/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
  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
  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 */
  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
  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
 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
 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 */
 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
 174 static bool ovl_type_merge(struct dentry *dentry)
 175 {
 176         return OVL_TYPE_MERGE(ovl_path_type(dentry));
 177 }
 178
 179 static bool ovl_type_origin(struct dentry *dentry)
 180 {
 181         return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
 182 }
 183
 184 static bool ovl_may_have_whiteouts(struct dentry *dentry)
 185 {
 186         return ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
 187 }
 188
 189 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 190                             struct cattr *attr, struct dentry *hardlink)
 191 {
 192         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 193         struct inode *udir = upperdir->d_inode;
 194         struct dentry *newdentry;
 195         int err;
 196
 197         if (!hardlink && !IS_POSIXACL(udir))
 198                 attr->mode &= ~current_umask();
 199
 200         inode_lock_nested(udir, I_MUTEX_PARENT);
 201         newdentry = lookup_one_len(dentry->d_name.name, upperdir,
 202                                    dentry->d_name.len);
 203         err = PTR_ERR(newdentry);
 204         if (IS_ERR(newdentry))
 205                 goto out_unlock;
 206         err = ovl_create_real(udir, newdentry, attr, hardlink, false);
 207         if (err)
 208                 goto out_dput;
 209
 210         if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry)) {
 211                 /* Setting opaque here is just an optimization, allow to fail */
 212                 ovl_set_opaque(dentry, newdentry);
 213         }
 214
 215         ovl_instantiate(dentry, inode, newdentry, !!hardlink);
 216         newdentry = NULL;
 217 out_dput:
 218         dput(newdentry);
 219 out_unlock:
 220         inode_unlock(udir);
 221         return err;
 222 }
 223
 224 static struct dentry *ovl_clear_empty(struct dentry *dentry,
 225                                       struct list_head *list)
 226 {
 227         struct dentry *workdir = ovl_workdir(dentry);
 228         struct inode *wdir = workdir->d_inode;
 229         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 230         struct inode *udir = upperdir->d_inode;
 231         struct path upperpath;
 232         struct dentry *upper;
 233         struct dentry *opaquedir;
 234         struct kstat stat;
 235         int err;
 236
 237         if (WARN_ON(!workdir))
 238                 return ERR_PTR(-EROFS);
 239
 240         err = ovl_lock_rename_workdir(workdir, upperdir);
 241         if (err)
 242                 goto out;
 243
 244         ovl_path_upper(dentry, &upperpath);
 245         err = vfs_getattr(&upperpath, &stat,
 246                           STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
 247         if (err)
 248                 goto out_unlock;
 249
 250         err = -ESTALE;
 251         if (!S_ISDIR(stat.mode))
 252                 goto out_unlock;
 253         upper = upperpath.dentry;
 254         if (upper->d_parent->d_inode != udir)
 255                 goto out_unlock;
 256
 257         opaquedir = ovl_lookup_temp(workdir);
 258         err = PTR_ERR(opaquedir);
 259         if (IS_ERR(opaquedir))
 260                 goto out_unlock;
 261
 262         err = ovl_create_real(wdir, opaquedir,
 263                               &(struct cattr){.mode = stat.mode}, NULL, true);
 264         if (err)
 265                 goto out_dput;
 266
 267         err = ovl_copy_xattr(upper, opaquedir);
 268         if (err)
 269                 goto out_cleanup;
 270
 271         err = ovl_set_opaque(dentry, opaquedir);
 272         if (err)
 273                 goto out_cleanup;
 274
 275         inode_lock(opaquedir->d_inode);
 276         err = ovl_set_attr(opaquedir, &stat);
 277         inode_unlock(opaquedir->d_inode);
 278         if (err)
 279                 goto out_cleanup;
 280
 281         err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
 282         if (err)
 283                 goto out_cleanup;
 284
 285         ovl_cleanup_whiteouts(upper, list);
 286         ovl_cleanup(wdir, upper);
 287         unlock_rename(workdir, upperdir);
 288
 289         /* dentry's upper doesn't match now, get rid of it */
 290         d_drop(dentry);
 291
 292         return opaquedir;
 293
 294 out_cleanup:
 295         ovl_cleanup(wdir, opaquedir);
 296 out_dput:
 297         dput(opaquedir);
 298 out_unlock:
 299         unlock_rename(workdir, upperdir);
 300 out:
 301         return ERR_PTR(err);
 302 }
 303
 304 static struct dentry *ovl_check_empty_and_clear(struct dentry *dentry)
 305 {
 306         int err;
 307         struct dentry *ret = NULL;
 308         LIST_HEAD(list);
 309
 310         err = ovl_check_empty_dir(dentry, &list);
 311         if (err) {
 312                 ret = ERR_PTR(err);
 313                 goto out_free;
 314         }
 315
 316         /*
 317          * When removing an empty opaque directory, then it makes no sense to
 318          * replace it with an exact replica of itself.
 319          *
 320          * If upperdentry has whiteouts, clear them.
 321          *
 322          * Can race with copy-up, since we don't hold the upperdir mutex.
 323          * Doesn't matter, since copy-up can't create a non-empty directory
 324          * from an empty one.
 325          */
 326         if (!list_empty(&list))
 327                 ret = ovl_clear_empty(dentry, &list);
 328
 329 out_free:
 330         ovl_cache_free(&list);
 331
 332         return ret;
 333 }
 334
 335 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
 336                              const struct posix_acl *acl)
 337 {
 338         void *buffer;
 339         size_t size;
 340         int err;
 341
 342         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
 343                 return 0;
 344
 345         size = posix_acl_to_xattr(NULL, acl, NULL, 0);
 346         buffer = kmalloc(size, GFP_KERNEL);
 347         if (!buffer)
 348                 return -ENOMEM;
 349
 350         size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
 351         err = size;
 352         if (err < 0)
 353                 goto out_free;
 354
 355         err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
 356 out_free:
 357         kfree(buffer);
 358         return err;
 359 }
 360
 361 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 362                                     struct cattr *cattr,
 363                                     struct dentry *hardlink)
 364 {
 365         struct dentry *workdir = ovl_workdir(dentry);
 366         struct inode *wdir = workdir->d_inode;
 367         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 368         struct inode *udir = upperdir->d_inode;
 369         struct dentry *upper;
 370         struct dentry *newdentry;
 371         int err;
 372         struct posix_acl *acl, *default_acl;
 373
 374         if (WARN_ON(!workdir))
 375                 return -EROFS;
 376
 377         if (!hardlink) {
 378                 err = posix_acl_create(dentry->d_parent->d_inode,
 379                                        &cattr->mode, &default_acl, &acl);
 380                 if (err)
 381                         return err;
 382         }
 383
 384         err = ovl_lock_rename_workdir(workdir, upperdir);
 385         if (err)
 386                 goto out;
 387
 388         newdentry = ovl_lookup_temp(workdir);
 389         err = PTR_ERR(newdentry);
 390         if (IS_ERR(newdentry))
 391                 goto out_unlock;
 392
 393         upper = lookup_one_len(dentry->d_name.name, upperdir,
 394                                dentry->d_name.len);
 395         err = PTR_ERR(upper);
 396         if (IS_ERR(upper))
 397                 goto out_dput;
 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
 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;
 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, old_cred,
 500                                         override_cred);
 501                         if (err) {
 502                                 put_cred(override_cred);
 503                                 goto out_revert_creds;
 504                         }
 505                 }
 506                 put_cred(override_creds(override_cred));
 507                 put_cred(override_cred);
 508
 509                 if (!ovl_dentry_is_whiteout(dentry))
 510                         err = ovl_create_upper(dentry, inode, attr,
 511                                                 hardlink);
 512                 else
 513                         err = ovl_create_over_whiteout(dentry, inode, attr,
 514                                                         hardlink);
 515         }
 516 out_revert_creds:
 517         revert_creds(old_cred);
 518         if (!err) {
 519                 struct inode *realinode = d_inode(ovl_dentry_upper(dentry));
 520
 521                 WARN_ON(inode->i_mode != realinode->i_mode);
 522                 WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
 523                 WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
 524         }
 525         return err;
 526 }
 527
 528 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 529                              const char *link)
 530 {
 531         int err;
 532         struct inode *inode;
 533         struct cattr attr = {
 534                 .rdev = rdev,
 535                 .link = link,
 536         };
 537
 538         err = ovl_want_write(dentry);
 539         if (err)
 540                 goto out;
 541
 542         err = -ENOMEM;
 543         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
 544         if (!inode)
 545                 goto out_drop_write;
 546
 547         inode_init_owner(inode, dentry->d_parent->d_inode, mode);
 548         attr.mode = inode->i_mode;
 549
 550         err = ovl_create_or_link(dentry, inode, &attr, NULL, false);
 551         if (err)
 552                 iput(inode);
 553
 554 out_drop_write:
 555         ovl_drop_write(dentry);
 556 out:
 557         return err;
 558 }
 559
 560 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 561                       bool excl)
 562 {
 563         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 564 }
 565
 566 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 567 {
 568         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 569 }
 570
 571 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 572                      dev_t rdev)
 573 {
 574         /* Don't allow creation of "whiteout" on overlay */
 575         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
 576                 return -EPERM;
 577
 578         return ovl_create_object(dentry, mode, rdev, NULL);
 579 }
 580
 581 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
 582                        const char *link)
 583 {
 584         return ovl_create_object(dentry, S_IFLNK, 0, link);
 585 }
 586
 587 static int ovl_link(struct dentry *old, struct inode *newdir,
 588                     struct dentry *new)
 589 {
 590         int err;
 591         bool locked = false;
 592         struct inode *inode;
 593
 594         err = ovl_want_write(old);
 595         if (err)
 596                 goto out;
 597
 598         err = ovl_copy_up(old);
 599         if (err)
 600                 goto out_drop_write;
 601
 602         err = ovl_nlink_start(old, &locked);
 603         if (err)
 604                 goto out_drop_write;
 605
 606         inode = d_inode(old);
 607         ihold(inode);
 608
 609         err = ovl_create_or_link(new, inode, NULL, ovl_dentry_upper(old),
 610                                  ovl_type_origin(old));
 611         if (err)
 612                 iput(inode);
 613
 614         ovl_nlink_end(old, locked);
 615 out_drop_write:
 616         ovl_drop_write(old);
 617 out:
 618         return err;
 619 }
 620
 621 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
 622 {
 623         return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
 624 }
 625
 626 static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
 627 {
 628         struct dentry *workdir = ovl_workdir(dentry);
 629         struct inode *wdir = workdir->d_inode;
 630         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 631         struct inode *udir = upperdir->d_inode;
 632         struct dentry *whiteout;
 633         struct dentry *upper;
 634         struct dentry *opaquedir = NULL;
 635         int err;
 636         int flags = 0;
 637
 638         if (WARN_ON(!workdir))
 639                 return -EROFS;
 640
 641         if (is_dir) {
 642                 opaquedir = ovl_check_empty_and_clear(dentry);
 643                 err = PTR_ERR(opaquedir);
 644                 if (IS_ERR(opaquedir))
 645                         goto out;
 646         }
 647
 648         err = ovl_lock_rename_workdir(workdir, upperdir);
 649         if (err)
 650                 goto out_dput;
 651
 652         upper = lookup_one_len(dentry->d_name.name, upperdir,
 653                                dentry->d_name.len);
 654         err = PTR_ERR(upper);
 655         if (IS_ERR(upper))
 656                 goto out_unlock;
 657
 658         err = -ESTALE;
 659         if ((opaquedir && upper != opaquedir) ||
 660             (!opaquedir && ovl_dentry_upper(dentry) &&
 661              !ovl_matches_upper(dentry, upper))) {
 662                 goto out_dput_upper;
 663         }
 664
 665         whiteout = ovl_whiteout(workdir, dentry);
 666         err = PTR_ERR(whiteout);
 667         if (IS_ERR(whiteout))
 668                 goto out_dput_upper;
 669
 670         if (d_is_dir(upper))
 671                 flags = RENAME_EXCHANGE;
 672
 673         err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
 674         if (err)
 675                 goto kill_whiteout;
 676         if (flags)
 677                 ovl_cleanup(wdir, upper);
 678
 679         ovl_dentry_version_inc(dentry->d_parent, true);
 680 out_d_drop:
 681         d_drop(dentry);
 682         dput(whiteout);
 683 out_dput_upper:
 684         dput(upper);
 685 out_unlock:
 686         unlock_rename(workdir, upperdir);
 687 out_dput:
 688         dput(opaquedir);
 689 out:
 690         return err;
 691
 692 kill_whiteout:
 693         ovl_cleanup(wdir, whiteout);
 694         goto out_d_drop;
 695 }
 696
 697 static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 698 {
 699         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 700         struct inode *dir = upperdir->d_inode;
 701         struct dentry *upper;
 702         struct dentry *opaquedir = NULL;
 703         int err;
 704
 705         /* Redirect/origin dir can be !ovl_lower_positive && not clean */
 706         if (is_dir && (ovl_dentry_get_redirect(dentry) ||
 707                        ovl_may_have_whiteouts(dentry))) {
 708                 opaquedir = ovl_check_empty_and_clear(dentry);
 709                 err = PTR_ERR(opaquedir);
 710                 if (IS_ERR(opaquedir))
 711                         goto out;
 712         }
 713
 714         inode_lock_nested(dir, I_MUTEX_PARENT);
 715         upper = lookup_one_len(dentry->d_name.name, upperdir,
 716                                dentry->d_name.len);
 717         err = PTR_ERR(upper);
 718         if (IS_ERR(upper))
 719                 goto out_unlock;
 720
 721         err = -ESTALE;
 722         if ((opaquedir && upper != opaquedir) ||
 723             (!opaquedir && !ovl_matches_upper(dentry, upper)))
 724                 goto out_dput_upper;
 725
 726         if (is_dir)
 727                 err = vfs_rmdir(dir, upper);
 728         else
 729                 err = vfs_unlink(dir, upper, NULL);
 730         ovl_dentry_version_inc(dentry->d_parent, ovl_type_origin(dentry));
 731
 732         /*
 733          * Keeping this dentry hashed would mean having to release
 734          * upperpath/lowerpath, which could only be done if we are the
 735          * sole user of this dentry.  Too tricky...  Just unhash for
 736          * now.
 737          */
 738         if (!err)
 739                 d_drop(dentry);
 740 out_dput_upper:
 741         dput(upper);
 742 out_unlock:
 743         inode_unlock(dir);
 744         dput(opaquedir);
 745 out:
 746         return err;
 747 }
 748
 749 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 750 {
 751         int err;
 752         bool locked = false;
 753         const struct cred *old_cred;
 754
 755         err = ovl_want_write(dentry);
 756         if (err)
 757                 goto out;
 758
 759         err = ovl_copy_up(dentry->d_parent);
 760         if (err)
 761                 goto out_drop_write;
 762
 763         err = ovl_nlink_start(dentry, &locked);
 764         if (err)
 765                 goto out_drop_write;
 766
 767         old_cred = ovl_override_creds(dentry->d_sb);
 768         if (!ovl_lower_positive(dentry))
 769                 err = ovl_remove_upper(dentry, is_dir);
 770         else
 771                 err = ovl_remove_and_whiteout(dentry, is_dir);
 772         revert_creds(old_cred);
 773         if (!err) {
 774                 if (is_dir)
 775                         clear_nlink(dentry->d_inode);
 776                 else
 777                         drop_nlink(dentry->d_inode);
 778         }
 779         ovl_nlink_end(dentry, locked);
 780 out_drop_write:
 781         ovl_drop_write(dentry);
 782 out:
 783         return err;
 784 }
 785
 786 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
 787 {
 788         return ovl_do_remove(dentry, false);
 789 }
 790
 791 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
 792 {
 793         return ovl_do_remove(dentry, true);
 794 }
 795
 796 static bool ovl_type_merge_or_lower(struct dentry *dentry)
 797 {
 798         enum ovl_path_type type = ovl_path_type(dentry);
 799
 800         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
 801 }
 802
 803 static bool ovl_can_move(struct dentry *dentry)
 804 {
 805         return ovl_redirect_dir(dentry->d_sb) ||
 806                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
 807 }
 808
 809 static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
 810 {
 811         char *buf, *ret;
 812         struct dentry *d, *tmp;
 813         int buflen = ovl_redirect_max + 1;
 814
 815         if (samedir) {
 816                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
 817                                GFP_KERNEL);
 818                 goto out;
 819         }
 820
 821         buf = ret = kmalloc(buflen, GFP_KERNEL);
 822         if (!buf)
 823                 goto out;
 824
 825         buflen--;
 826         buf[buflen] = '\0';
 827         for (d = dget(dentry); !IS_ROOT(d);) {
 828                 const char *name;
 829                 int thislen;
 830
 831                 spin_lock(&d->d_lock);
 832                 name = ovl_dentry_get_redirect(d);
 833                 if (name) {
 834                         thislen = strlen(name);
 835                 } else {
 836                         name = d->d_name.name;
 837                         thislen = d->d_name.len;
 838                 }
 839
 840                 /* If path is too long, fall back to userspace move */
 841                 if (thislen + (name[0] != '/') > buflen) {
 842                         ret = ERR_PTR(-EXDEV);
 843                         spin_unlock(&d->d_lock);
 844                         goto out_put;
 845                 }
 846
 847                 buflen -= thislen;
 848                 memcpy(&buf[buflen], name, thislen);
 849                 tmp = dget_dlock(d->d_parent);
 850                 spin_unlock(&d->d_lock);
 851
 852                 dput(d);
 853                 d = tmp;
 854
 855                 /* Absolute redirect: finished */
 856                 if (buf[buflen] == '/')
 857                         break;
 858                 buflen--;
 859                 buf[buflen] = '/';
 860         }
 861         ret = kstrdup(&buf[buflen], GFP_KERNEL);
 862 out_put:
 863         dput(d);
 864         kfree(buf);
 865 out:
 866         return ret ? ret : ERR_PTR(-ENOMEM);
 867 }
 868
 869 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
 870 {
 871         int err;
 872         const char *redirect = ovl_dentry_get_redirect(dentry);
 873
 874         if (redirect && (samedir || redirect[0] == '/'))
 875                 return 0;
 876
 877         redirect = ovl_get_redirect(dentry, samedir);
 878         if (IS_ERR(redirect))
 879                 return PTR_ERR(redirect);
 880
 881         err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
 882                                  OVL_XATTR_REDIRECT,
 883                                  redirect, strlen(redirect), -EXDEV);
 884         if (!err) {
 885                 spin_lock(&dentry->d_lock);
 886                 ovl_dentry_set_redirect(dentry, redirect);
 887                 spin_unlock(&dentry->d_lock);
 888         } else {
 889                 kfree(redirect);
 890                 pr_warn_ratelimited("overlay: failed to set redirect (%i)\n", err);
 891                 /* Fall back to userspace copy-up */
 892                 err = -EXDEV;
 893         }
 894         return err;
 895 }
 896
 897 static int ovl_rename(struct inode *olddir, struct dentry *old,
 898                       struct inode *newdir, struct dentry *new,
 899                       unsigned int flags)
 900 {
 901         int err;
 902         bool locked = false;
 903         struct dentry *old_upperdir;
 904         struct dentry *new_upperdir;
 905         struct dentry *olddentry;
 906         struct dentry *newdentry;
 907         struct dentry *trap;
 908         bool old_opaque;
 909         bool new_opaque;
 910         bool cleanup_whiteout = false;
 911         bool overwrite = !(flags & RENAME_EXCHANGE);
 912         bool is_dir = d_is_dir(old);
 913         bool new_is_dir = d_is_dir(new);
 914         bool samedir = olddir == newdir;
 915         struct dentry *opaquedir = NULL;
 916         const struct cred *old_cred = NULL;
 917
 918         err = -EINVAL;
 919         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
 920                 goto out;
 921
 922         flags &= ~RENAME_NOREPLACE;
 923
 924         /* Don't copy up directory trees */
 925         err = -EXDEV;
 926         if (!ovl_can_move(old))
 927                 goto out;
 928         if (!overwrite && !ovl_can_move(new))
 929                 goto out;
 930
 931         err = ovl_want_write(old);
 932         if (err)
 933                 goto out;
 934
 935         err = ovl_copy_up(old);
 936         if (err)
 937                 goto out_drop_write;
 938
 939         err = ovl_copy_up(new->d_parent);
 940         if (err)
 941                 goto out_drop_write;
 942         if (!overwrite) {
 943                 err = ovl_copy_up(new);
 944                 if (err)
 945                         goto out_drop_write;
 946         } else {
 947                 err = ovl_nlink_start(new, &locked);
 948                 if (err)
 949                         goto out_drop_write;
 950         }
 951
 952         old_cred = ovl_override_creds(old->d_sb);
 953
 954         if (overwrite && new_is_dir && (ovl_type_merge_or_lower(new) ||
 955                                         ovl_may_have_whiteouts(new))) {
 956                 opaquedir = ovl_check_empty_and_clear(new);
 957                 err = PTR_ERR(opaquedir);
 958                 if (IS_ERR(opaquedir)) {
 959                         opaquedir = NULL;
 960                         goto out_revert_creds;
 961                 }
 962         }
 963
 964         if (overwrite) {
 965                 if (ovl_lower_positive(old)) {
 966                         if (!ovl_dentry_is_whiteout(new)) {
 967                                 /* Whiteout source */
 968                                 flags |= RENAME_WHITEOUT;
 969                         } else {
 970                                 /* Switch whiteouts */
 971                                 flags |= RENAME_EXCHANGE;
 972                         }
 973                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
 974                         flags |= RENAME_EXCHANGE;
 975                         cleanup_whiteout = true;
 976                 }
 977         }
 978
 979         old_upperdir = ovl_dentry_upper(old->d_parent);
 980         new_upperdir = ovl_dentry_upper(new->d_parent);
 981
 982         if (!samedir) {
 983                 /*
 984                  * When moving a merge dir or non-dir with copy up origin into
 985                  * a new parent, we are marking the new parent dir "impure".
 986                  * When ovl_iterate() iterates an "impure" upper dir, it will
 987                  * lookup the origin inodes of the entries to fill d_ino.
 988                  */
 989                 if (ovl_type_origin(old)) {
 990                         err = ovl_set_impure(new->d_parent, new_upperdir);
 991                         if (err)
 992                                 goto out_revert_creds;
 993                 }
 994                 if (!overwrite && ovl_type_origin(new)) {
 995                         err = ovl_set_impure(old->d_parent, old_upperdir);
 996                         if (err)
 997                                 goto out_revert_creds;
 998                 }
 999         }
1000
1001         trap = lock_rename(new_upperdir, old_upperdir);
1002
1003         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
1004                                    old->d_name.len);
1005         err = PTR_ERR(olddentry);
1006         if (IS_ERR(olddentry))
1007                 goto out_unlock;
1008
1009         err = -ESTALE;
1010         if (!ovl_matches_upper(old, olddentry))
1011                 goto out_dput_old;
1012
1013         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
1014                                    new->d_name.len);
1015         err = PTR_ERR(newdentry);
1016         if (IS_ERR(newdentry))
1017                 goto out_dput_old;
1018
1019         old_opaque = ovl_dentry_is_opaque(old);
1020         new_opaque = ovl_dentry_is_opaque(new);
1021
1022         err = -ESTALE;
1023         if (d_inode(new) && ovl_dentry_upper(new)) {
1024                 if (opaquedir) {
1025                         if (newdentry != opaquedir)
1026                                 goto out_dput;
1027                 } else {
1028                         if (!ovl_matches_upper(new, newdentry))
1029                                 goto out_dput;
1030                 }
1031         } else {
1032                 if (!d_is_negative(newdentry) &&
1033                     (!new_opaque || !ovl_is_whiteout(newdentry)))
1034                         goto out_dput;
1035         }
1036
1037         if (olddentry == trap)
1038                 goto out_dput;
1039         if (newdentry == trap)
1040                 goto out_dput;
1041
1042         if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
1043                 goto out_dput;
1044
1045         err = 0;
1046         if (is_dir) {
1047                 if (ovl_type_merge_or_lower(old))
1048                         err = ovl_set_redirect(old, samedir);
1049                 else if (!old_opaque && ovl_type_merge(new->d_parent))
1050                         err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1051                 if (err)
1052                         goto out_dput;
1053         }
1054         if (!overwrite && new_is_dir) {
1055                 if (ovl_type_merge_or_lower(new))
1056                         err = ovl_set_redirect(new, samedir);
1057                 else if (!new_opaque && ovl_type_merge(old->d_parent))
1058                         err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1059                 if (err)
1060                         goto out_dput;
1061         }
1062
1063         err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1064                             new_upperdir->d_inode, newdentry, flags);
1065         if (err)
1066                 goto out_dput;
1067
1068         if (cleanup_whiteout)
1069                 ovl_cleanup(old_upperdir->d_inode, newdentry);
1070
1071         if (overwrite && d_inode(new)) {
1072                 if (new_is_dir)
1073                         clear_nlink(d_inode(new));
1074                 else
1075                         drop_nlink(d_inode(new));
1076         }
1077
1078         ovl_dentry_version_inc(old->d_parent, ovl_type_origin(old) ||
1079                                (!overwrite && ovl_type_origin(new)));
1080         ovl_dentry_version_inc(new->d_parent, ovl_type_origin(old) ||
1081                                (d_inode(new) && ovl_type_origin(new)));
1082
1083 out_dput:
1084         dput(newdentry);
1085 out_dput_old:
1086         dput(olddentry);
1087 out_unlock:
1088         unlock_rename(new_upperdir, old_upperdir);
1089 out_revert_creds:
1090         revert_creds(old_cred);
1091         ovl_nlink_end(new, locked);
1092 out_drop_write:
1093         ovl_drop_write(old);
1094 out:
1095         dput(opaquedir);
1096         return err;
1097 }
1098
1099 const struct inode_operations ovl_dir_inode_operations = {
1100         .lookup         = ovl_lookup,
1101         .mkdir          = ovl_mkdir,
1102         .symlink        = ovl_symlink,
1103         .unlink         = ovl_unlink,
1104         .rmdir          = ovl_rmdir,
1105         .rename         = ovl_rename,
1106         .link           = ovl_link,
1107         .setattr        = ovl_setattr,
1108         .create         = ovl_create,
1109         .mknod          = ovl_mknod,
1110         .permission     = ovl_permission,
1111         .getattr        = ovl_getattr,
1112         .listxattr      = ovl_listxattr,
1113         .get_acl        = ovl_get_acl,
1114         .update_time    = ovl_update_time,
1115 };