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