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