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/posix_acl.h>
  16 #include <linux/posix_acl_xattr.h>
  17 #include <linux/atomic.h>
  18 #include <linux/ratelimit.h>
  19 #include "overlayfs.h"
  20
  21 void ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
  22 {
  23         int err;
  24
  25         dget(wdentry);
  26         if (d_is_dir(wdentry))
  27                 err = ovl_do_rmdir(wdir, wdentry);
  28         else
  29                 err = ovl_do_unlink(wdir, wdentry);
  30         dput(wdentry);
  31
  32         if (err) {
  33                 pr_err("overlayfs: cleanup of '%pd2' failed (%i)\n",
  34                        wdentry, err);
  35         }
  36 }
  37
  38 struct dentry *ovl_lookup_temp(struct dentry *workdir, struct dentry *dentry)
  39 {
  40         struct dentry *temp;
  41         char name[20];
  42         static atomic_t temp_id = ATOMIC_INIT(0);
  43
  44         /* counter is allowed to wrap, since temp dentries are ephemeral */
  45         snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
  46
  47         temp = lookup_one_len(name, workdir, strlen(name));
  48         if (!IS_ERR(temp) && temp->d_inode) {
  49                 pr_err("overlayfs: workdir/%s already exists\n", name);
  50                 dput(temp);
  51                 temp = ERR_PTR(-EIO);
  52         }
  53
  54         return temp;
  55 }
  56
  57 /* caller holds i_mutex on workdir */
  58 static struct dentry *ovl_whiteout(struct dentry *workdir,
  59                                    struct dentry *dentry)
  60 {
  61         int err;
  62         struct dentry *whiteout;
  63         struct inode *wdir = workdir->d_inode;
  64
  65         whiteout = ovl_lookup_temp(workdir, dentry);
  66         if (IS_ERR(whiteout))
  67                 return whiteout;
  68
  69         err = ovl_do_whiteout(wdir, whiteout);
  70         if (err) {
  71                 dput(whiteout);
  72                 whiteout = ERR_PTR(err);
  73         }
  74
  75         return whiteout;
  76 }
  77
  78 int ovl_create_real(struct inode *dir, struct dentry *newdentry,
  79                     struct kstat *stat, const char *link,
  80                     struct dentry *hardlink, bool debug)
  81 {
  82         int err;
  83
  84         if (newdentry->d_inode)
  85                 return -ESTALE;
  86
  87         if (hardlink) {
  88                 err = ovl_do_link(hardlink, dir, newdentry, debug);
  89         } else {
  90                 switch (stat->mode & S_IFMT) {
  91                 case S_IFREG:
  92                         err = ovl_do_create(dir, newdentry, stat->mode, debug);
  93                         break;
  94
  95                 case S_IFDIR:
  96                         err = ovl_do_mkdir(dir, newdentry, stat->mode, debug);
  97                         break;
  98
  99                 case S_IFCHR:
 100                 case S_IFBLK:
 101                 case S_IFIFO:
 102                 case S_IFSOCK:
 103                         err = ovl_do_mknod(dir, newdentry,
 104                                            stat->mode, stat->rdev, debug);
 105                         break;
 106
 107                 case S_IFLNK:
 108                         err = ovl_do_symlink(dir, newdentry, link, debug);
 109                         break;
 110
 111                 default:
 112                         err = -EPERM;
 113                 }
 114         }
 115         if (!err && WARN_ON(!newdentry->d_inode)) {
 116                 /*
 117                  * Not quite sure if non-instantiated dentry is legal or not.
 118                  * VFS doesn't seem to care so check and warn here.
 119                  */
 120                 err = -ENOENT;
 121         }
 122         return err;
 123 }
 124
 125 static int ovl_set_opaque(struct dentry *upperdentry)
 126 {
 127         return ovl_do_setxattr(upperdentry, OVL_XATTR_OPAQUE, "y", 1, 0);
 128 }
 129
 130 static int ovl_dir_getattr(struct vfsmount *mnt, struct dentry *dentry,
 131                          struct kstat *stat)
 132 {
 133         int err;
 134         enum ovl_path_type type;
 135         struct path realpath;
 136         const struct cred *old_cred;
 137
 138         type = ovl_path_real(dentry, &realpath);
 139         old_cred = ovl_override_creds(dentry->d_sb);
 140         err = vfs_getattr(&realpath, stat);
 141         revert_creds(old_cred);
 142         if (err)
 143                 return err;
 144
 145         stat->dev = dentry->d_sb->s_dev;
 146         stat->ino = dentry->d_inode->i_ino;
 147
 148         /*
 149          * It's probably not worth it to count subdirs to get the
 150          * correct link count.  nlink=1 seems to pacify 'find' and
 151          * other utilities.
 152          */
 153         if (OVL_TYPE_MERGE(type))
 154                 stat->nlink = 1;
 155
 156         return 0;
 157 }
 158
 159 /* Common operations required to be done after creation of file on upper */
 160 static void ovl_instantiate(struct dentry *dentry, struct inode *inode,
 161                             struct dentry *newdentry, bool hardlink)
 162 {
 163         ovl_dentry_version_inc(dentry->d_parent);
 164         ovl_dentry_update(dentry, newdentry);
 165         if (!hardlink) {
 166                 ovl_inode_update(inode, d_inode(newdentry));
 167                 ovl_copyattr(newdentry->d_inode, inode);
 168         } else {
 169                 WARN_ON(ovl_inode_real(inode, NULL) != d_inode(newdentry));
 170                 inc_nlink(inode);
 171         }
 172         d_instantiate(dentry, inode);
 173 }
 174
 175 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 176                             struct kstat *stat, const char *link,
 177                             struct dentry *hardlink)
 178 {
 179         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 180         struct inode *udir = upperdir->d_inode;
 181         struct dentry *newdentry;
 182         int err;
 183
 184         if (!hardlink && !IS_POSIXACL(udir))
 185                 stat->mode &= ~current_umask();
 186
 187         inode_lock_nested(udir, I_MUTEX_PARENT);
 188         newdentry = lookup_one_len(dentry->d_name.name, upperdir,
 189                                    dentry->d_name.len);
 190         err = PTR_ERR(newdentry);
 191         if (IS_ERR(newdentry))
 192                 goto out_unlock;
 193         err = ovl_create_real(udir, newdentry, stat, link, hardlink, false);
 194         if (err)
 195                 goto out_dput;
 196
 197         ovl_instantiate(dentry, inode, newdentry, !!hardlink);
 198         newdentry = NULL;
 199 out_dput:
 200         dput(newdentry);
 201 out_unlock:
 202         inode_unlock(udir);
 203         return err;
 204 }
 205
 206 static int ovl_lock_rename_workdir(struct dentry *workdir,
 207                                    struct dentry *upperdir)
 208 {
 209         /* Workdir should not be the same as upperdir */
 210         if (workdir == upperdir)
 211                 goto err;
 212
 213         /* Workdir should not be subdir of upperdir and vice versa */
 214         if (lock_rename(workdir, upperdir) != NULL)
 215                 goto err_unlock;
 216
 217         return 0;
 218
 219 err_unlock:
 220         unlock_rename(workdir, upperdir);
 221 err:
 222         pr_err("overlayfs: failed to lock workdir+upperdir\n");
 223         return -EIO;
 224 }
 225
 226 static struct dentry *ovl_clear_empty(struct dentry *dentry,
 227                                       struct list_head *list)
 228 {
 229         struct dentry *workdir = ovl_workdir(dentry);
 230         struct inode *wdir = workdir->d_inode;
 231         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 232         struct inode *udir = upperdir->d_inode;
 233         struct path upperpath;
 234         struct dentry *upper;
 235         struct dentry *opaquedir;
 236         struct kstat stat;
 237         int err;
 238
 239         if (WARN_ON(!workdir))
 240                 return ERR_PTR(-EROFS);
 241
 242         err = ovl_lock_rename_workdir(workdir, upperdir);
 243         if (err)
 244                 goto out;
 245
 246         ovl_path_upper(dentry, &upperpath);
 247         err = vfs_getattr(&upperpath, &stat);
 248         if (err)
 249                 goto out_unlock;
 250
 251         err = -ESTALE;
 252         if (!S_ISDIR(stat.mode))
 253                 goto out_unlock;
 254         upper = upperpath.dentry;
 255         if (upper->d_parent->d_inode != udir)
 256                 goto out_unlock;
 257
 258         opaquedir = ovl_lookup_temp(workdir, dentry);
 259         err = PTR_ERR(opaquedir);
 260         if (IS_ERR(opaquedir))
 261                 goto out_unlock;
 262
 263         err = ovl_create_real(wdir, opaquedir, &stat, NULL, 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(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         enum ovl_path_type type = ovl_path_type(dentry);
 309         LIST_HEAD(list);
 310
 311         err = ovl_check_empty_dir(dentry, &list);
 312         if (err) {
 313                 ret = ERR_PTR(err);
 314                 goto out_free;
 315         }
 316
 317         /*
 318          * When removing an empty opaque directory, then it makes no sense to
 319          * replace it with an exact replica of itself.
 320          *
 321          * If no upperdentry then skip clearing whiteouts.
 322          *
 323          * Can race with copy-up, since we don't hold the upperdir mutex.
 324          * Doesn't matter, since copy-up can't create a non-empty directory
 325          * from an empty one.
 326          */
 327         if (OVL_TYPE_UPPER(type) && OVL_TYPE_MERGE(type))
 328                 ret = ovl_clear_empty(dentry, &list);
 329
 330 out_free:
 331         ovl_cache_free(&list);
 332
 333         return ret;
 334 }
 335
 336 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
 337                              const struct posix_acl *acl)
 338 {
 339         void *buffer;
 340         size_t size;
 341         int err;
 342
 343         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
 344                 return 0;
 345
 346         size = posix_acl_to_xattr(NULL, acl, NULL, 0);
 347         buffer = kmalloc(size, GFP_KERNEL);
 348         if (!buffer)
 349                 return -ENOMEM;
 350
 351         size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
 352         err = size;
 353         if (err < 0)
 354                 goto out_free;
 355
 356         err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
 357 out_free:
 358         kfree(buffer);
 359         return err;
 360 }
 361
 362 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 363                                     struct kstat *stat, const char *link,
 364                                     struct dentry *hardlink)
 365 {
 366         struct dentry *workdir = ovl_workdir(dentry);
 367         struct inode *wdir = workdir->d_inode;
 368         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 369         struct inode *udir = upperdir->d_inode;
 370         struct dentry *upper;
 371         struct dentry *newdentry;
 372         int err;
 373         struct posix_acl *acl, *default_acl;
 374
 375         if (WARN_ON(!workdir))
 376                 return -EROFS;
 377
 378         if (!hardlink) {
 379                 err = posix_acl_create(dentry->d_parent->d_inode,
 380                                        &stat->mode, &default_acl, &acl);
 381                 if (err)
 382                         return err;
 383         }
 384
 385         err = ovl_lock_rename_workdir(workdir, upperdir);
 386         if (err)
 387                 goto out;
 388
 389         newdentry = ovl_lookup_temp(workdir, dentry);
 390         err = PTR_ERR(newdentry);
 391         if (IS_ERR(newdentry))
 392                 goto out_unlock;
 393
 394         upper = lookup_one_len(dentry->d_name.name, upperdir,
 395                                dentry->d_name.len);
 396         err = PTR_ERR(upper);
 397         if (IS_ERR(upper))
 398                 goto out_dput;
 399
 400         err = ovl_create_real(wdir, newdentry, stat, link, hardlink, true);
 401         if (err)
 402                 goto out_dput2;
 403
 404         /*
 405          * mode could have been mutilated due to umask (e.g. sgid directory)
 406          */
 407         if (!hardlink &&
 408             !S_ISLNK(stat->mode) && newdentry->d_inode->i_mode != stat->mode) {
 409                 struct iattr attr = {
 410                         .ia_valid = ATTR_MODE,
 411                         .ia_mode = stat->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(stat->mode)) {
 432                 err = ovl_set_opaque(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 kstat *stat, const char *link,
 469                               struct dentry *hardlink)
 470 {
 471         int err;
 472         const struct cred *old_cred;
 473         struct cred *override_cred;
 474
 475         err = ovl_copy_up(dentry->d_parent);
 476         if (err)
 477                 return err;
 478
 479         old_cred = ovl_override_creds(dentry->d_sb);
 480         err = -ENOMEM;
 481         override_cred = prepare_creds();
 482         if (override_cred) {
 483                 override_cred->fsuid = inode->i_uid;
 484                 override_cred->fsgid = inode->i_gid;
 485                 if (!hardlink) {
 486                         err = security_dentry_create_files_as(dentry,
 487                                         stat->mode, &dentry->d_name, old_cred,
 488                                         override_cred);
 489                         if (err) {
 490                                 put_cred(override_cred);
 491                                 goto out_revert_creds;
 492                         }
 493                 }
 494                 put_cred(override_creds(override_cred));
 495                 put_cred(override_cred);
 496
 497                 if (!ovl_dentry_is_whiteout(dentry))
 498                         err = ovl_create_upper(dentry, inode, stat, link,
 499                                                 hardlink);
 500                 else
 501                         err = ovl_create_over_whiteout(dentry, inode, stat,
 502                                                         link, hardlink);
 503         }
 504 out_revert_creds:
 505         revert_creds(old_cred);
 506         if (!err) {
 507                 struct inode *realinode = d_inode(ovl_dentry_upper(dentry));
 508
 509                 WARN_ON(inode->i_mode != realinode->i_mode);
 510                 WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
 511                 WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
 512         }
 513         return err;
 514 }
 515
 516 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 517                              const char *link)
 518 {
 519         int err;
 520         struct inode *inode;
 521         struct kstat stat = {
 522                 .rdev = rdev,
 523         };
 524
 525         err = ovl_want_write(dentry);
 526         if (err)
 527                 goto out;
 528
 529         err = -ENOMEM;
 530         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
 531         if (!inode)
 532                 goto out_drop_write;
 533
 534         inode_init_owner(inode, dentry->d_parent->d_inode, mode);
 535         stat.mode = inode->i_mode;
 536
 537         err = ovl_create_or_link(dentry, inode, &stat, link, NULL);
 538         if (err)
 539                 iput(inode);
 540
 541 out_drop_write:
 542         ovl_drop_write(dentry);
 543 out:
 544         return err;
 545 }
 546
 547 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 548                       bool excl)
 549 {
 550         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 551 }
 552
 553 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 554 {
 555         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 556 }
 557
 558 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 559                      dev_t rdev)
 560 {
 561         /* Don't allow creation of "whiteout" on overlay */
 562         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
 563                 return -EPERM;
 564
 565         return ovl_create_object(dentry, mode, rdev, NULL);
 566 }
 567
 568 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
 569                        const char *link)
 570 {
 571         return ovl_create_object(dentry, S_IFLNK, 0, link);
 572 }
 573
 574 static int ovl_link(struct dentry *old, struct inode *newdir,
 575                     struct dentry *new)
 576 {
 577         int err;
 578         struct inode *inode;
 579
 580         err = ovl_want_write(old);
 581         if (err)
 582                 goto out;
 583
 584         err = ovl_copy_up(old);
 585         if (err)
 586                 goto out_drop_write;
 587
 588         inode = d_inode(old);
 589         ihold(inode);
 590
 591         err = ovl_create_or_link(new, inode, NULL, NULL, ovl_dentry_upper(old));
 592         if (err)
 593                 iput(inode);
 594
 595 out_drop_write:
 596         ovl_drop_write(old);
 597 out:
 598         return err;
 599 }
 600
 601 static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
 602 {
 603         struct dentry *workdir = ovl_workdir(dentry);
 604         struct inode *wdir = workdir->d_inode;
 605         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 606         struct inode *udir = upperdir->d_inode;
 607         struct dentry *whiteout;
 608         struct dentry *upper;
 609         struct dentry *opaquedir = NULL;
 610         int err;
 611         int flags = 0;
 612
 613         if (WARN_ON(!workdir))
 614                 return -EROFS;
 615
 616         if (is_dir) {
 617                 opaquedir = ovl_check_empty_and_clear(dentry);
 618                 err = PTR_ERR(opaquedir);
 619                 if (IS_ERR(opaquedir))
 620                         goto out;
 621         }
 622
 623         err = ovl_lock_rename_workdir(workdir, upperdir);
 624         if (err)
 625                 goto out_dput;
 626
 627         upper = lookup_one_len(dentry->d_name.name, upperdir,
 628                                dentry->d_name.len);
 629         err = PTR_ERR(upper);
 630         if (IS_ERR(upper))
 631                 goto out_unlock;
 632
 633         err = -ESTALE;
 634         if ((opaquedir && upper != opaquedir) ||
 635             (!opaquedir && ovl_dentry_upper(dentry) &&
 636              upper != ovl_dentry_upper(dentry))) {
 637                 goto out_dput_upper;
 638         }
 639
 640         whiteout = ovl_whiteout(workdir, dentry);
 641         err = PTR_ERR(whiteout);
 642         if (IS_ERR(whiteout))
 643                 goto out_dput_upper;
 644
 645         if (d_is_dir(upper))
 646                 flags = RENAME_EXCHANGE;
 647
 648         err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
 649         if (err)
 650                 goto kill_whiteout;
 651         if (flags)
 652                 ovl_cleanup(wdir, upper);
 653
 654         ovl_dentry_version_inc(dentry->d_parent);
 655 out_d_drop:
 656         d_drop(dentry);
 657         dput(whiteout);
 658 out_dput_upper:
 659         dput(upper);
 660 out_unlock:
 661         unlock_rename(workdir, upperdir);
 662 out_dput:
 663         dput(opaquedir);
 664 out:
 665         return err;
 666
 667 kill_whiteout:
 668         ovl_cleanup(wdir, whiteout);
 669         goto out_d_drop;
 670 }
 671
 672 static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 673 {
 674         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 675         struct inode *dir = upperdir->d_inode;
 676         struct dentry *upper;
 677         int err;
 678
 679         inode_lock_nested(dir, I_MUTEX_PARENT);
 680         upper = lookup_one_len(dentry->d_name.name, upperdir,
 681                                dentry->d_name.len);
 682         err = PTR_ERR(upper);
 683         if (IS_ERR(upper))
 684                 goto out_unlock;
 685
 686         err = -ESTALE;
 687         if (upper == ovl_dentry_upper(dentry)) {
 688                 if (is_dir)
 689                         err = vfs_rmdir(dir, upper);
 690                 else
 691                         err = vfs_unlink(dir, upper, NULL);
 692                 ovl_dentry_version_inc(dentry->d_parent);
 693         }
 694         dput(upper);
 695
 696         /*
 697          * Keeping this dentry hashed would mean having to release
 698          * upperpath/lowerpath, which could only be done if we are the
 699          * sole user of this dentry.  Too tricky...  Just unhash for
 700          * now.
 701          */
 702         if (!err)
 703                 d_drop(dentry);
 704 out_unlock:
 705         inode_unlock(dir);
 706
 707         return err;
 708 }
 709
 710 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 711 {
 712         enum ovl_path_type type;
 713         int err;
 714         const struct cred *old_cred;
 715
 716         err = ovl_want_write(dentry);
 717         if (err)
 718                 goto out;
 719
 720         err = ovl_copy_up(dentry->d_parent);
 721         if (err)
 722                 goto out_drop_write;
 723
 724         type = ovl_path_type(dentry);
 725
 726         old_cred = ovl_override_creds(dentry->d_sb);
 727         if (!ovl_lower_positive(dentry))
 728                 err = ovl_remove_upper(dentry, is_dir);
 729         else
 730                 err = ovl_remove_and_whiteout(dentry, is_dir);
 731         revert_creds(old_cred);
 732         if (!err) {
 733                 if (is_dir)
 734                         clear_nlink(dentry->d_inode);
 735                 else
 736                         drop_nlink(dentry->d_inode);
 737         }
 738 out_drop_write:
 739         ovl_drop_write(dentry);
 740 out:
 741         return err;
 742 }
 743
 744 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
 745 {
 746         return ovl_do_remove(dentry, false);
 747 }
 748
 749 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
 750 {
 751         return ovl_do_remove(dentry, true);
 752 }
 753
 754 static bool ovl_type_merge_or_lower(struct dentry *dentry)
 755 {
 756         enum ovl_path_type type = ovl_path_type(dentry);
 757
 758         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
 759 }
 760
 761 static bool ovl_can_move(struct dentry *dentry)
 762 {
 763         return ovl_redirect_dir(dentry->d_sb) ||
 764                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
 765 }
 766
 767 #define OVL_REDIRECT_MAX 256
 768
 769 static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
 770 {
 771         char *buf, *ret;
 772         struct dentry *d, *tmp;
 773         int buflen = OVL_REDIRECT_MAX + 1;
 774
 775         if (samedir) {
 776                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
 777                                GFP_KERNEL);
 778                 goto out;
 779         }
 780
 781         buf = ret = kmalloc(buflen, GFP_TEMPORARY);
 782         if (!buf)
 783                 goto out;
 784
 785         buflen--;
 786         buf[buflen] = '\0';
 787         for (d = dget(dentry); !IS_ROOT(d);) {
 788                 const char *name;
 789                 int thislen;
 790
 791                 spin_lock(&d->d_lock);
 792                 name = ovl_dentry_get_redirect(d);
 793                 if (name) {
 794                         thislen = strlen(name);
 795                 } else {
 796                         name = d->d_name.name;
 797                         thislen = d->d_name.len;
 798                 }
 799
 800                 /* If path is too long, fall back to userspace move */
 801                 if (thislen + (name[0] != '/') > buflen) {
 802                         ret = ERR_PTR(-EXDEV);
 803                         spin_unlock(&d->d_lock);
 804                         goto out_put;
 805                 }
 806
 807                 buflen -= thislen;
 808                 memcpy(&buf[buflen], name, thislen);
 809                 tmp = dget_dlock(d->d_parent);
 810                 spin_unlock(&d->d_lock);
 811
 812                 dput(d);
 813                 d = tmp;
 814
 815                 /* Absolute redirect: finished */
 816                 if (buf[buflen] == '/')
 817                         break;
 818                 buflen--;
 819                 buf[buflen] = '/';
 820         }
 821         ret = kstrdup(&buf[buflen], GFP_KERNEL);
 822 out_put:
 823         dput(d);
 824         kfree(buf);
 825 out:
 826         return ret ? ret : ERR_PTR(-ENOMEM);
 827 }
 828
 829 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
 830 {
 831         int err;
 832         const char *redirect = ovl_dentry_get_redirect(dentry);
 833
 834         if (redirect && (samedir || redirect[0] == '/'))
 835                 return 0;
 836
 837         redirect = ovl_get_redirect(dentry, samedir);
 838         if (IS_ERR(redirect))
 839                 return PTR_ERR(redirect);
 840
 841         err = ovl_do_setxattr(ovl_dentry_upper(dentry), OVL_XATTR_REDIRECT,
 842                               redirect, strlen(redirect), 0);
 843         if (!err) {
 844                 spin_lock(&dentry->d_lock);
 845                 ovl_dentry_set_redirect(dentry, redirect);
 846                 spin_unlock(&dentry->d_lock);
 847         } else {
 848                 kfree(redirect);
 849                 if (err == -EOPNOTSUPP)
 850                         ovl_clear_redirect_dir(dentry->d_sb);
 851                 else
 852                         pr_warn_ratelimited("overlay: failed to set redirect (%i)\n", err);
 853                 /* Fall back to userspace copy-up */
 854                 err = -EXDEV;
 855         }
 856         return err;
 857 }
 858
 859 static int ovl_rename(struct inode *olddir, struct dentry *old,
 860                       struct inode *newdir, struct dentry *new,
 861                       unsigned int flags)
 862 {
 863         int err;
 864         struct dentry *old_upperdir;
 865         struct dentry *new_upperdir;
 866         struct dentry *olddentry;
 867         struct dentry *newdentry;
 868         struct dentry *trap;
 869         bool old_opaque;
 870         bool new_opaque;
 871         bool cleanup_whiteout = false;
 872         bool overwrite = !(flags & RENAME_EXCHANGE);
 873         bool is_dir = d_is_dir(old);
 874         bool new_is_dir = d_is_dir(new);
 875         bool samedir = olddir == newdir;
 876         struct dentry *opaquedir = NULL;
 877         const struct cred *old_cred = NULL;
 878
 879         err = -EINVAL;
 880         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
 881                 goto out;
 882
 883         flags &= ~RENAME_NOREPLACE;
 884
 885         /* Don't copy up directory trees */
 886         err = -EXDEV;
 887         if (!ovl_can_move(old))
 888                 goto out;
 889         if (!overwrite && !ovl_can_move(new))
 890                 goto out;
 891
 892         err = ovl_want_write(old);
 893         if (err)
 894                 goto out;
 895
 896         err = ovl_copy_up(old);
 897         if (err)
 898                 goto out_drop_write;
 899
 900         err = ovl_copy_up(new->d_parent);
 901         if (err)
 902                 goto out_drop_write;
 903         if (!overwrite) {
 904                 err = ovl_copy_up(new);
 905                 if (err)
 906                         goto out_drop_write;
 907         }
 908
 909         old_cred = ovl_override_creds(old->d_sb);
 910
 911         if (overwrite && new_is_dir && ovl_type_merge_or_lower(new)) {
 912                 opaquedir = ovl_check_empty_and_clear(new);
 913                 err = PTR_ERR(opaquedir);
 914                 if (IS_ERR(opaquedir)) {
 915                         opaquedir = NULL;
 916                         goto out_revert_creds;
 917                 }
 918         }
 919
 920         if (overwrite) {
 921                 if (ovl_lower_positive(old)) {
 922                         if (!ovl_dentry_is_whiteout(new)) {
 923                                 /* Whiteout source */
 924                                 flags |= RENAME_WHITEOUT;
 925                         } else {
 926                                 /* Switch whiteouts */
 927                                 flags |= RENAME_EXCHANGE;
 928                         }
 929                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
 930                         flags |= RENAME_EXCHANGE;
 931                         cleanup_whiteout = true;
 932                 }
 933         }
 934
 935         old_upperdir = ovl_dentry_upper(old->d_parent);
 936         new_upperdir = ovl_dentry_upper(new->d_parent);
 937
 938         trap = lock_rename(new_upperdir, old_upperdir);
 939
 940         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
 941                                    old->d_name.len);
 942         err = PTR_ERR(olddentry);
 943         if (IS_ERR(olddentry))
 944                 goto out_unlock;
 945
 946         err = -ESTALE;
 947         if (olddentry != ovl_dentry_upper(old))
 948                 goto out_dput_old;
 949
 950         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
 951                                    new->d_name.len);
 952         err = PTR_ERR(newdentry);
 953         if (IS_ERR(newdentry))
 954                 goto out_dput_old;
 955
 956         old_opaque = ovl_dentry_is_opaque(old);
 957         new_opaque = ovl_dentry_is_opaque(new);
 958
 959         err = -ESTALE;
 960         if (ovl_dentry_upper(new)) {
 961                 if (opaquedir) {
 962                         if (newdentry != opaquedir)
 963                                 goto out_dput;
 964                 } else {
 965                         if (newdentry != ovl_dentry_upper(new))
 966                                 goto out_dput;
 967                 }
 968         } else {
 969                 if (!d_is_negative(newdentry) &&
 970                     (!new_opaque || !ovl_is_whiteout(newdentry)))
 971                         goto out_dput;
 972         }
 973
 974         if (olddentry == trap)
 975                 goto out_dput;
 976         if (newdentry == trap)
 977                 goto out_dput;
 978
 979         if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
 980                 goto out_dput;
 981
 982         if (is_dir) {
 983                 if (ovl_type_merge_or_lower(old)) {
 984                         err = ovl_set_redirect(old, samedir);
 985                         if (err)
 986                                 goto out_dput;
 987                 } else if (!old_opaque && ovl_lower_positive(new)) {
 988                         err = ovl_set_opaque(olddentry);
 989                         if (err)
 990                                 goto out_dput;
 991                         ovl_dentry_set_opaque(old, true);
 992                 }
 993         }
 994         if (!overwrite && new_is_dir) {
 995                 if (ovl_type_merge_or_lower(new)) {
 996                         err = ovl_set_redirect(new, samedir);
 997                         if (err)
 998                                 goto out_dput;
 999                 } else if (!new_opaque && ovl_lower_positive(old)) {
1000                         err = ovl_set_opaque(newdentry);
1001                         if (err)
1002                                 goto out_dput;
1003                         ovl_dentry_set_opaque(new, true);
1004                 }
1005         }
1006
1007         err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1008                             new_upperdir->d_inode, newdentry, flags);
1009         if (err)
1010                 goto out_dput;
1011
1012         if (cleanup_whiteout)
1013                 ovl_cleanup(old_upperdir->d_inode, newdentry);
1014
1015         ovl_dentry_version_inc(old->d_parent);
1016         ovl_dentry_version_inc(new->d_parent);
1017
1018 out_dput:
1019         dput(newdentry);
1020 out_dput_old:
1021         dput(olddentry);
1022 out_unlock:
1023         unlock_rename(new_upperdir, old_upperdir);
1024 out_revert_creds:
1025         revert_creds(old_cred);
1026 out_drop_write:
1027         ovl_drop_write(old);
1028 out:
1029         dput(opaquedir);
1030         return err;
1031 }
1032
1033 const struct inode_operations ovl_dir_inode_operations = {
1034         .lookup         = ovl_lookup,
1035         .mkdir          = ovl_mkdir,
1036         .symlink        = ovl_symlink,
1037         .unlink         = ovl_unlink,
1038         .rmdir          = ovl_rmdir,
1039         .rename         = ovl_rename,
1040         .link           = ovl_link,
1041         .setattr        = ovl_setattr,
1042         .create         = ovl_create,
1043         .mknod          = ovl_mknod,
1044         .permission     = ovl_permission,
1045         .getattr        = ovl_dir_getattr,
1046         .listxattr      = ovl_listxattr,
1047         .get_acl        = ovl_get_acl,
1048         .update_time    = ovl_update_time,
1049 };