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);
 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 int ovl_lock_rename_workdir(struct dentry *workdir,
 220                                    struct dentry *upperdir)
 221 {
 222         /* Workdir should not be the same as upperdir */
 223         if (workdir == upperdir)
 224                 goto err;
 225
 226         /* Workdir should not be subdir of upperdir and vice versa */
 227         if (lock_rename(workdir, upperdir) != NULL)
 228                 goto err_unlock;
 229
 230         return 0;
 231
 232 err_unlock:
 233         unlock_rename(workdir, upperdir);
 234 err:
 235         pr_err("overlayfs: failed to lock workdir+upperdir\n");
 236         return -EIO;
 237 }
 238
 239 static struct dentry *ovl_clear_empty(struct dentry *dentry,
 240                                       struct list_head *list)
 241 {
 242         struct dentry *workdir = ovl_workdir(dentry);
 243         struct inode *wdir = workdir->d_inode;
 244         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 245         struct inode *udir = upperdir->d_inode;
 246         struct path upperpath;
 247         struct dentry *upper;
 248         struct dentry *opaquedir;
 249         struct kstat stat;
 250         int err;
 251
 252         if (WARN_ON(!workdir))
 253                 return ERR_PTR(-EROFS);
 254
 255         err = ovl_lock_rename_workdir(workdir, upperdir);
 256         if (err)
 257                 goto out;
 258
 259         ovl_path_upper(dentry, &upperpath);
 260         err = vfs_getattr(&upperpath, &stat,
 261                           STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
 262         if (err)
 263                 goto out_unlock;
 264
 265         err = -ESTALE;
 266         if (!S_ISDIR(stat.mode))
 267                 goto out_unlock;
 268         upper = upperpath.dentry;
 269         if (upper->d_parent->d_inode != udir)
 270                 goto out_unlock;
 271
 272         opaquedir = ovl_lookup_temp(workdir);
 273         err = PTR_ERR(opaquedir);
 274         if (IS_ERR(opaquedir))
 275                 goto out_unlock;
 276
 277         err = ovl_create_real(wdir, opaquedir,
 278                               &(struct cattr){.mode = stat.mode}, NULL, true);
 279         if (err)
 280                 goto out_dput;
 281
 282         err = ovl_copy_xattr(upper, opaquedir);
 283         if (err)
 284                 goto out_cleanup;
 285
 286         err = ovl_set_opaque(dentry, opaquedir);
 287         if (err)
 288                 goto out_cleanup;
 289
 290         inode_lock(opaquedir->d_inode);
 291         err = ovl_set_attr(opaquedir, &stat);
 292         inode_unlock(opaquedir->d_inode);
 293         if (err)
 294                 goto out_cleanup;
 295
 296         err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
 297         if (err)
 298                 goto out_cleanup;
 299
 300         ovl_cleanup_whiteouts(upper, list);
 301         ovl_cleanup(wdir, upper);
 302         unlock_rename(workdir, upperdir);
 303
 304         /* dentry's upper doesn't match now, get rid of it */
 305         d_drop(dentry);
 306
 307         return opaquedir;
 308
 309 out_cleanup:
 310         ovl_cleanup(wdir, opaquedir);
 311 out_dput:
 312         dput(opaquedir);
 313 out_unlock:
 314         unlock_rename(workdir, upperdir);
 315 out:
 316         return ERR_PTR(err);
 317 }
 318
 319 static struct dentry *ovl_check_empty_and_clear(struct dentry *dentry)
 320 {
 321         int err;
 322         struct dentry *ret = NULL;
 323         enum ovl_path_type type = ovl_path_type(dentry);
 324         LIST_HEAD(list);
 325
 326         err = ovl_check_empty_dir(dentry, &list);
 327         if (err) {
 328                 ret = ERR_PTR(err);
 329                 goto out_free;
 330         }
 331
 332         /*
 333          * When removing an empty opaque directory, then it makes no sense to
 334          * replace it with an exact replica of itself.
 335          *
 336          * If no upperdentry then skip clearing whiteouts.
 337          *
 338          * Can race with copy-up, since we don't hold the upperdir mutex.
 339          * Doesn't matter, since copy-up can't create a non-empty directory
 340          * from an empty one.
 341          */
 342         if (OVL_TYPE_UPPER(type) && OVL_TYPE_MERGE(type))
 343                 ret = ovl_clear_empty(dentry, &list);
 344
 345 out_free:
 346         ovl_cache_free(&list);
 347
 348         return ret;
 349 }
 350
 351 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
 352                              const struct posix_acl *acl)
 353 {
 354         void *buffer;
 355         size_t size;
 356         int err;
 357
 358         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
 359                 return 0;
 360
 361         size = posix_acl_to_xattr(NULL, acl, NULL, 0);
 362         buffer = kmalloc(size, GFP_KERNEL);
 363         if (!buffer)
 364                 return -ENOMEM;
 365
 366         size = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
 367         err = size;
 368         if (err < 0)
 369                 goto out_free;
 370
 371         err = vfs_setxattr(upperdentry, name, buffer, size, XATTR_CREATE);
 372 out_free:
 373         kfree(buffer);
 374         return err;
 375 }
 376
 377 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 378                                     struct cattr *cattr,
 379                                     struct dentry *hardlink)
 380 {
 381         struct dentry *workdir = ovl_workdir(dentry);
 382         struct inode *wdir = workdir->d_inode;
 383         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 384         struct inode *udir = upperdir->d_inode;
 385         struct dentry *upper;
 386         struct dentry *newdentry;
 387         int err;
 388         struct posix_acl *acl, *default_acl;
 389
 390         if (WARN_ON(!workdir))
 391                 return -EROFS;
 392
 393         if (!hardlink) {
 394                 err = posix_acl_create(dentry->d_parent->d_inode,
 395                                        &cattr->mode, &default_acl, &acl);
 396                 if (err)
 397                         return err;
 398         }
 399
 400         err = ovl_lock_rename_workdir(workdir, upperdir);
 401         if (err)
 402                 goto out;
 403
 404         newdentry = ovl_lookup_temp(workdir);
 405         err = PTR_ERR(newdentry);
 406         if (IS_ERR(newdentry))
 407                 goto out_unlock;
 408
 409         upper = lookup_one_len(dentry->d_name.name, upperdir,
 410                                dentry->d_name.len);
 411         err = PTR_ERR(upper);
 412         if (IS_ERR(upper))
 413                 goto out_dput;
 414
 415         err = ovl_create_real(wdir, newdentry, cattr, hardlink, true);
 416         if (err)
 417                 goto out_dput2;
 418
 419         /*
 420          * mode could have been mutilated due to umask (e.g. sgid directory)
 421          */
 422         if (!hardlink &&
 423             !S_ISLNK(cattr->mode) &&
 424             newdentry->d_inode->i_mode != cattr->mode) {
 425                 struct iattr attr = {
 426                         .ia_valid = ATTR_MODE,
 427                         .ia_mode = cattr->mode,
 428                 };
 429                 inode_lock(newdentry->d_inode);
 430                 err = notify_change(newdentry, &attr, NULL);
 431                 inode_unlock(newdentry->d_inode);
 432                 if (err)
 433                         goto out_cleanup;
 434         }
 435         if (!hardlink) {
 436                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
 437                                         acl);
 438                 if (err)
 439                         goto out_cleanup;
 440
 441                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
 442                                         default_acl);
 443                 if (err)
 444                         goto out_cleanup;
 445         }
 446
 447         if (!hardlink && S_ISDIR(cattr->mode)) {
 448                 err = ovl_set_opaque(dentry, newdentry);
 449                 if (err)
 450                         goto out_cleanup;
 451
 452                 err = ovl_do_rename(wdir, newdentry, udir, upper,
 453                                     RENAME_EXCHANGE);
 454                 if (err)
 455                         goto out_cleanup;
 456
 457                 ovl_cleanup(wdir, upper);
 458         } else {
 459                 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
 460                 if (err)
 461                         goto out_cleanup;
 462         }
 463         ovl_instantiate(dentry, inode, newdentry, !!hardlink);
 464         newdentry = NULL;
 465 out_dput2:
 466         dput(upper);
 467 out_dput:
 468         dput(newdentry);
 469 out_unlock:
 470         unlock_rename(workdir, upperdir);
 471 out:
 472         if (!hardlink) {
 473                 posix_acl_release(acl);
 474                 posix_acl_release(default_acl);
 475         }
 476         return err;
 477
 478 out_cleanup:
 479         ovl_cleanup(wdir, newdentry);
 480         goto out_dput2;
 481 }
 482
 483 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
 484                               struct cattr *attr, struct dentry *hardlink)
 485 {
 486         int err;
 487         const struct cred *old_cred;
 488         struct cred *override_cred;
 489
 490         err = ovl_copy_up(dentry->d_parent);
 491         if (err)
 492                 return err;
 493
 494         old_cred = ovl_override_creds(dentry->d_sb);
 495         err = -ENOMEM;
 496         override_cred = prepare_creds();
 497         if (override_cred) {
 498                 override_cred->fsuid = inode->i_uid;
 499                 override_cred->fsgid = inode->i_gid;
 500                 if (!hardlink) {
 501                         err = security_dentry_create_files_as(dentry,
 502                                         attr->mode, &dentry->d_name, old_cred,
 503                                         override_cred);
 504                         if (err) {
 505                                 put_cred(override_cred);
 506                                 goto out_revert_creds;
 507                         }
 508                 }
 509                 put_cred(override_creds(override_cred));
 510                 put_cred(override_cred);
 511
 512                 if (!ovl_dentry_is_whiteout(dentry))
 513                         err = ovl_create_upper(dentry, inode, attr,
 514                                                 hardlink);
 515                 else
 516                         err = ovl_create_over_whiteout(dentry, inode, attr,
 517                                                         hardlink);
 518         }
 519 out_revert_creds:
 520         revert_creds(old_cred);
 521         if (!err) {
 522                 struct inode *realinode = d_inode(ovl_dentry_upper(dentry));
 523
 524                 WARN_ON(inode->i_mode != realinode->i_mode);
 525                 WARN_ON(!uid_eq(inode->i_uid, realinode->i_uid));
 526                 WARN_ON(!gid_eq(inode->i_gid, realinode->i_gid));
 527         }
 528         return err;
 529 }
 530
 531 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 532                              const char *link)
 533 {
 534         int err;
 535         struct inode *inode;
 536         struct cattr attr = {
 537                 .rdev = rdev,
 538                 .link = link,
 539         };
 540
 541         err = ovl_want_write(dentry);
 542         if (err)
 543                 goto out;
 544
 545         err = -ENOMEM;
 546         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
 547         if (!inode)
 548                 goto out_drop_write;
 549
 550         inode_init_owner(inode, dentry->d_parent->d_inode, mode);
 551         attr.mode = inode->i_mode;
 552
 553         err = ovl_create_or_link(dentry, inode, &attr, NULL);
 554         if (err)
 555                 iput(inode);
 556
 557 out_drop_write:
 558         ovl_drop_write(dentry);
 559 out:
 560         return err;
 561 }
 562
 563 static int ovl_create(struct inode *dir, struct dentry *dentry, umode_t mode,
 564                       bool excl)
 565 {
 566         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 567 }
 568
 569 static int ovl_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode)
 570 {
 571         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 572 }
 573
 574 static int ovl_mknod(struct inode *dir, struct dentry *dentry, umode_t mode,
 575                      dev_t rdev)
 576 {
 577         /* Don't allow creation of "whiteout" on overlay */
 578         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
 579                 return -EPERM;
 580
 581         return ovl_create_object(dentry, mode, rdev, NULL);
 582 }
 583
 584 static int ovl_symlink(struct inode *dir, struct dentry *dentry,
 585                        const char *link)
 586 {
 587         return ovl_create_object(dentry, S_IFLNK, 0, link);
 588 }
 589
 590 static int ovl_link(struct dentry *old, struct inode *newdir,
 591                     struct dentry *new)
 592 {
 593         int err;
 594         bool locked = false;
 595         struct inode *inode;
 596
 597         err = ovl_want_write(old);
 598         if (err)
 599                 goto out;
 600
 601         err = ovl_copy_up(old);
 602         if (err)
 603                 goto out_drop_write;
 604
 605         err = ovl_nlink_start(old, &locked);
 606         if (err)
 607                 goto out_drop_write;
 608
 609         inode = d_inode(old);
 610         ihold(inode);
 611
 612         err = ovl_create_or_link(new, inode, NULL, ovl_dentry_upper(old));
 613         if (err)
 614                 iput(inode);
 615
 616         ovl_nlink_end(old, locked);
 617 out_drop_write:
 618         ovl_drop_write(old);
 619 out:
 620         return err;
 621 }
 622
 623 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
 624 {
 625         return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
 626 }
 627
 628 static int ovl_remove_and_whiteout(struct dentry *dentry, bool is_dir)
 629 {
 630         struct dentry *workdir = ovl_workdir(dentry);
 631         struct inode *wdir = workdir->d_inode;
 632         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 633         struct inode *udir = upperdir->d_inode;
 634         struct dentry *whiteout;
 635         struct dentry *upper;
 636         struct dentry *opaquedir = NULL;
 637         int err;
 638         int flags = 0;
 639
 640         if (WARN_ON(!workdir))
 641                 return -EROFS;
 642
 643         if (is_dir) {
 644                 opaquedir = ovl_check_empty_and_clear(dentry);
 645                 err = PTR_ERR(opaquedir);
 646                 if (IS_ERR(opaquedir))
 647                         goto out;
 648         }
 649
 650         err = ovl_lock_rename_workdir(workdir, upperdir);
 651         if (err)
 652                 goto out_dput;
 653
 654         upper = lookup_one_len(dentry->d_name.name, upperdir,
 655                                dentry->d_name.len);
 656         err = PTR_ERR(upper);
 657         if (IS_ERR(upper))
 658                 goto out_unlock;
 659
 660         err = -ESTALE;
 661         if ((opaquedir && upper != opaquedir) ||
 662             (!opaquedir && ovl_dentry_upper(dentry) &&
 663              !ovl_matches_upper(dentry, upper))) {
 664                 goto out_dput_upper;
 665         }
 666
 667         whiteout = ovl_whiteout(workdir, dentry);
 668         err = PTR_ERR(whiteout);
 669         if (IS_ERR(whiteout))
 670                 goto out_dput_upper;
 671
 672         if (d_is_dir(upper))
 673                 flags = RENAME_EXCHANGE;
 674
 675         err = ovl_do_rename(wdir, whiteout, udir, upper, flags);
 676         if (err)
 677                 goto kill_whiteout;
 678         if (flags)
 679                 ovl_cleanup(wdir, upper);
 680
 681         ovl_dentry_version_inc(dentry->d_parent);
 682 out_d_drop:
 683         d_drop(dentry);
 684         dput(whiteout);
 685 out_dput_upper:
 686         dput(upper);
 687 out_unlock:
 688         unlock_rename(workdir, upperdir);
 689 out_dput:
 690         dput(opaquedir);
 691 out:
 692         return err;
 693
 694 kill_whiteout:
 695         ovl_cleanup(wdir, whiteout);
 696         goto out_d_drop;
 697 }
 698
 699 static int ovl_remove_upper(struct dentry *dentry, bool is_dir)
 700 {
 701         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 702         struct inode *dir = upperdir->d_inode;
 703         struct dentry *upper;
 704         struct dentry *opaquedir = NULL;
 705         int err;
 706
 707         /* Redirect dir can be !ovl_lower_positive && OVL_TYPE_MERGE */
 708         if (is_dir && ovl_dentry_get_redirect(dentry)) {
 709                 opaquedir = ovl_check_empty_and_clear(dentry);
 710                 err = PTR_ERR(opaquedir);
 711                 if (IS_ERR(opaquedir))
 712                         goto out;
 713         }
 714
 715         inode_lock_nested(dir, I_MUTEX_PARENT);
 716         upper = lookup_one_len(dentry->d_name.name, upperdir,
 717                                dentry->d_name.len);
 718         err = PTR_ERR(upper);
 719         if (IS_ERR(upper))
 720                 goto out_unlock;
 721
 722         err = -ESTALE;
 723         if ((opaquedir && upper != opaquedir) ||
 724             (!opaquedir && !ovl_matches_upper(dentry, upper)))
 725                 goto out_dput_upper;
 726
 727         if (is_dir)
 728                 err = vfs_rmdir(dir, upper);
 729         else
 730                 err = vfs_unlink(dir, upper, NULL);
 731         ovl_dentry_version_inc(dentry->d_parent);
 732
 733         /*
 734          * Keeping this dentry hashed would mean having to release
 735          * upperpath/lowerpath, which could only be done if we are the
 736          * sole user of this dentry.  Too tricky...  Just unhash for
 737          * now.
 738          */
 739         if (!err)
 740                 d_drop(dentry);
 741 out_dput_upper:
 742         dput(upper);
 743 out_unlock:
 744         inode_unlock(dir);
 745         dput(opaquedir);
 746 out:
 747         return err;
 748 }
 749
 750 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 751 {
 752         int err;
 753         bool locked = false;
 754         const struct cred *old_cred;
 755
 756         err = ovl_want_write(dentry);
 757         if (err)
 758                 goto out;
 759
 760         err = ovl_copy_up(dentry->d_parent);
 761         if (err)
 762                 goto out_drop_write;
 763
 764         err = ovl_nlink_start(dentry, &locked);
 765         if (err)
 766                 goto out_drop_write;
 767
 768         old_cred = ovl_override_creds(dentry->d_sb);
 769         if (!ovl_lower_positive(dentry))
 770                 err = ovl_remove_upper(dentry, is_dir);
 771         else
 772                 err = ovl_remove_and_whiteout(dentry, is_dir);
 773         revert_creds(old_cred);
 774         if (!err) {
 775                 if (is_dir)
 776                         clear_nlink(dentry->d_inode);
 777                 else
 778                         drop_nlink(dentry->d_inode);
 779         }
 780         ovl_nlink_end(dentry, locked);
 781 out_drop_write:
 782         ovl_drop_write(dentry);
 783 out:
 784         return err;
 785 }
 786
 787 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
 788 {
 789         return ovl_do_remove(dentry, false);
 790 }
 791
 792 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
 793 {
 794         return ovl_do_remove(dentry, true);
 795 }
 796
 797 static bool ovl_type_merge_or_lower(struct dentry *dentry)
 798 {
 799         enum ovl_path_type type = ovl_path_type(dentry);
 800
 801         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
 802 }
 803
 804 static bool ovl_can_move(struct dentry *dentry)
 805 {
 806         return ovl_redirect_dir(dentry->d_sb) ||
 807                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
 808 }
 809
 810 static char *ovl_get_redirect(struct dentry *dentry, bool samedir)
 811 {
 812         char *buf, *ret;
 813         struct dentry *d, *tmp;
 814         int buflen = ovl_redirect_max + 1;
 815
 816         if (samedir) {
 817                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
 818                                GFP_KERNEL);
 819                 goto out;
 820         }
 821
 822         buf = ret = kmalloc(buflen, GFP_TEMPORARY);
 823         if (!buf)
 824                 goto out;
 825
 826         buflen--;
 827         buf[buflen] = '\0';
 828         for (d = dget(dentry); !IS_ROOT(d);) {
 829                 const char *name;
 830                 int thislen;
 831
 832                 spin_lock(&d->d_lock);
 833                 name = ovl_dentry_get_redirect(d);
 834                 if (name) {
 835                         thislen = strlen(name);
 836                 } else {
 837                         name = d->d_name.name;
 838                         thislen = d->d_name.len;
 839                 }
 840
 841                 /* If path is too long, fall back to userspace move */
 842                 if (thislen + (name[0] != '/') > buflen) {
 843                         ret = ERR_PTR(-EXDEV);
 844                         spin_unlock(&d->d_lock);
 845                         goto out_put;
 846                 }
 847
 848                 buflen -= thislen;
 849                 memcpy(&buf[buflen], name, thislen);
 850                 tmp = dget_dlock(d->d_parent);
 851                 spin_unlock(&d->d_lock);
 852
 853                 dput(d);
 854                 d = tmp;
 855
 856                 /* Absolute redirect: finished */
 857                 if (buf[buflen] == '/')
 858                         break;
 859                 buflen--;
 860                 buf[buflen] = '/';
 861         }
 862         ret = kstrdup(&buf[buflen], GFP_KERNEL);
 863 out_put:
 864         dput(d);
 865         kfree(buf);
 866 out:
 867         return ret ? ret : ERR_PTR(-ENOMEM);
 868 }
 869
 870 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
 871 {
 872         int err;
 873         const char *redirect = ovl_dentry_get_redirect(dentry);
 874
 875         if (redirect && (samedir || redirect[0] == '/'))
 876                 return 0;
 877
 878         redirect = ovl_get_redirect(dentry, samedir);
 879         if (IS_ERR(redirect))
 880                 return PTR_ERR(redirect);
 881
 882         err = ovl_check_setxattr(dentry, ovl_dentry_upper(dentry),
 883                                  OVL_XATTR_REDIRECT,
 884                                  redirect, strlen(redirect), -EXDEV);
 885         if (!err) {
 886                 spin_lock(&dentry->d_lock);
 887                 ovl_dentry_set_redirect(dentry, redirect);
 888                 spin_unlock(&dentry->d_lock);
 889         } else {
 890                 kfree(redirect);
 891                 pr_warn_ratelimited("overlay: failed to set redirect (%i)\n", err);
 892                 /* Fall back to userspace copy-up */
 893                 err = -EXDEV;
 894         }
 895         return err;
 896 }
 897
 898 static int ovl_rename(struct inode *olddir, struct dentry *old,
 899                       struct inode *newdir, struct dentry *new,
 900                       unsigned int flags)
 901 {
 902         int err;
 903         bool locked = false;
 904         struct dentry *old_upperdir;
 905         struct dentry *new_upperdir;
 906         struct dentry *olddentry;
 907         struct dentry *newdentry;
 908         struct dentry *trap;
 909         bool old_opaque;
 910         bool new_opaque;
 911         bool cleanup_whiteout = false;
 912         bool overwrite = !(flags & RENAME_EXCHANGE);
 913         bool is_dir = d_is_dir(old);
 914         bool new_is_dir = d_is_dir(new);
 915         bool samedir = olddir == newdir;
 916         struct dentry *opaquedir = NULL;
 917         const struct cred *old_cred = NULL;
 918
 919         err = -EINVAL;
 920         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
 921                 goto out;
 922
 923         flags &= ~RENAME_NOREPLACE;
 924
 925         /* Don't copy up directory trees */
 926         err = -EXDEV;
 927         if (!ovl_can_move(old))
 928                 goto out;
 929         if (!overwrite && !ovl_can_move(new))
 930                 goto out;
 931
 932         err = ovl_want_write(old);
 933         if (err)
 934                 goto out;
 935
 936         err = ovl_copy_up(old);
 937         if (err)
 938                 goto out_drop_write;
 939
 940         err = ovl_copy_up(new->d_parent);
 941         if (err)
 942                 goto out_drop_write;
 943         if (!overwrite) {
 944                 err = ovl_copy_up(new);
 945                 if (err)
 946                         goto out_drop_write;
 947         } else {
 948                 err = ovl_nlink_start(new, &locked);
 949                 if (err)
 950                         goto out_drop_write;
 951         }
 952
 953         old_cred = ovl_override_creds(old->d_sb);
 954
 955         if (overwrite && new_is_dir && ovl_type_merge_or_lower(new)) {
 956                 opaquedir = ovl_check_empty_and_clear(new);
 957                 err = PTR_ERR(opaquedir);
 958                 if (IS_ERR(opaquedir)) {
 959                         opaquedir = NULL;
 960                         goto out_revert_creds;
 961                 }
 962         }
 963
 964         if (overwrite) {
 965                 if (ovl_lower_positive(old)) {
 966                         if (!ovl_dentry_is_whiteout(new)) {
 967                                 /* Whiteout source */
 968                                 flags |= RENAME_WHITEOUT;
 969                         } else {
 970                                 /* Switch whiteouts */
 971                                 flags |= RENAME_EXCHANGE;
 972                         }
 973                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
 974                         flags |= RENAME_EXCHANGE;
 975                         cleanup_whiteout = true;
 976                 }
 977         }
 978
 979         old_upperdir = ovl_dentry_upper(old->d_parent);
 980         new_upperdir = ovl_dentry_upper(new->d_parent);
 981
 982         if (!samedir) {
 983                 /*
 984                  * When moving a merge dir or non-dir with copy up origin into
 985                  * a new parent, we are marking the new parent dir "impure".
 986                  * When ovl_iterate() iterates an "impure" upper dir, it will
 987                  * lookup the origin inodes of the entries to fill d_ino.
 988                  */
 989                 if (ovl_type_origin(old)) {
 990                         err = ovl_set_impure(new->d_parent, new_upperdir);
 991                         if (err)
 992                                 goto out_revert_creds;
 993                 }
 994                 if (!overwrite && ovl_type_origin(new)) {
 995                         err = ovl_set_impure(old->d_parent, old_upperdir);
 996                         if (err)
 997                                 goto out_revert_creds;
 998                 }
 999         }
1000
1001         trap = lock_rename(new_upperdir, old_upperdir);
1002
1003         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
1004                                    old->d_name.len);
1005         err = PTR_ERR(olddentry);
1006         if (IS_ERR(olddentry))
1007                 goto out_unlock;
1008
1009         err = -ESTALE;
1010         if (!ovl_matches_upper(old, olddentry))
1011                 goto out_dput_old;
1012
1013         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
1014                                    new->d_name.len);
1015         err = PTR_ERR(newdentry);
1016         if (IS_ERR(newdentry))
1017                 goto out_dput_old;
1018
1019         old_opaque = ovl_dentry_is_opaque(old);
1020         new_opaque = ovl_dentry_is_opaque(new);
1021
1022         err = -ESTALE;
1023         if (d_inode(new) && ovl_dentry_upper(new)) {
1024                 if (opaquedir) {
1025                         if (newdentry != opaquedir)
1026                                 goto out_dput;
1027                 } else {
1028                         if (!ovl_matches_upper(new, newdentry))
1029                                 goto out_dput;
1030                 }
1031         } else {
1032                 if (!d_is_negative(newdentry) &&
1033                     (!new_opaque || !ovl_is_whiteout(newdentry)))
1034                         goto out_dput;
1035         }
1036
1037         if (olddentry == trap)
1038                 goto out_dput;
1039         if (newdentry == trap)
1040                 goto out_dput;
1041
1042         if (WARN_ON(olddentry->d_inode == newdentry->d_inode))
1043                 goto out_dput;
1044
1045         err = 0;
1046         if (is_dir) {
1047                 if (ovl_type_merge_or_lower(old))
1048                         err = ovl_set_redirect(old, samedir);
1049                 else if (!old_opaque && ovl_type_merge(new->d_parent))
1050                         err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1051                 if (err)
1052                         goto out_dput;
1053         }
1054         if (!overwrite && new_is_dir) {
1055                 if (ovl_type_merge_or_lower(new))
1056                         err = ovl_set_redirect(new, samedir);
1057                 else if (!new_opaque && ovl_type_merge(old->d_parent))
1058                         err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1059                 if (err)
1060                         goto out_dput;
1061         }
1062
1063         err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1064                             new_upperdir->d_inode, newdentry, flags);
1065         if (err)
1066                 goto out_dput;
1067
1068         if (cleanup_whiteout)
1069                 ovl_cleanup(old_upperdir->d_inode, newdentry);
1070
1071         if (overwrite && d_inode(new)) {
1072                 if (new_is_dir)
1073                         clear_nlink(d_inode(new));
1074                 else
1075                         drop_nlink(d_inode(new));
1076         }
1077
1078         ovl_dentry_version_inc(old->d_parent);
1079         ovl_dentry_version_inc(new->d_parent);
1080
1081 out_dput:
1082         dput(newdentry);
1083 out_dput_old:
1084         dput(olddentry);
1085 out_unlock:
1086         unlock_rename(new_upperdir, old_upperdir);
1087 out_revert_creds:
1088         revert_creds(old_cred);
1089         ovl_nlink_end(new, locked);
1090 out_drop_write:
1091         ovl_drop_write(old);
1092 out:
1093         dput(opaquedir);
1094         return err;
1095 }
1096
1097 const struct inode_operations ovl_dir_inode_operations = {
1098         .lookup         = ovl_lookup,
1099         .mkdir          = ovl_mkdir,
1100         .symlink        = ovl_symlink,
1101         .unlink         = ovl_unlink,
1102         .rmdir          = ovl_rmdir,
1103         .rename         = ovl_rename,
1104         .link           = ovl_link,
1105         .setattr        = ovl_setattr,
1106         .create         = ovl_create,
1107         .mknod          = ovl_mknod,
1108         .permission     = ovl_permission,
1109         .getattr        = ovl_getattr,
1110         .listxattr      = ovl_listxattr,
1111         .get_acl        = ovl_get_acl,
1112         .update_time    = ovl_update_time,
1113 };