fs/overlayfs/dir.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *
   4  * Copyright (C) 2011 Novell Inc.
   5  */
   6
   7 #include <linux/fs.h>
   8 #include <linux/namei.h>
   9 #include <linux/xattr.h>
  10 #include <linux/security.h>
  11 #include <linux/cred.h>
  12 #include <linux/module.h>
  13 #include <linux/posix_acl.h>
  14 #include <linux/posix_acl_xattr.h>
  15 #include <linux/atomic.h>
  16 #include <linux/ratelimit.h>
  17 #include <linux/backing-file.h>
  18 #include "overlayfs.h"
  19
  20 static unsigned short ovl_redirect_max = 256;
  21 module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
  22 MODULE_PARM_DESC(redirect_max,
  23                  "Maximum length of absolute redirect xattr value");
  24
  25 static int ovl_set_redirect(struct dentry *dentry, bool samedir);
  26
  27 int ovl_cleanup(struct ovl_fs *ofs, 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(ofs, wdir, wdentry);
  34         else
  35                 err = ovl_do_unlink(ofs, wdir, wdentry);
  36         dput(wdentry);
  37
  38         if (err) {
  39                 pr_err("cleanup of '%pd2' failed (%i)\n",
  40                        wdentry, err);
  41         }
  42
  43         return err;
  44 }
  45
  46 struct dentry *ovl_lookup_temp(struct ovl_fs *ofs, 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 = ovl_lookup_upper(ofs, name, workdir, strlen(name));
  56         if (!IS_ERR(temp) && temp->d_inode) {
  57                 pr_err("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 ovl_fs *ofs)
  67 {
  68         int err;
  69         struct dentry *whiteout;
  70         struct dentry *workdir = ofs->workdir;
  71         struct inode *wdir = workdir->d_inode;
  72
  73         if (!ofs->whiteout) {
  74                 whiteout = ovl_lookup_temp(ofs, workdir);
  75                 if (IS_ERR(whiteout))
  76                         goto out;
  77
  78                 err = ovl_do_whiteout(ofs, wdir, whiteout);
  79                 if (err) {
  80                         dput(whiteout);
  81                         whiteout = ERR_PTR(err);
  82                         goto out;
  83                 }
  84                 ofs->whiteout = whiteout;
  85         }
  86
  87         if (!ofs->no_shared_whiteout) {
  88                 whiteout = ovl_lookup_temp(ofs, workdir);
  89                 if (IS_ERR(whiteout))
  90                         goto out;
  91
  92                 err = ovl_do_link(ofs, ofs->whiteout, wdir, whiteout);
  93                 if (!err)
  94                         goto out;
  95
  96                 if (err != -EMLINK) {
  97                         pr_warn("Failed to link whiteout - disabling whiteout inode sharing(nlink=%u, err=%i)\n",
  98                                 ofs->whiteout->d_inode->i_nlink, err);
  99                         ofs->no_shared_whiteout = true;
 100                 }
 101                 dput(whiteout);
 102         }
 103         whiteout = ofs->whiteout;
 104         ofs->whiteout = NULL;
 105 out:
 106         return whiteout;
 107 }
 108
 109 /* Caller must hold i_mutex on both workdir and dir */
 110 int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
 111                              struct dentry *dentry)
 112 {
 113         struct inode *wdir = ofs->workdir->d_inode;
 114         struct dentry *whiteout;
 115         int err;
 116         int flags = 0;
 117
 118         whiteout = ovl_whiteout(ofs);
 119         err = PTR_ERR(whiteout);
 120         if (IS_ERR(whiteout))
 121                 return err;
 122
 123         if (d_is_dir(dentry))
 124                 flags = RENAME_EXCHANGE;
 125
 126         err = ovl_do_rename(ofs, wdir, whiteout, dir, dentry, flags);
 127         if (err)
 128                 goto kill_whiteout;
 129         if (flags)
 130                 ovl_cleanup(ofs, wdir, dentry);
 131
 132 out:
 133         dput(whiteout);
 134         return err;
 135
 136 kill_whiteout:
 137         ovl_cleanup(ofs, wdir, whiteout);
 138         goto out;
 139 }
 140
 141 int ovl_mkdir_real(struct ovl_fs *ofs, struct inode *dir,
 142                    struct dentry **newdentry, umode_t mode)
 143 {
 144         int err;
 145         struct dentry *d, *dentry = *newdentry;
 146
 147         err = ovl_do_mkdir(ofs, dir, dentry, mode);
 148         if (err)
 149                 return err;
 150
 151         if (likely(!d_unhashed(dentry)))
 152                 return 0;
 153
 154         /*
 155          * vfs_mkdir() may succeed and leave the dentry passed
 156          * to it unhashed and negative. If that happens, try to
 157          * lookup a new hashed and positive dentry.
 158          */
 159         d = ovl_lookup_upper(ofs, dentry->d_name.name, dentry->d_parent,
 160                              dentry->d_name.len);
 161         if (IS_ERR(d)) {
 162                 pr_warn("failed lookup after mkdir (%pd2, err=%i).\n",
 163                         dentry, err);
 164                 return PTR_ERR(d);
 165         }
 166         dput(dentry);
 167         *newdentry = d;
 168
 169         return 0;
 170 }
 171
 172 struct dentry *ovl_create_real(struct ovl_fs *ofs, struct inode *dir,
 173                                struct dentry *newdentry, struct ovl_cattr *attr)
 174 {
 175         int err;
 176
 177         if (IS_ERR(newdentry))
 178                 return newdentry;
 179
 180         err = -ESTALE;
 181         if (newdentry->d_inode)
 182                 goto out;
 183
 184         if (attr->hardlink) {
 185                 err = ovl_do_link(ofs, attr->hardlink, dir, newdentry);
 186         } else {
 187                 switch (attr->mode & S_IFMT) {
 188                 case S_IFREG:
 189                         err = ovl_do_create(ofs, dir, newdentry, attr->mode);
 190                         break;
 191
 192                 case S_IFDIR:
 193                         /* mkdir is special... */
 194                         err =  ovl_mkdir_real(ofs, dir, &newdentry, attr->mode);
 195                         break;
 196
 197                 case S_IFCHR:
 198                 case S_IFBLK:
 199                 case S_IFIFO:
 200                 case S_IFSOCK:
 201                         err = ovl_do_mknod(ofs, dir, newdentry, attr->mode,
 202                                            attr->rdev);
 203                         break;
 204
 205                 case S_IFLNK:
 206                         err = ovl_do_symlink(ofs, dir, newdentry, attr->link);
 207                         break;
 208
 209                 default:
 210                         err = -EPERM;
 211                 }
 212         }
 213         if (!err && WARN_ON(!newdentry->d_inode)) {
 214                 /*
 215                  * Not quite sure if non-instantiated dentry is legal or not.
 216                  * VFS doesn't seem to care so check and warn here.
 217                  */
 218                 err = -EIO;
 219         }
 220 out:
 221         if (err) {
 222                 dput(newdentry);
 223                 return ERR_PTR(err);
 224         }
 225         return newdentry;
 226 }
 227
 228 struct dentry *ovl_create_temp(struct ovl_fs *ofs, struct dentry *workdir,
 229                                struct ovl_cattr *attr)
 230 {
 231         return ovl_create_real(ofs, d_inode(workdir),
 232                                ovl_lookup_temp(ofs, workdir), attr);
 233 }
 234
 235 static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
 236                                int xerr)
 237 {
 238         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 239         int err;
 240
 241         err = ovl_check_setxattr(ofs, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
 242         if (!err)
 243                 ovl_dentry_set_opaque(dentry);
 244
 245         return err;
 246 }
 247
 248 static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
 249 {
 250         /*
 251          * Fail with -EIO when trying to create opaque dir and upper doesn't
 252          * support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
 253          * return a specific error for noxattr case.
 254          */
 255         return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
 256 }
 257
 258 /*
 259  * Common operations required to be done after creation of file on upper.
 260  * If @hardlink is false, then @inode is a pre-allocated inode, we may or
 261  * may not use to instantiate the new dentry.
 262  */
 263 static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
 264                            struct dentry *newdentry, bool hardlink, struct file *tmpfile)
 265 {
 266         struct ovl_inode_params oip = {
 267                 .upperdentry = newdentry,
 268                 .newinode = inode,
 269         };
 270
 271         ovl_dentry_set_upper_alias(dentry);
 272         ovl_dentry_init_reval(dentry, newdentry, NULL);
 273
 274         if (!hardlink) {
 275                 /*
 276                  * ovl_obtain_alias() can be called after ovl_create_real()
 277                  * and before we get here, so we may get an inode from cache
 278                  * with the same real upperdentry that is not the inode we
 279                  * pre-allocated.  In this case we will use the cached inode
 280                  * to instantiate the new dentry.
 281                  *
 282                  * XXX: if we ever use ovl_obtain_alias() to decode directory
 283                  * file handles, need to use ovl_get_inode_locked() and
 284                  * d_instantiate_new() here to prevent from creating two
 285                  * hashed directory inode aliases.
 286                  */
 287                 inode = ovl_get_inode(dentry->d_sb, &oip);
 288                 if (IS_ERR(inode))
 289                         return PTR_ERR(inode);
 290                 if (inode == oip.newinode)
 291                         ovl_set_flag(OVL_UPPERDATA, inode);
 292         } else {
 293                 WARN_ON(ovl_inode_real(inode) != d_inode(newdentry));
 294                 dput(newdentry);
 295                 inc_nlink(inode);
 296         }
 297
 298         if (tmpfile)
 299                 d_mark_tmpfile(tmpfile, inode);
 300
 301         d_instantiate(dentry, inode);
 302         if (inode != oip.newinode) {
 303                 pr_warn_ratelimited("newly created inode found in cache (%pd2)\n",
 304                                     dentry);
 305         }
 306
 307         /* Force lookup of new upper hardlink to find its lower */
 308         if (hardlink)
 309                 d_drop(dentry);
 310
 311         return 0;
 312 }
 313
 314 static bool ovl_type_merge(struct dentry *dentry)
 315 {
 316         return OVL_TYPE_MERGE(ovl_path_type(dentry));
 317 }
 318
 319 static bool ovl_type_origin(struct dentry *dentry)
 320 {
 321         return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
 322 }
 323
 324 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 325                             struct ovl_cattr *attr)
 326 {
 327         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 328         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 329         struct inode *udir = upperdir->d_inode;
 330         struct dentry *newdentry;
 331         int err;
 332
 333         inode_lock_nested(udir, I_MUTEX_PARENT);
 334         newdentry = ovl_create_real(ofs, udir,
 335                                     ovl_lookup_upper(ofs, dentry->d_name.name,
 336                                                      upperdir, dentry->d_name.len),
 337                                     attr);
 338         err = PTR_ERR(newdentry);
 339         if (IS_ERR(newdentry))
 340                 goto out_unlock;
 341
 342         if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry) &&
 343             !ovl_allow_offline_changes(ofs)) {
 344                 /* Setting opaque here is just an optimization, allow to fail */
 345                 ovl_set_opaque(dentry, newdentry);
 346         }
 347
 348         ovl_dir_modified(dentry->d_parent, false);
 349         err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink, NULL);
 350         if (err)
 351                 goto out_cleanup;
 352 out_unlock:
 353         inode_unlock(udir);
 354         return err;
 355
 356 out_cleanup:
 357         ovl_cleanup(ofs, udir, newdentry);
 358         dput(newdentry);
 359         goto out_unlock;
 360 }
 361
 362 static struct dentry *ovl_clear_empty(struct dentry *dentry,
 363                                       struct list_head *list)
 364 {
 365         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 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 path upperpath;
 371         struct dentry *upper;
 372         struct dentry *opaquedir;
 373         struct kstat stat;
 374         int err;
 375
 376         if (WARN_ON(!workdir))
 377                 return ERR_PTR(-EROFS);
 378
 379         err = ovl_lock_rename_workdir(workdir, upperdir);
 380         if (err)
 381                 goto out;
 382
 383         ovl_path_upper(dentry, &upperpath);
 384         err = vfs_getattr(&upperpath, &stat,
 385                           STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
 386         if (err)
 387                 goto out_unlock;
 388
 389         err = -ESTALE;
 390         if (!S_ISDIR(stat.mode))
 391                 goto out_unlock;
 392         upper = upperpath.dentry;
 393         if (upper->d_parent->d_inode != udir)
 394                 goto out_unlock;
 395
 396         opaquedir = ovl_create_temp(ofs, workdir, OVL_CATTR(stat.mode));
 397         err = PTR_ERR(opaquedir);
 398         if (IS_ERR(opaquedir))
 399                 goto out_unlock;
 400
 401         err = ovl_copy_xattr(dentry->d_sb, &upperpath, opaquedir);
 402         if (err)
 403                 goto out_cleanup;
 404
 405         err = ovl_set_opaque(dentry, opaquedir);
 406         if (err)
 407                 goto out_cleanup;
 408
 409         inode_lock(opaquedir->d_inode);
 410         err = ovl_set_attr(ofs, opaquedir, &stat);
 411         inode_unlock(opaquedir->d_inode);
 412         if (err)
 413                 goto out_cleanup;
 414
 415         err = ovl_do_rename(ofs, wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
 416         if (err)
 417                 goto out_cleanup;
 418
 419         ovl_cleanup_whiteouts(ofs, upper, list);
 420         ovl_cleanup(ofs, wdir, upper);
 421         unlock_rename(workdir, upperdir);
 422
 423         /* dentry's upper doesn't match now, get rid of it */
 424         d_drop(dentry);
 425
 426         return opaquedir;
 427
 428 out_cleanup:
 429         ovl_cleanup(ofs, wdir, opaquedir);
 430         dput(opaquedir);
 431 out_unlock:
 432         unlock_rename(workdir, upperdir);
 433 out:
 434         return ERR_PTR(err);
 435 }
 436
 437 static int ovl_set_upper_acl(struct ovl_fs *ofs, struct dentry *upperdentry,
 438                              const char *acl_name, struct posix_acl *acl)
 439 {
 440         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
 441                 return 0;
 442
 443         return ovl_do_set_acl(ofs, upperdentry, acl_name, acl);
 444 }
 445
 446 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 447                                     struct ovl_cattr *cattr)
 448 {
 449         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 450         struct dentry *workdir = ovl_workdir(dentry);
 451         struct inode *wdir = workdir->d_inode;
 452         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 453         struct inode *udir = upperdir->d_inode;
 454         struct dentry *upper;
 455         struct dentry *newdentry;
 456         int err;
 457         struct posix_acl *acl, *default_acl;
 458         bool hardlink = !!cattr->hardlink;
 459
 460         if (WARN_ON(!workdir))
 461                 return -EROFS;
 462
 463         if (!hardlink) {
 464                 err = posix_acl_create(dentry->d_parent->d_inode,
 465                                        &cattr->mode, &default_acl, &acl);
 466                 if (err)
 467                         return err;
 468         }
 469
 470         err = ovl_lock_rename_workdir(workdir, upperdir);
 471         if (err)
 472                 goto out;
 473
 474         upper = ovl_lookup_upper(ofs, dentry->d_name.name, upperdir,
 475                                  dentry->d_name.len);
 476         err = PTR_ERR(upper);
 477         if (IS_ERR(upper))
 478                 goto out_unlock;
 479
 480         err = -ESTALE;
 481         if (d_is_negative(upper) || !ovl_upper_is_whiteout(ofs, upper))
 482                 goto out_dput;
 483
 484         newdentry = ovl_create_temp(ofs, workdir, cattr);
 485         err = PTR_ERR(newdentry);
 486         if (IS_ERR(newdentry))
 487                 goto out_dput;
 488
 489         /*
 490          * mode could have been mutilated due to umask (e.g. sgid directory)
 491          */
 492         if (!hardlink &&
 493             !S_ISLNK(cattr->mode) &&
 494             newdentry->d_inode->i_mode != cattr->mode) {
 495                 struct iattr attr = {
 496                         .ia_valid = ATTR_MODE,
 497                         .ia_mode = cattr->mode,
 498                 };
 499                 inode_lock(newdentry->d_inode);
 500                 err = ovl_do_notify_change(ofs, newdentry, &attr);
 501                 inode_unlock(newdentry->d_inode);
 502                 if (err)
 503                         goto out_cleanup;
 504         }
 505         if (!hardlink) {
 506                 err = ovl_set_upper_acl(ofs, newdentry,
 507                                         XATTR_NAME_POSIX_ACL_ACCESS, acl);
 508                 if (err)
 509                         goto out_cleanup;
 510
 511                 err = ovl_set_upper_acl(ofs, newdentry,
 512                                         XATTR_NAME_POSIX_ACL_DEFAULT, default_acl);
 513                 if (err)
 514                         goto out_cleanup;
 515         }
 516
 517         if (!hardlink && S_ISDIR(cattr->mode)) {
 518                 err = ovl_set_opaque(dentry, newdentry);
 519                 if (err)
 520                         goto out_cleanup;
 521
 522                 err = ovl_do_rename(ofs, wdir, newdentry, udir, upper,
 523                                     RENAME_EXCHANGE);
 524                 if (err)
 525                         goto out_cleanup;
 526
 527                 ovl_cleanup(ofs, wdir, upper);
 528         } else {
 529                 err = ovl_do_rename(ofs, wdir, newdentry, udir, upper, 0);
 530                 if (err)
 531                         goto out_cleanup;
 532         }
 533         ovl_dir_modified(dentry->d_parent, false);
 534         err = ovl_instantiate(dentry, inode, newdentry, hardlink, NULL);
 535         if (err) {
 536                 ovl_cleanup(ofs, udir, newdentry);
 537                 dput(newdentry);
 538         }
 539 out_dput:
 540         dput(upper);
 541 out_unlock:
 542         unlock_rename(workdir, upperdir);
 543 out:
 544         if (!hardlink) {
 545                 posix_acl_release(acl);
 546                 posix_acl_release(default_acl);
 547         }
 548         return err;
 549
 550 out_cleanup:
 551         ovl_cleanup(ofs, wdir, newdentry);
 552         dput(newdentry);
 553         goto out_dput;
 554 }
 555
 556 static const struct cred *ovl_setup_cred_for_create(struct dentry *dentry,
 557                                                     struct inode *inode,
 558                                                     umode_t mode,
 559                                                     const struct cred *old_cred)
 560 {
 561         int err;
 562         struct cred *override_cred;
 563
 564         override_cred = prepare_creds();
 565         if (!override_cred)
 566                 return ERR_PTR(-ENOMEM);
 567
 568         override_cred->fsuid = inode->i_uid;
 569         override_cred->fsgid = inode->i_gid;
 570         err = security_dentry_create_files_as(dentry, mode, &dentry->d_name,
 571                                               old_cred, override_cred);
 572         if (err) {
 573                 put_cred(override_cred);
 574                 return ERR_PTR(err);
 575         }
 576
 577         /*
 578          * Caller is going to match this with revert_creds_light() and drop
 579          * referenec on the returned creds.
 580          * We must be called with creator creds already, otherwise we risk
 581          * leaking creds.
 582          */
 583         old_cred = override_creds_light(override_cred);
 584         WARN_ON_ONCE(old_cred != ovl_creds(dentry->d_sb));
 585
 586         return override_cred;
 587 }
 588
 589 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
 590                               struct ovl_cattr *attr, bool origin)
 591 {
 592         int err;
 593         const struct cred *old_cred, *new_cred = NULL;
 594         struct dentry *parent = dentry->d_parent;
 595
 596         old_cred = ovl_override_creds(dentry->d_sb);
 597
 598         /*
 599          * When linking a file with copy up origin into a new parent, mark the
 600          * new parent dir "impure".
 601          */
 602         if (origin) {
 603                 err = ovl_set_impure(parent, ovl_dentry_upper(parent));
 604                 if (err)
 605                         goto out_revert_creds;
 606         }
 607
 608         if (!attr->hardlink) {
 609                 /*
 610                  * In the creation cases(create, mkdir, mknod, symlink),
 611                  * ovl should transfer current's fs{u,g}id to underlying
 612                  * fs. Because underlying fs want to initialize its new
 613                  * inode owner using current's fs{u,g}id. And in this
 614                  * case, the @inode is a new inode that is initialized
 615                  * in inode_init_owner() to current's fs{u,g}id. So use
 616                  * the inode's i_{u,g}id to override the cred's fs{u,g}id.
 617                  *
 618                  * But in the other hardlink case, ovl_link() does not
 619                  * create a new inode, so just use the ovl mounter's
 620                  * fs{u,g}id.
 621                  */
 622                 new_cred = ovl_setup_cred_for_create(dentry, inode, attr->mode,
 623                                                      old_cred);
 624                 err = PTR_ERR(new_cred);
 625                 if (IS_ERR(new_cred)) {
 626                         new_cred = NULL;
 627                         goto out_revert_creds;
 628                 }
 629         }
 630
 631         if (!ovl_dentry_is_whiteout(dentry))
 632                 err = ovl_create_upper(dentry, inode, attr);
 633         else
 634                 err = ovl_create_over_whiteout(dentry, inode, attr);
 635
 636 out_revert_creds:
 637         ovl_revert_creds(old_cred);
 638         put_cred(new_cred);
 639         return err;
 640 }
 641
 642 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 643                              const char *link)
 644 {
 645         int err;
 646         struct inode *inode;
 647         struct ovl_cattr attr = {
 648                 .rdev = rdev,
 649                 .link = link,
 650         };
 651
 652         err = ovl_copy_up(dentry->d_parent);
 653         if (err)
 654                 return err;
 655
 656         err = ovl_want_write(dentry);
 657         if (err)
 658                 goto out;
 659
 660         /* Preallocate inode to be used by ovl_get_inode() */
 661         err = -ENOMEM;
 662         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
 663         if (!inode)
 664                 goto out_drop_write;
 665
 666         spin_lock(&inode->i_lock);
 667         inode->i_state |= I_CREATING;
 668         spin_unlock(&inode->i_lock);
 669
 670         inode_init_owner(&nop_mnt_idmap, inode, dentry->d_parent->d_inode, mode);
 671         attr.mode = inode->i_mode;
 672
 673         err = ovl_create_or_link(dentry, inode, &attr, false);
 674         /* Did we end up using the preallocated inode? */
 675         if (inode != d_inode(dentry))
 676                 iput(inode);
 677
 678 out_drop_write:
 679         ovl_drop_write(dentry);
 680 out:
 681         return err;
 682 }
 683
 684 static int ovl_create(struct mnt_idmap *idmap, struct inode *dir,
 685                       struct dentry *dentry, umode_t mode, bool excl)
 686 {
 687         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 688 }
 689
 690 static int ovl_mkdir(struct mnt_idmap *idmap, struct inode *dir,
 691                      struct dentry *dentry, umode_t mode)
 692 {
 693         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 694 }
 695
 696 static int ovl_mknod(struct mnt_idmap *idmap, struct inode *dir,
 697                      struct dentry *dentry, umode_t mode, dev_t rdev)
 698 {
 699         /* Don't allow creation of "whiteout" on overlay */
 700         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
 701                 return -EPERM;
 702
 703         return ovl_create_object(dentry, mode, rdev, NULL);
 704 }
 705
 706 static int ovl_symlink(struct mnt_idmap *idmap, struct inode *dir,
 707                        struct dentry *dentry, const char *link)
 708 {
 709         return ovl_create_object(dentry, S_IFLNK, 0, link);
 710 }
 711
 712 static int ovl_set_link_redirect(struct dentry *dentry)
 713 {
 714         const struct cred *old_cred;
 715         int err;
 716
 717         old_cred = ovl_override_creds(dentry->d_sb);
 718         err = ovl_set_redirect(dentry, false);
 719         ovl_revert_creds(old_cred);
 720
 721         return err;
 722 }
 723
 724 static int ovl_link(struct dentry *old, struct inode *newdir,
 725                     struct dentry *new)
 726 {
 727         int err;
 728         struct inode *inode;
 729
 730         err = ovl_copy_up(old);
 731         if (err)
 732                 goto out;
 733
 734         err = ovl_copy_up(new->d_parent);
 735         if (err)
 736                 goto out;
 737
 738         err = ovl_nlink_start(old);
 739         if (err)
 740                 goto out;
 741
 742         if (ovl_is_metacopy_dentry(old)) {
 743                 err = ovl_set_link_redirect(old);
 744                 if (err)
 745                         goto out_nlink_end;
 746         }
 747
 748         inode = d_inode(old);
 749         ihold(inode);
 750
 751         err = ovl_create_or_link(new, inode,
 752                         &(struct ovl_cattr) {.hardlink = ovl_dentry_upper(old)},
 753                         ovl_type_origin(old));
 754         if (err)
 755                 iput(inode);
 756
 757 out_nlink_end:
 758         ovl_nlink_end(old);
 759 out:
 760         return err;
 761 }
 762
 763 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
 764 {
 765         return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
 766 }
 767
 768 static int ovl_remove_and_whiteout(struct dentry *dentry,
 769                                    struct list_head *list)
 770 {
 771         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 772         struct dentry *workdir = ovl_workdir(dentry);
 773         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 774         struct dentry *upper;
 775         struct dentry *opaquedir = NULL;
 776         int err;
 777
 778         if (WARN_ON(!workdir))
 779                 return -EROFS;
 780
 781         if (!list_empty(list)) {
 782                 opaquedir = ovl_clear_empty(dentry, list);
 783                 err = PTR_ERR(opaquedir);
 784                 if (IS_ERR(opaquedir))
 785                         goto out;
 786         }
 787
 788         err = ovl_lock_rename_workdir(workdir, upperdir);
 789         if (err)
 790                 goto out_dput;
 791
 792         upper = ovl_lookup_upper(ofs, dentry->d_name.name, upperdir,
 793                                  dentry->d_name.len);
 794         err = PTR_ERR(upper);
 795         if (IS_ERR(upper))
 796                 goto out_unlock;
 797
 798         err = -ESTALE;
 799         if ((opaquedir && upper != opaquedir) ||
 800             (!opaquedir && ovl_dentry_upper(dentry) &&
 801              !ovl_matches_upper(dentry, upper))) {
 802                 goto out_dput_upper;
 803         }
 804
 805         err = ovl_cleanup_and_whiteout(ofs, d_inode(upperdir), upper);
 806         if (err)
 807                 goto out_d_drop;
 808
 809         ovl_dir_modified(dentry->d_parent, true);
 810 out_d_drop:
 811         d_drop(dentry);
 812 out_dput_upper:
 813         dput(upper);
 814 out_unlock:
 815         unlock_rename(workdir, upperdir);
 816 out_dput:
 817         dput(opaquedir);
 818 out:
 819         return err;
 820 }
 821
 822 static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
 823                             struct list_head *list)
 824 {
 825         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 826         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 827         struct inode *dir = upperdir->d_inode;
 828         struct dentry *upper;
 829         struct dentry *opaquedir = NULL;
 830         int err;
 831
 832         if (!list_empty(list)) {
 833                 opaquedir = ovl_clear_empty(dentry, list);
 834                 err = PTR_ERR(opaquedir);
 835                 if (IS_ERR(opaquedir))
 836                         goto out;
 837         }
 838
 839         inode_lock_nested(dir, I_MUTEX_PARENT);
 840         upper = ovl_lookup_upper(ofs, dentry->d_name.name, upperdir,
 841                                  dentry->d_name.len);
 842         err = PTR_ERR(upper);
 843         if (IS_ERR(upper))
 844                 goto out_unlock;
 845
 846         err = -ESTALE;
 847         if ((opaquedir && upper != opaquedir) ||
 848             (!opaquedir && !ovl_matches_upper(dentry, upper)))
 849                 goto out_dput_upper;
 850
 851         if (is_dir)
 852                 err = ovl_do_rmdir(ofs, dir, upper);
 853         else
 854                 err = ovl_do_unlink(ofs, dir, upper);
 855         ovl_dir_modified(dentry->d_parent, ovl_type_origin(dentry));
 856
 857         /*
 858          * Keeping this dentry hashed would mean having to release
 859          * upperpath/lowerpath, which could only be done if we are the
 860          * sole user of this dentry.  Too tricky...  Just unhash for
 861          * now.
 862          */
 863         if (!err)
 864                 d_drop(dentry);
 865 out_dput_upper:
 866         dput(upper);
 867 out_unlock:
 868         inode_unlock(dir);
 869         dput(opaquedir);
 870 out:
 871         return err;
 872 }
 873
 874 static bool ovl_pure_upper(struct dentry *dentry)
 875 {
 876         return !ovl_dentry_lower(dentry) &&
 877                !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
 878 }
 879
 880 static void ovl_drop_nlink(struct dentry *dentry)
 881 {
 882         struct inode *inode = d_inode(dentry);
 883         struct dentry *alias;
 884
 885         /* Try to find another, hashed alias */
 886         spin_lock(&inode->i_lock);
 887         hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
 888                 if (alias != dentry && !d_unhashed(alias))
 889                         break;
 890         }
 891         spin_unlock(&inode->i_lock);
 892
 893         /*
 894          * Changes to underlying layers may cause i_nlink to lose sync with
 895          * reality.  In this case prevent the link count from going to zero
 896          * prematurely.
 897          */
 898         if (inode->i_nlink > !!alias)
 899                 drop_nlink(inode);
 900 }
 901
 902 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 903 {
 904         int err;
 905         const struct cred *old_cred;
 906         bool lower_positive = ovl_lower_positive(dentry);
 907         LIST_HEAD(list);
 908
 909         /* No need to clean pure upper removed by vfs_rmdir() */
 910         if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
 911                 err = ovl_check_empty_dir(dentry, &list);
 912                 if (err)
 913                         goto out;
 914         }
 915
 916         err = ovl_copy_up(dentry->d_parent);
 917         if (err)
 918                 goto out;
 919
 920         err = ovl_nlink_start(dentry);
 921         if (err)
 922                 goto out;
 923
 924         old_cred = ovl_override_creds(dentry->d_sb);
 925         if (!lower_positive)
 926                 err = ovl_remove_upper(dentry, is_dir, &list);
 927         else
 928                 err = ovl_remove_and_whiteout(dentry, &list);
 929         ovl_revert_creds(old_cred);
 930         if (!err) {
 931                 if (is_dir)
 932                         clear_nlink(dentry->d_inode);
 933                 else
 934                         ovl_drop_nlink(dentry);
 935         }
 936         ovl_nlink_end(dentry);
 937
 938         /*
 939          * Copy ctime
 940          *
 941          * Note: we fail to update ctime if there was no copy-up, only a
 942          * whiteout
 943          */
 944         if (ovl_dentry_upper(dentry))
 945                 ovl_copyattr(d_inode(dentry));
 946
 947 out:
 948         ovl_cache_free(&list);
 949         return err;
 950 }
 951
 952 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
 953 {
 954         return ovl_do_remove(dentry, false);
 955 }
 956
 957 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
 958 {
 959         return ovl_do_remove(dentry, true);
 960 }
 961
 962 static bool ovl_type_merge_or_lower(struct dentry *dentry)
 963 {
 964         enum ovl_path_type type = ovl_path_type(dentry);
 965
 966         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
 967 }
 968
 969 static bool ovl_can_move(struct dentry *dentry)
 970 {
 971         return ovl_redirect_dir(OVL_FS(dentry->d_sb)) ||
 972                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
 973 }
 974
 975 static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
 976 {
 977         char *buf, *ret;
 978         struct dentry *d, *tmp;
 979         int buflen = ovl_redirect_max + 1;
 980
 981         if (!abs_redirect) {
 982                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
 983                                GFP_KERNEL);
 984                 goto out;
 985         }
 986
 987         buf = ret = kmalloc(buflen, GFP_KERNEL);
 988         if (!buf)
 989                 goto out;
 990
 991         buflen--;
 992         buf[buflen] = '\0';
 993         for (d = dget(dentry); !IS_ROOT(d);) {
 994                 const char *name;
 995                 int thislen;
 996
 997                 spin_lock(&d->d_lock);
 998                 name = ovl_dentry_get_redirect(d);
 999                 if (name) {
1000                         thislen = strlen(name);
1001                 } else {
1002                         name = d->d_name.name;
1003                         thislen = d->d_name.len;
1004                 }
1005
1006                 /* If path is too long, fall back to userspace move */
1007                 if (thislen + (name[0] != '/') > buflen) {
1008                         ret = ERR_PTR(-EXDEV);
1009                         spin_unlock(&d->d_lock);
1010                         goto out_put;
1011                 }
1012
1013                 buflen -= thislen;
1014                 memcpy(&buf[buflen], name, thislen);
1015                 spin_unlock(&d->d_lock);
1016                 tmp = dget_parent(d);
1017
1018                 dput(d);
1019                 d = tmp;
1020
1021                 /* Absolute redirect: finished */
1022                 if (buf[buflen] == '/')
1023                         break;
1024                 buflen--;
1025                 buf[buflen] = '/';
1026         }
1027         ret = kstrdup(&buf[buflen], GFP_KERNEL);
1028 out_put:
1029         dput(d);
1030         kfree(buf);
1031 out:
1032         return ret ? ret : ERR_PTR(-ENOMEM);
1033 }
1034
1035 static bool ovl_need_absolute_redirect(struct dentry *dentry, bool samedir)
1036 {
1037         struct dentry *lowerdentry;
1038
1039         if (!samedir)
1040                 return true;
1041
1042         if (d_is_dir(dentry))
1043                 return false;
1044
1045         /*
1046          * For non-dir hardlinked files, we need absolute redirects
1047          * in general as two upper hardlinks could be in different
1048          * dirs. We could put a relative redirect now and convert
1049          * it to absolute redirect later. But when nlink > 1 and
1050          * indexing is on, that means relative redirect needs to be
1051          * converted to absolute during copy up of another lower
1052          * hardllink as well.
1053          *
1054          * So without optimizing too much, just check if lower is
1055          * a hard link or not. If lower is hard link, put absolute
1056          * redirect.
1057          */
1058         lowerdentry = ovl_dentry_lower(dentry);
1059         return (d_inode(lowerdentry)->i_nlink > 1);
1060 }
1061
1062 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
1063 {
1064         int err;
1065         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
1066         const char *redirect = ovl_dentry_get_redirect(dentry);
1067         bool absolute_redirect = ovl_need_absolute_redirect(dentry, samedir);
1068
1069         if (redirect && (!absolute_redirect || redirect[0] == '/'))
1070                 return 0;
1071
1072         redirect = ovl_get_redirect(dentry, absolute_redirect);
1073         if (IS_ERR(redirect))
1074                 return PTR_ERR(redirect);
1075
1076         err = ovl_check_setxattr(ofs, ovl_dentry_upper(dentry),
1077                                  OVL_XATTR_REDIRECT,
1078                                  redirect, strlen(redirect), -EXDEV);
1079         if (!err) {
1080                 spin_lock(&dentry->d_lock);
1081                 ovl_dentry_set_redirect(dentry, redirect);
1082                 spin_unlock(&dentry->d_lock);
1083         } else {
1084                 kfree(redirect);
1085                 pr_warn_ratelimited("failed to set redirect (%i)\n",
1086                                     err);
1087                 /* Fall back to userspace copy-up */
1088                 err = -EXDEV;
1089         }
1090         return err;
1091 }
1092
1093 static int ovl_rename(struct mnt_idmap *idmap, struct inode *olddir,
1094                       struct dentry *old, struct inode *newdir,
1095                       struct dentry *new, unsigned int flags)
1096 {
1097         int err;
1098         struct dentry *old_upperdir;
1099         struct dentry *new_upperdir;
1100         struct dentry *olddentry;
1101         struct dentry *newdentry;
1102         struct dentry *trap;
1103         bool old_opaque;
1104         bool new_opaque;
1105         bool cleanup_whiteout = false;
1106         bool update_nlink = false;
1107         bool overwrite = !(flags & RENAME_EXCHANGE);
1108         bool is_dir = d_is_dir(old);
1109         bool new_is_dir = d_is_dir(new);
1110         bool samedir = olddir == newdir;
1111         struct dentry *opaquedir = NULL;
1112         const struct cred *old_cred = NULL;
1113         struct ovl_fs *ofs = OVL_FS(old->d_sb);
1114         LIST_HEAD(list);
1115
1116         err = -EINVAL;
1117         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
1118                 goto out;
1119
1120         flags &= ~RENAME_NOREPLACE;
1121
1122         /* Don't copy up directory trees */
1123         err = -EXDEV;
1124         if (!ovl_can_move(old))
1125                 goto out;
1126         if (!overwrite && !ovl_can_move(new))
1127                 goto out;
1128
1129         if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
1130                 err = ovl_check_empty_dir(new, &list);
1131                 if (err)
1132                         goto out;
1133         }
1134
1135         if (overwrite) {
1136                 if (ovl_lower_positive(old)) {
1137                         if (!ovl_dentry_is_whiteout(new)) {
1138                                 /* Whiteout source */
1139                                 flags |= RENAME_WHITEOUT;
1140                         } else {
1141                                 /* Switch whiteouts */
1142                                 flags |= RENAME_EXCHANGE;
1143                         }
1144                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
1145                         flags |= RENAME_EXCHANGE;
1146                         cleanup_whiteout = true;
1147                 }
1148         }
1149
1150         err = ovl_copy_up(old);
1151         if (err)
1152                 goto out;
1153
1154         err = ovl_copy_up(new->d_parent);
1155         if (err)
1156                 goto out;
1157         if (!overwrite) {
1158                 err = ovl_copy_up(new);
1159                 if (err)
1160                         goto out;
1161         } else if (d_inode(new)) {
1162                 err = ovl_nlink_start(new);
1163                 if (err)
1164                         goto out;
1165
1166                 update_nlink = true;
1167         }
1168
1169         if (!update_nlink) {
1170                 /* ovl_nlink_start() took ovl_want_write() */
1171                 err = ovl_want_write(old);
1172                 if (err)
1173                         goto out;
1174         }
1175
1176         old_cred = ovl_override_creds(old->d_sb);
1177
1178         if (!list_empty(&list)) {
1179                 opaquedir = ovl_clear_empty(new, &list);
1180                 err = PTR_ERR(opaquedir);
1181                 if (IS_ERR(opaquedir)) {
1182                         opaquedir = NULL;
1183                         goto out_revert_creds;
1184                 }
1185         }
1186
1187         old_upperdir = ovl_dentry_upper(old->d_parent);
1188         new_upperdir = ovl_dentry_upper(new->d_parent);
1189
1190         if (!samedir) {
1191                 /*
1192                  * When moving a merge dir or non-dir with copy up origin into
1193                  * a new parent, we are marking the new parent dir "impure".
1194                  * When ovl_iterate() iterates an "impure" upper dir, it will
1195                  * lookup the origin inodes of the entries to fill d_ino.
1196                  */
1197                 if (ovl_type_origin(old)) {
1198                         err = ovl_set_impure(new->d_parent, new_upperdir);
1199                         if (err)
1200                                 goto out_revert_creds;
1201                 }
1202                 if (!overwrite && ovl_type_origin(new)) {
1203                         err = ovl_set_impure(old->d_parent, old_upperdir);
1204                         if (err)
1205                                 goto out_revert_creds;
1206                 }
1207         }
1208
1209         trap = lock_rename(new_upperdir, old_upperdir);
1210         if (IS_ERR(trap)) {
1211                 err = PTR_ERR(trap);
1212                 goto out_revert_creds;
1213         }
1214
1215         olddentry = ovl_lookup_upper(ofs, old->d_name.name, old_upperdir,
1216                                      old->d_name.len);
1217         err = PTR_ERR(olddentry);
1218         if (IS_ERR(olddentry))
1219                 goto out_unlock;
1220
1221         err = -ESTALE;
1222         if (!ovl_matches_upper(old, olddentry))
1223                 goto out_dput_old;
1224
1225         newdentry = ovl_lookup_upper(ofs, new->d_name.name, new_upperdir,
1226                                      new->d_name.len);
1227         err = PTR_ERR(newdentry);
1228         if (IS_ERR(newdentry))
1229                 goto out_dput_old;
1230
1231         old_opaque = ovl_dentry_is_opaque(old);
1232         new_opaque = ovl_dentry_is_opaque(new);
1233
1234         err = -ESTALE;
1235         if (d_inode(new) && ovl_dentry_upper(new)) {
1236                 if (opaquedir) {
1237                         if (newdentry != opaquedir)
1238                                 goto out_dput;
1239                 } else {
1240                         if (!ovl_matches_upper(new, newdentry))
1241                                 goto out_dput;
1242                 }
1243         } else {
1244                 if (!d_is_negative(newdentry)) {
1245                         if (!new_opaque || !ovl_upper_is_whiteout(ofs, newdentry))
1246                                 goto out_dput;
1247                 } else {
1248                         if (flags & RENAME_EXCHANGE)
1249                                 goto out_dput;
1250                 }
1251         }
1252
1253         if (olddentry == trap)
1254                 goto out_dput;
1255         if (newdentry == trap)
1256                 goto out_dput;
1257
1258         if (olddentry->d_inode == newdentry->d_inode)
1259                 goto out_dput;
1260
1261         err = 0;
1262         if (ovl_type_merge_or_lower(old))
1263                 err = ovl_set_redirect(old, samedir);
1264         else if (is_dir && !old_opaque && ovl_type_merge(new->d_parent))
1265                 err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1266         if (err)
1267                 goto out_dput;
1268
1269         if (!overwrite && ovl_type_merge_or_lower(new))
1270                 err = ovl_set_redirect(new, samedir);
1271         else if (!overwrite && new_is_dir && !new_opaque &&
1272                  ovl_type_merge(old->d_parent))
1273                 err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1274         if (err)
1275                 goto out_dput;
1276
1277         err = ovl_do_rename(ofs, old_upperdir->d_inode, olddentry,
1278                             new_upperdir->d_inode, newdentry, flags);
1279         if (err)
1280                 goto out_dput;
1281
1282         if (cleanup_whiteout)
1283                 ovl_cleanup(ofs, old_upperdir->d_inode, newdentry);
1284
1285         if (overwrite && d_inode(new)) {
1286                 if (new_is_dir)
1287                         clear_nlink(d_inode(new));
1288                 else
1289                         ovl_drop_nlink(new);
1290         }
1291
1292         ovl_dir_modified(old->d_parent, ovl_type_origin(old) ||
1293                          (!overwrite && ovl_type_origin(new)));
1294         ovl_dir_modified(new->d_parent, ovl_type_origin(old) ||
1295                          (d_inode(new) && ovl_type_origin(new)));
1296
1297         /* copy ctime: */
1298         ovl_copyattr(d_inode(old));
1299         if (d_inode(new) && ovl_dentry_upper(new))
1300                 ovl_copyattr(d_inode(new));
1301
1302 out_dput:
1303         dput(newdentry);
1304 out_dput_old:
1305         dput(olddentry);
1306 out_unlock:
1307         unlock_rename(new_upperdir, old_upperdir);
1308 out_revert_creds:
1309         ovl_revert_creds(old_cred);
1310         if (update_nlink)
1311                 ovl_nlink_end(new);
1312         else
1313                 ovl_drop_write(old);
1314 out:
1315         dput(opaquedir);
1316         ovl_cache_free(&list);
1317         return err;
1318 }
1319
1320 static int ovl_create_tmpfile(struct file *file, struct dentry *dentry,
1321                               struct inode *inode, umode_t mode)
1322 {
1323         const struct cred *old_cred, *new_cred = NULL;
1324         struct path realparentpath;
1325         struct file *realfile;
1326         struct ovl_file *of;
1327         struct dentry *newdentry;
1328         /* It's okay to set O_NOATIME, since the owner will be current fsuid */
1329         int flags = file->f_flags | OVL_OPEN_FLAGS;
1330         int err;
1331
1332         old_cred = ovl_override_creds(dentry->d_sb);
1333         new_cred = ovl_setup_cred_for_create(dentry, inode, mode, old_cred);
1334         err = PTR_ERR(new_cred);
1335         if (IS_ERR(new_cred)) {
1336                 new_cred = NULL;
1337                 goto out_revert_creds;
1338         }
1339
1340         ovl_path_upper(dentry->d_parent, &realparentpath);
1341         realfile = backing_tmpfile_open(&file->f_path, flags, &realparentpath,
1342                                         mode, current_cred());
1343         err = PTR_ERR_OR_ZERO(realfile);
1344         pr_debug("tmpfile/open(%pd2, 0%o) = %i\n", realparentpath.dentry, mode, err);
1345         if (err)
1346                 goto out_revert_creds;
1347
1348         of = ovl_file_alloc(realfile);
1349         if (!of) {
1350                 fput(realfile);
1351                 err = -ENOMEM;
1352                 goto out_revert_creds;
1353         }
1354
1355         /* ovl_instantiate() consumes the newdentry reference on success */
1356         newdentry = dget(realfile->f_path.dentry);
1357         err = ovl_instantiate(dentry, inode, newdentry, false, file);
1358         if (!err) {
1359                 file->private_data = of;
1360         } else {
1361                 dput(newdentry);
1362                 ovl_file_free(of);
1363         }
1364 out_revert_creds:
1365         ovl_revert_creds(old_cred);
1366         put_cred(new_cred);
1367         return err;
1368 }
1369
1370 static int ovl_dummy_open(struct inode *inode, struct file *file)
1371 {
1372         return 0;
1373 }
1374
1375 static int ovl_tmpfile(struct mnt_idmap *idmap, struct inode *dir,
1376                        struct file *file, umode_t mode)
1377 {
1378         int err;
1379         struct dentry *dentry = file->f_path.dentry;
1380         struct inode *inode;
1381
1382         if (!OVL_FS(dentry->d_sb)->tmpfile)
1383                 return -EOPNOTSUPP;
1384
1385         err = ovl_copy_up(dentry->d_parent);
1386         if (err)
1387                 return err;
1388
1389         err = ovl_want_write(dentry);
1390         if (err)
1391                 return err;
1392
1393         err = -ENOMEM;
1394         inode = ovl_new_inode(dentry->d_sb, mode, 0);
1395         if (!inode)
1396                 goto drop_write;
1397
1398         inode_init_owner(&nop_mnt_idmap, inode, dir, mode);
1399         err = ovl_create_tmpfile(file, dentry, inode, inode->i_mode);
1400         if (err)
1401                 goto put_inode;
1402
1403         /*
1404          * Check if the preallocated inode was actually used.  Having something
1405          * else assigned to the dentry shouldn't happen as that would indicate
1406          * that the backing tmpfile "leaked" out of overlayfs.
1407          */
1408         err = -EIO;
1409         if (WARN_ON(inode != d_inode(dentry)))
1410                 goto put_realfile;
1411
1412         /* inode reference was transferred to dentry */
1413         inode = NULL;
1414         err = finish_open(file, dentry, ovl_dummy_open);
1415 put_realfile:
1416         /* Without FMODE_OPENED ->release() won't be called on @file */
1417         if (!(file->f_mode & FMODE_OPENED))
1418                 ovl_file_free(file->private_data);
1419 put_inode:
1420         iput(inode);
1421 drop_write:
1422         ovl_drop_write(dentry);
1423         return err;
1424 }
1425
1426 const struct inode_operations ovl_dir_inode_operations = {
1427         .lookup         = ovl_lookup,
1428         .mkdir          = ovl_mkdir,
1429         .symlink        = ovl_symlink,
1430         .unlink         = ovl_unlink,
1431         .rmdir          = ovl_rmdir,
1432         .rename         = ovl_rename,
1433         .link           = ovl_link,
1434         .setattr        = ovl_setattr,
1435         .create         = ovl_create,
1436         .mknod          = ovl_mknod,
1437         .permission     = ovl_permission,
1438         .getattr        = ovl_getattr,
1439         .listxattr      = ovl_listxattr,
1440         .get_inode_acl  = ovl_get_inode_acl,
1441         .get_acl        = ovl_get_acl,
1442         .set_acl        = ovl_set_acl,
1443         .update_time    = ovl_update_time,
1444         .fileattr_get   = ovl_fileattr_get,
1445         .fileattr_set   = ovl_fileattr_set,
1446         .tmpfile        = ovl_tmpfile,
1447 };