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 "overlayfs.h"
  18
  19 static unsigned short ovl_redirect_max = 256;
  20 module_param_named(redirect_max, ovl_redirect_max, ushort, 0644);
  21 MODULE_PARM_DESC(redirect_max,
  22                  "Maximum length of absolute redirect xattr value");
  23
  24 static int ovl_set_redirect(struct dentry *dentry, bool samedir);
  25
  26 int ovl_cleanup(struct inode *wdir, struct dentry *wdentry)
  27 {
  28         int err;
  29
  30         dget(wdentry);
  31         if (d_is_dir(wdentry))
  32                 err = ovl_do_rmdir(wdir, wdentry);
  33         else
  34                 err = ovl_do_unlink(wdir, wdentry);
  35         dput(wdentry);
  36
  37         if (err) {
  38                 pr_err("cleanup of '%pd2' failed (%i)\n",
  39                        wdentry, err);
  40         }
  41
  42         return err;
  43 }
  44
  45 struct dentry *ovl_lookup_temp(struct dentry *workdir)
  46 {
  47         struct dentry *temp;
  48         char name[20];
  49         static atomic_t temp_id = ATOMIC_INIT(0);
  50
  51         /* counter is allowed to wrap, since temp dentries are ephemeral */
  52         snprintf(name, sizeof(name), "#%x", atomic_inc_return(&temp_id));
  53
  54         temp = lookup_one_len(name, workdir, strlen(name));
  55         if (!IS_ERR(temp) && temp->d_inode) {
  56                 pr_err("workdir/%s already exists\n", name);
  57                 dput(temp);
  58                 temp = ERR_PTR(-EIO);
  59         }
  60
  61         return temp;
  62 }
  63
  64 /* caller holds i_mutex on workdir */
  65 static struct dentry *ovl_whiteout(struct ovl_fs *ofs)
  66 {
  67         int err;
  68         struct dentry *whiteout;
  69         struct dentry *workdir = ofs->workdir;
  70         struct inode *wdir = workdir->d_inode;
  71
  72         if (!ofs->whiteout) {
  73                 whiteout = ovl_lookup_temp(workdir);
  74                 if (IS_ERR(whiteout))
  75                         goto out;
  76
  77                 err = ovl_do_whiteout(wdir, whiteout);
  78                 if (err) {
  79                         dput(whiteout);
  80                         whiteout = ERR_PTR(err);
  81                         goto out;
  82                 }
  83                 ofs->whiteout = whiteout;
  84         }
  85
  86         if (ofs->share_whiteout) {
  87                 whiteout = ovl_lookup_temp(workdir);
  88                 if (IS_ERR(whiteout))
  89                         goto out;
  90
  91                 err = ovl_do_link(ofs->whiteout, wdir, whiteout);
  92                 if (!err)
  93                         goto out;
  94
  95                 if (err != -EMLINK) {
  96                         pr_warn("Failed to link whiteout - disabling whiteout inode sharing(nlink=%u, err=%i)\n",
  97                                 ofs->whiteout->d_inode->i_nlink, err);
  98                         ofs->share_whiteout = false;
  99                 }
 100                 dput(whiteout);
 101         }
 102         whiteout = ofs->whiteout;
 103         ofs->whiteout = NULL;
 104 out:
 105         return whiteout;
 106 }
 107
 108 /* Caller must hold i_mutex on both workdir and dir */
 109 int ovl_cleanup_and_whiteout(struct ovl_fs *ofs, struct inode *dir,
 110                              struct dentry *dentry)
 111 {
 112         struct inode *wdir = ofs->workdir->d_inode;
 113         struct dentry *whiteout;
 114         int err;
 115         int flags = 0;
 116
 117         whiteout = ovl_whiteout(ofs);
 118         err = PTR_ERR(whiteout);
 119         if (IS_ERR(whiteout))
 120                 return err;
 121
 122         if (d_is_dir(dentry))
 123                 flags = RENAME_EXCHANGE;
 124
 125         err = ovl_do_rename(wdir, whiteout, dir, dentry, flags);
 126         if (err)
 127                 goto kill_whiteout;
 128         if (flags)
 129                 ovl_cleanup(wdir, dentry);
 130
 131 out:
 132         dput(whiteout);
 133         return err;
 134
 135 kill_whiteout:
 136         ovl_cleanup(wdir, whiteout);
 137         goto out;
 138 }
 139
 140 static int ovl_mkdir_real(struct inode *dir, struct dentry **newdentry,
 141                           umode_t mode)
 142 {
 143         int err;
 144         struct dentry *d, *dentry = *newdentry;
 145
 146         err = ovl_do_mkdir(dir, dentry, mode);
 147         if (err)
 148                 return err;
 149
 150         if (likely(!d_unhashed(dentry)))
 151                 return 0;
 152
 153         /*
 154          * vfs_mkdir() may succeed and leave the dentry passed
 155          * to it unhashed and negative. If that happens, try to
 156          * lookup a new hashed and positive dentry.
 157          */
 158         d = lookup_one_len(dentry->d_name.name, dentry->d_parent,
 159                            dentry->d_name.len);
 160         if (IS_ERR(d)) {
 161                 pr_warn("failed lookup after mkdir (%pd2, err=%i).\n",
 162                         dentry, err);
 163                 return PTR_ERR(d);
 164         }
 165         dput(dentry);
 166         *newdentry = d;
 167
 168         return 0;
 169 }
 170
 171 struct dentry *ovl_create_real(struct inode *dir, struct dentry *newdentry,
 172                                struct ovl_cattr *attr)
 173 {
 174         int err;
 175
 176         if (IS_ERR(newdentry))
 177                 return newdentry;
 178
 179         err = -ESTALE;
 180         if (newdentry->d_inode)
 181                 goto out;
 182
 183         if (attr->hardlink) {
 184                 err = ovl_do_link(attr->hardlink, dir, newdentry);
 185         } else {
 186                 switch (attr->mode & S_IFMT) {
 187                 case S_IFREG:
 188                         err = ovl_do_create(dir, newdentry, attr->mode);
 189                         break;
 190
 191                 case S_IFDIR:
 192                         /* mkdir is special... */
 193                         err =  ovl_mkdir_real(dir, &newdentry, attr->mode);
 194                         break;
 195
 196                 case S_IFCHR:
 197                 case S_IFBLK:
 198                 case S_IFIFO:
 199                 case S_IFSOCK:
 200                         err = ovl_do_mknod(dir, newdentry, attr->mode,
 201                                            attr->rdev);
 202                         break;
 203
 204                 case S_IFLNK:
 205                         err = ovl_do_symlink(dir, newdentry, attr->link);
 206                         break;
 207
 208                 default:
 209                         err = -EPERM;
 210                 }
 211         }
 212         if (!err && WARN_ON(!newdentry->d_inode)) {
 213                 /*
 214                  * Not quite sure if non-instantiated dentry is legal or not.
 215                  * VFS doesn't seem to care so check and warn here.
 216                  */
 217                 err = -EIO;
 218         }
 219 out:
 220         if (err) {
 221                 dput(newdentry);
 222                 return ERR_PTR(err);
 223         }
 224         return newdentry;
 225 }
 226
 227 struct dentry *ovl_create_temp(struct dentry *workdir, struct ovl_cattr *attr)
 228 {
 229         return ovl_create_real(d_inode(workdir), ovl_lookup_temp(workdir),
 230                                attr);
 231 }
 232
 233 static int ovl_set_opaque_xerr(struct dentry *dentry, struct dentry *upper,
 234                                int xerr)
 235 {
 236         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 237         int err;
 238
 239         err = ovl_check_setxattr(ofs, upper, OVL_XATTR_OPAQUE, "y", 1, xerr);
 240         if (!err)
 241                 ovl_dentry_set_opaque(dentry);
 242
 243         return err;
 244 }
 245
 246 static int ovl_set_opaque(struct dentry *dentry, struct dentry *upperdentry)
 247 {
 248         /*
 249          * Fail with -EIO when trying to create opaque dir and upper doesn't
 250          * support xattrs. ovl_rename() calls ovl_set_opaque_xerr(-EXDEV) to
 251          * return a specific error for noxattr case.
 252          */
 253         return ovl_set_opaque_xerr(dentry, upperdentry, -EIO);
 254 }
 255
 256 /*
 257  * Common operations required to be done after creation of file on upper.
 258  * If @hardlink is false, then @inode is a pre-allocated inode, we may or
 259  * may not use to instantiate the new dentry.
 260  */
 261 static int ovl_instantiate(struct dentry *dentry, struct inode *inode,
 262                            struct dentry *newdentry, bool hardlink)
 263 {
 264         struct ovl_inode_params oip = {
 265                 .upperdentry = newdentry,
 266                 .newinode = inode,
 267         };
 268
 269         ovl_dir_modified(dentry->d_parent, false);
 270         ovl_dentry_set_upper_alias(dentry);
 271         ovl_dentry_update_reval(dentry, newdentry,
 272                         DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE);
 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         d_instantiate(dentry, inode);
 299         if (inode != oip.newinode) {
 300                 pr_warn_ratelimited("newly created inode found in cache (%pd2)\n",
 301                                     dentry);
 302         }
 303
 304         /* Force lookup of new upper hardlink to find its lower */
 305         if (hardlink)
 306                 d_drop(dentry);
 307
 308         return 0;
 309 }
 310
 311 static bool ovl_type_merge(struct dentry *dentry)
 312 {
 313         return OVL_TYPE_MERGE(ovl_path_type(dentry));
 314 }
 315
 316 static bool ovl_type_origin(struct dentry *dentry)
 317 {
 318         return OVL_TYPE_ORIGIN(ovl_path_type(dentry));
 319 }
 320
 321 static int ovl_create_upper(struct dentry *dentry, struct inode *inode,
 322                             struct ovl_cattr *attr)
 323 {
 324         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 325         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 326         struct inode *udir = upperdir->d_inode;
 327         struct dentry *newdentry;
 328         int err;
 329
 330         if (!attr->hardlink && !IS_POSIXACL(udir))
 331                 attr->mode &= ~current_umask();
 332
 333         inode_lock_nested(udir, I_MUTEX_PARENT);
 334         newdentry = ovl_create_real(udir,
 335                                     lookup_one_len(dentry->d_name.name,
 336                                                    upperdir,
 337                                                    dentry->d_name.len),
 338                                     attr);
 339         err = PTR_ERR(newdentry);
 340         if (IS_ERR(newdentry))
 341                 goto out_unlock;
 342
 343         if (ovl_type_merge(dentry->d_parent) && d_is_dir(newdentry) &&
 344             !ovl_allow_offline_changes(ofs)) {
 345                 /* Setting opaque here is just an optimization, allow to fail */
 346                 ovl_set_opaque(dentry, newdentry);
 347         }
 348
 349         err = ovl_instantiate(dentry, inode, newdentry, !!attr->hardlink);
 350         if (err)
 351                 goto out_cleanup;
 352 out_unlock:
 353         inode_unlock(udir);
 354         return err;
 355
 356 out_cleanup:
 357         ovl_cleanup(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 dentry *workdir = ovl_workdir(dentry);
 366         struct inode *wdir = workdir->d_inode;
 367         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 368         struct inode *udir = upperdir->d_inode;
 369         struct path upperpath;
 370         struct dentry *upper;
 371         struct dentry *opaquedir;
 372         struct kstat stat;
 373         int err;
 374
 375         if (WARN_ON(!workdir))
 376                 return ERR_PTR(-EROFS);
 377
 378         err = ovl_lock_rename_workdir(workdir, upperdir);
 379         if (err)
 380                 goto out;
 381
 382         ovl_path_upper(dentry, &upperpath);
 383         err = vfs_getattr(&upperpath, &stat,
 384                           STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
 385         if (err)
 386                 goto out_unlock;
 387
 388         err = -ESTALE;
 389         if (!S_ISDIR(stat.mode))
 390                 goto out_unlock;
 391         upper = upperpath.dentry;
 392         if (upper->d_parent->d_inode != udir)
 393                 goto out_unlock;
 394
 395         opaquedir = ovl_create_temp(workdir, OVL_CATTR(stat.mode));
 396         err = PTR_ERR(opaquedir);
 397         if (IS_ERR(opaquedir))
 398                 goto out_unlock;
 399
 400         err = ovl_copy_xattr(dentry->d_sb, upper, opaquedir);
 401         if (err)
 402                 goto out_cleanup;
 403
 404         err = ovl_set_opaque(dentry, opaquedir);
 405         if (err)
 406                 goto out_cleanup;
 407
 408         inode_lock(opaquedir->d_inode);
 409         err = ovl_set_attr(opaquedir, &stat);
 410         inode_unlock(opaquedir->d_inode);
 411         if (err)
 412                 goto out_cleanup;
 413
 414         err = ovl_do_rename(wdir, opaquedir, udir, upper, RENAME_EXCHANGE);
 415         if (err)
 416                 goto out_cleanup;
 417
 418         ovl_cleanup_whiteouts(upper, list);
 419         ovl_cleanup(wdir, upper);
 420         unlock_rename(workdir, upperdir);
 421
 422         /* dentry's upper doesn't match now, get rid of it */
 423         d_drop(dentry);
 424
 425         return opaquedir;
 426
 427 out_cleanup:
 428         ovl_cleanup(wdir, opaquedir);
 429         dput(opaquedir);
 430 out_unlock:
 431         unlock_rename(workdir, upperdir);
 432 out:
 433         return ERR_PTR(err);
 434 }
 435
 436 static int ovl_set_upper_acl(struct dentry *upperdentry, const char *name,
 437                              const struct posix_acl *acl)
 438 {
 439         void *buffer;
 440         size_t size;
 441         int err;
 442
 443         if (!IS_ENABLED(CONFIG_FS_POSIX_ACL) || !acl)
 444                 return 0;
 445
 446         size = posix_acl_xattr_size(acl->a_count);
 447         buffer = kmalloc(size, GFP_KERNEL);
 448         if (!buffer)
 449                 return -ENOMEM;
 450
 451         err = posix_acl_to_xattr(&init_user_ns, acl, buffer, size);
 452         if (err < 0)
 453                 goto out_free;
 454
 455         err = vfs_setxattr(&init_user_ns, upperdentry, name, buffer, size, XATTR_CREATE);
 456 out_free:
 457         kfree(buffer);
 458         return err;
 459 }
 460
 461 static int ovl_create_over_whiteout(struct dentry *dentry, struct inode *inode,
 462                                     struct ovl_cattr *cattr)
 463 {
 464         struct dentry *workdir = ovl_workdir(dentry);
 465         struct inode *wdir = workdir->d_inode;
 466         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 467         struct inode *udir = upperdir->d_inode;
 468         struct dentry *upper;
 469         struct dentry *newdentry;
 470         int err;
 471         struct posix_acl *acl, *default_acl;
 472         bool hardlink = !!cattr->hardlink;
 473
 474         if (WARN_ON(!workdir))
 475                 return -EROFS;
 476
 477         if (!hardlink) {
 478                 err = posix_acl_create(dentry->d_parent->d_inode,
 479                                        &cattr->mode, &default_acl, &acl);
 480                 if (err)
 481                         return err;
 482         }
 483
 484         err = ovl_lock_rename_workdir(workdir, upperdir);
 485         if (err)
 486                 goto out;
 487
 488         upper = lookup_one_len(dentry->d_name.name, upperdir,
 489                                dentry->d_name.len);
 490         err = PTR_ERR(upper);
 491         if (IS_ERR(upper))
 492                 goto out_unlock;
 493
 494         err = -ESTALE;
 495         if (d_is_negative(upper) || !IS_WHITEOUT(d_inode(upper)))
 496                 goto out_dput;
 497
 498         newdentry = ovl_create_temp(workdir, cattr);
 499         err = PTR_ERR(newdentry);
 500         if (IS_ERR(newdentry))
 501                 goto out_dput;
 502
 503         /*
 504          * mode could have been mutilated due to umask (e.g. sgid directory)
 505          */
 506         if (!hardlink &&
 507             !S_ISLNK(cattr->mode) &&
 508             newdentry->d_inode->i_mode != cattr->mode) {
 509                 struct iattr attr = {
 510                         .ia_valid = ATTR_MODE,
 511                         .ia_mode = cattr->mode,
 512                 };
 513                 inode_lock(newdentry->d_inode);
 514                 err = notify_change(&init_user_ns, newdentry, &attr, NULL);
 515                 inode_unlock(newdentry->d_inode);
 516                 if (err)
 517                         goto out_cleanup;
 518         }
 519         if (!hardlink) {
 520                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_ACCESS,
 521                                         acl);
 522                 if (err)
 523                         goto out_cleanup;
 524
 525                 err = ovl_set_upper_acl(newdentry, XATTR_NAME_POSIX_ACL_DEFAULT,
 526                                         default_acl);
 527                 if (err)
 528                         goto out_cleanup;
 529         }
 530
 531         if (!hardlink && S_ISDIR(cattr->mode)) {
 532                 err = ovl_set_opaque(dentry, newdentry);
 533                 if (err)
 534                         goto out_cleanup;
 535
 536                 err = ovl_do_rename(wdir, newdentry, udir, upper,
 537                                     RENAME_EXCHANGE);
 538                 if (err)
 539                         goto out_cleanup;
 540
 541                 ovl_cleanup(wdir, upper);
 542         } else {
 543                 err = ovl_do_rename(wdir, newdentry, udir, upper, 0);
 544                 if (err)
 545                         goto out_cleanup;
 546         }
 547         err = ovl_instantiate(dentry, inode, newdentry, hardlink);
 548         if (err) {
 549                 ovl_cleanup(udir, newdentry);
 550                 dput(newdentry);
 551         }
 552 out_dput:
 553         dput(upper);
 554 out_unlock:
 555         unlock_rename(workdir, upperdir);
 556 out:
 557         if (!hardlink) {
 558                 posix_acl_release(acl);
 559                 posix_acl_release(default_acl);
 560         }
 561         return err;
 562
 563 out_cleanup:
 564         ovl_cleanup(wdir, newdentry);
 565         dput(newdentry);
 566         goto out_dput;
 567 }
 568
 569 static int ovl_create_or_link(struct dentry *dentry, struct inode *inode,
 570                               struct ovl_cattr *attr, bool origin)
 571 {
 572         int err;
 573         const struct cred *old_cred;
 574         struct cred *override_cred;
 575         struct dentry *parent = dentry->d_parent;
 576
 577         err = ovl_copy_up(parent);
 578         if (err)
 579                 return err;
 580
 581         old_cred = ovl_override_creds(dentry->d_sb);
 582
 583         /*
 584          * When linking a file with copy up origin into a new parent, mark the
 585          * new parent dir "impure".
 586          */
 587         if (origin) {
 588                 err = ovl_set_impure(parent, ovl_dentry_upper(parent));
 589                 if (err)
 590                         goto out_revert_creds;
 591         }
 592
 593         err = -ENOMEM;
 594         override_cred = prepare_creds();
 595         if (override_cred) {
 596                 override_cred->fsuid = inode->i_uid;
 597                 override_cred->fsgid = inode->i_gid;
 598                 if (!attr->hardlink) {
 599                         err = security_dentry_create_files_as(dentry,
 600                                         attr->mode, &dentry->d_name, old_cred,
 601                                         override_cred);
 602                         if (err) {
 603                                 put_cred(override_cred);
 604                                 goto out_revert_creds;
 605                         }
 606                 }
 607                 put_cred(override_creds(override_cred));
 608                 put_cred(override_cred);
 609
 610                 if (!ovl_dentry_is_whiteout(dentry))
 611                         err = ovl_create_upper(dentry, inode, attr);
 612                 else
 613                         err = ovl_create_over_whiteout(dentry, inode, attr);
 614         }
 615 out_revert_creds:
 616         revert_creds(old_cred);
 617         return err;
 618 }
 619
 620 static int ovl_create_object(struct dentry *dentry, int mode, dev_t rdev,
 621                              const char *link)
 622 {
 623         int err;
 624         struct inode *inode;
 625         struct ovl_cattr attr = {
 626                 .rdev = rdev,
 627                 .link = link,
 628         };
 629
 630         err = ovl_want_write(dentry);
 631         if (err)
 632                 goto out;
 633
 634         /* Preallocate inode to be used by ovl_get_inode() */
 635         err = -ENOMEM;
 636         inode = ovl_new_inode(dentry->d_sb, mode, rdev);
 637         if (!inode)
 638                 goto out_drop_write;
 639
 640         spin_lock(&inode->i_lock);
 641         inode->i_state |= I_CREATING;
 642         spin_unlock(&inode->i_lock);
 643
 644         inode_init_owner(&init_user_ns, inode, dentry->d_parent->d_inode, mode);
 645         attr.mode = inode->i_mode;
 646
 647         err = ovl_create_or_link(dentry, inode, &attr, false);
 648         /* Did we end up using the preallocated inode? */
 649         if (inode != d_inode(dentry))
 650                 iput(inode);
 651
 652 out_drop_write:
 653         ovl_drop_write(dentry);
 654 out:
 655         return err;
 656 }
 657
 658 static int ovl_create(struct user_namespace *mnt_userns, struct inode *dir,
 659                       struct dentry *dentry, umode_t mode, bool excl)
 660 {
 661         return ovl_create_object(dentry, (mode & 07777) | S_IFREG, 0, NULL);
 662 }
 663
 664 static int ovl_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 665                      struct dentry *dentry, umode_t mode)
 666 {
 667         return ovl_create_object(dentry, (mode & 07777) | S_IFDIR, 0, NULL);
 668 }
 669
 670 static int ovl_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 671                      struct dentry *dentry, umode_t mode, dev_t rdev)
 672 {
 673         /* Don't allow creation of "whiteout" on overlay */
 674         if (S_ISCHR(mode) && rdev == WHITEOUT_DEV)
 675                 return -EPERM;
 676
 677         return ovl_create_object(dentry, mode, rdev, NULL);
 678 }
 679
 680 static int ovl_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 681                        struct dentry *dentry, const char *link)
 682 {
 683         return ovl_create_object(dentry, S_IFLNK, 0, link);
 684 }
 685
 686 static int ovl_set_link_redirect(struct dentry *dentry)
 687 {
 688         const struct cred *old_cred;
 689         int err;
 690
 691         old_cred = ovl_override_creds(dentry->d_sb);
 692         err = ovl_set_redirect(dentry, false);
 693         revert_creds(old_cred);
 694
 695         return err;
 696 }
 697
 698 static int ovl_link(struct dentry *old, struct inode *newdir,
 699                     struct dentry *new)
 700 {
 701         int err;
 702         struct inode *inode;
 703
 704         err = ovl_want_write(old);
 705         if (err)
 706                 goto out;
 707
 708         err = ovl_copy_up(old);
 709         if (err)
 710                 goto out_drop_write;
 711
 712         err = ovl_copy_up(new->d_parent);
 713         if (err)
 714                 goto out_drop_write;
 715
 716         if (ovl_is_metacopy_dentry(old)) {
 717                 err = ovl_set_link_redirect(old);
 718                 if (err)
 719                         goto out_drop_write;
 720         }
 721
 722         err = ovl_nlink_start(old);
 723         if (err)
 724                 goto out_drop_write;
 725
 726         inode = d_inode(old);
 727         ihold(inode);
 728
 729         err = ovl_create_or_link(new, inode,
 730                         &(struct ovl_cattr) {.hardlink = ovl_dentry_upper(old)},
 731                         ovl_type_origin(old));
 732         if (err)
 733                 iput(inode);
 734
 735         ovl_nlink_end(old);
 736 out_drop_write:
 737         ovl_drop_write(old);
 738 out:
 739         return err;
 740 }
 741
 742 static bool ovl_matches_upper(struct dentry *dentry, struct dentry *upper)
 743 {
 744         return d_inode(ovl_dentry_upper(dentry)) == d_inode(upper);
 745 }
 746
 747 static int ovl_remove_and_whiteout(struct dentry *dentry,
 748                                    struct list_head *list)
 749 {
 750         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 751         struct dentry *workdir = ovl_workdir(dentry);
 752         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 753         struct dentry *upper;
 754         struct dentry *opaquedir = NULL;
 755         int err;
 756
 757         if (WARN_ON(!workdir))
 758                 return -EROFS;
 759
 760         if (!list_empty(list)) {
 761                 opaquedir = ovl_clear_empty(dentry, list);
 762                 err = PTR_ERR(opaquedir);
 763                 if (IS_ERR(opaquedir))
 764                         goto out;
 765         }
 766
 767         err = ovl_lock_rename_workdir(workdir, upperdir);
 768         if (err)
 769                 goto out_dput;
 770
 771         upper = lookup_one_len(dentry->d_name.name, upperdir,
 772                                dentry->d_name.len);
 773         err = PTR_ERR(upper);
 774         if (IS_ERR(upper))
 775                 goto out_unlock;
 776
 777         err = -ESTALE;
 778         if ((opaquedir && upper != opaquedir) ||
 779             (!opaquedir && ovl_dentry_upper(dentry) &&
 780              !ovl_matches_upper(dentry, upper))) {
 781                 goto out_dput_upper;
 782         }
 783
 784         err = ovl_cleanup_and_whiteout(ofs, d_inode(upperdir), upper);
 785         if (err)
 786                 goto out_d_drop;
 787
 788         ovl_dir_modified(dentry->d_parent, true);
 789 out_d_drop:
 790         d_drop(dentry);
 791 out_dput_upper:
 792         dput(upper);
 793 out_unlock:
 794         unlock_rename(workdir, upperdir);
 795 out_dput:
 796         dput(opaquedir);
 797 out:
 798         return err;
 799 }
 800
 801 static int ovl_remove_upper(struct dentry *dentry, bool is_dir,
 802                             struct list_head *list)
 803 {
 804         struct dentry *upperdir = ovl_dentry_upper(dentry->d_parent);
 805         struct inode *dir = upperdir->d_inode;
 806         struct dentry *upper;
 807         struct dentry *opaquedir = NULL;
 808         int err;
 809
 810         if (!list_empty(list)) {
 811                 opaquedir = ovl_clear_empty(dentry, list);
 812                 err = PTR_ERR(opaquedir);
 813                 if (IS_ERR(opaquedir))
 814                         goto out;
 815         }
 816
 817         inode_lock_nested(dir, I_MUTEX_PARENT);
 818         upper = lookup_one_len(dentry->d_name.name, upperdir,
 819                                dentry->d_name.len);
 820         err = PTR_ERR(upper);
 821         if (IS_ERR(upper))
 822                 goto out_unlock;
 823
 824         err = -ESTALE;
 825         if ((opaquedir && upper != opaquedir) ||
 826             (!opaquedir && !ovl_matches_upper(dentry, upper)))
 827                 goto out_dput_upper;
 828
 829         if (is_dir)
 830                 err = vfs_rmdir(&init_user_ns, dir, upper);
 831         else
 832                 err = vfs_unlink(&init_user_ns, dir, upper, NULL);
 833         ovl_dir_modified(dentry->d_parent, ovl_type_origin(dentry));
 834
 835         /*
 836          * Keeping this dentry hashed would mean having to release
 837          * upperpath/lowerpath, which could only be done if we are the
 838          * sole user of this dentry.  Too tricky...  Just unhash for
 839          * now.
 840          */
 841         if (!err)
 842                 d_drop(dentry);
 843 out_dput_upper:
 844         dput(upper);
 845 out_unlock:
 846         inode_unlock(dir);
 847         dput(opaquedir);
 848 out:
 849         return err;
 850 }
 851
 852 static bool ovl_pure_upper(struct dentry *dentry)
 853 {
 854         return !ovl_dentry_lower(dentry) &&
 855                !ovl_test_flag(OVL_WHITEOUTS, d_inode(dentry));
 856 }
 857
 858 static void ovl_drop_nlink(struct dentry *dentry)
 859 {
 860         struct inode *inode = d_inode(dentry);
 861         struct dentry *alias;
 862
 863         /* Try to find another, hashed alias */
 864         spin_lock(&inode->i_lock);
 865         hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
 866                 if (alias != dentry && !d_unhashed(alias))
 867                         break;
 868         }
 869         spin_unlock(&inode->i_lock);
 870
 871         /*
 872          * Changes to underlying layers may cause i_nlink to lose sync with
 873          * reality.  In this case prevent the link count from going to zero
 874          * prematurely.
 875          */
 876         if (inode->i_nlink > !!alias)
 877                 drop_nlink(inode);
 878 }
 879
 880 static int ovl_do_remove(struct dentry *dentry, bool is_dir)
 881 {
 882         int err;
 883         const struct cred *old_cred;
 884         struct dentry *upperdentry;
 885         bool lower_positive = ovl_lower_positive(dentry);
 886         LIST_HEAD(list);
 887
 888         /* No need to clean pure upper removed by vfs_rmdir() */
 889         if (is_dir && (lower_positive || !ovl_pure_upper(dentry))) {
 890                 err = ovl_check_empty_dir(dentry, &list);
 891                 if (err)
 892                         goto out;
 893         }
 894
 895         err = ovl_want_write(dentry);
 896         if (err)
 897                 goto out;
 898
 899         err = ovl_copy_up(dentry->d_parent);
 900         if (err)
 901                 goto out_drop_write;
 902
 903         err = ovl_nlink_start(dentry);
 904         if (err)
 905                 goto out_drop_write;
 906
 907         old_cred = ovl_override_creds(dentry->d_sb);
 908         if (!lower_positive)
 909                 err = ovl_remove_upper(dentry, is_dir, &list);
 910         else
 911                 err = ovl_remove_and_whiteout(dentry, &list);
 912         revert_creds(old_cred);
 913         if (!err) {
 914                 if (is_dir)
 915                         clear_nlink(dentry->d_inode);
 916                 else
 917                         ovl_drop_nlink(dentry);
 918         }
 919         ovl_nlink_end(dentry);
 920
 921         /*
 922          * Copy ctime
 923          *
 924          * Note: we fail to update ctime if there was no copy-up, only a
 925          * whiteout
 926          */
 927         upperdentry = ovl_dentry_upper(dentry);
 928         if (upperdentry)
 929                 ovl_copyattr(d_inode(upperdentry), d_inode(dentry));
 930
 931 out_drop_write:
 932         ovl_drop_write(dentry);
 933 out:
 934         ovl_cache_free(&list);
 935         return err;
 936 }
 937
 938 static int ovl_unlink(struct inode *dir, struct dentry *dentry)
 939 {
 940         return ovl_do_remove(dentry, false);
 941 }
 942
 943 static int ovl_rmdir(struct inode *dir, struct dentry *dentry)
 944 {
 945         return ovl_do_remove(dentry, true);
 946 }
 947
 948 static bool ovl_type_merge_or_lower(struct dentry *dentry)
 949 {
 950         enum ovl_path_type type = ovl_path_type(dentry);
 951
 952         return OVL_TYPE_MERGE(type) || !OVL_TYPE_UPPER(type);
 953 }
 954
 955 static bool ovl_can_move(struct dentry *dentry)
 956 {
 957         return ovl_redirect_dir(dentry->d_sb) ||
 958                 !d_is_dir(dentry) || !ovl_type_merge_or_lower(dentry);
 959 }
 960
 961 static char *ovl_get_redirect(struct dentry *dentry, bool abs_redirect)
 962 {
 963         char *buf, *ret;
 964         struct dentry *d, *tmp;
 965         int buflen = ovl_redirect_max + 1;
 966
 967         if (!abs_redirect) {
 968                 ret = kstrndup(dentry->d_name.name, dentry->d_name.len,
 969                                GFP_KERNEL);
 970                 goto out;
 971         }
 972
 973         buf = ret = kmalloc(buflen, GFP_KERNEL);
 974         if (!buf)
 975                 goto out;
 976
 977         buflen--;
 978         buf[buflen] = '\0';
 979         for (d = dget(dentry); !IS_ROOT(d);) {
 980                 const char *name;
 981                 int thislen;
 982
 983                 spin_lock(&d->d_lock);
 984                 name = ovl_dentry_get_redirect(d);
 985                 if (name) {
 986                         thislen = strlen(name);
 987                 } else {
 988                         name = d->d_name.name;
 989                         thislen = d->d_name.len;
 990                 }
 991
 992                 /* If path is too long, fall back to userspace move */
 993                 if (thislen + (name[0] != '/') > buflen) {
 994                         ret = ERR_PTR(-EXDEV);
 995                         spin_unlock(&d->d_lock);
 996                         goto out_put;
 997                 }
 998
 999                 buflen -= thislen;
1000                 memcpy(&buf[buflen], name, thislen);
1001                 spin_unlock(&d->d_lock);
1002                 tmp = dget_parent(d);
1003
1004                 dput(d);
1005                 d = tmp;
1006
1007                 /* Absolute redirect: finished */
1008                 if (buf[buflen] == '/')
1009                         break;
1010                 buflen--;
1011                 buf[buflen] = '/';
1012         }
1013         ret = kstrdup(&buf[buflen], GFP_KERNEL);
1014 out_put:
1015         dput(d);
1016         kfree(buf);
1017 out:
1018         return ret ? ret : ERR_PTR(-ENOMEM);
1019 }
1020
1021 static bool ovl_need_absolute_redirect(struct dentry *dentry, bool samedir)
1022 {
1023         struct dentry *lowerdentry;
1024
1025         if (!samedir)
1026                 return true;
1027
1028         if (d_is_dir(dentry))
1029                 return false;
1030
1031         /*
1032          * For non-dir hardlinked files, we need absolute redirects
1033          * in general as two upper hardlinks could be in different
1034          * dirs. We could put a relative redirect now and convert
1035          * it to absolute redirect later. But when nlink > 1 and
1036          * indexing is on, that means relative redirect needs to be
1037          * converted to absolute during copy up of another lower
1038          * hardllink as well.
1039          *
1040          * So without optimizing too much, just check if lower is
1041          * a hard link or not. If lower is hard link, put absolute
1042          * redirect.
1043          */
1044         lowerdentry = ovl_dentry_lower(dentry);
1045         return (d_inode(lowerdentry)->i_nlink > 1);
1046 }
1047
1048 static int ovl_set_redirect(struct dentry *dentry, bool samedir)
1049 {
1050         int err;
1051         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
1052         const char *redirect = ovl_dentry_get_redirect(dentry);
1053         bool absolute_redirect = ovl_need_absolute_redirect(dentry, samedir);
1054
1055         if (redirect && (!absolute_redirect || redirect[0] == '/'))
1056                 return 0;
1057
1058         redirect = ovl_get_redirect(dentry, absolute_redirect);
1059         if (IS_ERR(redirect))
1060                 return PTR_ERR(redirect);
1061
1062         err = ovl_check_setxattr(ofs, ovl_dentry_upper(dentry),
1063                                  OVL_XATTR_REDIRECT,
1064                                  redirect, strlen(redirect), -EXDEV);
1065         if (!err) {
1066                 spin_lock(&dentry->d_lock);
1067                 ovl_dentry_set_redirect(dentry, redirect);
1068                 spin_unlock(&dentry->d_lock);
1069         } else {
1070                 kfree(redirect);
1071                 pr_warn_ratelimited("failed to set redirect (%i)\n",
1072                                     err);
1073                 /* Fall back to userspace copy-up */
1074                 err = -EXDEV;
1075         }
1076         return err;
1077 }
1078
1079 static int ovl_rename(struct user_namespace *mnt_userns, struct inode *olddir,
1080                       struct dentry *old, struct inode *newdir,
1081                       struct dentry *new, unsigned int flags)
1082 {
1083         int err;
1084         struct dentry *old_upperdir;
1085         struct dentry *new_upperdir;
1086         struct dentry *olddentry;
1087         struct dentry *newdentry;
1088         struct dentry *trap;
1089         bool old_opaque;
1090         bool new_opaque;
1091         bool cleanup_whiteout = false;
1092         bool update_nlink = false;
1093         bool overwrite = !(flags & RENAME_EXCHANGE);
1094         bool is_dir = d_is_dir(old);
1095         bool new_is_dir = d_is_dir(new);
1096         bool samedir = olddir == newdir;
1097         struct dentry *opaquedir = NULL;
1098         const struct cred *old_cred = NULL;
1099         LIST_HEAD(list);
1100
1101         err = -EINVAL;
1102         if (flags & ~(RENAME_EXCHANGE | RENAME_NOREPLACE))
1103                 goto out;
1104
1105         flags &= ~RENAME_NOREPLACE;
1106
1107         /* Don't copy up directory trees */
1108         err = -EXDEV;
1109         if (!ovl_can_move(old))
1110                 goto out;
1111         if (!overwrite && !ovl_can_move(new))
1112                 goto out;
1113
1114         if (overwrite && new_is_dir && !ovl_pure_upper(new)) {
1115                 err = ovl_check_empty_dir(new, &list);
1116                 if (err)
1117                         goto out;
1118         }
1119
1120         if (overwrite) {
1121                 if (ovl_lower_positive(old)) {
1122                         if (!ovl_dentry_is_whiteout(new)) {
1123                                 /* Whiteout source */
1124                                 flags |= RENAME_WHITEOUT;
1125                         } else {
1126                                 /* Switch whiteouts */
1127                                 flags |= RENAME_EXCHANGE;
1128                         }
1129                 } else if (is_dir && ovl_dentry_is_whiteout(new)) {
1130                         flags |= RENAME_EXCHANGE;
1131                         cleanup_whiteout = true;
1132                 }
1133         }
1134
1135         err = ovl_want_write(old);
1136         if (err)
1137                 goto out;
1138
1139         err = ovl_copy_up(old);
1140         if (err)
1141                 goto out_drop_write;
1142
1143         err = ovl_copy_up(new->d_parent);
1144         if (err)
1145                 goto out_drop_write;
1146         if (!overwrite) {
1147                 err = ovl_copy_up(new);
1148                 if (err)
1149                         goto out_drop_write;
1150         } else if (d_inode(new)) {
1151                 err = ovl_nlink_start(new);
1152                 if (err)
1153                         goto out_drop_write;
1154
1155                 update_nlink = true;
1156         }
1157
1158         old_cred = ovl_override_creds(old->d_sb);
1159
1160         if (!list_empty(&list)) {
1161                 opaquedir = ovl_clear_empty(new, &list);
1162                 err = PTR_ERR(opaquedir);
1163                 if (IS_ERR(opaquedir)) {
1164                         opaquedir = NULL;
1165                         goto out_revert_creds;
1166                 }
1167         }
1168
1169         old_upperdir = ovl_dentry_upper(old->d_parent);
1170         new_upperdir = ovl_dentry_upper(new->d_parent);
1171
1172         if (!samedir) {
1173                 /*
1174                  * When moving a merge dir or non-dir with copy up origin into
1175                  * a new parent, we are marking the new parent dir "impure".
1176                  * When ovl_iterate() iterates an "impure" upper dir, it will
1177                  * lookup the origin inodes of the entries to fill d_ino.
1178                  */
1179                 if (ovl_type_origin(old)) {
1180                         err = ovl_set_impure(new->d_parent, new_upperdir);
1181                         if (err)
1182                                 goto out_revert_creds;
1183                 }
1184                 if (!overwrite && ovl_type_origin(new)) {
1185                         err = ovl_set_impure(old->d_parent, old_upperdir);
1186                         if (err)
1187                                 goto out_revert_creds;
1188                 }
1189         }
1190
1191         trap = lock_rename(new_upperdir, old_upperdir);
1192
1193         olddentry = lookup_one_len(old->d_name.name, old_upperdir,
1194                                    old->d_name.len);
1195         err = PTR_ERR(olddentry);
1196         if (IS_ERR(olddentry))
1197                 goto out_unlock;
1198
1199         err = -ESTALE;
1200         if (!ovl_matches_upper(old, olddentry))
1201                 goto out_dput_old;
1202
1203         newdentry = lookup_one_len(new->d_name.name, new_upperdir,
1204                                    new->d_name.len);
1205         err = PTR_ERR(newdentry);
1206         if (IS_ERR(newdentry))
1207                 goto out_dput_old;
1208
1209         old_opaque = ovl_dentry_is_opaque(old);
1210         new_opaque = ovl_dentry_is_opaque(new);
1211
1212         err = -ESTALE;
1213         if (d_inode(new) && ovl_dentry_upper(new)) {
1214                 if (opaquedir) {
1215                         if (newdentry != opaquedir)
1216                                 goto out_dput;
1217                 } else {
1218                         if (!ovl_matches_upper(new, newdentry))
1219                                 goto out_dput;
1220                 }
1221         } else {
1222                 if (!d_is_negative(newdentry)) {
1223                         if (!new_opaque || !ovl_is_whiteout(newdentry))
1224                                 goto out_dput;
1225                 } else {
1226                         if (flags & RENAME_EXCHANGE)
1227                                 goto out_dput;
1228                 }
1229         }
1230
1231         if (olddentry == trap)
1232                 goto out_dput;
1233         if (newdentry == trap)
1234                 goto out_dput;
1235
1236         if (olddentry->d_inode == newdentry->d_inode)
1237                 goto out_dput;
1238
1239         err = 0;
1240         if (ovl_type_merge_or_lower(old))
1241                 err = ovl_set_redirect(old, samedir);
1242         else if (is_dir && !old_opaque && ovl_type_merge(new->d_parent))
1243                 err = ovl_set_opaque_xerr(old, olddentry, -EXDEV);
1244         if (err)
1245                 goto out_dput;
1246
1247         if (!overwrite && ovl_type_merge_or_lower(new))
1248                 err = ovl_set_redirect(new, samedir);
1249         else if (!overwrite && new_is_dir && !new_opaque &&
1250                  ovl_type_merge(old->d_parent))
1251                 err = ovl_set_opaque_xerr(new, newdentry, -EXDEV);
1252         if (err)
1253                 goto out_dput;
1254
1255         err = ovl_do_rename(old_upperdir->d_inode, olddentry,
1256                             new_upperdir->d_inode, newdentry, flags);
1257         if (err)
1258                 goto out_dput;
1259
1260         if (cleanup_whiteout)
1261                 ovl_cleanup(old_upperdir->d_inode, newdentry);
1262
1263         if (overwrite && d_inode(new)) {
1264                 if (new_is_dir)
1265                         clear_nlink(d_inode(new));
1266                 else
1267                         ovl_drop_nlink(new);
1268         }
1269
1270         ovl_dir_modified(old->d_parent, ovl_type_origin(old) ||
1271                          (!overwrite && ovl_type_origin(new)));
1272         ovl_dir_modified(new->d_parent, ovl_type_origin(old) ||
1273                          (d_inode(new) && ovl_type_origin(new)));
1274
1275         /* copy ctime: */
1276         ovl_copyattr(d_inode(olddentry), d_inode(old));
1277         if (d_inode(new) && ovl_dentry_upper(new))
1278                 ovl_copyattr(d_inode(newdentry), d_inode(new));
1279
1280 out_dput:
1281         dput(newdentry);
1282 out_dput_old:
1283         dput(olddentry);
1284 out_unlock:
1285         unlock_rename(new_upperdir, old_upperdir);
1286 out_revert_creds:
1287         revert_creds(old_cred);
1288         if (update_nlink)
1289                 ovl_nlink_end(new);
1290 out_drop_write:
1291         ovl_drop_write(old);
1292 out:
1293         dput(opaquedir);
1294         ovl_cache_free(&list);
1295         return err;
1296 }
1297
1298 const struct inode_operations ovl_dir_inode_operations = {
1299         .lookup         = ovl_lookup,
1300         .mkdir          = ovl_mkdir,
1301         .symlink        = ovl_symlink,
1302         .unlink         = ovl_unlink,
1303         .rmdir          = ovl_rmdir,
1304         .rename         = ovl_rename,
1305         .link           = ovl_link,
1306         .setattr        = ovl_setattr,
1307         .create         = ovl_create,
1308         .mknod          = ovl_mknod,
1309         .permission     = ovl_permission,
1310         .getattr        = ovl_getattr,
1311         .listxattr      = ovl_listxattr,
1312         .get_acl        = ovl_get_acl,
1313         .update_time    = ovl_update_time,
1314         .fileattr_get   = ovl_fileattr_get,
1315         .fileattr_set   = ovl_fileattr_set,
1316 };