fs/overlayfs/namei.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2011 Novell Inc.
   4  * Copyright (C) 2016 Red Hat, Inc.
   5  */
   6
   7 #include <linux/fs.h>
   8 #include <linux/cred.h>
   9 #include <linux/ctype.h>
  10 #include <linux/namei.h>
  11 #include <linux/xattr.h>
  12 #include <linux/ratelimit.h>
  13 #include <linux/mount.h>
  14 #include <linux/exportfs.h>
  15 #include "overlayfs.h"
  16
  17 struct ovl_lookup_data {
  18         struct super_block *sb;
  19         const struct ovl_layer *layer;
  20         struct qstr name;
  21         bool is_dir;
  22         bool opaque;
  23         bool xwhiteouts;
  24         bool stop;
  25         bool last;
  26         char *redirect;
  27         int metacopy;
  28         /* Referring to last redirect xattr */
  29         bool absolute_redirect;
  30 };
  31
  32 static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d,
  33                               size_t prelen, const char *post)
  34 {
  35         int res;
  36         char *buf;
  37         struct ovl_fs *ofs = OVL_FS(d->sb);
  38
  39         d->absolute_redirect = false;
  40         buf = ovl_get_redirect_xattr(ofs, path, prelen + strlen(post));
  41         if (IS_ERR_OR_NULL(buf))
  42                 return PTR_ERR(buf);
  43
  44         if (buf[0] == '/') {
  45                 d->absolute_redirect = true;
  46                 /*
  47                  * One of the ancestor path elements in an absolute path
  48                  * lookup in ovl_lookup_layer() could have been opaque and
  49                  * that will stop further lookup in lower layers (d->stop=true)
  50                  * But we have found an absolute redirect in descendant path
  51                  * element and that should force continue lookup in lower
  52                  * layers (reset d->stop).
  53                  */
  54                 d->stop = false;
  55         } else {
  56                 res = strlen(buf) + 1;
  57                 memmove(buf + prelen, buf, res);
  58                 memcpy(buf, d->name.name, prelen);
  59         }
  60
  61         strcat(buf, post);
  62         kfree(d->redirect);
  63         d->redirect = buf;
  64         d->name.name = d->redirect;
  65         d->name.len = strlen(d->redirect);
  66
  67         return 0;
  68 }
  69
  70 static int ovl_acceptable(void *ctx, struct dentry *dentry)
  71 {
  72         /*
  73          * A non-dir origin may be disconnected, which is fine, because
  74          * we only need it for its unique inode number.
  75          */
  76         if (!d_is_dir(dentry))
  77                 return 1;
  78
  79         /* Don't decode a deleted empty directory */
  80         if (d_unhashed(dentry))
  81                 return 0;
  82
  83         /* Check if directory belongs to the layer we are decoding from */
  84         return is_subdir(dentry, ((struct vfsmount *)ctx)->mnt_root);
  85 }
  86
  87 /*
  88  * Check validity of an overlay file handle buffer.
  89  *
  90  * Return 0 for a valid file handle.
  91  * Return -ENODATA for "origin unknown".
  92  * Return <0 for an invalid file handle.
  93  */
  94 int ovl_check_fb_len(struct ovl_fb *fb, int fb_len)
  95 {
  96         if (fb_len < sizeof(struct ovl_fb) || fb_len < fb->len)
  97                 return -EINVAL;
  98
  99         if (fb->magic != OVL_FH_MAGIC)
 100                 return -EINVAL;
 101
 102         /* Treat larger version and unknown flags as "origin unknown" */
 103         if (fb->version > OVL_FH_VERSION || fb->flags & ~OVL_FH_FLAG_ALL)
 104                 return -ENODATA;
 105
 106         /* Treat endianness mismatch as "origin unknown" */
 107         if (!(fb->flags & OVL_FH_FLAG_ANY_ENDIAN) &&
 108             (fb->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN)
 109                 return -ENODATA;
 110
 111         return 0;
 112 }
 113
 114 static struct ovl_fh *ovl_get_fh(struct ovl_fs *ofs, struct dentry *upperdentry,
 115                                  enum ovl_xattr ox)
 116 {
 117         int res, err;
 118         struct ovl_fh *fh = NULL;
 119
 120         res = ovl_getxattr_upper(ofs, upperdentry, ox, NULL, 0);
 121         if (res < 0) {
 122                 if (res == -ENODATA || res == -EOPNOTSUPP)
 123                         return NULL;
 124                 goto fail;
 125         }
 126         /* Zero size value means "copied up but origin unknown" */
 127         if (res == 0)
 128                 return NULL;
 129
 130         fh = kzalloc(res + OVL_FH_WIRE_OFFSET, GFP_KERNEL);
 131         if (!fh)
 132                 return ERR_PTR(-ENOMEM);
 133
 134         res = ovl_getxattr_upper(ofs, upperdentry, ox, fh->buf, res);
 135         if (res < 0)
 136                 goto fail;
 137
 138         err = ovl_check_fb_len(&fh->fb, res);
 139         if (err < 0) {
 140                 if (err == -ENODATA)
 141                         goto out;
 142                 goto invalid;
 143         }
 144
 145         return fh;
 146
 147 out:
 148         kfree(fh);
 149         return NULL;
 150
 151 fail:
 152         pr_warn_ratelimited("failed to get origin (%i)\n", res);
 153         goto out;
 154 invalid:
 155         pr_warn_ratelimited("invalid origin (%*phN)\n", res, fh);
 156         goto out;
 157 }
 158
 159 struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
 160                                   struct vfsmount *mnt, bool connected)
 161 {
 162         struct dentry *real;
 163         int bytes;
 164
 165         if (!capable(CAP_DAC_READ_SEARCH))
 166                 return NULL;
 167
 168         /*
 169          * Make sure that the stored uuid matches the uuid of the lower
 170          * layer where file handle will be decoded.
 171          * In case of uuid=off option just make sure that stored uuid is null.
 172          */
 173         if (ovl_origin_uuid(ofs) ?
 174             !uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid) :
 175             !uuid_is_null(&fh->fb.uuid))
 176                 return NULL;
 177
 178         bytes = (fh->fb.len - offsetof(struct ovl_fb, fid));
 179         real = exportfs_decode_fh(mnt, (struct fid *)fh->fb.fid,
 180                                   bytes >> 2, (int)fh->fb.type,
 181                                   connected ? ovl_acceptable : NULL, mnt);
 182         if (IS_ERR(real)) {
 183                 /*
 184                  * Treat stale file handle to lower file as "origin unknown".
 185                  * upper file handle could become stale when upper file is
 186                  * unlinked and this information is needed to handle stale
 187                  * index entries correctly.
 188                  */
 189                 if (real == ERR_PTR(-ESTALE) &&
 190                     !(fh->fb.flags & OVL_FH_FLAG_PATH_UPPER))
 191                         real = NULL;
 192                 return real;
 193         }
 194
 195         if (ovl_dentry_weird(real)) {
 196                 dput(real);
 197                 return NULL;
 198         }
 199
 200         return real;
 201 }
 202
 203 static struct dentry *ovl_lookup_positive_unlocked(struct ovl_lookup_data *d,
 204                                                    const char *name,
 205                                                    struct dentry *base, int len,
 206                                                    bool drop_negative)
 207 {
 208         struct dentry *ret = lookup_one_unlocked(mnt_idmap(d->layer->mnt), name,
 209                                                  base, len);
 210
 211         if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
 212                 if (drop_negative && ret->d_lockref.count == 1) {
 213                         spin_lock(&ret->d_lock);
 214                         /* Recheck condition under lock */
 215                         if (d_is_negative(ret) && ret->d_lockref.count == 1)
 216                                 __d_drop(ret);
 217                         spin_unlock(&ret->d_lock);
 218                 }
 219                 dput(ret);
 220                 ret = ERR_PTR(-ENOENT);
 221         }
 222         return ret;
 223 }
 224
 225 static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d,
 226                              const char *name, unsigned int namelen,
 227                              size_t prelen, const char *post,
 228                              struct dentry **ret, bool drop_negative)
 229 {
 230         struct ovl_fs *ofs = OVL_FS(d->sb);
 231         struct dentry *this;
 232         struct path path;
 233         int err;
 234         bool last_element = !post[0];
 235         bool is_upper = d->layer->idx == 0;
 236         char val;
 237
 238         this = ovl_lookup_positive_unlocked(d, name, base, namelen, drop_negative);
 239         if (IS_ERR(this)) {
 240                 err = PTR_ERR(this);
 241                 this = NULL;
 242                 if (err == -ENOENT || err == -ENAMETOOLONG)
 243                         goto out;
 244                 goto out_err;
 245         }
 246
 247         if (ovl_dentry_weird(this)) {
 248                 /* Don't support traversing automounts and other weirdness */
 249                 err = -EREMOTE;
 250                 goto out_err;
 251         }
 252
 253         path.dentry = this;
 254         path.mnt = d->layer->mnt;
 255         if (ovl_path_is_whiteout(ofs, &path)) {
 256                 d->stop = d->opaque = true;
 257                 goto put_and_out;
 258         }
 259         /*
 260          * This dentry should be a regular file if previous layer lookup
 261          * found a metacopy dentry.
 262          */
 263         if (last_element && d->metacopy && !d_is_reg(this)) {
 264                 d->stop = true;
 265                 goto put_and_out;
 266         }
 267
 268         if (!d_can_lookup(this)) {
 269                 if (d->is_dir || !last_element) {
 270                         d->stop = true;
 271                         goto put_and_out;
 272                 }
 273                 err = ovl_check_metacopy_xattr(ofs, &path, NULL);
 274                 if (err < 0)
 275                         goto out_err;
 276
 277                 d->metacopy = err;
 278                 d->stop = !d->metacopy;
 279                 if (!d->metacopy || d->last)
 280                         goto out;
 281         } else {
 282                 if (ovl_lookup_trap_inode(d->sb, this)) {
 283                         /* Caught in a trap of overlapping layers */
 284                         err = -ELOOP;
 285                         goto out_err;
 286                 }
 287
 288                 if (last_element)
 289                         d->is_dir = true;
 290                 if (d->last)
 291                         goto out;
 292
 293                 /* overlay.opaque=x means xwhiteouts directory */
 294                 val = ovl_get_opaquedir_val(ofs, &path);
 295                 if (last_element && !is_upper && val == 'x') {
 296                         d->xwhiteouts = true;
 297                         ovl_layer_set_xwhiteouts(ofs, d->layer);
 298                 } else if (val == 'y') {
 299                         d->stop = true;
 300                         if (last_element)
 301                                 d->opaque = true;
 302                         goto out;
 303                 }
 304         }
 305         err = ovl_check_redirect(&path, d, prelen, post);
 306         if (err)
 307                 goto out_err;
 308 out:
 309         *ret = this;
 310         return 0;
 311
 312 put_and_out:
 313         dput(this);
 314         this = NULL;
 315         goto out;
 316
 317 out_err:
 318         dput(this);
 319         return err;
 320 }
 321
 322 static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d,
 323                             struct dentry **ret, bool drop_negative)
 324 {
 325         /* Counting down from the end, since the prefix can change */
 326         size_t rem = d->name.len - 1;
 327         struct dentry *dentry = NULL;
 328         int err;
 329
 330         if (d->name.name[0] != '/')
 331                 return ovl_lookup_single(base, d, d->name.name, d->name.len,
 332                                          0, "", ret, drop_negative);
 333
 334         while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) {
 335                 const char *s = d->name.name + d->name.len - rem;
 336                 const char *next = strchrnul(s, '/');
 337                 size_t thislen = next - s;
 338                 bool end = !next[0];
 339
 340                 /* Verify we did not go off the rails */
 341                 if (WARN_ON(s[-1] != '/'))
 342                         return -EIO;
 343
 344                 err = ovl_lookup_single(base, d, s, thislen,
 345                                         d->name.len - rem, next, &base,
 346                                         drop_negative);
 347                 dput(dentry);
 348                 if (err)
 349                         return err;
 350                 dentry = base;
 351                 if (end)
 352                         break;
 353
 354                 rem -= thislen + 1;
 355
 356                 if (WARN_ON(rem >= d->name.len))
 357                         return -EIO;
 358         }
 359         *ret = dentry;
 360         return 0;
 361 }
 362
 363 static int ovl_lookup_data_layer(struct dentry *dentry, const char *redirect,
 364                                  const struct ovl_layer *layer,
 365                                  struct path *datapath)
 366 {
 367         int err;
 368
 369         err = vfs_path_lookup(layer->mnt->mnt_root, layer->mnt, redirect,
 370                         LOOKUP_BENEATH | LOOKUP_NO_SYMLINKS | LOOKUP_NO_XDEV,
 371                         datapath);
 372         pr_debug("lookup lowerdata (%pd2, redirect=\"%s\", layer=%d, err=%i)\n",
 373                  dentry, redirect, layer->idx, err);
 374
 375         if (err)
 376                 return err;
 377
 378         err = -EREMOTE;
 379         if (ovl_dentry_weird(datapath->dentry))
 380                 goto out_path_put;
 381
 382         err = -ENOENT;
 383         /* Only regular file is acceptable as lower data */
 384         if (!d_is_reg(datapath->dentry))
 385                 goto out_path_put;
 386
 387         return 0;
 388
 389 out_path_put:
 390         path_put(datapath);
 391
 392         return err;
 393 }
 394
 395 /* Lookup in data-only layers by absolute redirect to layer root */
 396 static int ovl_lookup_data_layers(struct dentry *dentry, const char *redirect,
 397                                   struct ovl_path *lowerdata)
 398 {
 399         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 400         const struct ovl_layer *layer;
 401         struct path datapath;
 402         int err = -ENOENT;
 403         int i;
 404
 405         layer = &ofs->layers[ofs->numlayer - ofs->numdatalayer];
 406         for (i = 0; i < ofs->numdatalayer; i++, layer++) {
 407                 err = ovl_lookup_data_layer(dentry, redirect, layer, &datapath);
 408                 if (!err) {
 409                         mntput(datapath.mnt);
 410                         lowerdata->dentry = datapath.dentry;
 411                         lowerdata->layer = layer;
 412                         return 0;
 413                 }
 414         }
 415
 416         return err;
 417 }
 418
 419 int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected,
 420                         struct dentry *upperdentry, struct ovl_path **stackp)
 421 {
 422         struct dentry *origin = NULL;
 423         int i;
 424
 425         for (i = 1; i <= ovl_numlowerlayer(ofs); i++) {
 426                 /*
 427                  * If lower fs uuid is not unique among lower fs we cannot match
 428                  * fh->uuid to layer.
 429                  */
 430                 if (ofs->layers[i].fsid &&
 431                     ofs->layers[i].fs->bad_uuid)
 432                         continue;
 433
 434                 origin = ovl_decode_real_fh(ofs, fh, ofs->layers[i].mnt,
 435                                             connected);
 436                 if (origin)
 437                         break;
 438         }
 439
 440         if (!origin)
 441                 return -ESTALE;
 442         else if (IS_ERR(origin))
 443                 return PTR_ERR(origin);
 444
 445         if (upperdentry && !ovl_upper_is_whiteout(ofs, upperdentry) &&
 446             inode_wrong_type(d_inode(upperdentry), d_inode(origin)->i_mode))
 447                 goto invalid;
 448
 449         if (!*stackp)
 450                 *stackp = kmalloc(sizeof(struct ovl_path), GFP_KERNEL);
 451         if (!*stackp) {
 452                 dput(origin);
 453                 return -ENOMEM;
 454         }
 455         **stackp = (struct ovl_path){
 456                 .dentry = origin,
 457                 .layer = &ofs->layers[i]
 458         };
 459
 460         return 0;
 461
 462 invalid:
 463         pr_warn_ratelimited("invalid origin (%pd2, ftype=%x, origin ftype=%x).\n",
 464                             upperdentry, d_inode(upperdentry)->i_mode & S_IFMT,
 465                             d_inode(origin)->i_mode & S_IFMT);
 466         dput(origin);
 467         return -ESTALE;
 468 }
 469
 470 static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry,
 471                             struct ovl_path **stackp)
 472 {
 473         struct ovl_fh *fh = ovl_get_fh(ofs, upperdentry, OVL_XATTR_ORIGIN);
 474         int err;
 475
 476         if (IS_ERR_OR_NULL(fh))
 477                 return PTR_ERR(fh);
 478
 479         err = ovl_check_origin_fh(ofs, fh, false, upperdentry, stackp);
 480         kfree(fh);
 481
 482         if (err) {
 483                 if (err == -ESTALE)
 484                         return 0;
 485                 return err;
 486         }
 487
 488         return 0;
 489 }
 490
 491 /*
 492  * Verify that @fh matches the file handle stored in xattr @name.
 493  * Return 0 on match, -ESTALE on mismatch, < 0 on error.
 494  */
 495 static int ovl_verify_fh(struct ovl_fs *ofs, struct dentry *dentry,
 496                          enum ovl_xattr ox, const struct ovl_fh *fh)
 497 {
 498         struct ovl_fh *ofh = ovl_get_fh(ofs, dentry, ox);
 499         int err = 0;
 500
 501         if (!ofh)
 502                 return -ENODATA;
 503
 504         if (IS_ERR(ofh))
 505                 return PTR_ERR(ofh);
 506
 507         if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.len))
 508                 err = -ESTALE;
 509
 510         kfree(ofh);
 511         return err;
 512 }
 513
 514 int ovl_verify_set_fh(struct ovl_fs *ofs, struct dentry *dentry,
 515                       enum ovl_xattr ox, const struct ovl_fh *fh,
 516                       bool is_upper, bool set)
 517 {
 518         int err;
 519
 520         err = ovl_verify_fh(ofs, dentry, ox, fh);
 521         if (set && err == -ENODATA)
 522                 err = ovl_setxattr(ofs, dentry, ox, fh->buf, fh->fb.len);
 523
 524         return err;
 525 }
 526
 527 /*
 528  * Verify that @real dentry matches the file handle stored in xattr @name.
 529  *
 530  * If @set is true and there is no stored file handle, encode @real and store
 531  * file handle in xattr @name.
 532  *
 533  * Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error.
 534  */
 535 int ovl_verify_origin_xattr(struct ovl_fs *ofs, struct dentry *dentry,
 536                             enum ovl_xattr ox, struct dentry *real,
 537                             bool is_upper, bool set)
 538 {
 539         struct inode *inode;
 540         struct ovl_fh *fh;
 541         int err;
 542
 543         fh = ovl_encode_real_fh(ofs, d_inode(real), is_upper);
 544         err = PTR_ERR(fh);
 545         if (IS_ERR(fh)) {
 546                 fh = NULL;
 547                 goto fail;
 548         }
 549
 550         err = ovl_verify_set_fh(ofs, dentry, ox, fh, is_upper, set);
 551         if (err)
 552                 goto fail;
 553
 554 out:
 555         kfree(fh);
 556         return err;
 557
 558 fail:
 559         inode = d_inode(real);
 560         pr_warn_ratelimited("failed to verify %s (%pd2, ino=%lu, err=%i)\n",
 561                             is_upper ? "upper" : "origin", real,
 562                             inode ? inode->i_ino : 0, err);
 563         goto out;
 564 }
 565
 566
 567 /* Get upper dentry from index */
 568 struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index,
 569                                bool connected)
 570 {
 571         struct ovl_fh *fh;
 572         struct dentry *upper;
 573
 574         if (!d_is_dir(index))
 575                 return dget(index);
 576
 577         fh = ovl_get_fh(ofs, index, OVL_XATTR_UPPER);
 578         if (IS_ERR_OR_NULL(fh))
 579                 return ERR_CAST(fh);
 580
 581         upper = ovl_decode_real_fh(ofs, fh, ovl_upper_mnt(ofs), connected);
 582         kfree(fh);
 583
 584         if (IS_ERR_OR_NULL(upper))
 585                 return upper ?: ERR_PTR(-ESTALE);
 586
 587         if (!d_is_dir(upper)) {
 588                 pr_warn_ratelimited("invalid index upper (%pd2, upper=%pd2).\n",
 589                                     index, upper);
 590                 dput(upper);
 591                 return ERR_PTR(-EIO);
 592         }
 593
 594         return upper;
 595 }
 596
 597 /*
 598  * Verify that an index entry name matches the origin file handle stored in
 599  * OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path.
 600  * Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error.
 601  */
 602 int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index)
 603 {
 604         struct ovl_fh *fh = NULL;
 605         size_t len;
 606         struct ovl_path origin = { };
 607         struct ovl_path *stack = &origin;
 608         struct dentry *upper = NULL;
 609         int err;
 610
 611         if (!d_inode(index))
 612                 return 0;
 613
 614         err = -EINVAL;
 615         if (index->d_name.len < sizeof(struct ovl_fb)*2)
 616                 goto fail;
 617
 618         err = -ENOMEM;
 619         len = index->d_name.len / 2;
 620         fh = kzalloc(len + OVL_FH_WIRE_OFFSET, GFP_KERNEL);
 621         if (!fh)
 622                 goto fail;
 623
 624         err = -EINVAL;
 625         if (hex2bin(fh->buf, index->d_name.name, len))
 626                 goto fail;
 627
 628         err = ovl_check_fb_len(&fh->fb, len);
 629         if (err)
 630                 goto fail;
 631
 632         /*
 633          * Whiteout index entries are used as an indication that an exported
 634          * overlay file handle should be treated as stale (i.e. after unlink
 635          * of the overlay inode). These entries contain no origin xattr.
 636          */
 637         if (ovl_is_whiteout(index))
 638                 goto out;
 639
 640         /*
 641          * Verifying directory index entries are not stale is expensive, so
 642          * only verify stale dir index if NFS export is enabled.
 643          */
 644         if (d_is_dir(index) && !ofs->config.nfs_export)
 645                 goto out;
 646
 647         /*
 648          * Directory index entries should have 'upper' xattr pointing to the
 649          * real upper dir. Non-dir index entries are hardlinks to the upper
 650          * real inode. For non-dir index, we can read the copy up origin xattr
 651          * directly from the index dentry, but for dir index we first need to
 652          * decode the upper directory.
 653          */
 654         upper = ovl_index_upper(ofs, index, false);
 655         if (IS_ERR_OR_NULL(upper)) {
 656                 err = PTR_ERR(upper);
 657                 /*
 658                  * Directory index entries with no 'upper' xattr need to be
 659                  * removed. When dir index entry has a stale 'upper' xattr,
 660                  * we assume that upper dir was removed and we treat the dir
 661                  * index as orphan entry that needs to be whited out.
 662                  */
 663                 if (err == -ESTALE)
 664                         goto orphan;
 665                 else if (!err)
 666                         err = -ESTALE;
 667                 goto fail;
 668         }
 669
 670         err = ovl_verify_fh(ofs, upper, OVL_XATTR_ORIGIN, fh);
 671         dput(upper);
 672         if (err)
 673                 goto fail;
 674
 675         /* Check if non-dir index is orphan and don't warn before cleaning it */
 676         if (!d_is_dir(index) && d_inode(index)->i_nlink == 1) {
 677                 err = ovl_check_origin_fh(ofs, fh, false, index, &stack);
 678                 if (err)
 679                         goto fail;
 680
 681                 if (ovl_get_nlink(ofs, origin.dentry, index, 0) == 0)
 682                         goto orphan;
 683         }
 684
 685 out:
 686         dput(origin.dentry);
 687         kfree(fh);
 688         return err;
 689
 690 fail:
 691         pr_warn_ratelimited("failed to verify index (%pd2, ftype=%x, err=%i)\n",
 692                             index, d_inode(index)->i_mode & S_IFMT, err);
 693         goto out;
 694
 695 orphan:
 696         pr_warn_ratelimited("orphan index entry (%pd2, ftype=%x, nlink=%u)\n",
 697                             index, d_inode(index)->i_mode & S_IFMT,
 698                             d_inode(index)->i_nlink);
 699         err = -ENOENT;
 700         goto out;
 701 }
 702
 703 int ovl_get_index_name_fh(const struct ovl_fh *fh, struct qstr *name)
 704 {
 705         char *n, *s;
 706
 707         n = kcalloc(fh->fb.len, 2, GFP_KERNEL);
 708         if (!n)
 709                 return -ENOMEM;
 710
 711         s  = bin2hex(n, fh->buf, fh->fb.len);
 712         *name = (struct qstr) QSTR_INIT(n, s - n);
 713
 714         return 0;
 715
 716 }
 717
 718 /*
 719  * Lookup in indexdir for the index entry of a lower real inode or a copy up
 720  * origin inode. The index entry name is the hex representation of the lower
 721  * inode file handle.
 722  *
 723  * If the index dentry in negative, then either no lower aliases have been
 724  * copied up yet, or aliases have been copied up in older kernels and are
 725  * not indexed.
 726  *
 727  * If the index dentry for a copy up origin inode is positive, but points
 728  * to an inode different than the upper inode, then either the upper inode
 729  * has been copied up and not indexed or it was indexed, but since then
 730  * index dir was cleared. Either way, that index cannot be used to identify
 731  * the overlay inode.
 732  */
 733 int ovl_get_index_name(struct ovl_fs *ofs, struct dentry *origin,
 734                        struct qstr *name)
 735 {
 736         struct ovl_fh *fh;
 737         int err;
 738
 739         fh = ovl_encode_real_fh(ofs, d_inode(origin), false);
 740         if (IS_ERR(fh))
 741                 return PTR_ERR(fh);
 742
 743         err = ovl_get_index_name_fh(fh, name);
 744
 745         kfree(fh);
 746         return err;
 747 }
 748
 749 /* Lookup index by file handle for NFS export */
 750 struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
 751 {
 752         struct dentry *index;
 753         struct qstr name;
 754         int err;
 755
 756         err = ovl_get_index_name_fh(fh, &name);
 757         if (err)
 758                 return ERR_PTR(err);
 759
 760         index = lookup_positive_unlocked(name.name, ofs->workdir, name.len);
 761         kfree(name.name);
 762         if (IS_ERR(index)) {
 763                 if (PTR_ERR(index) == -ENOENT)
 764                         index = NULL;
 765                 return index;
 766         }
 767
 768         if (ovl_is_whiteout(index))
 769                 err = -ESTALE;
 770         else if (ovl_dentry_weird(index))
 771                 err = -EIO;
 772         else
 773                 return index;
 774
 775         dput(index);
 776         return ERR_PTR(err);
 777 }
 778
 779 struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
 780                                 struct dentry *origin, bool verify)
 781 {
 782         struct dentry *index;
 783         struct inode *inode;
 784         struct qstr name;
 785         bool is_dir = d_is_dir(origin);
 786         int err;
 787
 788         err = ovl_get_index_name(ofs, origin, &name);
 789         if (err)
 790                 return ERR_PTR(err);
 791
 792         index = lookup_one_positive_unlocked(ovl_upper_mnt_idmap(ofs), name.name,
 793                                              ofs->workdir, name.len);
 794         if (IS_ERR(index)) {
 795                 err = PTR_ERR(index);
 796                 if (err == -ENOENT) {
 797                         index = NULL;
 798                         goto out;
 799                 }
 800                 pr_warn_ratelimited("failed inode index lookup (ino=%lu, key=%.*s, err=%i);\n"
 801                                     "overlayfs: mount with '-o index=off' to disable inodes index.\n",
 802                                     d_inode(origin)->i_ino, name.len, name.name,
 803                                     err);
 804                 goto out;
 805         }
 806
 807         inode = d_inode(index);
 808         if (ovl_is_whiteout(index) && !verify) {
 809                 /*
 810                  * When index lookup is called with !verify for decoding an
 811                  * overlay file handle, a whiteout index implies that decode
 812                  * should treat file handle as stale and no need to print a
 813                  * warning about it.
 814                  */
 815                 dput(index);
 816                 index = ERR_PTR(-ESTALE);
 817                 goto out;
 818         } else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) ||
 819                    inode_wrong_type(inode, d_inode(origin)->i_mode)) {
 820                 /*
 821                  * Index should always be of the same file type as origin
 822                  * except for the case of a whiteout index. A whiteout
 823                  * index should only exist if all lower aliases have been
 824                  * unlinked, which means that finding a lower origin on lookup
 825                  * whose index is a whiteout should be treated as an error.
 826                  */
 827                 pr_warn_ratelimited("bad index found (index=%pd2, ftype=%x, origin ftype=%x).\n",
 828                                     index, d_inode(index)->i_mode & S_IFMT,
 829                                     d_inode(origin)->i_mode & S_IFMT);
 830                 goto fail;
 831         } else if (is_dir && verify) {
 832                 if (!upper) {
 833                         pr_warn_ratelimited("suspected uncovered redirected dir found (origin=%pd2, index=%pd2).\n",
 834                                             origin, index);
 835                         goto fail;
 836                 }
 837
 838                 /* Verify that dir index 'upper' xattr points to upper dir */
 839                 err = ovl_verify_upper(ofs, index, upper, false);
 840                 if (err) {
 841                         if (err == -ESTALE) {
 842                                 pr_warn_ratelimited("suspected multiply redirected dir found (upper=%pd2, origin=%pd2, index=%pd2).\n",
 843                                                     upper, origin, index);
 844                         }
 845                         goto fail;
 846                 }
 847         } else if (upper && d_inode(upper) != inode) {
 848                 goto out_dput;
 849         }
 850 out:
 851         kfree(name.name);
 852         return index;
 853
 854 out_dput:
 855         dput(index);
 856         index = NULL;
 857         goto out;
 858
 859 fail:
 860         dput(index);
 861         index = ERR_PTR(-EIO);
 862         goto out;
 863 }
 864
 865 /*
 866  * Returns next layer in stack starting from top.
 867  * Returns -1 if this is the last layer.
 868  */
 869 int ovl_path_next(int idx, struct dentry *dentry, struct path *path,
 870                   const struct ovl_layer **layer)
 871 {
 872         struct ovl_entry *oe = OVL_E(dentry);
 873         struct ovl_path *lowerstack = ovl_lowerstack(oe);
 874
 875         BUG_ON(idx < 0);
 876         if (idx == 0) {
 877                 ovl_path_upper(dentry, path);
 878                 if (path->dentry) {
 879                         *layer = &OVL_FS(dentry->d_sb)->layers[0];
 880                         return ovl_numlower(oe) ? 1 : -1;
 881                 }
 882                 idx++;
 883         }
 884         BUG_ON(idx > ovl_numlower(oe));
 885         path->dentry = lowerstack[idx - 1].dentry;
 886         *layer = lowerstack[idx - 1].layer;
 887         path->mnt = (*layer)->mnt;
 888
 889         return (idx < ovl_numlower(oe)) ? idx + 1 : -1;
 890 }
 891
 892 /* Fix missing 'origin' xattr */
 893 static int ovl_fix_origin(struct ovl_fs *ofs, struct dentry *dentry,
 894                           struct dentry *lower, struct dentry *upper)
 895 {
 896         const struct ovl_fh *fh;
 897         int err;
 898
 899         if (ovl_check_origin_xattr(ofs, upper))
 900                 return 0;
 901
 902         fh = ovl_get_origin_fh(ofs, lower);
 903         if (IS_ERR(fh))
 904                 return PTR_ERR(fh);
 905
 906         err = ovl_want_write(dentry);
 907         if (err)
 908                 goto out;
 909
 910         err = ovl_set_origin_fh(ofs, fh, upper);
 911         if (!err)
 912                 err = ovl_set_impure(dentry->d_parent, upper->d_parent);
 913
 914         ovl_drop_write(dentry);
 915 out:
 916         kfree(fh);
 917         return err;
 918 }
 919
 920 static int ovl_maybe_validate_verity(struct dentry *dentry)
 921 {
 922         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 923         struct inode *inode = d_inode(dentry);
 924         struct path datapath, metapath;
 925         int err;
 926
 927         if (!ofs->config.verity_mode ||
 928             !ovl_is_metacopy_dentry(dentry) ||
 929             ovl_test_flag(OVL_VERIFIED_DIGEST, inode))
 930                 return 0;
 931
 932         if (!ovl_test_flag(OVL_HAS_DIGEST, inode)) {
 933                 if (ofs->config.verity_mode == OVL_VERITY_REQUIRE) {
 934                         pr_warn_ratelimited("metacopy file '%pd' has no digest specified\n",
 935                                             dentry);
 936                         return -EIO;
 937                 }
 938                 return 0;
 939         }
 940
 941         ovl_path_lowerdata(dentry, &datapath);
 942         if (!datapath.dentry)
 943                 return -EIO;
 944
 945         ovl_path_real(dentry, &metapath);
 946         if (!metapath.dentry)
 947                 return -EIO;
 948
 949         err = ovl_inode_lock_interruptible(inode);
 950         if (err)
 951                 return err;
 952
 953         if (!ovl_test_flag(OVL_VERIFIED_DIGEST, inode)) {
 954                 const struct cred *old_cred;
 955
 956                 old_cred = ovl_override_creds(dentry->d_sb);
 957
 958                 err = ovl_validate_verity(ofs, &metapath, &datapath);
 959                 if (err == 0)
 960                         ovl_set_flag(OVL_VERIFIED_DIGEST, inode);
 961
 962                 ovl_revert_creds(old_cred);
 963         }
 964
 965         ovl_inode_unlock(inode);
 966
 967         return err;
 968 }
 969
 970 /* Lazy lookup of lowerdata */
 971 static int ovl_maybe_lookup_lowerdata(struct dentry *dentry)
 972 {
 973         struct inode *inode = d_inode(dentry);
 974         const char *redirect = ovl_lowerdata_redirect(inode);
 975         struct ovl_path datapath = {};
 976         const struct cred *old_cred;
 977         int err;
 978
 979         if (!redirect || ovl_dentry_lowerdata(dentry))
 980                 return 0;
 981
 982         if (redirect[0] != '/')
 983                 return -EIO;
 984
 985         err = ovl_inode_lock_interruptible(inode);
 986         if (err)
 987                 return err;
 988
 989         err = 0;
 990         /* Someone got here before us? */
 991         if (ovl_dentry_lowerdata(dentry))
 992                 goto out;
 993
 994         old_cred = ovl_override_creds(dentry->d_sb);
 995         err = ovl_lookup_data_layers(dentry, redirect, &datapath);
 996         ovl_revert_creds(old_cred);
 997         if (err)
 998                 goto out_err;
 999
1000         err = ovl_dentry_set_lowerdata(dentry, &datapath);
1001         if (err)
1002                 goto out_err;
1003
1004 out:
1005         ovl_inode_unlock(inode);
1006         dput(datapath.dentry);
1007
1008         return err;
1009
1010 out_err:
1011         pr_warn_ratelimited("lazy lowerdata lookup failed (%pd2, err=%i)\n",
1012                             dentry, err);
1013         goto out;
1014 }
1015
1016 int ovl_verify_lowerdata(struct dentry *dentry)
1017 {
1018         int err;
1019
1020         err = ovl_maybe_lookup_lowerdata(dentry);
1021         if (err)
1022                 return err;
1023
1024         return ovl_maybe_validate_verity(dentry);
1025 }
1026
1027 struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
1028                           unsigned int flags)
1029 {
1030         struct ovl_entry *oe = NULL;
1031         const struct cred *old_cred;
1032         struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
1033         struct ovl_entry *poe = OVL_E(dentry->d_parent);
1034         struct ovl_entry *roe = OVL_E(dentry->d_sb->s_root);
1035         struct ovl_path *stack = NULL, *origin_path = NULL;
1036         struct dentry *upperdir, *upperdentry = NULL;
1037         struct dentry *origin = NULL;
1038         struct dentry *index = NULL;
1039         unsigned int ctr = 0;
1040         struct inode *inode = NULL;
1041         bool upperopaque = false;
1042         char *upperredirect = NULL;
1043         struct dentry *this;
1044         unsigned int i;
1045         int err;
1046         bool uppermetacopy = false;
1047         int metacopy_size = 0;
1048         struct ovl_lookup_data d = {
1049                 .sb = dentry->d_sb,
1050                 .name = dentry->d_name,
1051                 .is_dir = false,
1052                 .opaque = false,
1053                 .stop = false,
1054                 .last = ovl_redirect_follow(ofs) ? false : !ovl_numlower(poe),
1055                 .redirect = NULL,
1056                 .metacopy = 0,
1057         };
1058
1059         if (dentry->d_name.len > ofs->namelen)
1060                 return ERR_PTR(-ENAMETOOLONG);
1061
1062         old_cred = ovl_override_creds(dentry->d_sb);
1063         upperdir = ovl_dentry_upper(dentry->d_parent);
1064         if (upperdir) {
1065                 d.layer = &ofs->layers[0];
1066                 err = ovl_lookup_layer(upperdir, &d, &upperdentry, true);
1067                 if (err)
1068                         goto out;
1069
1070                 if (upperdentry && upperdentry->d_flags & DCACHE_OP_REAL) {
1071                         dput(upperdentry);
1072                         err = -EREMOTE;
1073                         goto out;
1074                 }
1075                 if (upperdentry && !d.is_dir) {
1076                         /*
1077                          * Lookup copy up origin by decoding origin file handle.
1078                          * We may get a disconnected dentry, which is fine,
1079                          * because we only need to hold the origin inode in
1080                          * cache and use its inode number.  We may even get a
1081                          * connected dentry, that is not under any of the lower
1082                          * layers root.  That is also fine for using it's inode
1083                          * number - it's the same as if we held a reference
1084                          * to a dentry in lower layer that was moved under us.
1085                          */
1086                         err = ovl_check_origin(ofs, upperdentry, &origin_path);
1087                         if (err)
1088                                 goto out_put_upper;
1089
1090                         if (d.metacopy)
1091                                 uppermetacopy = true;
1092                         metacopy_size = d.metacopy;
1093                 }
1094
1095                 if (d.redirect) {
1096                         err = -ENOMEM;
1097                         upperredirect = kstrdup(d.redirect, GFP_KERNEL);
1098                         if (!upperredirect)
1099                                 goto out_put_upper;
1100                         if (d.redirect[0] == '/')
1101                                 poe = roe;
1102                 }
1103                 upperopaque = d.opaque;
1104         }
1105
1106         if (!d.stop && ovl_numlower(poe)) {
1107                 err = -ENOMEM;
1108                 stack = ovl_stack_alloc(ofs->numlayer - 1);
1109                 if (!stack)
1110                         goto out_put_upper;
1111         }
1112
1113         for (i = 0; !d.stop && i < ovl_numlower(poe); i++) {
1114                 struct ovl_path lower = ovl_lowerstack(poe)[i];
1115
1116                 if (!ovl_redirect_follow(ofs))
1117                         d.last = i == ovl_numlower(poe) - 1;
1118                 else if (d.is_dir || !ofs->numdatalayer)
1119                         d.last = lower.layer->idx == ovl_numlower(roe);
1120
1121                 d.layer = lower.layer;
1122                 err = ovl_lookup_layer(lower.dentry, &d, &this, false);
1123                 if (err)
1124                         goto out_put;
1125
1126                 if (!this)
1127                         continue;
1128
1129                 if ((uppermetacopy || d.metacopy) && !ofs->config.metacopy) {
1130                         dput(this);
1131                         err = -EPERM;
1132                         pr_warn_ratelimited("refusing to follow metacopy origin for (%pd2)\n", dentry);
1133                         goto out_put;
1134                 }
1135
1136                 /*
1137                  * If no origin fh is stored in upper of a merge dir, store fh
1138                  * of lower dir and set upper parent "impure".
1139                  */
1140                 if (upperdentry && !ctr && !ofs->noxattr && d.is_dir) {
1141                         err = ovl_fix_origin(ofs, dentry, this, upperdentry);
1142                         if (err) {
1143                                 dput(this);
1144                                 goto out_put;
1145                         }
1146                 }
1147
1148                 /*
1149                  * When "verify_lower" feature is enabled, do not merge with a
1150                  * lower dir that does not match a stored origin xattr. In any
1151                  * case, only verified origin is used for index lookup.
1152                  *
1153                  * For non-dir dentry, if index=on, then ensure origin
1154                  * matches the dentry found using path based lookup,
1155                  * otherwise error out.
1156                  */
1157                 if (upperdentry && !ctr &&
1158                     ((d.is_dir && ovl_verify_lower(dentry->d_sb)) ||
1159                      (!d.is_dir && ofs->config.index && origin_path))) {
1160                         err = ovl_verify_origin(ofs, upperdentry, this, false);
1161                         if (err) {
1162                                 dput(this);
1163                                 if (d.is_dir)
1164                                         break;
1165                                 goto out_put;
1166                         }
1167                         origin = this;
1168                 }
1169
1170                 if (!upperdentry && !d.is_dir && !ctr && d.metacopy)
1171                         metacopy_size = d.metacopy;
1172
1173                 if (d.metacopy && ctr) {
1174                         /*
1175                          * Do not store intermediate metacopy dentries in
1176                          * lower chain, except top most lower metacopy dentry.
1177                          * Continue the loop so that if there is an absolute
1178                          * redirect on this dentry, poe can be reset to roe.
1179                          */
1180                         dput(this);
1181                         this = NULL;
1182                 } else {
1183                         stack[ctr].dentry = this;
1184                         stack[ctr].layer = lower.layer;
1185                         ctr++;
1186                 }
1187
1188                 /*
1189                  * Following redirects can have security consequences: it's like
1190                  * a symlink into the lower layer without the permission checks.
1191                  * This is only a problem if the upper layer is untrusted (e.g
1192                  * comes from an USB drive).  This can allow a non-readable file
1193                  * or directory to become readable.
1194                  *
1195                  * Only following redirects when redirects are enabled disables
1196                  * this attack vector when not necessary.
1197                  */
1198                 err = -EPERM;
1199                 if (d.redirect && !ovl_redirect_follow(ofs)) {
1200                         pr_warn_ratelimited("refusing to follow redirect for (%pd2)\n",
1201                                             dentry);
1202                         goto out_put;
1203                 }
1204
1205                 if (d.stop)
1206                         break;
1207
1208                 if (d.redirect && d.redirect[0] == '/' && poe != roe) {
1209                         poe = roe;
1210                         /* Find the current layer on the root dentry */
1211                         i = lower.layer->idx - 1;
1212                 }
1213         }
1214
1215         /* Defer lookup of lowerdata in data-only layers to first access */
1216         if (d.metacopy && ctr && ofs->numdatalayer && d.absolute_redirect) {
1217                 d.metacopy = 0;
1218                 ctr++;
1219         }
1220
1221         /*
1222          * For regular non-metacopy upper dentries, there is no lower
1223          * path based lookup, hence ctr will be zero. If a dentry is found
1224          * using ORIGIN xattr on upper, install it in stack.
1225          *
1226          * For metacopy dentry, path based lookup will find lower dentries.
1227          * Just make sure a corresponding data dentry has been found.
1228          */
1229         if (d.metacopy || (uppermetacopy && !ctr)) {
1230                 pr_warn_ratelimited("metacopy with no lower data found - abort lookup (%pd2)\n",
1231                                     dentry);
1232                 err = -EIO;
1233                 goto out_put;
1234         } else if (!d.is_dir && upperdentry && !ctr && origin_path) {
1235                 if (WARN_ON(stack != NULL)) {
1236                         err = -EIO;
1237                         goto out_put;
1238                 }
1239                 stack = origin_path;
1240                 ctr = 1;
1241                 origin = origin_path->dentry;
1242                 origin_path = NULL;
1243         }
1244
1245         /*
1246          * Always lookup index if there is no-upperdentry.
1247          *
1248          * For the case of upperdentry, we have set origin by now if it
1249          * needed to be set. There are basically three cases.
1250          *
1251          * For directories, lookup index by lower inode and verify it matches
1252          * upper inode. We only trust dir index if we verified that lower dir
1253          * matches origin, otherwise dir index entries may be inconsistent
1254          * and we ignore them.
1255          *
1256          * For regular upper, we already set origin if upper had ORIGIN
1257          * xattr. There is no verification though as there is no path
1258          * based dentry lookup in lower in this case.
1259          *
1260          * For metacopy upper, we set a verified origin already if index
1261          * is enabled and if upper had an ORIGIN xattr.
1262          *
1263          */
1264         if (!upperdentry && ctr)
1265                 origin = stack[0].dentry;
1266
1267         if (origin && ovl_indexdir(dentry->d_sb) &&
1268             (!d.is_dir || ovl_index_all(dentry->d_sb))) {
1269                 index = ovl_lookup_index(ofs, upperdentry, origin, true);
1270                 if (IS_ERR(index)) {
1271                         err = PTR_ERR(index);
1272                         index = NULL;
1273                         goto out_put;
1274                 }
1275         }
1276
1277         if (ctr) {
1278                 oe = ovl_alloc_entry(ctr);
1279                 err = -ENOMEM;
1280                 if (!oe)
1281                         goto out_put;
1282
1283                 ovl_stack_cpy(ovl_lowerstack(oe), stack, ctr);
1284         }
1285
1286         if (upperopaque)
1287                 ovl_dentry_set_opaque(dentry);
1288         if (d.xwhiteouts)
1289                 ovl_dentry_set_xwhiteouts(dentry);
1290
1291         if (upperdentry)
1292                 ovl_dentry_set_upper_alias(dentry);
1293         else if (index) {
1294                 struct path upperpath = {
1295                         .dentry = upperdentry = dget(index),
1296                         .mnt = ovl_upper_mnt(ofs),
1297                 };
1298
1299                 /*
1300                  * It's safe to assign upperredirect here: the previous
1301                  * assignment of happens only if upperdentry is non-NULL, and
1302                  * this one only if upperdentry is NULL.
1303                  */
1304                 upperredirect = ovl_get_redirect_xattr(ofs, &upperpath, 0);
1305                 if (IS_ERR(upperredirect)) {
1306                         err = PTR_ERR(upperredirect);
1307                         upperredirect = NULL;
1308                         goto out_free_oe;
1309                 }
1310                 err = ovl_check_metacopy_xattr(ofs, &upperpath, NULL);
1311                 if (err < 0)
1312                         goto out_free_oe;
1313                 uppermetacopy = err;
1314                 metacopy_size = err;
1315         }
1316
1317         if (upperdentry || ctr) {
1318                 struct ovl_inode_params oip = {
1319                         .upperdentry = upperdentry,
1320                         .oe = oe,
1321                         .index = index,
1322                         .redirect = upperredirect,
1323                 };
1324
1325                 /* Store lowerdata redirect for lazy lookup */
1326                 if (ctr > 1 && !d.is_dir && !stack[ctr - 1].dentry) {
1327                         oip.lowerdata_redirect = d.redirect;
1328                         d.redirect = NULL;
1329                 }
1330                 inode = ovl_get_inode(dentry->d_sb, &oip);
1331                 err = PTR_ERR(inode);
1332                 if (IS_ERR(inode))
1333                         goto out_free_oe;
1334                 if (upperdentry && !uppermetacopy)
1335                         ovl_set_flag(OVL_UPPERDATA, inode);
1336
1337                 if (metacopy_size > OVL_METACOPY_MIN_SIZE)
1338                         ovl_set_flag(OVL_HAS_DIGEST, inode);
1339         }
1340
1341         ovl_dentry_init_reval(dentry, upperdentry, OVL_I_E(inode));
1342
1343         ovl_revert_creds(old_cred);
1344         if (origin_path) {
1345                 dput(origin_path->dentry);
1346                 kfree(origin_path);
1347         }
1348         dput(index);
1349         ovl_stack_free(stack, ctr);
1350         kfree(d.redirect);
1351         return d_splice_alias(inode, dentry);
1352
1353 out_free_oe:
1354         ovl_free_entry(oe);
1355 out_put:
1356         dput(index);
1357         ovl_stack_free(stack, ctr);
1358 out_put_upper:
1359         if (origin_path) {
1360                 dput(origin_path->dentry);
1361                 kfree(origin_path);
1362         }
1363         dput(upperdentry);
1364         kfree(upperredirect);
1365 out:
1366         kfree(d.redirect);
1367         ovl_revert_creds(old_cred);
1368         return ERR_PTR(err);
1369 }
1370
1371 bool ovl_lower_positive(struct dentry *dentry)
1372 {
1373         struct ovl_entry *poe = OVL_E(dentry->d_parent);
1374         const struct qstr *name = &dentry->d_name;
1375         const struct cred *old_cred;
1376         unsigned int i;
1377         bool positive = false;
1378         bool done = false;
1379
1380         /*
1381          * If dentry is negative, then lower is positive iff this is a
1382          * whiteout.
1383          */
1384         if (!dentry->d_inode)
1385                 return ovl_dentry_is_opaque(dentry);
1386
1387         /* Negative upper -> positive lower */
1388         if (!ovl_dentry_upper(dentry))
1389                 return true;
1390
1391         old_cred = ovl_override_creds(dentry->d_sb);
1392         /* Positive upper -> have to look up lower to see whether it exists */
1393         for (i = 0; !done && !positive && i < ovl_numlower(poe); i++) {
1394                 struct dentry *this;
1395                 struct ovl_path *parentpath = &ovl_lowerstack(poe)[i];
1396
1397                 this = lookup_one_positive_unlocked(
1398                                 mnt_idmap(parentpath->layer->mnt),
1399                                 name->name, parentpath->dentry, name->len);
1400                 if (IS_ERR(this)) {
1401                         switch (PTR_ERR(this)) {
1402                         case -ENOENT:
1403                         case -ENAMETOOLONG:
1404                                 break;
1405
1406                         default:
1407                                 /*
1408                                  * Assume something is there, we just couldn't
1409                                  * access it.
1410                                  */
1411                                 positive = true;
1412                                 break;
1413                         }
1414                 } else {
1415                         struct path path = {
1416                                 .dentry = this,
1417                                 .mnt = parentpath->layer->mnt,
1418                         };
1419                         positive = !ovl_path_is_whiteout(OVL_FS(dentry->d_sb), &path);
1420                         done = true;
1421                         dput(this);
1422                 }
1423         }
1424         ovl_revert_creds(old_cred);
1425
1426         return positive;
1427 }