fs/overlayfs/super.c

   1 /*
   2  *
   3  * Copyright (C) 2011 Novell Inc.
   4  *
   5  * This program is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 as published by
   7  * the Free Software Foundation.
   8  */
   9
  10 #include <uapi/linux/magic.h>
  11 #include <linux/fs.h>
  12 #include <linux/namei.h>
  13 #include <linux/xattr.h>
  14 #include <linux/mount.h>
  15 #include <linux/parser.h>
  16 #include <linux/module.h>
  17 #include <linux/statfs.h>
  18 #include <linux/seq_file.h>
  19 #include <linux/posix_acl_xattr.h>
  20 #include "overlayfs.h"
  21 #include "ovl_entry.h"
  22
  23 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
  24 MODULE_DESCRIPTION("Overlay filesystem");
  25 MODULE_LICENSE("GPL");
  26
  27
  28 struct ovl_dir_cache;
  29
  30 #define OVL_MAX_STACK 500
  31
  32 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
  33 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
  34 MODULE_PARM_DESC(ovl_redirect_dir_def,
  35                  "Default to on or off for the redirect_dir feature");
  36
  37 static void ovl_dentry_release(struct dentry *dentry)
  38 {
  39         struct ovl_entry *oe = dentry->d_fsdata;
  40
  41         if (oe) {
  42                 unsigned int i;
  43
  44                 dput(oe->__upperdentry);
  45                 kfree(oe->redirect);
  46                 for (i = 0; i < oe->numlower; i++)
  47                         dput(oe->lowerstack[i].dentry);
  48                 kfree_rcu(oe, rcu);
  49         }
  50 }
  51
  52 static struct dentry *ovl_d_real(struct dentry *dentry,
  53                                  const struct inode *inode,
  54                                  unsigned int open_flags)
  55 {
  56         struct dentry *real;
  57
  58         if (!d_is_reg(dentry)) {
  59                 if (!inode || inode == d_inode(dentry))
  60                         return dentry;
  61                 goto bug;
  62         }
  63
  64         if (d_is_negative(dentry))
  65                 return dentry;
  66
  67         if (open_flags) {
  68                 int err = ovl_open_maybe_copy_up(dentry, open_flags);
  69
  70                 if (err)
  71                         return ERR_PTR(err);
  72         }
  73
  74         real = ovl_dentry_upper(dentry);
  75         if (real && (!inode || inode == d_inode(real)))
  76                 return real;
  77
  78         real = ovl_dentry_lower(dentry);
  79         if (!real)
  80                 goto bug;
  81
  82         /* Handle recursion */
  83         real = d_real(real, inode, open_flags);
  84
  85         if (!inode || inode == d_inode(real))
  86                 return real;
  87 bug:
  88         WARN(1, "ovl_d_real(%pd4, %s:%lu): real dentry not found\n", dentry,
  89              inode ? inode->i_sb->s_id : "NULL", inode ? inode->i_ino : 0);
  90         return dentry;
  91 }
  92
  93 static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
  94 {
  95         struct ovl_entry *oe = dentry->d_fsdata;
  96         unsigned int i;
  97         int ret = 1;
  98
  99         for (i = 0; i < oe->numlower; i++) {
 100                 struct dentry *d = oe->lowerstack[i].dentry;
 101
 102                 if (d->d_flags & DCACHE_OP_REVALIDATE) {
 103                         ret = d->d_op->d_revalidate(d, flags);
 104                         if (ret < 0)
 105                                 return ret;
 106                         if (!ret) {
 107                                 if (!(flags & LOOKUP_RCU))
 108                                         d_invalidate(d);
 109                                 return -ESTALE;
 110                         }
 111                 }
 112         }
 113         return 1;
 114 }
 115
 116 static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
 117 {
 118         struct ovl_entry *oe = dentry->d_fsdata;
 119         unsigned int i;
 120         int ret = 1;
 121
 122         for (i = 0; i < oe->numlower; i++) {
 123                 struct dentry *d = oe->lowerstack[i].dentry;
 124
 125                 if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE) {
 126                         ret = d->d_op->d_weak_revalidate(d, flags);
 127                         if (ret <= 0)
 128                                 break;
 129                 }
 130         }
 131         return ret;
 132 }
 133
 134 static const struct dentry_operations ovl_dentry_operations = {
 135         .d_release = ovl_dentry_release,
 136         .d_real = ovl_d_real,
 137 };
 138
 139 static const struct dentry_operations ovl_reval_dentry_operations = {
 140         .d_release = ovl_dentry_release,
 141         .d_real = ovl_d_real,
 142         .d_revalidate = ovl_dentry_revalidate,
 143         .d_weak_revalidate = ovl_dentry_weak_revalidate,
 144 };
 145
 146 static void ovl_put_super(struct super_block *sb)
 147 {
 148         struct ovl_fs *ufs = sb->s_fs_info;
 149         unsigned i;
 150
 151         dput(ufs->workdir);
 152         mntput(ufs->upper_mnt);
 153         for (i = 0; i < ufs->numlower; i++)
 154                 mntput(ufs->lower_mnt[i]);
 155         kfree(ufs->lower_mnt);
 156
 157         kfree(ufs->config.lowerdir);
 158         kfree(ufs->config.upperdir);
 159         kfree(ufs->config.workdir);
 160         put_cred(ufs->creator_cred);
 161         kfree(ufs);
 162 }
 163
 164 /**
 165  * ovl_statfs
 166  * @sb: The overlayfs super block
 167  * @buf: The struct kstatfs to fill in with stats
 168  *
 169  * Get the filesystem statistics.  As writes always target the upper layer
 170  * filesystem pass the statfs to the upper filesystem (if it exists)
 171  */
 172 static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
 173 {
 174         struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
 175         struct dentry *root_dentry = dentry->d_sb->s_root;
 176         struct path path;
 177         int err;
 178
 179         ovl_path_real(root_dentry, &path);
 180
 181         err = vfs_statfs(&path, buf);
 182         if (!err) {
 183                 buf->f_namelen = ofs->namelen;
 184                 buf->f_type = OVERLAYFS_SUPER_MAGIC;
 185         }
 186
 187         return err;
 188 }
 189
 190 /**
 191  * ovl_show_options
 192  *
 193  * Prints the mount options for a given superblock.
 194  * Returns zero; does not fail.
 195  */
 196 static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 197 {
 198         struct super_block *sb = dentry->d_sb;
 199         struct ovl_fs *ufs = sb->s_fs_info;
 200
 201         seq_show_option(m, "lowerdir", ufs->config.lowerdir);
 202         if (ufs->config.upperdir) {
 203                 seq_show_option(m, "upperdir", ufs->config.upperdir);
 204                 seq_show_option(m, "workdir", ufs->config.workdir);
 205         }
 206         if (ufs->config.default_permissions)
 207                 seq_puts(m, ",default_permissions");
 208         if (ufs->config.redirect_dir != ovl_redirect_dir_def)
 209                 seq_printf(m, ",redirect_dir=%s",
 210                            ufs->config.redirect_dir ? "on" : "off");
 211         return 0;
 212 }
 213
 214 static int ovl_remount(struct super_block *sb, int *flags, char *data)
 215 {
 216         struct ovl_fs *ufs = sb->s_fs_info;
 217
 218         if (!(*flags & MS_RDONLY) && (!ufs->upper_mnt || !ufs->workdir))
 219                 return -EROFS;
 220
 221         return 0;
 222 }
 223
 224 static const struct super_operations ovl_super_operations = {
 225         .put_super      = ovl_put_super,
 226         .statfs         = ovl_statfs,
 227         .show_options   = ovl_show_options,
 228         .remount_fs     = ovl_remount,
 229         .drop_inode     = generic_delete_inode,
 230 };
 231
 232 enum {
 233         OPT_LOWERDIR,
 234         OPT_UPPERDIR,
 235         OPT_WORKDIR,
 236         OPT_DEFAULT_PERMISSIONS,
 237         OPT_REDIRECT_DIR_ON,
 238         OPT_REDIRECT_DIR_OFF,
 239         OPT_ERR,
 240 };
 241
 242 static const match_table_t ovl_tokens = {
 243         {OPT_LOWERDIR,                  "lowerdir=%s"},
 244         {OPT_UPPERDIR,                  "upperdir=%s"},
 245         {OPT_WORKDIR,                   "workdir=%s"},
 246         {OPT_DEFAULT_PERMISSIONS,       "default_permissions"},
 247         {OPT_REDIRECT_DIR_ON,           "redirect_dir=on"},
 248         {OPT_REDIRECT_DIR_OFF,          "redirect_dir=off"},
 249         {OPT_ERR,                       NULL}
 250 };
 251
 252 static char *ovl_next_opt(char **s)
 253 {
 254         char *sbegin = *s;
 255         char *p;
 256
 257         if (sbegin == NULL)
 258                 return NULL;
 259
 260         for (p = sbegin; *p; p++) {
 261                 if (*p == '\\') {
 262                         p++;
 263                         if (!*p)
 264                                 break;
 265                 } else if (*p == ',') {
 266                         *p = '\0';
 267                         *s = p + 1;
 268                         return sbegin;
 269                 }
 270         }
 271         *s = NULL;
 272         return sbegin;
 273 }
 274
 275 static int ovl_parse_opt(char *opt, struct ovl_config *config)
 276 {
 277         char *p;
 278
 279         while ((p = ovl_next_opt(&opt)) != NULL) {
 280                 int token;
 281                 substring_t args[MAX_OPT_ARGS];
 282
 283                 if (!*p)
 284                         continue;
 285
 286                 token = match_token(p, ovl_tokens, args);
 287                 switch (token) {
 288                 case OPT_UPPERDIR:
 289                         kfree(config->upperdir);
 290                         config->upperdir = match_strdup(&args[0]);
 291                         if (!config->upperdir)
 292                                 return -ENOMEM;
 293                         break;
 294
 295                 case OPT_LOWERDIR:
 296                         kfree(config->lowerdir);
 297                         config->lowerdir = match_strdup(&args[0]);
 298                         if (!config->lowerdir)
 299                                 return -ENOMEM;
 300                         break;
 301
 302                 case OPT_WORKDIR:
 303                         kfree(config->workdir);
 304                         config->workdir = match_strdup(&args[0]);
 305                         if (!config->workdir)
 306                                 return -ENOMEM;
 307                         break;
 308
 309                 case OPT_DEFAULT_PERMISSIONS:
 310                         config->default_permissions = true;
 311                         break;
 312
 313                 case OPT_REDIRECT_DIR_ON:
 314                         config->redirect_dir = true;
 315                         break;
 316
 317                 case OPT_REDIRECT_DIR_OFF:
 318                         config->redirect_dir = false;
 319                         break;
 320
 321                 default:
 322                         pr_err("overlayfs: unrecognized mount option \"%s\" or missing value\n", p);
 323                         return -EINVAL;
 324                 }
 325         }
 326
 327         /* Workdir is useless in non-upper mount */
 328         if (!config->upperdir && config->workdir) {
 329                 pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 330                         config->workdir);
 331                 kfree(config->workdir);
 332                 config->workdir = NULL;
 333         }
 334
 335         return 0;
 336 }
 337
 338 #define OVL_WORKDIR_NAME "work"
 339
 340 static struct dentry *ovl_workdir_create(struct vfsmount *mnt,
 341                                          struct dentry *dentry)
 342 {
 343         struct inode *dir = dentry->d_inode;
 344         struct dentry *work;
 345         int err;
 346         bool retried = false;
 347
 348         err = mnt_want_write(mnt);
 349         if (err)
 350                 return ERR_PTR(err);
 351
 352         inode_lock_nested(dir, I_MUTEX_PARENT);
 353 retry:
 354         work = lookup_one_len(OVL_WORKDIR_NAME, dentry,
 355                               strlen(OVL_WORKDIR_NAME));
 356
 357         if (!IS_ERR(work)) {
 358                 struct iattr attr = {
 359                         .ia_valid = ATTR_MODE,
 360                         .ia_mode = S_IFDIR | 0,
 361                 };
 362
 363                 if (work->d_inode) {
 364                         err = -EEXIST;
 365                         if (retried)
 366                                 goto out_dput;
 367
 368                         retried = true;
 369                         ovl_workdir_cleanup(dir, mnt, work, 0);
 370                         dput(work);
 371                         goto retry;
 372                 }
 373
 374                 err = ovl_create_real(dir, work,
 375                                       &(struct cattr){.mode = S_IFDIR | 0},
 376                                       NULL, true);
 377                 if (err)
 378                         goto out_dput;
 379
 380                 /*
 381                  * Try to remove POSIX ACL xattrs from workdir.  We are good if:
 382                  *
 383                  * a) success (there was a POSIX ACL xattr and was removed)
 384                  * b) -ENODATA (there was no POSIX ACL xattr)
 385                  * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
 386                  *
 387                  * There are various other error values that could effectively
 388                  * mean that the xattr doesn't exist (e.g. -ERANGE is returned
 389                  * if the xattr name is too long), but the set of filesystems
 390                  * allowed as upper are limited to "normal" ones, where checking
 391                  * for the above two errors is sufficient.
 392                  */
 393                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_DEFAULT);
 394                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 395                         goto out_dput;
 396
 397                 err = vfs_removexattr(work, XATTR_NAME_POSIX_ACL_ACCESS);
 398                 if (err && err != -ENODATA && err != -EOPNOTSUPP)
 399                         goto out_dput;
 400
 401                 /* Clear any inherited mode bits */
 402                 inode_lock(work->d_inode);
 403                 err = notify_change(work, &attr, NULL);
 404                 inode_unlock(work->d_inode);
 405                 if (err)
 406                         goto out_dput;
 407         }
 408 out_unlock:
 409         inode_unlock(dir);
 410         mnt_drop_write(mnt);
 411
 412         return work;
 413
 414 out_dput:
 415         dput(work);
 416         work = ERR_PTR(err);
 417         goto out_unlock;
 418 }
 419
 420 static void ovl_unescape(char *s)
 421 {
 422         char *d = s;
 423
 424         for (;; s++, d++) {
 425                 if (*s == '\\')
 426                         s++;
 427                 *d = *s;
 428                 if (!*s)
 429                         break;
 430         }
 431 }
 432
 433 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 434 {
 435         int err = -EINVAL;
 436
 437         if (!*name) {
 438                 pr_err("overlayfs: empty lowerdir\n");
 439                 goto out;
 440         }
 441         err = kern_path(name, LOOKUP_FOLLOW, path);
 442         if (err) {
 443                 pr_err("overlayfs: failed to resolve '%s': %i\n", name, err);
 444                 goto out;
 445         }
 446         err = -EINVAL;
 447         if (ovl_dentry_weird(path->dentry)) {
 448                 pr_err("overlayfs: filesystem on '%s' not supported\n", name);
 449                 goto out_put;
 450         }
 451         if (!d_is_dir(path->dentry)) {
 452                 pr_err("overlayfs: '%s' not a directory\n", name);
 453                 goto out_put;
 454         }
 455         return 0;
 456
 457 out_put:
 458         path_put(path);
 459 out:
 460         return err;
 461 }
 462
 463 static int ovl_mount_dir(const char *name, struct path *path)
 464 {
 465         int err = -ENOMEM;
 466         char *tmp = kstrdup(name, GFP_KERNEL);
 467
 468         if (tmp) {
 469                 ovl_unescape(tmp);
 470                 err = ovl_mount_dir_noesc(tmp, path);
 471
 472                 if (!err)
 473                         if (ovl_dentry_remote(path->dentry)) {
 474                                 pr_err("overlayfs: filesystem on '%s' not supported as upperdir\n",
 475                                        tmp);
 476                                 path_put(path);
 477                                 err = -EINVAL;
 478                         }
 479                 kfree(tmp);
 480         }
 481         return err;
 482 }
 483
 484 static int ovl_check_namelen(struct path *path, struct ovl_fs *ofs,
 485                              const char *name)
 486 {
 487         struct kstatfs statfs;
 488         int err = vfs_statfs(path, &statfs);
 489
 490         if (err)
 491                 pr_err("overlayfs: statfs failed on '%s'\n", name);
 492         else
 493                 ofs->namelen = max(ofs->namelen, statfs.f_namelen);
 494
 495         return err;
 496 }
 497
 498 static int ovl_lower_dir(const char *name, struct path *path,
 499                          struct ovl_fs *ofs, int *stack_depth, bool *remote)
 500 {
 501         int err;
 502
 503         err = ovl_mount_dir_noesc(name, path);
 504         if (err)
 505                 goto out;
 506
 507         err = ovl_check_namelen(path, ofs, name);
 508         if (err)
 509                 goto out_put;
 510
 511         *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
 512
 513         if (ovl_dentry_remote(path->dentry))
 514                 *remote = true;
 515
 516         return 0;
 517
 518 out_put:
 519         path_put(path);
 520 out:
 521         return err;
 522 }
 523
 524 /* Workdir should not be subdir of upperdir and vice versa */
 525 static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
 526 {
 527         bool ok = false;
 528
 529         if (workdir != upperdir) {
 530                 ok = (lock_rename(workdir, upperdir) == NULL);
 531                 unlock_rename(workdir, upperdir);
 532         }
 533         return ok;
 534 }
 535
 536 static unsigned int ovl_split_lowerdirs(char *str)
 537 {
 538         unsigned int ctr = 1;
 539         char *s, *d;
 540
 541         for (s = d = str;; s++, d++) {
 542                 if (*s == '\\') {
 543                         s++;
 544                 } else if (*s == ':') {
 545                         *d = '\0';
 546                         ctr++;
 547                         continue;
 548                 }
 549                 *d = *s;
 550                 if (!*s)
 551                         break;
 552         }
 553         return ctr;
 554 }
 555
 556 static int __maybe_unused
 557 ovl_posix_acl_xattr_get(const struct xattr_handler *handler,
 558                         struct dentry *dentry, struct inode *inode,
 559                         const char *name, void *buffer, size_t size)
 560 {
 561         return ovl_xattr_get(dentry, handler->name, buffer, size);
 562 }
 563
 564 static int __maybe_unused
 565 ovl_posix_acl_xattr_set(const struct xattr_handler *handler,
 566                         struct dentry *dentry, struct inode *inode,
 567                         const char *name, const void *value,
 568                         size_t size, int flags)
 569 {
 570         struct dentry *workdir = ovl_workdir(dentry);
 571         struct inode *realinode = ovl_inode_real(inode, NULL);
 572         struct posix_acl *acl = NULL;
 573         int err;
 574
 575         /* Check that everything is OK before copy-up */
 576         if (value) {
 577                 acl = posix_acl_from_xattr(&init_user_ns, value, size);
 578                 if (IS_ERR(acl))
 579                         return PTR_ERR(acl);
 580         }
 581         err = -EOPNOTSUPP;
 582         if (!IS_POSIXACL(d_inode(workdir)))
 583                 goto out_acl_release;
 584         if (!realinode->i_op->set_acl)
 585                 goto out_acl_release;
 586         if (handler->flags == ACL_TYPE_DEFAULT && !S_ISDIR(inode->i_mode)) {
 587                 err = acl ? -EACCES : 0;
 588                 goto out_acl_release;
 589         }
 590         err = -EPERM;
 591         if (!inode_owner_or_capable(inode))
 592                 goto out_acl_release;
 593
 594         posix_acl_release(acl);
 595
 596         /*
 597          * Check if sgid bit needs to be cleared (actual setacl operation will
 598          * be done with mounter's capabilities and so that won't do it for us).
 599          */
 600         if (unlikely(inode->i_mode & S_ISGID) &&
 601             handler->flags == ACL_TYPE_ACCESS &&
 602             !in_group_p(inode->i_gid) &&
 603             !capable_wrt_inode_uidgid(inode, CAP_FSETID)) {
 604                 struct iattr iattr = { .ia_valid = ATTR_KILL_SGID };
 605
 606                 err = ovl_setattr(dentry, &iattr);
 607                 if (err)
 608                         return err;
 609         }
 610
 611         err = ovl_xattr_set(dentry, handler->name, value, size, flags);
 612         if (!err)
 613                 ovl_copyattr(ovl_inode_real(inode, NULL), inode);
 614
 615         return err;
 616
 617 out_acl_release:
 618         posix_acl_release(acl);
 619         return err;
 620 }
 621
 622 static int ovl_own_xattr_get(const struct xattr_handler *handler,
 623                              struct dentry *dentry, struct inode *inode,
 624                              const char *name, void *buffer, size_t size)
 625 {
 626         return -EOPNOTSUPP;
 627 }
 628
 629 static int ovl_own_xattr_set(const struct xattr_handler *handler,
 630                              struct dentry *dentry, struct inode *inode,
 631                              const char *name, const void *value,
 632                              size_t size, int flags)
 633 {
 634         return -EOPNOTSUPP;
 635 }
 636
 637 static int ovl_other_xattr_get(const struct xattr_handler *handler,
 638                                struct dentry *dentry, struct inode *inode,
 639                                const char *name, void *buffer, size_t size)
 640 {
 641         return ovl_xattr_get(dentry, name, buffer, size);
 642 }
 643
 644 static int ovl_other_xattr_set(const struct xattr_handler *handler,
 645                                struct dentry *dentry, struct inode *inode,
 646                                const char *name, const void *value,
 647                                size_t size, int flags)
 648 {
 649         return ovl_xattr_set(dentry, name, value, size, flags);
 650 }
 651
 652 static const struct xattr_handler __maybe_unused
 653 ovl_posix_acl_access_xattr_handler = {
 654         .name = XATTR_NAME_POSIX_ACL_ACCESS,
 655         .flags = ACL_TYPE_ACCESS,
 656         .get = ovl_posix_acl_xattr_get,
 657         .set = ovl_posix_acl_xattr_set,
 658 };
 659
 660 static const struct xattr_handler __maybe_unused
 661 ovl_posix_acl_default_xattr_handler = {
 662         .name = XATTR_NAME_POSIX_ACL_DEFAULT,
 663         .flags = ACL_TYPE_DEFAULT,
 664         .get = ovl_posix_acl_xattr_get,
 665         .set = ovl_posix_acl_xattr_set,
 666 };
 667
 668 static const struct xattr_handler ovl_own_xattr_handler = {
 669         .prefix = OVL_XATTR_PREFIX,
 670         .get = ovl_own_xattr_get,
 671         .set = ovl_own_xattr_set,
 672 };
 673
 674 static const struct xattr_handler ovl_other_xattr_handler = {
 675         .prefix = "", /* catch all */
 676         .get = ovl_other_xattr_get,
 677         .set = ovl_other_xattr_set,
 678 };
 679
 680 static const struct xattr_handler *ovl_xattr_handlers[] = {
 681 #ifdef CONFIG_FS_POSIX_ACL
 682         &ovl_posix_acl_access_xattr_handler,
 683         &ovl_posix_acl_default_xattr_handler,
 684 #endif
 685         &ovl_own_xattr_handler,
 686         &ovl_other_xattr_handler,
 687         NULL
 688 };
 689
 690 static int ovl_fill_super(struct super_block *sb, void *data, int silent)
 691 {
 692         struct path upperpath = { NULL, NULL };
 693         struct path workpath = { NULL, NULL };
 694         struct dentry *root_dentry;
 695         struct inode *realinode;
 696         struct ovl_entry *oe;
 697         struct ovl_fs *ufs;
 698         struct path *stack = NULL;
 699         char *lowertmp;
 700         char *lower;
 701         unsigned int numlower;
 702         unsigned int stacklen = 0;
 703         unsigned int i;
 704         bool remote = false;
 705         int err;
 706
 707         err = -ENOMEM;
 708         ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
 709         if (!ufs)
 710                 goto out;
 711
 712         ufs->config.redirect_dir = ovl_redirect_dir_def;
 713         err = ovl_parse_opt((char *) data, &ufs->config);
 714         if (err)
 715                 goto out_free_config;
 716
 717         err = -EINVAL;
 718         if (!ufs->config.lowerdir) {
 719                 if (!silent)
 720                         pr_err("overlayfs: missing 'lowerdir'\n");
 721                 goto out_free_config;
 722         }
 723
 724         sb->s_stack_depth = 0;
 725         sb->s_maxbytes = MAX_LFS_FILESIZE;
 726         if (ufs->config.upperdir) {
 727                 if (!ufs->config.workdir) {
 728                         pr_err("overlayfs: missing 'workdir'\n");
 729                         goto out_free_config;
 730                 }
 731
 732                 err = ovl_mount_dir(ufs->config.upperdir, &upperpath);
 733                 if (err)
 734                         goto out_free_config;
 735
 736                 /* Upper fs should not be r/o */
 737                 if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {
 738                         pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");
 739                         err = -EINVAL;
 740                         goto out_put_upperpath;
 741                 }
 742
 743                 err = ovl_check_namelen(&upperpath, ufs, ufs->config.upperdir);
 744                 if (err)
 745                         goto out_put_upperpath;
 746
 747                 err = ovl_mount_dir(ufs->config.workdir, &workpath);
 748                 if (err)
 749                         goto out_put_upperpath;
 750
 751                 err = -EINVAL;
 752                 if (upperpath.mnt != workpath.mnt) {
 753                         pr_err("overlayfs: workdir and upperdir must reside under the same mount\n");
 754                         goto out_put_workpath;
 755                 }
 756                 if (!ovl_workdir_ok(workpath.dentry, upperpath.dentry)) {
 757                         pr_err("overlayfs: workdir and upperdir must be separate subtrees\n");
 758                         goto out_put_workpath;
 759                 }
 760                 sb->s_stack_depth = upperpath.mnt->mnt_sb->s_stack_depth;
 761         }
 762         err = -ENOMEM;
 763         lowertmp = kstrdup(ufs->config.lowerdir, GFP_KERNEL);
 764         if (!lowertmp)
 765                 goto out_put_workpath;
 766
 767         err = -EINVAL;
 768         stacklen = ovl_split_lowerdirs(lowertmp);
 769         if (stacklen > OVL_MAX_STACK) {
 770                 pr_err("overlayfs: too many lower directories, limit is %d\n",
 771                        OVL_MAX_STACK);
 772                 goto out_free_lowertmp;
 773         } else if (!ufs->config.upperdir && stacklen == 1) {
 774                 pr_err("overlayfs: at least 2 lowerdir are needed while upperdir nonexistent\n");
 775                 goto out_free_lowertmp;
 776         }
 777
 778         err = -ENOMEM;
 779         stack = kcalloc(stacklen, sizeof(struct path), GFP_KERNEL);
 780         if (!stack)
 781                 goto out_free_lowertmp;
 782
 783         err = -EINVAL;
 784         lower = lowertmp;
 785         for (numlower = 0; numlower < stacklen; numlower++) {
 786                 err = ovl_lower_dir(lower, &stack[numlower], ufs,
 787                                     &sb->s_stack_depth, &remote);
 788                 if (err)
 789                         goto out_put_lowerpath;
 790
 791                 lower = strchr(lower, '\0') + 1;
 792         }
 793
 794         err = -EINVAL;
 795         sb->s_stack_depth++;
 796         if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
 797                 pr_err("overlayfs: maximum fs stacking depth exceeded\n");
 798                 goto out_put_lowerpath;
 799         }
 800
 801         if (ufs->config.upperdir) {
 802                 ufs->upper_mnt = clone_private_mount(&upperpath);
 803                 err = PTR_ERR(ufs->upper_mnt);
 804                 if (IS_ERR(ufs->upper_mnt)) {
 805                         pr_err("overlayfs: failed to clone upperpath\n");
 806                         goto out_put_lowerpath;
 807                 }
 808                 /* Don't inherit atime flags */
 809                 ufs->upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
 810
 811                 sb->s_time_gran = ufs->upper_mnt->mnt_sb->s_time_gran;
 812
 813                 ufs->workdir = ovl_workdir_create(ufs->upper_mnt, workpath.dentry);
 814                 err = PTR_ERR(ufs->workdir);
 815                 if (IS_ERR(ufs->workdir)) {
 816                         pr_warn("overlayfs: failed to create directory %s/%s (errno: %i); mounting read-only\n",
 817                                 ufs->config.workdir, OVL_WORKDIR_NAME, -err);
 818                         sb->s_flags |= MS_RDONLY;
 819                         ufs->workdir = NULL;
 820                 }
 821
 822                 /*
 823                  * Upper should support d_type, else whiteouts are visible.
 824                  * Given workdir and upper are on same fs, we can do
 825                  * iterate_dir() on workdir. This check requires successful
 826                  * creation of workdir in previous step.
 827                  */
 828                 if (ufs->workdir) {
 829                         err = ovl_check_d_type_supported(&workpath);
 830                         if (err < 0)
 831                                 goto out_put_workdir;
 832
 833                         /*
 834                          * We allowed this configuration and don't want to
 835                          * break users over kernel upgrade. So warn instead
 836                          * of erroring out.
 837                          */
 838                         if (!err)
 839                                 pr_warn("overlayfs: upper fs needs to support d_type.\n");
 840                 }
 841         }
 842
 843         err = -ENOMEM;
 844         ufs->lower_mnt = kcalloc(numlower, sizeof(struct vfsmount *), GFP_KERNEL);
 845         if (ufs->lower_mnt == NULL)
 846                 goto out_put_workdir;
 847         for (i = 0; i < numlower; i++) {
 848                 struct vfsmount *mnt = clone_private_mount(&stack[i]);
 849
 850                 err = PTR_ERR(mnt);
 851                 if (IS_ERR(mnt)) {
 852                         pr_err("overlayfs: failed to clone lowerpath\n");
 853                         goto out_put_lower_mnt;
 854                 }
 855                 /*
 856                  * Make lower_mnt R/O.  That way fchmod/fchown on lower file
 857                  * will fail instead of modifying lower fs.
 858                  */
 859                 mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
 860
 861                 ufs->lower_mnt[ufs->numlower] = mnt;
 862                 ufs->numlower++;
 863         }
 864
 865         /* If the upper fs is nonexistent, we mark overlayfs r/o too */
 866         if (!ufs->upper_mnt)
 867                 sb->s_flags |= MS_RDONLY;
 868
 869         if (remote)
 870                 sb->s_d_op = &ovl_reval_dentry_operations;
 871         else
 872                 sb->s_d_op = &ovl_dentry_operations;
 873
 874         ufs->creator_cred = prepare_creds();
 875         if (!ufs->creator_cred)
 876                 goto out_put_lower_mnt;
 877
 878         err = -ENOMEM;
 879         oe = ovl_alloc_entry(numlower);
 880         if (!oe)
 881                 goto out_put_cred;
 882
 883         sb->s_magic = OVERLAYFS_SUPER_MAGIC;
 884         sb->s_op = &ovl_super_operations;
 885         sb->s_xattr = ovl_xattr_handlers;
 886         sb->s_fs_info = ufs;
 887         sb->s_flags |= MS_POSIXACL | MS_NOREMOTELOCK;
 888
 889         root_dentry = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
 890         if (!root_dentry)
 891                 goto out_free_oe;
 892
 893         mntput(upperpath.mnt);
 894         for (i = 0; i < numlower; i++)
 895                 mntput(stack[i].mnt);
 896         path_put(&workpath);
 897         kfree(lowertmp);
 898
 899         oe->__upperdentry = upperpath.dentry;
 900         for (i = 0; i < numlower; i++) {
 901                 oe->lowerstack[i].dentry = stack[i].dentry;
 902                 oe->lowerstack[i].mnt = ufs->lower_mnt[i];
 903         }
 904         kfree(stack);
 905
 906         root_dentry->d_fsdata = oe;
 907
 908         realinode = d_inode(ovl_dentry_real(root_dentry));
 909         ovl_inode_init(d_inode(root_dentry), realinode, !!upperpath.dentry);
 910         ovl_copyattr(realinode, d_inode(root_dentry));
 911
 912         sb->s_root = root_dentry;
 913
 914         return 0;
 915
 916 out_free_oe:
 917         kfree(oe);
 918 out_put_cred:
 919         put_cred(ufs->creator_cred);
 920 out_put_lower_mnt:
 921         for (i = 0; i < ufs->numlower; i++)
 922                 mntput(ufs->lower_mnt[i]);
 923         kfree(ufs->lower_mnt);
 924 out_put_workdir:
 925         dput(ufs->workdir);
 926         mntput(ufs->upper_mnt);
 927 out_put_lowerpath:
 928         for (i = 0; i < numlower; i++)
 929                 path_put(&stack[i]);
 930         kfree(stack);
 931 out_free_lowertmp:
 932         kfree(lowertmp);
 933 out_put_workpath:
 934         path_put(&workpath);
 935 out_put_upperpath:
 936         path_put(&upperpath);
 937 out_free_config:
 938         kfree(ufs->config.lowerdir);
 939         kfree(ufs->config.upperdir);
 940         kfree(ufs->config.workdir);
 941         kfree(ufs);
 942 out:
 943         return err;
 944 }
 945
 946 static struct dentry *ovl_mount(struct file_system_type *fs_type, int flags,
 947                                 const char *dev_name, void *raw_data)
 948 {
 949         return mount_nodev(fs_type, flags, raw_data, ovl_fill_super);
 950 }
 951
 952 static struct file_system_type ovl_fs_type = {
 953         .owner          = THIS_MODULE,
 954         .name           = "overlay",
 955         .mount          = ovl_mount,
 956         .kill_sb        = kill_anon_super,
 957 };
 958 MODULE_ALIAS_FS("overlay");
 959
 960 static int __init ovl_init(void)
 961 {
 962         return register_filesystem(&ovl_fs_type);
 963 }
 964
 965 static void __exit ovl_exit(void)
 966 {
 967         unregister_filesystem(&ovl_fs_type);
 968 }
 969
 970 module_init(ovl_init);
 971 module_exit(ovl_exit);