fs/overlayfs/params.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 #include <linux/fs.h>
   4 #include <linux/module.h>
   5 #include <linux/namei.h>
   6 #include <linux/fs_context.h>
   7 #include <linux/fs_parser.h>
   8 #include <linux/posix_acl_xattr.h>
   9 #include <linux/seq_file.h>
  10 #include <linux/xattr.h>
  11 #include "overlayfs.h"
  12 #include "params.h"
  13
  14 static bool ovl_redirect_dir_def = IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_DIR);
  15 module_param_named(redirect_dir, ovl_redirect_dir_def, bool, 0644);
  16 MODULE_PARM_DESC(redirect_dir,
  17                  "Default to on or off for the redirect_dir feature");
  18
  19 static bool ovl_redirect_always_follow =
  20         IS_ENABLED(CONFIG_OVERLAY_FS_REDIRECT_ALWAYS_FOLLOW);
  21 module_param_named(redirect_always_follow, ovl_redirect_always_follow,
  22                    bool, 0644);
  23 MODULE_PARM_DESC(redirect_always_follow,
  24                  "Follow redirects even if redirect_dir feature is turned off");
  25
  26 static bool ovl_xino_auto_def = IS_ENABLED(CONFIG_OVERLAY_FS_XINO_AUTO);
  27 module_param_named(xino_auto, ovl_xino_auto_def, bool, 0644);
  28 MODULE_PARM_DESC(xino_auto,
  29                  "Auto enable xino feature");
  30
  31 static bool ovl_index_def = IS_ENABLED(CONFIG_OVERLAY_FS_INDEX);
  32 module_param_named(index, ovl_index_def, bool, 0644);
  33 MODULE_PARM_DESC(index,
  34                  "Default to on or off for the inodes index feature");
  35
  36 static bool ovl_nfs_export_def = IS_ENABLED(CONFIG_OVERLAY_FS_NFS_EXPORT);
  37 module_param_named(nfs_export, ovl_nfs_export_def, bool, 0644);
  38 MODULE_PARM_DESC(nfs_export,
  39                  "Default to on or off for the NFS export feature");
  40
  41 static bool ovl_metacopy_def = IS_ENABLED(CONFIG_OVERLAY_FS_METACOPY);
  42 module_param_named(metacopy, ovl_metacopy_def, bool, 0644);
  43 MODULE_PARM_DESC(metacopy,
  44                  "Default to on or off for the metadata only copy up feature");
  45
  46 enum ovl_opt {
  47         Opt_lowerdir,
  48         Opt_lowerdir_add,
  49         Opt_datadir_add,
  50         Opt_upperdir,
  51         Opt_workdir,
  52         Opt_default_permissions,
  53         Opt_redirect_dir,
  54         Opt_index,
  55         Opt_uuid,
  56         Opt_nfs_export,
  57         Opt_userxattr,
  58         Opt_xino,
  59         Opt_metacopy,
  60         Opt_verity,
  61         Opt_volatile,
  62 };
  63
  64 static const struct constant_table ovl_parameter_bool[] = {
  65         { "on",         true  },
  66         { "off",        false },
  67         {}
  68 };
  69
  70 static const struct constant_table ovl_parameter_uuid[] = {
  71         { "off",        OVL_UUID_OFF  },
  72         { "null",       OVL_UUID_NULL },
  73         { "auto",       OVL_UUID_AUTO },
  74         { "on",         OVL_UUID_ON   },
  75         {}
  76 };
  77
  78 static const char *ovl_uuid_mode(struct ovl_config *config)
  79 {
  80         return ovl_parameter_uuid[config->uuid].name;
  81 }
  82
  83 static int ovl_uuid_def(void)
  84 {
  85         return OVL_UUID_AUTO;
  86 }
  87
  88 static const struct constant_table ovl_parameter_xino[] = {
  89         { "off",        OVL_XINO_OFF  },
  90         { "auto",       OVL_XINO_AUTO },
  91         { "on",         OVL_XINO_ON   },
  92         {}
  93 };
  94
  95 const char *ovl_xino_mode(struct ovl_config *config)
  96 {
  97         return ovl_parameter_xino[config->xino].name;
  98 }
  99
 100 static int ovl_xino_def(void)
 101 {
 102         return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
 103 }
 104
 105 const struct constant_table ovl_parameter_redirect_dir[] = {
 106         { "off",        OVL_REDIRECT_OFF      },
 107         { "follow",     OVL_REDIRECT_FOLLOW   },
 108         { "nofollow",   OVL_REDIRECT_NOFOLLOW },
 109         { "on",         OVL_REDIRECT_ON       },
 110         {}
 111 };
 112
 113 static const char *ovl_redirect_mode(struct ovl_config *config)
 114 {
 115         return ovl_parameter_redirect_dir[config->redirect_mode].name;
 116 }
 117
 118 static int ovl_redirect_mode_def(void)
 119 {
 120         return ovl_redirect_dir_def       ? OVL_REDIRECT_ON :
 121                ovl_redirect_always_follow ? OVL_REDIRECT_FOLLOW :
 122                                             OVL_REDIRECT_NOFOLLOW;
 123 }
 124
 125 static const struct constant_table ovl_parameter_verity[] = {
 126         { "off",        OVL_VERITY_OFF     },
 127         { "on",         OVL_VERITY_ON      },
 128         { "require",    OVL_VERITY_REQUIRE },
 129         {}
 130 };
 131
 132 static const char *ovl_verity_mode(struct ovl_config *config)
 133 {
 134         return ovl_parameter_verity[config->verity_mode].name;
 135 }
 136
 137 static int ovl_verity_mode_def(void)
 138 {
 139         return OVL_VERITY_OFF;
 140 }
 141
 142 #define fsparam_string_empty(NAME, OPT) \
 143         __fsparam(fs_param_is_string, NAME, OPT, fs_param_can_be_empty, NULL)
 144
 145
 146 const struct fs_parameter_spec ovl_parameter_spec[] = {
 147         fsparam_string_empty("lowerdir",    Opt_lowerdir),
 148         fsparam_string("lowerdir+",         Opt_lowerdir_add),
 149         fsparam_string("datadir+",          Opt_datadir_add),
 150         fsparam_string("upperdir",          Opt_upperdir),
 151         fsparam_string("workdir",           Opt_workdir),
 152         fsparam_flag("default_permissions", Opt_default_permissions),
 153         fsparam_enum("redirect_dir",        Opt_redirect_dir, ovl_parameter_redirect_dir),
 154         fsparam_enum("index",               Opt_index, ovl_parameter_bool),
 155         fsparam_enum("uuid",                Opt_uuid, ovl_parameter_uuid),
 156         fsparam_enum("nfs_export",          Opt_nfs_export, ovl_parameter_bool),
 157         fsparam_flag("userxattr",           Opt_userxattr),
 158         fsparam_enum("xino",                Opt_xino, ovl_parameter_xino),
 159         fsparam_enum("metacopy",            Opt_metacopy, ovl_parameter_bool),
 160         fsparam_enum("verity",              Opt_verity, ovl_parameter_verity),
 161         fsparam_flag("volatile",            Opt_volatile),
 162         {}
 163 };
 164
 165 static char *ovl_next_opt(char **s)
 166 {
 167         char *sbegin = *s;
 168         char *p;
 169
 170         if (sbegin == NULL)
 171                 return NULL;
 172
 173         for (p = sbegin; *p; p++) {
 174                 if (*p == '\\') {
 175                         p++;
 176                         if (!*p)
 177                                 break;
 178                 } else if (*p == ',') {
 179                         *p = '\0';
 180                         *s = p + 1;
 181                         return sbegin;
 182                 }
 183         }
 184         *s = NULL;
 185         return sbegin;
 186 }
 187
 188 static int ovl_parse_monolithic(struct fs_context *fc, void *data)
 189 {
 190         return vfs_parse_monolithic_sep(fc, data, ovl_next_opt);
 191 }
 192
 193 static ssize_t ovl_parse_param_split_lowerdirs(char *str)
 194 {
 195         ssize_t nr_layers = 1, nr_colons = 0;
 196         char *s, *d;
 197
 198         for (s = d = str;; s++, d++) {
 199                 if (*s == '\\') {
 200                         /* keep esc chars in split lowerdir */
 201                         *d++ = *s++;
 202                 } else if (*s == ':') {
 203                         bool next_colon = (*(s + 1) == ':');
 204
 205                         nr_colons++;
 206                         if (nr_colons == 2 && next_colon) {
 207                                 pr_err("only single ':' or double '::' sequences of unescaped colons in lowerdir mount option allowed.\n");
 208                                 return -EINVAL;
 209                         }
 210                         /* count layers, not colons */
 211                         if (!next_colon)
 212                                 nr_layers++;
 213
 214                         *d = '\0';
 215                         continue;
 216                 }
 217
 218                 *d = *s;
 219                 if (!*s) {
 220                         /* trailing colons */
 221                         if (nr_colons) {
 222                                 pr_err("unescaped trailing colons in lowerdir mount option.\n");
 223                                 return -EINVAL;
 224                         }
 225                         break;
 226                 }
 227                 nr_colons = 0;
 228         }
 229
 230         return nr_layers;
 231 }
 232
 233 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 234 {
 235         int err = -EINVAL;
 236
 237         if (!*name) {
 238                 pr_err("empty lowerdir\n");
 239                 goto out;
 240         }
 241         err = kern_path(name, LOOKUP_FOLLOW, path);
 242         if (err) {
 243                 pr_err("failed to resolve '%s': %i\n", name, err);
 244                 goto out;
 245         }
 246         return 0;
 247
 248 out:
 249         return err;
 250 }
 251
 252 static void ovl_unescape(char *s)
 253 {
 254         char *d = s;
 255
 256         for (;; s++, d++) {
 257                 if (*s == '\\')
 258                         s++;
 259                 *d = *s;
 260                 if (!*s)
 261                         break;
 262         }
 263 }
 264
 265 static int ovl_mount_dir(const char *name, struct path *path)
 266 {
 267         int err = -ENOMEM;
 268         char *tmp = kstrdup(name, GFP_KERNEL);
 269
 270         if (tmp) {
 271                 ovl_unescape(tmp);
 272                 err = ovl_mount_dir_noesc(tmp, path);
 273                 kfree(tmp);
 274         }
 275         return err;
 276 }
 277
 278 static int ovl_mount_dir_check(struct fs_context *fc, const struct path *path,
 279                                enum ovl_opt layer, const char *name, bool upper)
 280 {
 281         struct ovl_fs_context *ctx = fc->fs_private;
 282
 283         if (!d_is_dir(path->dentry))
 284                 return invalfc(fc, "%s is not a directory", name);
 285
 286         /*
 287          * Root dentries of case-insensitive capable filesystems might
 288          * not have the dentry operations set, but still be incompatible
 289          * with overlayfs.  Check explicitly to prevent post-mount
 290          * failures.
 291          */
 292         if (sb_has_encoding(path->mnt->mnt_sb))
 293                 return invalfc(fc, "case-insensitive capable filesystem on %s not supported", name);
 294
 295         if (ovl_dentry_weird(path->dentry))
 296                 return invalfc(fc, "filesystem on %s not supported", name);
 297
 298         /*
 299          * Check whether upper path is read-only here to report failures
 300          * early. Don't forget to recheck when the superblock is created
 301          * as the mount attributes could change.
 302          */
 303         if (upper) {
 304                 if (path->dentry->d_flags & DCACHE_OP_REAL)
 305                         return invalfc(fc, "filesystem on %s not supported as upperdir", name);
 306                 if (__mnt_is_readonly(path->mnt))
 307                         return invalfc(fc, "filesystem on %s is read-only", name);
 308         } else {
 309                 if (ctx->lowerdir_all && layer != Opt_lowerdir)
 310                         return invalfc(fc, "lowerdir+ and datadir+ cannot follow lowerdir");
 311                 if (ctx->nr_data && layer == Opt_lowerdir_add)
 312                         return invalfc(fc, "regular lower layers cannot follow data layers");
 313                 if (ctx->nr == OVL_MAX_STACK)
 314                         return invalfc(fc, "too many lower directories, limit is %d",
 315                                        OVL_MAX_STACK);
 316         }
 317         return 0;
 318 }
 319
 320 static int ovl_ctx_realloc_lower(struct fs_context *fc)
 321 {
 322         struct ovl_fs_context *ctx = fc->fs_private;
 323         struct ovl_fs_context_layer *l;
 324         size_t nr;
 325
 326         if (ctx->nr < ctx->capacity)
 327                 return 0;
 328
 329         nr = min_t(size_t, max(4096 / sizeof(*l), ctx->capacity * 2),
 330                    OVL_MAX_STACK);
 331         l = krealloc_array(ctx->lower, nr, sizeof(*l), GFP_KERNEL_ACCOUNT);
 332         if (!l)
 333                 return -ENOMEM;
 334
 335         ctx->lower = l;
 336         ctx->capacity = nr;
 337         return 0;
 338 }
 339
 340 static void ovl_add_layer(struct fs_context *fc, enum ovl_opt layer,
 341                          struct path *path, char **pname)
 342 {
 343         struct ovl_fs *ofs = fc->s_fs_info;
 344         struct ovl_config *config = &ofs->config;
 345         struct ovl_fs_context *ctx = fc->fs_private;
 346         struct ovl_fs_context_layer *l;
 347
 348         switch (layer) {
 349         case Opt_workdir:
 350                 swap(config->workdir, *pname);
 351                 swap(ctx->work, *path);
 352                 break;
 353         case Opt_upperdir:
 354                 swap(config->upperdir, *pname);
 355                 swap(ctx->upper, *path);
 356                 break;
 357         case Opt_datadir_add:
 358                 ctx->nr_data++;
 359                 fallthrough;
 360         case Opt_lowerdir_add:
 361                 WARN_ON(ctx->nr >= ctx->capacity);
 362                 l = &ctx->lower[ctx->nr++];
 363                 memset(l, 0, sizeof(*l));
 364                 swap(l->name, *pname);
 365                 swap(l->path, *path);
 366                 break;
 367         default:
 368                 WARN_ON(1);
 369         }
 370 }
 371
 372 static int ovl_parse_layer(struct fs_context *fc, struct fs_parameter *param,
 373                            enum ovl_opt layer)
 374 {
 375         char *name = kstrdup(param->string, GFP_KERNEL);
 376         bool upper = (layer == Opt_upperdir || layer == Opt_workdir);
 377         struct path path;
 378         int err;
 379
 380         if (!name)
 381                 return -ENOMEM;
 382
 383         if (upper)
 384                 err = ovl_mount_dir(name, &path);
 385         else
 386                 err = ovl_mount_dir_noesc(name, &path);
 387         if (err)
 388                 goto out_free;
 389
 390         err = ovl_mount_dir_check(fc, &path, layer, name, upper);
 391         if (err)
 392                 goto out_put;
 393
 394         if (!upper) {
 395                 err = ovl_ctx_realloc_lower(fc);
 396                 if (err)
 397                         goto out_put;
 398         }
 399
 400         /* Store the user provided path string in ctx to show in mountinfo */
 401         ovl_add_layer(fc, layer, &path, &name);
 402
 403 out_put:
 404         path_put(&path);
 405 out_free:
 406         kfree(name);
 407         return err;
 408 }
 409
 410 static void ovl_reset_lowerdirs(struct ovl_fs_context *ctx)
 411 {
 412         struct ovl_fs_context_layer *l = ctx->lower;
 413
 414         // Reset old user provided lowerdir string
 415         kfree(ctx->lowerdir_all);
 416         ctx->lowerdir_all = NULL;
 417
 418         for (size_t nr = 0; nr < ctx->nr; nr++, l++) {
 419                 path_put(&l->path);
 420                 kfree(l->name);
 421                 l->name = NULL;
 422         }
 423         ctx->nr = 0;
 424         ctx->nr_data = 0;
 425 }
 426
 427 /*
 428  * Parse lowerdir= mount option:
 429  *
 430  * e.g.: lowerdir=/lower1:/lower2:/lower3::/data1::/data2
 431  *     Set "/lower1", "/lower2", and "/lower3" as lower layers and
 432  *     "/data1" and "/data2" as data lower layers. Any existing lower
 433  *     layers are replaced.
 434  */
 435 static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 436 {
 437         int err;
 438         struct ovl_fs_context *ctx = fc->fs_private;
 439         struct ovl_fs_context_layer *l;
 440         char *dup = NULL, *iter;
 441         ssize_t nr_lower, nr;
 442         bool data_layer = false;
 443
 444         /*
 445          * Ensure we're backwards compatible with mount(2)
 446          * by allowing relative paths.
 447          */
 448
 449         /* drop all existing lower layers */
 450         ovl_reset_lowerdirs(ctx);
 451
 452         if (!*name)
 453                 return 0;
 454
 455         if (*name == ':') {
 456                 pr_err("cannot append lower layer");
 457                 return -EINVAL;
 458         }
 459
 460         // Store user provided lowerdir string to show in mount options
 461         ctx->lowerdir_all = kstrdup(name, GFP_KERNEL);
 462         if (!ctx->lowerdir_all)
 463                 return -ENOMEM;
 464
 465         dup = kstrdup(name, GFP_KERNEL);
 466         if (!dup)
 467                 return -ENOMEM;
 468
 469         err = -EINVAL;
 470         nr_lower = ovl_parse_param_split_lowerdirs(dup);
 471         if (nr_lower < 0)
 472                 goto out_err;
 473
 474         if (nr_lower > OVL_MAX_STACK) {
 475                 pr_err("too many lower directories, limit is %d\n", OVL_MAX_STACK);
 476                 goto out_err;
 477         }
 478
 479         if (nr_lower > ctx->capacity) {
 480                 err = -ENOMEM;
 481                 l = krealloc_array(ctx->lower, nr_lower, sizeof(*ctx->lower),
 482                                    GFP_KERNEL_ACCOUNT);
 483                 if (!l)
 484                         goto out_err;
 485
 486                 ctx->lower = l;
 487                 ctx->capacity = nr_lower;
 488         }
 489
 490         iter = dup;
 491         l = ctx->lower;
 492         for (nr = 0; nr < nr_lower; nr++, l++) {
 493                 ctx->nr++;
 494                 memset(l, 0, sizeof(*l));
 495
 496                 err = ovl_mount_dir(iter, &l->path);
 497                 if (err)
 498                         goto out_put;
 499
 500                 err = ovl_mount_dir_check(fc, &l->path, Opt_lowerdir, iter, false);
 501                 if (err)
 502                         goto out_put;
 503
 504                 err = -ENOMEM;
 505                 l->name = kstrdup(iter, GFP_KERNEL_ACCOUNT);
 506                 if (!l->name)
 507                         goto out_put;
 508
 509                 if (data_layer)
 510                         ctx->nr_data++;
 511
 512                 /* Calling strchr() again would overrun. */
 513                 if (ctx->nr == nr_lower)
 514                         break;
 515
 516                 err = -EINVAL;
 517                 iter = strchr(iter, '\0') + 1;
 518                 if (*iter) {
 519                         /*
 520                          * This is a regular layer so we require that
 521                          * there are no data layers.
 522                          */
 523                         if (ctx->nr_data > 0) {
 524                                 pr_err("regular lower layers cannot follow data lower layers");
 525                                 goto out_put;
 526                         }
 527
 528                         data_layer = false;
 529                         continue;
 530                 }
 531
 532                 /* This is a data lower layer. */
 533                 data_layer = true;
 534                 iter++;
 535         }
 536         kfree(dup);
 537         return 0;
 538
 539 out_put:
 540         ovl_reset_lowerdirs(ctx);
 541
 542 out_err:
 543         kfree(dup);
 544
 545         /* Intentionally don't realloc to a smaller size. */
 546         return err;
 547 }
 548
 549 static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
 550 {
 551         int err = 0;
 552         struct fs_parse_result result;
 553         struct ovl_fs *ofs = fc->s_fs_info;
 554         struct ovl_config *config = &ofs->config;
 555         struct ovl_fs_context *ctx = fc->fs_private;
 556         int opt;
 557
 558         if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
 559                 /*
 560                  * On remount overlayfs has always ignored all mount
 561                  * options no matter if malformed or not so for
 562                  * backwards compatibility we do the same here.
 563                  */
 564                 if (fc->oldapi)
 565                         return 0;
 566
 567                 /*
 568                  * Give us the freedom to allow changing mount options
 569                  * with the new mount api in the future. So instead of
 570                  * silently ignoring everything we report a proper
 571                  * error. This is only visible for users of the new
 572                  * mount api.
 573                  */
 574                 return invalfc(fc, "No changes allowed in reconfigure");
 575         }
 576
 577         opt = fs_parse(fc, ovl_parameter_spec, param, &result);
 578         if (opt < 0)
 579                 return opt;
 580
 581         switch (opt) {
 582         case Opt_lowerdir:
 583                 err = ovl_parse_param_lowerdir(param->string, fc);
 584                 break;
 585         case Opt_lowerdir_add:
 586         case Opt_datadir_add:
 587         case Opt_upperdir:
 588         case Opt_workdir:
 589                 err = ovl_parse_layer(fc, param, opt);
 590                 break;
 591         case Opt_default_permissions:
 592                 config->default_permissions = true;
 593                 break;
 594         case Opt_redirect_dir:
 595                 config->redirect_mode = result.uint_32;
 596                 if (config->redirect_mode == OVL_REDIRECT_OFF) {
 597                         config->redirect_mode = ovl_redirect_always_follow ?
 598                                                 OVL_REDIRECT_FOLLOW :
 599                                                 OVL_REDIRECT_NOFOLLOW;
 600                 }
 601                 ctx->set.redirect = true;
 602                 break;
 603         case Opt_index:
 604                 config->index = result.uint_32;
 605                 ctx->set.index = true;
 606                 break;
 607         case Opt_uuid:
 608                 config->uuid = result.uint_32;
 609                 break;
 610         case Opt_nfs_export:
 611                 config->nfs_export = result.uint_32;
 612                 ctx->set.nfs_export = true;
 613                 break;
 614         case Opt_xino:
 615                 config->xino = result.uint_32;
 616                 break;
 617         case Opt_metacopy:
 618                 config->metacopy = result.uint_32;
 619                 ctx->set.metacopy = true;
 620                 break;
 621         case Opt_verity:
 622                 config->verity_mode = result.uint_32;
 623                 break;
 624         case Opt_volatile:
 625                 config->ovl_volatile = true;
 626                 break;
 627         case Opt_userxattr:
 628                 config->userxattr = true;
 629                 break;
 630         default:
 631                 pr_err("unrecognized mount option \"%s\" or missing value\n",
 632                        param->key);
 633                 return -EINVAL;
 634         }
 635
 636         return err;
 637 }
 638
 639 static int ovl_get_tree(struct fs_context *fc)
 640 {
 641         return get_tree_nodev(fc, ovl_fill_super);
 642 }
 643
 644 static inline void ovl_fs_context_free(struct ovl_fs_context *ctx)
 645 {
 646         ovl_reset_lowerdirs(ctx);
 647         path_put(&ctx->upper);
 648         path_put(&ctx->work);
 649         kfree(ctx->lower);
 650         kfree(ctx);
 651 }
 652
 653 static void ovl_free(struct fs_context *fc)
 654 {
 655         struct ovl_fs *ofs = fc->s_fs_info;
 656         struct ovl_fs_context *ctx = fc->fs_private;
 657
 658         /*
 659          * ofs is stored in the fs_context when it is initialized.
 660          * ofs is transferred to the superblock on a successful mount,
 661          * but if an error occurs before the transfer we have to free
 662          * it here.
 663          */
 664         if (ofs)
 665                 ovl_free_fs(ofs);
 666
 667         if (ctx)
 668                 ovl_fs_context_free(ctx);
 669 }
 670
 671 static int ovl_reconfigure(struct fs_context *fc)
 672 {
 673         struct super_block *sb = fc->root->d_sb;
 674         struct ovl_fs *ofs = OVL_FS(sb);
 675         struct super_block *upper_sb;
 676         int ret = 0;
 677
 678         if (!(fc->sb_flags & SB_RDONLY) && ovl_force_readonly(ofs))
 679                 return -EROFS;
 680
 681         if (fc->sb_flags & SB_RDONLY && !sb_rdonly(sb)) {
 682                 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 683                 if (ovl_should_sync(ofs)) {
 684                         down_read(&upper_sb->s_umount);
 685                         ret = sync_filesystem(upper_sb);
 686                         up_read(&upper_sb->s_umount);
 687                 }
 688         }
 689
 690         return ret;
 691 }
 692
 693 static const struct fs_context_operations ovl_context_ops = {
 694         .parse_monolithic = ovl_parse_monolithic,
 695         .parse_param = ovl_parse_param,
 696         .get_tree    = ovl_get_tree,
 697         .reconfigure = ovl_reconfigure,
 698         .free        = ovl_free,
 699 };
 700
 701 /*
 702  * This is called during fsopen() and will record the user namespace of
 703  * the caller in fc->user_ns since we've raised FS_USERNS_MOUNT. We'll
 704  * need it when we actually create the superblock to verify that the
 705  * process creating the superblock is in the same user namespace as
 706  * process that called fsopen().
 707  */
 708 int ovl_init_fs_context(struct fs_context *fc)
 709 {
 710         struct ovl_fs_context *ctx;
 711         struct ovl_fs *ofs;
 712
 713         ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
 714         if (!ctx)
 715                 return -ENOMEM;
 716
 717         /*
 718          * By default we allocate for three lower layers. It's likely
 719          * that it'll cover most users.
 720          */
 721         ctx->lower = kmalloc_array(3, sizeof(*ctx->lower), GFP_KERNEL_ACCOUNT);
 722         if (!ctx->lower)
 723                 goto out_err;
 724         ctx->capacity = 3;
 725
 726         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
 727         if (!ofs)
 728                 goto out_err;
 729
 730         ofs->config.redirect_mode       = ovl_redirect_mode_def();
 731         ofs->config.index               = ovl_index_def;
 732         ofs->config.uuid                = ovl_uuid_def();
 733         ofs->config.nfs_export          = ovl_nfs_export_def;
 734         ofs->config.xino                = ovl_xino_def();
 735         ofs->config.metacopy            = ovl_metacopy_def;
 736
 737         fc->s_fs_info           = ofs;
 738         fc->fs_private          = ctx;
 739         fc->ops                 = &ovl_context_ops;
 740         return 0;
 741
 742 out_err:
 743         ovl_fs_context_free(ctx);
 744         return -ENOMEM;
 745
 746 }
 747
 748 void ovl_free_fs(struct ovl_fs *ofs)
 749 {
 750         struct vfsmount **mounts;
 751         unsigned i;
 752
 753         iput(ofs->workbasedir_trap);
 754         iput(ofs->workdir_trap);
 755         dput(ofs->whiteout);
 756         dput(ofs->workdir);
 757         if (ofs->workdir_locked)
 758                 ovl_inuse_unlock(ofs->workbasedir);
 759         dput(ofs->workbasedir);
 760         if (ofs->upperdir_locked)
 761                 ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
 762
 763         /* Reuse ofs->config.lowerdirs as a vfsmount array before freeing it */
 764         mounts = (struct vfsmount **) ofs->config.lowerdirs;
 765         for (i = 0; i < ofs->numlayer; i++) {
 766                 iput(ofs->layers[i].trap);
 767                 kfree(ofs->config.lowerdirs[i]);
 768                 mounts[i] = ofs->layers[i].mnt;
 769         }
 770         kern_unmount_array(mounts, ofs->numlayer);
 771         kfree(ofs->layers);
 772         for (i = 0; i < ofs->numfs; i++)
 773                 free_anon_bdev(ofs->fs[i].pseudo_dev);
 774         kfree(ofs->fs);
 775
 776         kfree(ofs->config.lowerdirs);
 777         kfree(ofs->config.upperdir);
 778         kfree(ofs->config.workdir);
 779         if (ofs->creator_cred)
 780                 put_cred(ofs->creator_cred);
 781         kfree(ofs);
 782 }
 783
 784 int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
 785                          struct ovl_config *config)
 786 {
 787         struct ovl_opt_set set = ctx->set;
 788
 789         if (ctx->nr_data > 0 && !config->metacopy) {
 790                 pr_err("lower data-only dirs require metacopy support.\n");
 791                 return -EINVAL;
 792         }
 793
 794         /* Workdir/index are useless in non-upper mount */
 795         if (!config->upperdir) {
 796                 if (config->workdir) {
 797                         pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 798                                 config->workdir);
 799                         kfree(config->workdir);
 800                         config->workdir = NULL;
 801                 }
 802                 if (config->index && set.index) {
 803                         pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
 804                         set.index = false;
 805                 }
 806                 config->index = false;
 807         }
 808
 809         if (!config->upperdir && config->ovl_volatile) {
 810                 pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
 811                 config->ovl_volatile = false;
 812         }
 813
 814         if (!config->upperdir && config->uuid == OVL_UUID_ON) {
 815                 pr_info("option \"uuid=on\" requires an upper fs, falling back to uuid=null.\n");
 816                 config->uuid = OVL_UUID_NULL;
 817         }
 818
 819         /* Resolve verity -> metacopy dependency */
 820         if (config->verity_mode && !config->metacopy) {
 821                 /* Don't allow explicit specified conflicting combinations */
 822                 if (set.metacopy) {
 823                         pr_err("conflicting options: metacopy=off,verity=%s\n",
 824                                ovl_verity_mode(config));
 825                         return -EINVAL;
 826                 }
 827                 /* Otherwise automatically enable metacopy. */
 828                 config->metacopy = true;
 829         }
 830
 831         /*
 832          * This is to make the logic below simpler.  It doesn't make any other
 833          * difference, since redirect_dir=on is only used for upper.
 834          */
 835         if (!config->upperdir && config->redirect_mode == OVL_REDIRECT_FOLLOW)
 836                 config->redirect_mode = OVL_REDIRECT_ON;
 837
 838         /* Resolve verity -> metacopy -> redirect_dir dependency */
 839         if (config->metacopy && config->redirect_mode != OVL_REDIRECT_ON) {
 840                 if (set.metacopy && set.redirect) {
 841                         pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
 842                                ovl_redirect_mode(config));
 843                         return -EINVAL;
 844                 }
 845                 if (config->verity_mode && set.redirect) {
 846                         pr_err("conflicting options: verity=%s,redirect_dir=%s\n",
 847                                ovl_verity_mode(config), ovl_redirect_mode(config));
 848                         return -EINVAL;
 849                 }
 850                 if (set.redirect) {
 851                         /*
 852                          * There was an explicit redirect_dir=... that resulted
 853                          * in this conflict.
 854                          */
 855                         pr_info("disabling metacopy due to redirect_dir=%s\n",
 856                                 ovl_redirect_mode(config));
 857                         config->metacopy = false;
 858                 } else {
 859                         /* Automatically enable redirect otherwise. */
 860                         config->redirect_mode = OVL_REDIRECT_ON;
 861                 }
 862         }
 863
 864         /* Resolve nfs_export -> index dependency */
 865         if (config->nfs_export && !config->index) {
 866                 if (!config->upperdir &&
 867                     config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 868                         pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
 869                         config->nfs_export = false;
 870                 } else if (set.nfs_export && set.index) {
 871                         pr_err("conflicting options: nfs_export=on,index=off\n");
 872                         return -EINVAL;
 873                 } else if (set.index) {
 874                         /*
 875                          * There was an explicit index=off that resulted
 876                          * in this conflict.
 877                          */
 878                         pr_info("disabling nfs_export due to index=off\n");
 879                         config->nfs_export = false;
 880                 } else {
 881                         /* Automatically enable index otherwise. */
 882                         config->index = true;
 883                 }
 884         }
 885
 886         /* Resolve nfs_export -> !metacopy && !verity dependency */
 887         if (config->nfs_export && config->metacopy) {
 888                 if (set.nfs_export && set.metacopy) {
 889                         pr_err("conflicting options: nfs_export=on,metacopy=on\n");
 890                         return -EINVAL;
 891                 }
 892                 if (set.metacopy) {
 893                         /*
 894                          * There was an explicit metacopy=on that resulted
 895                          * in this conflict.
 896                          */
 897                         pr_info("disabling nfs_export due to metacopy=on\n");
 898                         config->nfs_export = false;
 899                 } else if (config->verity_mode) {
 900                         /*
 901                          * There was an explicit verity=.. that resulted
 902                          * in this conflict.
 903                          */
 904                         pr_info("disabling nfs_export due to verity=%s\n",
 905                                 ovl_verity_mode(config));
 906                         config->nfs_export = false;
 907                 } else {
 908                         /*
 909                          * There was an explicit nfs_export=on that resulted
 910                          * in this conflict.
 911                          */
 912                         pr_info("disabling metacopy due to nfs_export=on\n");
 913                         config->metacopy = false;
 914                 }
 915         }
 916
 917
 918         /* Resolve userxattr -> !redirect && !metacopy && !verity dependency */
 919         if (config->userxattr) {
 920                 if (set.redirect &&
 921                     config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 922                         pr_err("conflicting options: userxattr,redirect_dir=%s\n",
 923                                ovl_redirect_mode(config));
 924                         return -EINVAL;
 925                 }
 926                 if (config->metacopy && set.metacopy) {
 927                         pr_err("conflicting options: userxattr,metacopy=on\n");
 928                         return -EINVAL;
 929                 }
 930                 if (config->verity_mode) {
 931                         pr_err("conflicting options: userxattr,verity=%s\n",
 932                                ovl_verity_mode(config));
 933                         return -EINVAL;
 934                 }
 935                 /*
 936                  * Silently disable default setting of redirect and metacopy.
 937                  * This shall be the default in the future as well: these
 938                  * options must be explicitly enabled if used together with
 939                  * userxattr.
 940                  */
 941                 config->redirect_mode = OVL_REDIRECT_NOFOLLOW;
 942                 config->metacopy = false;
 943         }
 944
 945         return 0;
 946 }
 947
 948 /**
 949  * ovl_show_options
 950  * @m: the seq_file handle
 951  * @dentry: The dentry to query
 952  *
 953  * Prints the mount options for a given superblock.
 954  * Returns zero; does not fail.
 955  */
 956 int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 957 {
 958         struct super_block *sb = dentry->d_sb;
 959         struct ovl_fs *ofs = OVL_FS(sb);
 960         size_t nr, nr_merged_lower, nr_lower = 0;
 961         char **lowerdirs = ofs->config.lowerdirs;
 962
 963         /*
 964          * lowerdirs[0] holds the colon separated list that user provided
 965          * with lowerdir mount option.
 966          * lowerdirs[1..numlayer] hold the lowerdir paths that were added
 967          * using the lowerdir+ and datadir+ mount options.
 968          * For now, we do not allow mixing the legacy lowerdir mount option
 969          * with the new lowerdir+ and datadir+ mount options.
 970          */
 971         if (lowerdirs[0]) {
 972                 seq_show_option(m, "lowerdir", lowerdirs[0]);
 973         } else {
 974                 nr_lower = ofs->numlayer;
 975                 nr_merged_lower = nr_lower - ofs->numdatalayer;
 976         }
 977         for (nr = 1; nr < nr_lower; nr++) {
 978                 if (nr < nr_merged_lower)
 979                         seq_show_option(m, "lowerdir+", lowerdirs[nr]);
 980                 else
 981                         seq_show_option(m, "datadir+", lowerdirs[nr]);
 982         }
 983         if (ofs->config.upperdir) {
 984                 seq_show_option(m, "upperdir", ofs->config.upperdir);
 985                 seq_show_option(m, "workdir", ofs->config.workdir);
 986         }
 987         if (ofs->config.default_permissions)
 988                 seq_puts(m, ",default_permissions");
 989         if (ofs->config.redirect_mode != ovl_redirect_mode_def())
 990                 seq_printf(m, ",redirect_dir=%s",
 991                            ovl_redirect_mode(&ofs->config));
 992         if (ofs->config.index != ovl_index_def)
 993                 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
 994         if (ofs->config.uuid != ovl_uuid_def())
 995                 seq_printf(m, ",uuid=%s", ovl_uuid_mode(&ofs->config));
 996         if (ofs->config.nfs_export != ovl_nfs_export_def)
 997                 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
 998                                                 "on" : "off");
 999         if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(ofs))
1000                 seq_printf(m, ",xino=%s", ovl_xino_mode(&ofs->config));
1001         if (ofs->config.metacopy != ovl_metacopy_def)
1002                 seq_printf(m, ",metacopy=%s",
1003                            ofs->config.metacopy ? "on" : "off");
1004         if (ofs->config.ovl_volatile)
1005                 seq_puts(m, ",volatile");
1006         if (ofs->config.userxattr)
1007                 seq_puts(m, ",userxattr");
1008         if (ofs->config.verity_mode != ovl_verity_mode_def())
1009                 seq_printf(m, ",verity=%s",
1010                            ovl_verity_mode(&ofs->config));
1011         return 0;
1012 }