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 {
  47         Opt_lowerdir,
  48         Opt_upperdir,
  49         Opt_workdir,
  50         Opt_default_permissions,
  51         Opt_redirect_dir,
  52         Opt_index,
  53         Opt_uuid,
  54         Opt_nfs_export,
  55         Opt_userxattr,
  56         Opt_xino,
  57         Opt_metacopy,
  58         Opt_verity,
  59         Opt_volatile,
  60 };
  61
  62 static const struct constant_table ovl_parameter_bool[] = {
  63         { "on",         true  },
  64         { "off",        false },
  65         {}
  66 };
  67
  68 static const struct constant_table ovl_parameter_uuid[] = {
  69         { "off",        OVL_UUID_OFF  },
  70         { "null",       OVL_UUID_NULL },
  71         { "auto",       OVL_UUID_AUTO },
  72         { "on",         OVL_UUID_ON   },
  73         {}
  74 };
  75
  76 static const char *ovl_uuid_mode(struct ovl_config *config)
  77 {
  78         return ovl_parameter_uuid[config->uuid].name;
  79 }
  80
  81 static int ovl_uuid_def(void)
  82 {
  83         return OVL_UUID_AUTO;
  84 }
  85
  86 static const struct constant_table ovl_parameter_xino[] = {
  87         { "off",        OVL_XINO_OFF  },
  88         { "auto",       OVL_XINO_AUTO },
  89         { "on",         OVL_XINO_ON   },
  90         {}
  91 };
  92
  93 const char *ovl_xino_mode(struct ovl_config *config)
  94 {
  95         return ovl_parameter_xino[config->xino].name;
  96 }
  97
  98 static int ovl_xino_def(void)
  99 {
 100         return ovl_xino_auto_def ? OVL_XINO_AUTO : OVL_XINO_OFF;
 101 }
 102
 103 const struct constant_table ovl_parameter_redirect_dir[] = {
 104         { "off",        OVL_REDIRECT_OFF      },
 105         { "follow",     OVL_REDIRECT_FOLLOW   },
 106         { "nofollow",   OVL_REDIRECT_NOFOLLOW },
 107         { "on",         OVL_REDIRECT_ON       },
 108         {}
 109 };
 110
 111 static const char *ovl_redirect_mode(struct ovl_config *config)
 112 {
 113         return ovl_parameter_redirect_dir[config->redirect_mode].name;
 114 }
 115
 116 static int ovl_redirect_mode_def(void)
 117 {
 118         return ovl_redirect_dir_def       ? OVL_REDIRECT_ON :
 119                ovl_redirect_always_follow ? OVL_REDIRECT_FOLLOW :
 120                                             OVL_REDIRECT_NOFOLLOW;
 121 }
 122
 123 static const struct constant_table ovl_parameter_verity[] = {
 124         { "off",        OVL_VERITY_OFF     },
 125         { "on",         OVL_VERITY_ON      },
 126         { "require",    OVL_VERITY_REQUIRE },
 127         {}
 128 };
 129
 130 static const char *ovl_verity_mode(struct ovl_config *config)
 131 {
 132         return ovl_parameter_verity[config->verity_mode].name;
 133 }
 134
 135 static int ovl_verity_mode_def(void)
 136 {
 137         return OVL_VERITY_OFF;
 138 }
 139
 140 #define fsparam_string_empty(NAME, OPT) \
 141         __fsparam(fs_param_is_string, NAME, OPT, fs_param_can_be_empty, NULL)
 142
 143 const struct fs_parameter_spec ovl_parameter_spec[] = {
 144         fsparam_string_empty("lowerdir",    Opt_lowerdir),
 145         fsparam_string("upperdir",          Opt_upperdir),
 146         fsparam_string("workdir",           Opt_workdir),
 147         fsparam_flag("default_permissions", Opt_default_permissions),
 148         fsparam_enum("redirect_dir",        Opt_redirect_dir, ovl_parameter_redirect_dir),
 149         fsparam_enum("index",               Opt_index, ovl_parameter_bool),
 150         fsparam_enum("uuid",                Opt_uuid, ovl_parameter_uuid),
 151         fsparam_enum("nfs_export",          Opt_nfs_export, ovl_parameter_bool),
 152         fsparam_flag("userxattr",           Opt_userxattr),
 153         fsparam_enum("xino",                Opt_xino, ovl_parameter_xino),
 154         fsparam_enum("metacopy",            Opt_metacopy, ovl_parameter_bool),
 155         fsparam_enum("verity",              Opt_verity, ovl_parameter_verity),
 156         fsparam_flag("volatile",            Opt_volatile),
 157         {}
 158 };
 159
 160 static char *ovl_next_opt(char **s)
 161 {
 162         char *sbegin = *s;
 163         char *p;
 164
 165         if (sbegin == NULL)
 166                 return NULL;
 167
 168         for (p = sbegin; *p; p++) {
 169                 if (*p == '\\') {
 170                         p++;
 171                         if (!*p)
 172                                 break;
 173                 } else if (*p == ',') {
 174                         *p = '\0';
 175                         *s = p + 1;
 176                         return sbegin;
 177                 }
 178         }
 179         *s = NULL;
 180         return sbegin;
 181 }
 182
 183 static int ovl_parse_monolithic(struct fs_context *fc, void *data)
 184 {
 185         return vfs_parse_monolithic_sep(fc, data, ovl_next_opt);
 186 }
 187
 188 static ssize_t ovl_parse_param_split_lowerdirs(char *str)
 189 {
 190         ssize_t nr_layers = 1, nr_colons = 0;
 191         char *s, *d;
 192
 193         for (s = d = str;; s++, d++) {
 194                 if (*s == '\\') {
 195                         /* keep esc chars in split lowerdir */
 196                         *d++ = *s++;
 197                 } else if (*s == ':') {
 198                         bool next_colon = (*(s + 1) == ':');
 199
 200                         nr_colons++;
 201                         if (nr_colons == 2 && next_colon) {
 202                                 pr_err("only single ':' or double '::' sequences of unescaped colons in lowerdir mount option allowed.\n");
 203                                 return -EINVAL;
 204                         }
 205                         /* count layers, not colons */
 206                         if (!next_colon)
 207                                 nr_layers++;
 208
 209                         *d = '\0';
 210                         continue;
 211                 }
 212
 213                 *d = *s;
 214                 if (!*s) {
 215                         /* trailing colons */
 216                         if (nr_colons) {
 217                                 pr_err("unescaped trailing colons in lowerdir mount option.\n");
 218                                 return -EINVAL;
 219                         }
 220                         break;
 221                 }
 222                 nr_colons = 0;
 223         }
 224
 225         return nr_layers;
 226 }
 227
 228 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 229 {
 230         int err = -EINVAL;
 231
 232         if (!*name) {
 233                 pr_err("empty lowerdir\n");
 234                 goto out;
 235         }
 236         err = kern_path(name, LOOKUP_FOLLOW, path);
 237         if (err) {
 238                 pr_err("failed to resolve '%s': %i\n", name, err);
 239                 goto out;
 240         }
 241         err = -EINVAL;
 242         if (ovl_dentry_weird(path->dentry)) {
 243                 pr_err("filesystem on '%s' not supported\n", name);
 244                 goto out_put;
 245         }
 246         if (!d_is_dir(path->dentry)) {
 247                 pr_err("'%s' not a directory\n", name);
 248                 goto out_put;
 249         }
 250         return 0;
 251
 252 out_put:
 253         path_put_init(path);
 254 out:
 255         return err;
 256 }
 257
 258 static void ovl_unescape(char *s)
 259 {
 260         char *d = s;
 261
 262         for (;; s++, d++) {
 263                 if (*s == '\\')
 264                         s++;
 265                 *d = *s;
 266                 if (!*s)
 267                         break;
 268         }
 269 }
 270
 271 static int ovl_mount_dir(const char *name, struct path *path, bool upper)
 272 {
 273         int err = -ENOMEM;
 274         char *tmp = kstrdup(name, GFP_KERNEL);
 275
 276         if (tmp) {
 277                 ovl_unescape(tmp);
 278                 err = ovl_mount_dir_noesc(tmp, path);
 279
 280                 if (!err && upper && path->dentry->d_flags & DCACHE_OP_REAL) {
 281                         pr_err("filesystem on '%s' not supported as upperdir\n",
 282                                tmp);
 283                         path_put_init(path);
 284                         err = -EINVAL;
 285                 }
 286                 kfree(tmp);
 287         }
 288         return err;
 289 }
 290
 291 static int ovl_parse_param_upperdir(const char *name, struct fs_context *fc,
 292                                     bool workdir)
 293 {
 294         int err;
 295         struct ovl_fs *ofs = fc->s_fs_info;
 296         struct ovl_config *config = &ofs->config;
 297         struct ovl_fs_context *ctx = fc->fs_private;
 298         struct path path;
 299         char *dup;
 300
 301         err = ovl_mount_dir(name, &path, true);
 302         if (err)
 303                 return err;
 304
 305         /*
 306          * Check whether upper path is read-only here to report failures
 307          * early. Don't forget to recheck when the superblock is created
 308          * as the mount attributes could change.
 309          */
 310         if (__mnt_is_readonly(path.mnt)) {
 311                 path_put(&path);
 312                 return -EINVAL;
 313         }
 314
 315         dup = kstrdup(name, GFP_KERNEL);
 316         if (!dup) {
 317                 path_put(&path);
 318                 return -ENOMEM;
 319         }
 320
 321         if (workdir) {
 322                 kfree(config->workdir);
 323                 config->workdir = dup;
 324                 path_put(&ctx->work);
 325                 ctx->work = path;
 326         } else {
 327                 kfree(config->upperdir);
 328                 config->upperdir = dup;
 329                 path_put(&ctx->upper);
 330                 ctx->upper = path;
 331         }
 332         return 0;
 333 }
 334
 335 static void ovl_parse_param_drop_lowerdir(struct ovl_fs_context *ctx)
 336 {
 337         for (size_t nr = 0; nr < ctx->nr; nr++) {
 338                 path_put(&ctx->lower[nr].path);
 339                 kfree(ctx->lower[nr].name);
 340                 ctx->lower[nr].name = NULL;
 341         }
 342         ctx->nr = 0;
 343         ctx->nr_data = 0;
 344 }
 345
 346 /*
 347  * Parse lowerdir= mount option:
 348  *
 349  * (1) lowerdir=/lower1:/lower2:/lower3::/data1::/data2
 350  *     Set "/lower1", "/lower2", and "/lower3" as lower layers and
 351  *     "/data1" and "/data2" as data lower layers. Any existing lower
 352  *     layers are replaced.
 353  */
 354 static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 355 {
 356         int err;
 357         struct ovl_fs_context *ctx = fc->fs_private;
 358         struct ovl_fs_context_layer *l;
 359         char *dup = NULL, *dup_iter;
 360         ssize_t nr_lower = 0, nr = 0, nr_data = 0;
 361         bool append = false, data_layer = false;
 362
 363         /*
 364          * Ensure we're backwards compatible with mount(2)
 365          * by allowing relative paths.
 366          */
 367
 368         /* drop all existing lower layers */
 369         if (!*name) {
 370                 ovl_parse_param_drop_lowerdir(ctx);
 371                 return 0;
 372         }
 373
 374         if (*name == ':') {
 375                 pr_err("cannot append lower layer");
 376                 return -EINVAL;
 377         }
 378
 379         dup = kstrdup(name, GFP_KERNEL);
 380         if (!dup)
 381                 return -ENOMEM;
 382
 383         err = -EINVAL;
 384         nr_lower = ovl_parse_param_split_lowerdirs(dup);
 385         if (nr_lower < 0)
 386                 goto out_err;
 387
 388         if ((nr_lower > OVL_MAX_STACK) ||
 389             (append && (size_add(ctx->nr, nr_lower) > OVL_MAX_STACK))) {
 390                 pr_err("too many lower directories, limit is %d\n", OVL_MAX_STACK);
 391                 goto out_err;
 392         }
 393
 394         if (!append)
 395                 ovl_parse_param_drop_lowerdir(ctx);
 396
 397         /*
 398          * (1) append
 399          *
 400          * We want nr <= nr_lower <= capacity We know nr > 0 and nr <=
 401          * capacity. If nr == 0 this wouldn't be append. If nr +
 402          * nr_lower is <= capacity then nr <= nr_lower <= capacity
 403          * already holds. If nr + nr_lower exceeds capacity, we realloc.
 404          *
 405          * (2) replace
 406          *
 407          * Ensure we're backwards compatible with mount(2) which allows
 408          * "lowerdir=/a:/b:/c,lowerdir=/d:/e:/f" causing the last
 409          * specified lowerdir mount option to win.
 410          *
 411          * We want nr <= nr_lower <= capacity We know either (i) nr == 0
 412          * or (ii) nr > 0. We also know nr_lower > 0. The capacity
 413          * could've been changed multiple times already so we only know
 414          * nr <= capacity. If nr + nr_lower > capacity we realloc,
 415          * otherwise nr <= nr_lower <= capacity holds already.
 416          */
 417         nr_lower += ctx->nr;
 418         if (nr_lower > ctx->capacity) {
 419                 err = -ENOMEM;
 420                 l = krealloc_array(ctx->lower, nr_lower, sizeof(*ctx->lower),
 421                                    GFP_KERNEL_ACCOUNT);
 422                 if (!l)
 423                         goto out_err;
 424
 425                 ctx->lower = l;
 426                 ctx->capacity = nr_lower;
 427         }
 428
 429         /*
 430          *   (3) By (1) and (2) we know nr <= nr_lower <= capacity.
 431          *   (4) If ctx->nr == 0 => replace
 432          *       We have verified above that the lowerdir mount option
 433          *       isn't an append, i.e., the lowerdir mount option
 434          *       doesn't start with ":" or "::".
 435          * (4.1) The lowerdir mount options only contains regular lower
 436          *       layers ":".
 437          *       => Nothing to verify.
 438          * (4.2) The lowerdir mount options contains regular ":" and
 439          *       data "::" layers.
 440          *       => We need to verify that data lower layers "::" aren't
 441          *          followed by regular ":" lower layers
 442          *   (5) If ctx->nr > 0 => append
 443          *       We know that there's at least one regular layer
 444          *       otherwise we would've failed when parsing the previous
 445          *       lowerdir mount option.
 446          * (5.1) The lowerdir mount option is a regular layer ":" append
 447          *       => We need to verify that no data layers have been
 448          *          specified before.
 449          * (5.2) The lowerdir mount option is a data layer "::" append
 450          *       We know that there's at least one regular layer or
 451          *       other data layers. => There's nothing to verify.
 452          */
 453         dup_iter = dup;
 454         for (nr = ctx->nr; nr < nr_lower; nr++) {
 455                 l = &ctx->lower[nr];
 456                 memset(l, 0, sizeof(*l));
 457
 458                 err = ovl_mount_dir(dup_iter, &l->path, false);
 459                 if (err)
 460                         goto out_put;
 461
 462                 err = -ENOMEM;
 463                 l->name = kstrdup(dup_iter, GFP_KERNEL_ACCOUNT);
 464                 if (!l->name)
 465                         goto out_put;
 466
 467                 if (data_layer)
 468                         nr_data++;
 469
 470                 /* Calling strchr() again would overrun. */
 471                 if ((nr + 1) == nr_lower)
 472                         break;
 473
 474                 err = -EINVAL;
 475                 dup_iter = strchr(dup_iter, '\0') + 1;
 476                 if (*dup_iter) {
 477                         /*
 478                          * This is a regular layer so we require that
 479                          * there are no data layers.
 480                          */
 481                         if ((ctx->nr_data + nr_data) > 0) {
 482                                 pr_err("regular lower layers cannot follow data lower layers");
 483                                 goto out_put;
 484                         }
 485
 486                         data_layer = false;
 487                         continue;
 488                 }
 489
 490                 /* This is a data lower layer. */
 491                 data_layer = true;
 492                 dup_iter++;
 493         }
 494         ctx->nr = nr_lower;
 495         ctx->nr_data += nr_data;
 496         kfree(dup);
 497         return 0;
 498
 499 out_put:
 500         /*
 501          * We know nr >= ctx->nr < nr_lower. If we failed somewhere
 502          * we want to undo until nr == ctx->nr. This is correct for
 503          * both ctx->nr == 0 and ctx->nr > 0.
 504          */
 505         for (; nr >= ctx->nr; nr--) {
 506                 l = &ctx->lower[nr];
 507                 kfree(l->name);
 508                 l->name = NULL;
 509                 path_put(&l->path);
 510
 511                 /* don't overflow */
 512                 if (nr == 0)
 513                         break;
 514         }
 515
 516 out_err:
 517         kfree(dup);
 518
 519         /* Intentionally don't realloc to a smaller size. */
 520         return err;
 521 }
 522
 523 static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
 524 {
 525         int err = 0;
 526         struct fs_parse_result result;
 527         struct ovl_fs *ofs = fc->s_fs_info;
 528         struct ovl_config *config = &ofs->config;
 529         struct ovl_fs_context *ctx = fc->fs_private;
 530         int opt;
 531
 532         if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
 533                 /*
 534                  * On remount overlayfs has always ignored all mount
 535                  * options no matter if malformed or not so for
 536                  * backwards compatibility we do the same here.
 537                  */
 538                 if (fc->oldapi)
 539                         return 0;
 540
 541                 /*
 542                  * Give us the freedom to allow changing mount options
 543                  * with the new mount api in the future. So instead of
 544                  * silently ignoring everything we report a proper
 545                  * error. This is only visible for users of the new
 546                  * mount api.
 547                  */
 548                 return invalfc(fc, "No changes allowed in reconfigure");
 549         }
 550
 551         opt = fs_parse(fc, ovl_parameter_spec, param, &result);
 552         if (opt < 0)
 553                 return opt;
 554
 555         switch (opt) {
 556         case Opt_lowerdir:
 557                 err = ovl_parse_param_lowerdir(param->string, fc);
 558                 break;
 559         case Opt_upperdir:
 560                 fallthrough;
 561         case Opt_workdir:
 562                 err = ovl_parse_param_upperdir(param->string, fc,
 563                                                (Opt_workdir == opt));
 564                 break;
 565         case Opt_default_permissions:
 566                 config->default_permissions = true;
 567                 break;
 568         case Opt_redirect_dir:
 569                 config->redirect_mode = result.uint_32;
 570                 if (config->redirect_mode == OVL_REDIRECT_OFF) {
 571                         config->redirect_mode = ovl_redirect_always_follow ?
 572                                                 OVL_REDIRECT_FOLLOW :
 573                                                 OVL_REDIRECT_NOFOLLOW;
 574                 }
 575                 ctx->set.redirect = true;
 576                 break;
 577         case Opt_index:
 578                 config->index = result.uint_32;
 579                 ctx->set.index = true;
 580                 break;
 581         case Opt_uuid:
 582                 config->uuid = result.uint_32;
 583                 break;
 584         case Opt_nfs_export:
 585                 config->nfs_export = result.uint_32;
 586                 ctx->set.nfs_export = true;
 587                 break;
 588         case Opt_xino:
 589                 config->xino = result.uint_32;
 590                 break;
 591         case Opt_metacopy:
 592                 config->metacopy = result.uint_32;
 593                 ctx->set.metacopy = true;
 594                 break;
 595         case Opt_verity:
 596                 config->verity_mode = result.uint_32;
 597                 break;
 598         case Opt_volatile:
 599                 config->ovl_volatile = true;
 600                 break;
 601         case Opt_userxattr:
 602                 config->userxattr = true;
 603                 break;
 604         default:
 605                 pr_err("unrecognized mount option \"%s\" or missing value\n",
 606                        param->key);
 607                 return -EINVAL;
 608         }
 609
 610         return err;
 611 }
 612
 613 static int ovl_get_tree(struct fs_context *fc)
 614 {
 615         return get_tree_nodev(fc, ovl_fill_super);
 616 }
 617
 618 static inline void ovl_fs_context_free(struct ovl_fs_context *ctx)
 619 {
 620         ovl_parse_param_drop_lowerdir(ctx);
 621         path_put(&ctx->upper);
 622         path_put(&ctx->work);
 623         kfree(ctx->lower);
 624         kfree(ctx);
 625 }
 626
 627 static void ovl_free(struct fs_context *fc)
 628 {
 629         struct ovl_fs *ofs = fc->s_fs_info;
 630         struct ovl_fs_context *ctx = fc->fs_private;
 631
 632         /*
 633          * ofs is stored in the fs_context when it is initialized.
 634          * ofs is transferred to the superblock on a successful mount,
 635          * but if an error occurs before the transfer we have to free
 636          * it here.
 637          */
 638         if (ofs)
 639                 ovl_free_fs(ofs);
 640
 641         if (ctx)
 642                 ovl_fs_context_free(ctx);
 643 }
 644
 645 static int ovl_reconfigure(struct fs_context *fc)
 646 {
 647         struct super_block *sb = fc->root->d_sb;
 648         struct ovl_fs *ofs = OVL_FS(sb);
 649         struct super_block *upper_sb;
 650         int ret = 0;
 651
 652         if (!(fc->sb_flags & SB_RDONLY) && ovl_force_readonly(ofs))
 653                 return -EROFS;
 654
 655         if (fc->sb_flags & SB_RDONLY && !sb_rdonly(sb)) {
 656                 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 657                 if (ovl_should_sync(ofs)) {
 658                         down_read(&upper_sb->s_umount);
 659                         ret = sync_filesystem(upper_sb);
 660                         up_read(&upper_sb->s_umount);
 661                 }
 662         }
 663
 664         return ret;
 665 }
 666
 667 static const struct fs_context_operations ovl_context_ops = {
 668         .parse_monolithic = ovl_parse_monolithic,
 669         .parse_param = ovl_parse_param,
 670         .get_tree    = ovl_get_tree,
 671         .reconfigure = ovl_reconfigure,
 672         .free        = ovl_free,
 673 };
 674
 675 /*
 676  * This is called during fsopen() and will record the user namespace of
 677  * the caller in fc->user_ns since we've raised FS_USERNS_MOUNT. We'll
 678  * need it when we actually create the superblock to verify that the
 679  * process creating the superblock is in the same user namespace as
 680  * process that called fsopen().
 681  */
 682 int ovl_init_fs_context(struct fs_context *fc)
 683 {
 684         struct ovl_fs_context *ctx;
 685         struct ovl_fs *ofs;
 686
 687         ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
 688         if (!ctx)
 689                 return -ENOMEM;
 690
 691         /*
 692          * By default we allocate for three lower layers. It's likely
 693          * that it'll cover most users.
 694          */
 695         ctx->lower = kmalloc_array(3, sizeof(*ctx->lower), GFP_KERNEL_ACCOUNT);
 696         if (!ctx->lower)
 697                 goto out_err;
 698         ctx->capacity = 3;
 699
 700         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
 701         if (!ofs)
 702                 goto out_err;
 703
 704         ofs->config.redirect_mode       = ovl_redirect_mode_def();
 705         ofs->config.index               = ovl_index_def;
 706         ofs->config.uuid                = ovl_uuid_def();
 707         ofs->config.nfs_export          = ovl_nfs_export_def;
 708         ofs->config.xino                = ovl_xino_def();
 709         ofs->config.metacopy            = ovl_metacopy_def;
 710
 711         fc->s_fs_info           = ofs;
 712         fc->fs_private          = ctx;
 713         fc->ops                 = &ovl_context_ops;
 714         return 0;
 715
 716 out_err:
 717         ovl_fs_context_free(ctx);
 718         return -ENOMEM;
 719
 720 }
 721
 722 void ovl_free_fs(struct ovl_fs *ofs)
 723 {
 724         struct vfsmount **mounts;
 725         unsigned i;
 726
 727         iput(ofs->workbasedir_trap);
 728         iput(ofs->indexdir_trap);
 729         iput(ofs->workdir_trap);
 730         dput(ofs->whiteout);
 731         dput(ofs->indexdir);
 732         dput(ofs->workdir);
 733         if (ofs->workdir_locked)
 734                 ovl_inuse_unlock(ofs->workbasedir);
 735         dput(ofs->workbasedir);
 736         if (ofs->upperdir_locked)
 737                 ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
 738
 739         /* Reuse ofs->config.lowerdirs as a vfsmount array before freeing it */
 740         mounts = (struct vfsmount **) ofs->config.lowerdirs;
 741         for (i = 0; i < ofs->numlayer; i++) {
 742                 iput(ofs->layers[i].trap);
 743                 kfree(ofs->config.lowerdirs[i]);
 744                 mounts[i] = ofs->layers[i].mnt;
 745         }
 746         kern_unmount_array(mounts, ofs->numlayer);
 747         kfree(ofs->layers);
 748         for (i = 0; i < ofs->numfs; i++)
 749                 free_anon_bdev(ofs->fs[i].pseudo_dev);
 750         kfree(ofs->fs);
 751
 752         kfree(ofs->config.lowerdirs);
 753         kfree(ofs->config.upperdir);
 754         kfree(ofs->config.workdir);
 755         if (ofs->creator_cred)
 756                 put_cred(ofs->creator_cred);
 757         kfree(ofs);
 758 }
 759
 760 int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
 761                          struct ovl_config *config)
 762 {
 763         struct ovl_opt_set set = ctx->set;
 764
 765         if (ctx->nr_data > 0 && !config->metacopy) {
 766                 pr_err("lower data-only dirs require metacopy support.\n");
 767                 return -EINVAL;
 768         }
 769
 770         /* Workdir/index are useless in non-upper mount */
 771         if (!config->upperdir) {
 772                 if (config->workdir) {
 773                         pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 774                                 config->workdir);
 775                         kfree(config->workdir);
 776                         config->workdir = NULL;
 777                 }
 778                 if (config->index && set.index) {
 779                         pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
 780                         set.index = false;
 781                 }
 782                 config->index = false;
 783         }
 784
 785         if (!config->upperdir && config->ovl_volatile) {
 786                 pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
 787                 config->ovl_volatile = false;
 788         }
 789
 790         if (!config->upperdir && config->uuid == OVL_UUID_ON) {
 791                 pr_info("option \"uuid=on\" requires an upper fs, falling back to uuid=null.\n");
 792                 config->uuid = OVL_UUID_NULL;
 793         }
 794
 795         /* Resolve verity -> metacopy dependency */
 796         if (config->verity_mode && !config->metacopy) {
 797                 /* Don't allow explicit specified conflicting combinations */
 798                 if (set.metacopy) {
 799                         pr_err("conflicting options: metacopy=off,verity=%s\n",
 800                                ovl_verity_mode(config));
 801                         return -EINVAL;
 802                 }
 803                 /* Otherwise automatically enable metacopy. */
 804                 config->metacopy = true;
 805         }
 806
 807         /*
 808          * This is to make the logic below simpler.  It doesn't make any other
 809          * difference, since redirect_dir=on is only used for upper.
 810          */
 811         if (!config->upperdir && config->redirect_mode == OVL_REDIRECT_FOLLOW)
 812                 config->redirect_mode = OVL_REDIRECT_ON;
 813
 814         /* Resolve verity -> metacopy -> redirect_dir dependency */
 815         if (config->metacopy && config->redirect_mode != OVL_REDIRECT_ON) {
 816                 if (set.metacopy && set.redirect) {
 817                         pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
 818                                ovl_redirect_mode(config));
 819                         return -EINVAL;
 820                 }
 821                 if (config->verity_mode && set.redirect) {
 822                         pr_err("conflicting options: verity=%s,redirect_dir=%s\n",
 823                                ovl_verity_mode(config), ovl_redirect_mode(config));
 824                         return -EINVAL;
 825                 }
 826                 if (set.redirect) {
 827                         /*
 828                          * There was an explicit redirect_dir=... that resulted
 829                          * in this conflict.
 830                          */
 831                         pr_info("disabling metacopy due to redirect_dir=%s\n",
 832                                 ovl_redirect_mode(config));
 833                         config->metacopy = false;
 834                 } else {
 835                         /* Automatically enable redirect otherwise. */
 836                         config->redirect_mode = OVL_REDIRECT_ON;
 837                 }
 838         }
 839
 840         /* Resolve nfs_export -> index dependency */
 841         if (config->nfs_export && !config->index) {
 842                 if (!config->upperdir &&
 843                     config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 844                         pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
 845                         config->nfs_export = false;
 846                 } else if (set.nfs_export && set.index) {
 847                         pr_err("conflicting options: nfs_export=on,index=off\n");
 848                         return -EINVAL;
 849                 } else if (set.index) {
 850                         /*
 851                          * There was an explicit index=off that resulted
 852                          * in this conflict.
 853                          */
 854                         pr_info("disabling nfs_export due to index=off\n");
 855                         config->nfs_export = false;
 856                 } else {
 857                         /* Automatically enable index otherwise. */
 858                         config->index = true;
 859                 }
 860         }
 861
 862         /* Resolve nfs_export -> !metacopy && !verity dependency */
 863         if (config->nfs_export && config->metacopy) {
 864                 if (set.nfs_export && set.metacopy) {
 865                         pr_err("conflicting options: nfs_export=on,metacopy=on\n");
 866                         return -EINVAL;
 867                 }
 868                 if (set.metacopy) {
 869                         /*
 870                          * There was an explicit metacopy=on that resulted
 871                          * in this conflict.
 872                          */
 873                         pr_info("disabling nfs_export due to metacopy=on\n");
 874                         config->nfs_export = false;
 875                 } else if (config->verity_mode) {
 876                         /*
 877                          * There was an explicit verity=.. that resulted
 878                          * in this conflict.
 879                          */
 880                         pr_info("disabling nfs_export due to verity=%s\n",
 881                                 ovl_verity_mode(config));
 882                         config->nfs_export = false;
 883                 } else {
 884                         /*
 885                          * There was an explicit nfs_export=on that resulted
 886                          * in this conflict.
 887                          */
 888                         pr_info("disabling metacopy due to nfs_export=on\n");
 889                         config->metacopy = false;
 890                 }
 891         }
 892
 893
 894         /* Resolve userxattr -> !redirect && !metacopy && !verity dependency */
 895         if (config->userxattr) {
 896                 if (set.redirect &&
 897                     config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 898                         pr_err("conflicting options: userxattr,redirect_dir=%s\n",
 899                                ovl_redirect_mode(config));
 900                         return -EINVAL;
 901                 }
 902                 if (config->metacopy && set.metacopy) {
 903                         pr_err("conflicting options: userxattr,metacopy=on\n");
 904                         return -EINVAL;
 905                 }
 906                 if (config->verity_mode) {
 907                         pr_err("conflicting options: userxattr,verity=%s\n",
 908                                ovl_verity_mode(config));
 909                         return -EINVAL;
 910                 }
 911                 /*
 912                  * Silently disable default setting of redirect and metacopy.
 913                  * This shall be the default in the future as well: these
 914                  * options must be explicitly enabled if used together with
 915                  * userxattr.
 916                  */
 917                 config->redirect_mode = OVL_REDIRECT_NOFOLLOW;
 918                 config->metacopy = false;
 919         }
 920
 921         return 0;
 922 }
 923
 924 /**
 925  * ovl_show_options
 926  * @m: the seq_file handle
 927  * @dentry: The dentry to query
 928  *
 929  * Prints the mount options for a given superblock.
 930  * Returns zero; does not fail.
 931  */
 932 int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 933 {
 934         struct super_block *sb = dentry->d_sb;
 935         struct ovl_fs *ofs = OVL_FS(sb);
 936         size_t nr, nr_merged_lower = ofs->numlayer - ofs->numdatalayer;
 937
 938         /*
 939          * lowerdirs[] starts from offset 1, then
 940          * >= 0 regular lower layers prefixed with : and
 941          * >= 0 data-only lower layers prefixed with ::
 942          *
 943          * we need to escase comma and space like seq_show_option() does and
 944          * we also need to escape the colon separator from lowerdir paths.
 945          */
 946         seq_puts(m, ",lowerdir=");
 947         for (nr = 1; nr < ofs->numlayer; nr++) {
 948                 if (nr > 1)
 949                         seq_putc(m, ':');
 950                 if (nr >= nr_merged_lower)
 951                         seq_putc(m, ':');
 952                 seq_escape(m, ofs->config.lowerdirs[nr], ":, \t\n\\");
 953         }
 954         if (ofs->config.upperdir) {
 955                 seq_show_option(m, "upperdir", ofs->config.upperdir);
 956                 seq_show_option(m, "workdir", ofs->config.workdir);
 957         }
 958         if (ofs->config.default_permissions)
 959                 seq_puts(m, ",default_permissions");
 960         if (ofs->config.redirect_mode != ovl_redirect_mode_def())
 961                 seq_printf(m, ",redirect_dir=%s",
 962                            ovl_redirect_mode(&ofs->config));
 963         if (ofs->config.index != ovl_index_def)
 964                 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
 965         if (ofs->config.uuid != ovl_uuid_def())
 966                 seq_printf(m, ",uuid=%s", ovl_uuid_mode(&ofs->config));
 967         if (ofs->config.nfs_export != ovl_nfs_export_def)
 968                 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
 969                                                 "on" : "off");
 970         if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(ofs))
 971                 seq_printf(m, ",xino=%s", ovl_xino_mode(&ofs->config));
 972         if (ofs->config.metacopy != ovl_metacopy_def)
 973                 seq_printf(m, ",metacopy=%s",
 974                            ofs->config.metacopy ? "on" : "off");
 975         if (ofs->config.ovl_volatile)
 976                 seq_puts(m, ",volatile");
 977         if (ofs->config.userxattr)
 978                 seq_puts(m, ",userxattr");
 979         if (ofs->config.verity_mode != ovl_verity_mode_def())
 980                 seq_printf(m, ",verity=%s",
 981                            ovl_verity_mode(&ofs->config));
 982         return 0;
 983 }