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 ssize_t ovl_parse_param_split_lowerdirs(char *str)
 161 {
 162         ssize_t nr_layers = 1, nr_colons = 0;
 163         char *s, *d;
 164
 165         for (s = d = str;; s++, d++) {
 166                 if (*s == '\\') {
 167                         s++;
 168                 } else if (*s == ':') {
 169                         bool next_colon = (*(s + 1) == ':');
 170
 171                         nr_colons++;
 172                         if (nr_colons == 2 && next_colon) {
 173                                 pr_err("only single ':' or double '::' sequences of unescaped colons in lowerdir mount option allowed.\n");
 174                                 return -EINVAL;
 175                         }
 176                         /* count layers, not colons */
 177                         if (!next_colon)
 178                                 nr_layers++;
 179
 180                         *d = '\0';
 181                         continue;
 182                 }
 183
 184                 *d = *s;
 185                 if (!*s) {
 186                         /* trailing colons */
 187                         if (nr_colons) {
 188                                 pr_err("unescaped trailing colons in lowerdir mount option.\n");
 189                                 return -EINVAL;
 190                         }
 191                         break;
 192                 }
 193                 nr_colons = 0;
 194         }
 195
 196         return nr_layers;
 197 }
 198
 199 static int ovl_mount_dir_noesc(const char *name, struct path *path)
 200 {
 201         int err = -EINVAL;
 202
 203         if (!*name) {
 204                 pr_err("empty lowerdir\n");
 205                 goto out;
 206         }
 207         err = kern_path(name, LOOKUP_FOLLOW, path);
 208         if (err) {
 209                 pr_err("failed to resolve '%s': %i\n", name, err);
 210                 goto out;
 211         }
 212         err = -EINVAL;
 213         if (ovl_dentry_weird(path->dentry)) {
 214                 pr_err("filesystem on '%s' not supported\n", name);
 215                 goto out_put;
 216         }
 217         if (!d_is_dir(path->dentry)) {
 218                 pr_err("'%s' not a directory\n", name);
 219                 goto out_put;
 220         }
 221         return 0;
 222
 223 out_put:
 224         path_put_init(path);
 225 out:
 226         return err;
 227 }
 228
 229 static void ovl_unescape(char *s)
 230 {
 231         char *d = s;
 232
 233         for (;; s++, d++) {
 234                 if (*s == '\\')
 235                         s++;
 236                 *d = *s;
 237                 if (!*s)
 238                         break;
 239         }
 240 }
 241
 242 static int ovl_mount_dir(const char *name, struct path *path)
 243 {
 244         int err = -ENOMEM;
 245         char *tmp = kstrdup(name, GFP_KERNEL);
 246
 247         if (tmp) {
 248                 ovl_unescape(tmp);
 249                 err = ovl_mount_dir_noesc(tmp, path);
 250
 251                 if (!err && path->dentry->d_flags & DCACHE_OP_REAL) {
 252                         pr_err("filesystem on '%s' not supported as upperdir\n",
 253                                tmp);
 254                         path_put_init(path);
 255                         err = -EINVAL;
 256                 }
 257                 kfree(tmp);
 258         }
 259         return err;
 260 }
 261
 262 static int ovl_parse_param_upperdir(const char *name, struct fs_context *fc,
 263                                     bool workdir)
 264 {
 265         int err;
 266         struct ovl_fs *ofs = fc->s_fs_info;
 267         struct ovl_config *config = &ofs->config;
 268         struct ovl_fs_context *ctx = fc->fs_private;
 269         struct path path;
 270         char *dup;
 271
 272         err = ovl_mount_dir(name, &path);
 273         if (err)
 274                 return err;
 275
 276         /*
 277          * Check whether upper path is read-only here to report failures
 278          * early. Don't forget to recheck when the superblock is created
 279          * as the mount attributes could change.
 280          */
 281         if (__mnt_is_readonly(path.mnt)) {
 282                 path_put(&path);
 283                 return -EINVAL;
 284         }
 285
 286         dup = kstrdup(name, GFP_KERNEL);
 287         if (!dup) {
 288                 path_put(&path);
 289                 return -ENOMEM;
 290         }
 291
 292         if (workdir) {
 293                 kfree(config->workdir);
 294                 config->workdir = dup;
 295                 path_put(&ctx->work);
 296                 ctx->work = path;
 297         } else {
 298                 kfree(config->upperdir);
 299                 config->upperdir = dup;
 300                 path_put(&ctx->upper);
 301                 ctx->upper = path;
 302         }
 303         return 0;
 304 }
 305
 306 static void ovl_parse_param_drop_lowerdir(struct ovl_fs_context *ctx)
 307 {
 308         for (size_t nr = 0; nr < ctx->nr; nr++) {
 309                 path_put(&ctx->lower[nr].path);
 310                 kfree(ctx->lower[nr].name);
 311                 ctx->lower[nr].name = NULL;
 312         }
 313         ctx->nr = 0;
 314         ctx->nr_data = 0;
 315 }
 316
 317 /*
 318  * Parse lowerdir= mount option:
 319  *
 320  * (1) lowerdir=/lower1:/lower2:/lower3::/data1::/data2
 321  *     Set "/lower1", "/lower2", and "/lower3" as lower layers and
 322  *     "/data1" and "/data2" as data lower layers. Any existing lower
 323  *     layers are replaced.
 324  * (2) lowerdir=:/lower4
 325  *     Append "/lower4" to current stack of lower layers. This requires
 326  *     that there already is at least one lower layer configured.
 327  * (3) lowerdir=::/lower5
 328  *     Append data "/lower5" as data lower layer. This requires that
 329  *     there's at least one regular lower layer present.
 330  */
 331 static int ovl_parse_param_lowerdir(const char *name, struct fs_context *fc)
 332 {
 333         int err;
 334         struct ovl_fs_context *ctx = fc->fs_private;
 335         struct ovl_fs_context_layer *l;
 336         char *dup = NULL, *dup_iter;
 337         ssize_t nr_lower = 0, nr = 0, nr_data = 0;
 338         bool append = false, data_layer = false;
 339
 340         /*
 341          * Ensure we're backwards compatible with mount(2)
 342          * by allowing relative paths.
 343          */
 344
 345         /* drop all existing lower layers */
 346         if (!*name) {
 347                 ovl_parse_param_drop_lowerdir(ctx);
 348                 return 0;
 349         }
 350
 351         if (strncmp(name, "::", 2) == 0) {
 352                 /*
 353                  * This is a data layer.
 354                  * There must be at least one regular lower layer
 355                  * specified.
 356                  */
 357                 if (ctx->nr == 0) {
 358                         pr_err("data lower layers without regular lower layers not allowed");
 359                         return -EINVAL;
 360                 }
 361
 362                 /* Skip the leading "::". */
 363                 name += 2;
 364                 data_layer = true;
 365                 /*
 366                  * A data layer is automatically an append as there
 367                  * must've been at least one regular lower layer.
 368                  */
 369                 append = true;
 370         } else if (*name == ':') {
 371                 /*
 372                  * This is a regular lower layer.
 373                  * If users want to append a layer enforce that they
 374                  * have already specified a first layer before. It's
 375                  * better to be strict.
 376                  */
 377                 if (ctx->nr == 0) {
 378                         pr_err("cannot append layer if no previous layer has been specified");
 379                         return -EINVAL;
 380                 }
 381
 382                 /*
 383                  * Once a sequence of data layers has started regular
 384                  * lower layers are forbidden.
 385                  */
 386                 if (ctx->nr_data > 0) {
 387                         pr_err("regular lower layers cannot follow data lower layers");
 388                         return -EINVAL;
 389                 }
 390
 391                 /* Skip the leading ":". */
 392                 name++;
 393                 append = true;
 394         }
 395
 396         dup = kstrdup(name, GFP_KERNEL);
 397         if (!dup)
 398                 return -ENOMEM;
 399
 400         err = -EINVAL;
 401         nr_lower = ovl_parse_param_split_lowerdirs(dup);
 402         if (nr_lower < 0)
 403                 goto out_err;
 404
 405         if ((nr_lower > OVL_MAX_STACK) ||
 406             (append && (size_add(ctx->nr, nr_lower) > OVL_MAX_STACK))) {
 407                 pr_err("too many lower directories, limit is %d\n", OVL_MAX_STACK);
 408                 goto out_err;
 409         }
 410
 411         if (!append)
 412                 ovl_parse_param_drop_lowerdir(ctx);
 413
 414         /*
 415          * (1) append
 416          *
 417          * We want nr <= nr_lower <= capacity We know nr > 0 and nr <=
 418          * capacity. If nr == 0 this wouldn't be append. If nr +
 419          * nr_lower is <= capacity then nr <= nr_lower <= capacity
 420          * already holds. If nr + nr_lower exceeds capacity, we realloc.
 421          *
 422          * (2) replace
 423          *
 424          * Ensure we're backwards compatible with mount(2) which allows
 425          * "lowerdir=/a:/b:/c,lowerdir=/d:/e:/f" causing the last
 426          * specified lowerdir mount option to win.
 427          *
 428          * We want nr <= nr_lower <= capacity We know either (i) nr == 0
 429          * or (ii) nr > 0. We also know nr_lower > 0. The capacity
 430          * could've been changed multiple times already so we only know
 431          * nr <= capacity. If nr + nr_lower > capacity we realloc,
 432          * otherwise nr <= nr_lower <= capacity holds already.
 433          */
 434         nr_lower += ctx->nr;
 435         if (nr_lower > ctx->capacity) {
 436                 err = -ENOMEM;
 437                 l = krealloc_array(ctx->lower, nr_lower, sizeof(*ctx->lower),
 438                                    GFP_KERNEL_ACCOUNT);
 439                 if (!l)
 440                         goto out_err;
 441
 442                 ctx->lower = l;
 443                 ctx->capacity = nr_lower;
 444         }
 445
 446         /*
 447          *   (3) By (1) and (2) we know nr <= nr_lower <= capacity.
 448          *   (4) If ctx->nr == 0 => replace
 449          *       We have verified above that the lowerdir mount option
 450          *       isn't an append, i.e., the lowerdir mount option
 451          *       doesn't start with ":" or "::".
 452          * (4.1) The lowerdir mount options only contains regular lower
 453          *       layers ":".
 454          *       => Nothing to verify.
 455          * (4.2) The lowerdir mount options contains regular ":" and
 456          *       data "::" layers.
 457          *       => We need to verify that data lower layers "::" aren't
 458          *          followed by regular ":" lower layers
 459          *   (5) If ctx->nr > 0 => append
 460          *       We know that there's at least one regular layer
 461          *       otherwise we would've failed when parsing the previous
 462          *       lowerdir mount option.
 463          * (5.1) The lowerdir mount option is a regular layer ":" append
 464          *       => We need to verify that no data layers have been
 465          *          specified before.
 466          * (5.2) The lowerdir mount option is a data layer "::" append
 467          *       We know that there's at least one regular layer or
 468          *       other data layers. => There's nothing to verify.
 469          */
 470         dup_iter = dup;
 471         for (nr = ctx->nr; nr < nr_lower; nr++) {
 472                 l = &ctx->lower[nr];
 473                 memset(l, 0, sizeof(*l));
 474
 475                 err = ovl_mount_dir_noesc(dup_iter, &l->path);
 476                 if (err)
 477                         goto out_put;
 478
 479                 err = -ENOMEM;
 480                 l->name = kstrdup(dup_iter, GFP_KERNEL_ACCOUNT);
 481                 if (!l->name)
 482                         goto out_put;
 483
 484                 if (data_layer)
 485                         nr_data++;
 486
 487                 /* Calling strchr() again would overrun. */
 488                 if ((nr + 1) == nr_lower)
 489                         break;
 490
 491                 err = -EINVAL;
 492                 dup_iter = strchr(dup_iter, '\0') + 1;
 493                 if (*dup_iter) {
 494                         /*
 495                          * This is a regular layer so we require that
 496                          * there are no data layers.
 497                          */
 498                         if ((ctx->nr_data + nr_data) > 0) {
 499                                 pr_err("regular lower layers cannot follow data lower layers");
 500                                 goto out_put;
 501                         }
 502
 503                         data_layer = false;
 504                         continue;
 505                 }
 506
 507                 /* This is a data lower layer. */
 508                 data_layer = true;
 509                 dup_iter++;
 510         }
 511         ctx->nr = nr_lower;
 512         ctx->nr_data += nr_data;
 513         kfree(dup);
 514         return 0;
 515
 516 out_put:
 517         /*
 518          * We know nr >= ctx->nr < nr_lower. If we failed somewhere
 519          * we want to undo until nr == ctx->nr. This is correct for
 520          * both ctx->nr == 0 and ctx->nr > 0.
 521          */
 522         for (; nr >= ctx->nr; nr--) {
 523                 l = &ctx->lower[nr];
 524                 kfree(l->name);
 525                 l->name = NULL;
 526                 path_put(&l->path);
 527
 528                 /* don't overflow */
 529                 if (nr == 0)
 530                         break;
 531         }
 532
 533 out_err:
 534         kfree(dup);
 535
 536         /* Intentionally don't realloc to a smaller size. */
 537         return err;
 538 }
 539
 540 static int ovl_parse_param(struct fs_context *fc, struct fs_parameter *param)
 541 {
 542         int err = 0;
 543         struct fs_parse_result result;
 544         struct ovl_fs *ofs = fc->s_fs_info;
 545         struct ovl_config *config = &ofs->config;
 546         struct ovl_fs_context *ctx = fc->fs_private;
 547         int opt;
 548
 549         if (fc->purpose == FS_CONTEXT_FOR_RECONFIGURE) {
 550                 /*
 551                  * On remount overlayfs has always ignored all mount
 552                  * options no matter if malformed or not so for
 553                  * backwards compatibility we do the same here.
 554                  */
 555                 if (fc->oldapi)
 556                         return 0;
 557
 558                 /*
 559                  * Give us the freedom to allow changing mount options
 560                  * with the new mount api in the future. So instead of
 561                  * silently ignoring everything we report a proper
 562                  * error. This is only visible for users of the new
 563                  * mount api.
 564                  */
 565                 return invalfc(fc, "No changes allowed in reconfigure");
 566         }
 567
 568         opt = fs_parse(fc, ovl_parameter_spec, param, &result);
 569         if (opt < 0)
 570                 return opt;
 571
 572         switch (opt) {
 573         case Opt_lowerdir:
 574                 err = ovl_parse_param_lowerdir(param->string, fc);
 575                 break;
 576         case Opt_upperdir:
 577                 fallthrough;
 578         case Opt_workdir:
 579                 err = ovl_parse_param_upperdir(param->string, fc,
 580                                                (Opt_workdir == opt));
 581                 break;
 582         case Opt_default_permissions:
 583                 config->default_permissions = true;
 584                 break;
 585         case Opt_redirect_dir:
 586                 config->redirect_mode = result.uint_32;
 587                 if (config->redirect_mode == OVL_REDIRECT_OFF) {
 588                         config->redirect_mode = ovl_redirect_always_follow ?
 589                                                 OVL_REDIRECT_FOLLOW :
 590                                                 OVL_REDIRECT_NOFOLLOW;
 591                 }
 592                 ctx->set.redirect = true;
 593                 break;
 594         case Opt_index:
 595                 config->index = result.uint_32;
 596                 ctx->set.index = true;
 597                 break;
 598         case Opt_uuid:
 599                 config->uuid = result.uint_32;
 600                 break;
 601         case Opt_nfs_export:
 602                 config->nfs_export = result.uint_32;
 603                 ctx->set.nfs_export = true;
 604                 break;
 605         case Opt_xino:
 606                 config->xino = result.uint_32;
 607                 break;
 608         case Opt_metacopy:
 609                 config->metacopy = result.uint_32;
 610                 ctx->set.metacopy = true;
 611                 break;
 612         case Opt_verity:
 613                 config->verity_mode = result.uint_32;
 614                 break;
 615         case Opt_volatile:
 616                 config->ovl_volatile = true;
 617                 break;
 618         case Opt_userxattr:
 619                 config->userxattr = true;
 620                 break;
 621         default:
 622                 pr_err("unrecognized mount option \"%s\" or missing value\n",
 623                        param->key);
 624                 return -EINVAL;
 625         }
 626
 627         return err;
 628 }
 629
 630 static int ovl_get_tree(struct fs_context *fc)
 631 {
 632         return get_tree_nodev(fc, ovl_fill_super);
 633 }
 634
 635 static inline void ovl_fs_context_free(struct ovl_fs_context *ctx)
 636 {
 637         ovl_parse_param_drop_lowerdir(ctx);
 638         path_put(&ctx->upper);
 639         path_put(&ctx->work);
 640         kfree(ctx->lower);
 641         kfree(ctx);
 642 }
 643
 644 static void ovl_free(struct fs_context *fc)
 645 {
 646         struct ovl_fs *ofs = fc->s_fs_info;
 647         struct ovl_fs_context *ctx = fc->fs_private;
 648
 649         /*
 650          * ofs is stored in the fs_context when it is initialized.
 651          * ofs is transferred to the superblock on a successful mount,
 652          * but if an error occurs before the transfer we have to free
 653          * it here.
 654          */
 655         if (ofs)
 656                 ovl_free_fs(ofs);
 657
 658         if (ctx)
 659                 ovl_fs_context_free(ctx);
 660 }
 661
 662 static int ovl_reconfigure(struct fs_context *fc)
 663 {
 664         struct super_block *sb = fc->root->d_sb;
 665         struct ovl_fs *ofs = OVL_FS(sb);
 666         struct super_block *upper_sb;
 667         int ret = 0;
 668
 669         if (!(fc->sb_flags & SB_RDONLY) && ovl_force_readonly(ofs))
 670                 return -EROFS;
 671
 672         if (fc->sb_flags & SB_RDONLY && !sb_rdonly(sb)) {
 673                 upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
 674                 if (ovl_should_sync(ofs)) {
 675                         down_read(&upper_sb->s_umount);
 676                         ret = sync_filesystem(upper_sb);
 677                         up_read(&upper_sb->s_umount);
 678                 }
 679         }
 680
 681         return ret;
 682 }
 683
 684 static const struct fs_context_operations ovl_context_ops = {
 685         .parse_param = ovl_parse_param,
 686         .get_tree    = ovl_get_tree,
 687         .reconfigure = ovl_reconfigure,
 688         .free        = ovl_free,
 689 };
 690
 691 /*
 692  * This is called during fsopen() and will record the user namespace of
 693  * the caller in fc->user_ns since we've raised FS_USERNS_MOUNT. We'll
 694  * need it when we actually create the superblock to verify that the
 695  * process creating the superblock is in the same user namespace as
 696  * process that called fsopen().
 697  */
 698 int ovl_init_fs_context(struct fs_context *fc)
 699 {
 700         struct ovl_fs_context *ctx;
 701         struct ovl_fs *ofs;
 702
 703         ctx = kzalloc(sizeof(*ctx), GFP_KERNEL_ACCOUNT);
 704         if (!ctx)
 705                 return -ENOMEM;
 706
 707         /*
 708          * By default we allocate for three lower layers. It's likely
 709          * that it'll cover most users.
 710          */
 711         ctx->lower = kmalloc_array(3, sizeof(*ctx->lower), GFP_KERNEL_ACCOUNT);
 712         if (!ctx->lower)
 713                 goto out_err;
 714         ctx->capacity = 3;
 715
 716         ofs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);
 717         if (!ofs)
 718                 goto out_err;
 719
 720         ofs->config.redirect_mode       = ovl_redirect_mode_def();
 721         ofs->config.index               = ovl_index_def;
 722         ofs->config.uuid                = ovl_uuid_def();
 723         ofs->config.nfs_export          = ovl_nfs_export_def;
 724         ofs->config.xino                = ovl_xino_def();
 725         ofs->config.metacopy            = ovl_metacopy_def;
 726
 727         fc->s_fs_info           = ofs;
 728         fc->fs_private          = ctx;
 729         fc->ops                 = &ovl_context_ops;
 730         return 0;
 731
 732 out_err:
 733         ovl_fs_context_free(ctx);
 734         return -ENOMEM;
 735
 736 }
 737
 738 void ovl_free_fs(struct ovl_fs *ofs)
 739 {
 740         struct vfsmount **mounts;
 741         unsigned i;
 742
 743         iput(ofs->workbasedir_trap);
 744         iput(ofs->indexdir_trap);
 745         iput(ofs->workdir_trap);
 746         dput(ofs->whiteout);
 747         dput(ofs->indexdir);
 748         dput(ofs->workdir);
 749         if (ofs->workdir_locked)
 750                 ovl_inuse_unlock(ofs->workbasedir);
 751         dput(ofs->workbasedir);
 752         if (ofs->upperdir_locked)
 753                 ovl_inuse_unlock(ovl_upper_mnt(ofs)->mnt_root);
 754
 755         /* Hack!  Reuse ofs->layers as a vfsmount array before freeing it */
 756         mounts = (struct vfsmount **) ofs->layers;
 757         for (i = 0; i < ofs->numlayer; i++) {
 758                 iput(ofs->layers[i].trap);
 759                 mounts[i] = ofs->layers[i].mnt;
 760                 kfree(ofs->layers[i].name);
 761         }
 762         kern_unmount_array(mounts, ofs->numlayer);
 763         kfree(ofs->layers);
 764         for (i = 0; i < ofs->numfs; i++)
 765                 free_anon_bdev(ofs->fs[i].pseudo_dev);
 766         kfree(ofs->fs);
 767
 768         kfree(ofs->config.upperdir);
 769         kfree(ofs->config.workdir);
 770         if (ofs->creator_cred)
 771                 put_cred(ofs->creator_cred);
 772         kfree(ofs);
 773 }
 774
 775 int ovl_fs_params_verify(const struct ovl_fs_context *ctx,
 776                          struct ovl_config *config)
 777 {
 778         struct ovl_opt_set set = ctx->set;
 779
 780         if (ctx->nr_data > 0 && !config->metacopy) {
 781                 pr_err("lower data-only dirs require metacopy support.\n");
 782                 return -EINVAL;
 783         }
 784
 785         /* Workdir/index are useless in non-upper mount */
 786         if (!config->upperdir) {
 787                 if (config->workdir) {
 788                         pr_info("option \"workdir=%s\" is useless in a non-upper mount, ignore\n",
 789                                 config->workdir);
 790                         kfree(config->workdir);
 791                         config->workdir = NULL;
 792                 }
 793                 if (config->index && set.index) {
 794                         pr_info("option \"index=on\" is useless in a non-upper mount, ignore\n");
 795                         set.index = false;
 796                 }
 797                 config->index = false;
 798         }
 799
 800         if (!config->upperdir && config->ovl_volatile) {
 801                 pr_info("option \"volatile\" is meaningless in a non-upper mount, ignoring it.\n");
 802                 config->ovl_volatile = false;
 803         }
 804
 805         if (!config->upperdir && config->uuid == OVL_UUID_ON) {
 806                 pr_info("option \"uuid=on\" requires an upper fs, falling back to uuid=null.\n");
 807                 config->uuid = OVL_UUID_NULL;
 808         }
 809
 810         /* Resolve verity -> metacopy dependency */
 811         if (config->verity_mode && !config->metacopy) {
 812                 /* Don't allow explicit specified conflicting combinations */
 813                 if (set.metacopy) {
 814                         pr_err("conflicting options: metacopy=off,verity=%s\n",
 815                                ovl_verity_mode(config));
 816                         return -EINVAL;
 817                 }
 818                 /* Otherwise automatically enable metacopy. */
 819                 config->metacopy = true;
 820         }
 821
 822         /*
 823          * This is to make the logic below simpler.  It doesn't make any other
 824          * difference, since redirect_dir=on is only used for upper.
 825          */
 826         if (!config->upperdir && config->redirect_mode == OVL_REDIRECT_FOLLOW)
 827                 config->redirect_mode = OVL_REDIRECT_ON;
 828
 829         /* Resolve verity -> metacopy -> redirect_dir dependency */
 830         if (config->metacopy && config->redirect_mode != OVL_REDIRECT_ON) {
 831                 if (set.metacopy && set.redirect) {
 832                         pr_err("conflicting options: metacopy=on,redirect_dir=%s\n",
 833                                ovl_redirect_mode(config));
 834                         return -EINVAL;
 835                 }
 836                 if (config->verity_mode && set.redirect) {
 837                         pr_err("conflicting options: verity=%s,redirect_dir=%s\n",
 838                                ovl_verity_mode(config), ovl_redirect_mode(config));
 839                         return -EINVAL;
 840                 }
 841                 if (set.redirect) {
 842                         /*
 843                          * There was an explicit redirect_dir=... that resulted
 844                          * in this conflict.
 845                          */
 846                         pr_info("disabling metacopy due to redirect_dir=%s\n",
 847                                 ovl_redirect_mode(config));
 848                         config->metacopy = false;
 849                 } else {
 850                         /* Automatically enable redirect otherwise. */
 851                         config->redirect_mode = OVL_REDIRECT_ON;
 852                 }
 853         }
 854
 855         /* Resolve nfs_export -> index dependency */
 856         if (config->nfs_export && !config->index) {
 857                 if (!config->upperdir &&
 858                     config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 859                         pr_info("NFS export requires \"redirect_dir=nofollow\" on non-upper mount, falling back to nfs_export=off.\n");
 860                         config->nfs_export = false;
 861                 } else if (set.nfs_export && set.index) {
 862                         pr_err("conflicting options: nfs_export=on,index=off\n");
 863                         return -EINVAL;
 864                 } else if (set.index) {
 865                         /*
 866                          * There was an explicit index=off that resulted
 867                          * in this conflict.
 868                          */
 869                         pr_info("disabling nfs_export due to index=off\n");
 870                         config->nfs_export = false;
 871                 } else {
 872                         /* Automatically enable index otherwise. */
 873                         config->index = true;
 874                 }
 875         }
 876
 877         /* Resolve nfs_export -> !metacopy && !verity dependency */
 878         if (config->nfs_export && config->metacopy) {
 879                 if (set.nfs_export && set.metacopy) {
 880                         pr_err("conflicting options: nfs_export=on,metacopy=on\n");
 881                         return -EINVAL;
 882                 }
 883                 if (set.metacopy) {
 884                         /*
 885                          * There was an explicit metacopy=on that resulted
 886                          * in this conflict.
 887                          */
 888                         pr_info("disabling nfs_export due to metacopy=on\n");
 889                         config->nfs_export = false;
 890                 } else if (config->verity_mode) {
 891                         /*
 892                          * There was an explicit verity=.. that resulted
 893                          * in this conflict.
 894                          */
 895                         pr_info("disabling nfs_export due to verity=%s\n",
 896                                 ovl_verity_mode(config));
 897                         config->nfs_export = false;
 898                 } else {
 899                         /*
 900                          * There was an explicit nfs_export=on that resulted
 901                          * in this conflict.
 902                          */
 903                         pr_info("disabling metacopy due to nfs_export=on\n");
 904                         config->metacopy = false;
 905                 }
 906         }
 907
 908
 909         /* Resolve userxattr -> !redirect && !metacopy && !verity dependency */
 910         if (config->userxattr) {
 911                 if (set.redirect &&
 912                     config->redirect_mode != OVL_REDIRECT_NOFOLLOW) {
 913                         pr_err("conflicting options: userxattr,redirect_dir=%s\n",
 914                                ovl_redirect_mode(config));
 915                         return -EINVAL;
 916                 }
 917                 if (config->metacopy && set.metacopy) {
 918                         pr_err("conflicting options: userxattr,metacopy=on\n");
 919                         return -EINVAL;
 920                 }
 921                 if (config->verity_mode) {
 922                         pr_err("conflicting options: userxattr,verity=%s\n",
 923                                ovl_verity_mode(config));
 924                         return -EINVAL;
 925                 }
 926                 /*
 927                  * Silently disable default setting of redirect and metacopy.
 928                  * This shall be the default in the future as well: these
 929                  * options must be explicitly enabled if used together with
 930                  * userxattr.
 931                  */
 932                 config->redirect_mode = OVL_REDIRECT_NOFOLLOW;
 933                 config->metacopy = false;
 934         }
 935
 936         return 0;
 937 }
 938
 939 /**
 940  * ovl_show_options
 941  * @m: the seq_file handle
 942  * @dentry: The dentry to query
 943  *
 944  * Prints the mount options for a given superblock.
 945  * Returns zero; does not fail.
 946  */
 947 int ovl_show_options(struct seq_file *m, struct dentry *dentry)
 948 {
 949         struct super_block *sb = dentry->d_sb;
 950         struct ovl_fs *ofs = OVL_FS(sb);
 951         size_t nr, nr_merged_lower = ofs->numlayer - ofs->numdatalayer;
 952         const struct ovl_layer *data_layers = &ofs->layers[nr_merged_lower];
 953
 954         /* ofs->layers[0] is the upper layer */
 955         seq_printf(m, ",lowerdir=%s", ofs->layers[1].name);
 956         /* dump regular lower layers */
 957         for (nr = 2; nr < nr_merged_lower; nr++)
 958                 seq_printf(m, ":%s", ofs->layers[nr].name);
 959         /* dump data lower layers */
 960         for (nr = 0; nr < ofs->numdatalayer; nr++)
 961                 seq_printf(m, "::%s", data_layers[nr].name);
 962         if (ofs->config.upperdir) {
 963                 seq_show_option(m, "upperdir", ofs->config.upperdir);
 964                 seq_show_option(m, "workdir", ofs->config.workdir);
 965         }
 966         if (ofs->config.default_permissions)
 967                 seq_puts(m, ",default_permissions");
 968         if (ofs->config.redirect_mode != ovl_redirect_mode_def())
 969                 seq_printf(m, ",redirect_dir=%s",
 970                            ovl_redirect_mode(&ofs->config));
 971         if (ofs->config.index != ovl_index_def)
 972                 seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
 973         if (ofs->config.uuid != ovl_uuid_def())
 974                 seq_printf(m, ",uuid=%s", ovl_uuid_mode(&ofs->config));
 975         if (ofs->config.nfs_export != ovl_nfs_export_def)
 976                 seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
 977                                                 "on" : "off");
 978         if (ofs->config.xino != ovl_xino_def() && !ovl_same_fs(ofs))
 979                 seq_printf(m, ",xino=%s", ovl_xino_mode(&ofs->config));
 980         if (ofs->config.metacopy != ovl_metacopy_def)
 981                 seq_printf(m, ",metacopy=%s",
 982                            ofs->config.metacopy ? "on" : "off");
 983         if (ofs->config.ovl_volatile)
 984                 seq_puts(m, ",volatile");
 985         if (ofs->config.userxattr)
 986                 seq_puts(m, ",userxattr");
 987         if (ofs->config.verity_mode != ovl_verity_mode_def())
 988                 seq_printf(m, ",verity=%s",
 989                            ovl_verity_mode(&ofs->config));
 990         return 0;
 991 }