fs/fs_parser.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /* Filesystem parameter parser.
   3  *
   4  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   5  * Written by David Howells (dhowells@redhat.com)
   6  */
   7
   8 #include <linux/export.h>
   9 #include <linux/fs_context.h>
  10 #include <linux/fs_parser.h>
  11 #include <linux/slab.h>
  12 #include <linux/security.h>
  13 #include <linux/namei.h>
  14 #include "internal.h"
  15
  16 static const struct constant_table bool_names[] = {
  17         { "0",          false },
  18         { "1",          true },
  19         { "false",      false },
  20         { "no",         false },
  21         { "true",       true },
  22         { "yes",        true },
  23 };
  24
  25 /**
  26  * lookup_constant - Look up a constant by name in an ordered table
  27  * @tbl: The table of constants to search.
  28  * @tbl_size: The size of the table.
  29  * @name: The name to look up.
  30  * @not_found: The value to return if the name is not found.
  31  */
  32 int __lookup_constant(const struct constant_table *tbl, size_t tbl_size,
  33                       const char *name, int not_found)
  34 {
  35         unsigned int i;
  36
  37         for (i = 0; i < tbl_size; i++)
  38                 if (strcmp(name, tbl[i].name) == 0)
  39                         return tbl[i].value;
  40
  41         return not_found;
  42 }
  43 EXPORT_SYMBOL(__lookup_constant);
  44
  45 static const struct fs_parameter_spec *fs_lookup_key(
  46         const struct fs_parameter_description *desc,
  47         const char *name)
  48 {
  49         const struct fs_parameter_spec *p;
  50
  51         if (!desc->specs)
  52                 return NULL;
  53
  54         for (p = desc->specs; p->name; p++)
  55                 if (strcmp(p->name, name) == 0)
  56                         return p;
  57
  58         return NULL;
  59 }
  60
  61 /*
  62  * fs_parse - Parse a filesystem configuration parameter
  63  * @fc: The filesystem context to log errors through.
  64  * @desc: The parameter description to use.
  65  * @param: The parameter.
  66  * @result: Where to place the result of the parse
  67  *
  68  * Parse a filesystem configuration parameter and attempt a conversion for a
  69  * simple parameter for which this is requested.  If successful, the determined
  70  * parameter ID is placed into @result->key, the desired type is indicated in
  71  * @result->t and any converted value is placed into an appropriate member of
  72  * the union in @result.
  73  *
  74  * The function returns the parameter number if the parameter was matched,
  75  * -ENOPARAM if it wasn't matched and @desc->ignore_unknown indicated that
  76  * unknown parameters are okay and -EINVAL if there was a conversion issue or
  77  * the parameter wasn't recognised and unknowns aren't okay.
  78  */
  79 int fs_parse(struct fs_context *fc,
  80              const struct fs_parameter_description *desc,
  81              struct fs_parameter *param,
  82              struct fs_parse_result *result)
  83 {
  84         const struct fs_parameter_spec *p;
  85         const struct fs_parameter_enum *e;
  86         int ret = -ENOPARAM, b;
  87
  88         result->has_value = !!param->string;
  89         result->negated = false;
  90         result->uint_64 = 0;
  91
  92         p = fs_lookup_key(desc, param->key);
  93         if (!p) {
  94                 /* If we didn't find something that looks like "noxxx", see if
  95                  * "xxx" takes the "no"-form negative - but only if there
  96                  * wasn't an value.
  97                  */
  98                 if (result->has_value)
  99                         goto unknown_parameter;
 100                 if (param->key[0] != 'n' || param->key[1] != 'o' || !param->key[2])
 101                         goto unknown_parameter;
 102
 103                 p = fs_lookup_key(desc, param->key + 2);
 104                 if (!p)
 105                         goto unknown_parameter;
 106                 if (!(p->flags & fs_param_neg_with_no))
 107                         goto unknown_parameter;
 108                 result->boolean = false;
 109                 result->negated = true;
 110         }
 111
 112         if (p->flags & fs_param_deprecated)
 113                 warnf(fc, "%s: Deprecated parameter '%s'",
 114                       desc->name, param->key);
 115
 116         if (result->negated)
 117                 goto okay;
 118
 119         /* Certain parameter types only take a string and convert it. */
 120         switch (p->type) {
 121         case __fs_param_wasnt_defined:
 122                 return -EINVAL;
 123         case fs_param_is_u32:
 124         case fs_param_is_u32_octal:
 125         case fs_param_is_u32_hex:
 126         case fs_param_is_s32:
 127         case fs_param_is_u64:
 128         case fs_param_is_enum:
 129         case fs_param_is_string:
 130                 if (param->type != fs_value_is_string)
 131                         goto bad_value;
 132                 if (!result->has_value) {
 133                         if (p->flags & fs_param_v_optional)
 134                                 goto okay;
 135                         goto bad_value;
 136                 }
 137                 /* Fall through */
 138         default:
 139                 break;
 140         }
 141
 142         /* Try to turn the type we were given into the type desired by the
 143          * parameter and give an error if we can't.
 144          */
 145         switch (p->type) {
 146         case fs_param_is_flag:
 147                 if (param->type != fs_value_is_flag &&
 148                     (param->type != fs_value_is_string || result->has_value))
 149                         return invalf(fc, "%s: Unexpected value for '%s'",
 150                                       desc->name, param->key);
 151                 result->boolean = true;
 152                 goto okay;
 153
 154         case fs_param_is_bool:
 155                 switch (param->type) {
 156                 case fs_value_is_flag:
 157                         result->boolean = true;
 158                         goto okay;
 159                 case fs_value_is_string:
 160                         if (param->size == 0) {
 161                                 result->boolean = true;
 162                                 goto okay;
 163                         }
 164                         b = lookup_constant(bool_names, param->string, -1);
 165                         if (b == -1)
 166                                 goto bad_value;
 167                         result->boolean = b;
 168                         goto okay;
 169                 default:
 170                         goto bad_value;
 171                 }
 172
 173         case fs_param_is_u32:
 174                 ret = kstrtouint(param->string, 0, &result->uint_32);
 175                 goto maybe_okay;
 176         case fs_param_is_u32_octal:
 177                 ret = kstrtouint(param->string, 8, &result->uint_32);
 178                 goto maybe_okay;
 179         case fs_param_is_u32_hex:
 180                 ret = kstrtouint(param->string, 16, &result->uint_32);
 181                 goto maybe_okay;
 182         case fs_param_is_s32:
 183                 ret = kstrtoint(param->string, 0, &result->int_32);
 184                 goto maybe_okay;
 185         case fs_param_is_u64:
 186                 ret = kstrtoull(param->string, 0, &result->uint_64);
 187                 goto maybe_okay;
 188
 189         case fs_param_is_enum:
 190                 for (e = desc->enums; e->name[0]; e++) {
 191                         if (e->opt == p->opt &&
 192                             strcmp(e->name, param->string) == 0) {
 193                                 result->uint_32 = e->value;
 194                                 goto okay;
 195                         }
 196                 }
 197                 goto bad_value;
 198
 199         case fs_param_is_string:
 200                 goto okay;
 201         case fs_param_is_blob:
 202                 if (param->type != fs_value_is_blob)
 203                         goto bad_value;
 204                 goto okay;
 205
 206         case fs_param_is_fd: {
 207                 if (param->type != fs_value_is_file)
 208                         goto bad_value;
 209                 goto okay;
 210         }
 211
 212         case fs_param_is_blockdev:
 213         case fs_param_is_path:
 214                 goto okay;
 215         default:
 216                 BUG();
 217         }
 218
 219 maybe_okay:
 220         if (ret < 0)
 221                 goto bad_value;
 222 okay:
 223         return p->opt;
 224
 225 bad_value:
 226         return invalf(fc, "%s: Bad value for '%s'", desc->name, param->key);
 227 unknown_parameter:
 228         return -ENOPARAM;
 229 }
 230 EXPORT_SYMBOL(fs_parse);
 231
 232 /**
 233  * fs_lookup_param - Look up a path referred to by a parameter
 234  * @fc: The filesystem context to log errors through.
 235  * @param: The parameter.
 236  * @want_bdev: T if want a blockdev
 237  * @_path: The result of the lookup
 238  */
 239 int fs_lookup_param(struct fs_context *fc,
 240                     struct fs_parameter *param,
 241                     bool want_bdev,
 242                     struct path *_path)
 243 {
 244         struct filename *f;
 245         unsigned int flags = 0;
 246         bool put_f;
 247         int ret;
 248
 249         switch (param->type) {
 250         case fs_value_is_string:
 251                 f = getname_kernel(param->string);
 252                 if (IS_ERR(f))
 253                         return PTR_ERR(f);
 254                 put_f = true;
 255                 break;
 256         case fs_value_is_filename_empty:
 257                 flags = LOOKUP_EMPTY;
 258                 /* Fall through */
 259         case fs_value_is_filename:
 260                 f = param->name;
 261                 put_f = false;
 262                 break;
 263         default:
 264                 return invalf(fc, "%s: not usable as path", param->key);
 265         }
 266
 267         f->refcnt++; /* filename_lookup() drops our ref. */
 268         ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
 269         if (ret < 0) {
 270                 errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
 271                 goto out;
 272         }
 273
 274         if (want_bdev &&
 275             !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
 276                 path_put(_path);
 277                 _path->dentry = NULL;
 278                 _path->mnt = NULL;
 279                 errorf(fc, "%s: Non-blockdev passed as '%s'",
 280                        param->key, f->name);
 281                 ret = -ENOTBLK;
 282         }
 283
 284 out:
 285         if (put_f)
 286                 putname(f);
 287         return ret;
 288 }
 289 EXPORT_SYMBOL(fs_lookup_param);
 290
 291 #ifdef CONFIG_VALIDATE_FS_PARSER
 292 /**
 293  * validate_constant_table - Validate a constant table
 294  * @name: Name to use in reporting
 295  * @tbl: The constant table to validate.
 296  * @tbl_size: The size of the table.
 297  * @low: The lowest permissible value.
 298  * @high: The highest permissible value.
 299  * @special: One special permissible value outside of the range.
 300  */
 301 bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
 302                              int low, int high, int special)
 303 {
 304         size_t i;
 305         bool good = true;
 306
 307         if (tbl_size == 0) {
 308                 pr_warn("VALIDATE C-TBL: Empty\n");
 309                 return true;
 310         }
 311
 312         for (i = 0; i < tbl_size; i++) {
 313                 if (!tbl[i].name) {
 314                         pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
 315                         good = false;
 316                 } else if (i > 0 && tbl[i - 1].name) {
 317                         int c = strcmp(tbl[i-1].name, tbl[i].name);
 318
 319                         if (c == 0) {
 320                                 pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
 321                                        i, tbl[i].name);
 322                                 good = false;
 323                         }
 324                         if (c > 0) {
 325                                 pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
 326                                        i, tbl[i-1].name, tbl[i].name);
 327                                 good = false;
 328                         }
 329                 }
 330
 331                 if (tbl[i].value != special &&
 332                     (tbl[i].value < low || tbl[i].value > high)) {
 333                         pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
 334                                i, tbl[i].name, tbl[i].value, low, high);
 335                         good = false;
 336                 }
 337         }
 338
 339         return good;
 340 }
 341
 342 /**
 343  * fs_validate_description - Validate a parameter description
 344  * @desc: The parameter description to validate.
 345  */
 346 bool fs_validate_description(const struct fs_parameter_description *desc)
 347 {
 348         const struct fs_parameter_spec *param, *p2;
 349         const struct fs_parameter_enum *e;
 350         const char *name = desc->name;
 351         unsigned int nr_params = 0;
 352         bool good = true, enums = false;
 353
 354         pr_notice("*** VALIDATE %s ***\n", name);
 355
 356         if (!name[0]) {
 357                 pr_err("VALIDATE Parser: No name\n");
 358                 name = "Unknown";
 359                 good = false;
 360         }
 361
 362         if (desc->specs) {
 363                 for (param = desc->specs; param->name; param++) {
 364                         enum fs_parameter_type t = param->type;
 365
 366                         /* Check that the type is in range */
 367                         if (t == __fs_param_wasnt_defined ||
 368                             t >= nr__fs_parameter_type) {
 369                                 pr_err("VALIDATE %s: PARAM[%s] Bad type %u\n",
 370                                        name, param->name, t);
 371                                 good = false;
 372                         } else if (t == fs_param_is_enum) {
 373                                 enums = true;
 374                         }
 375
 376                         /* Check for duplicate parameter names */
 377                         for (p2 = desc->specs; p2 < param; p2++) {
 378                                 if (strcmp(param->name, p2->name) == 0) {
 379                                         pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
 380                                                name, param->name);
 381                                         good = false;
 382                                 }
 383                         }
 384                 }
 385
 386                 nr_params = param - desc->specs;
 387         }
 388
 389         if (desc->enums) {
 390                 if (!nr_params) {
 391                         pr_err("VALIDATE %s: Enum table but no parameters\n",
 392                                name);
 393                         good = false;
 394                         goto no_enums;
 395                 }
 396                 if (!enums) {
 397                         pr_err("VALIDATE %s: Enum table but no enum-type values\n",
 398                                name);
 399                         good = false;
 400                         goto no_enums;
 401                 }
 402
 403                 for (e = desc->enums; e->name[0]; e++) {
 404                         /* Check that all entries in the enum table have at
 405                          * least one parameter that uses them.
 406                          */
 407                         for (param = desc->specs; param->name; param++) {
 408                                 if (param->opt == e->opt &&
 409                                     param->type != fs_param_is_enum) {
 410                                         pr_err("VALIDATE %s: e[%tu] enum val for %s\n",
 411                                                name, e - desc->enums, param->name);
 412                                         good = false;
 413                                 }
 414                         }
 415                 }
 416
 417                 /* Check that all enum-type parameters have at least one enum
 418                  * value in the enum table.
 419                  */
 420                 for (param = desc->specs; param->name; param++) {
 421                         if (param->type != fs_param_is_enum)
 422                                 continue;
 423                         for (e = desc->enums; e->name[0]; e++)
 424                                 if (e->opt == param->opt)
 425                                         break;
 426                         if (!e->name[0]) {
 427                                 pr_err("VALIDATE %s: PARAM[%s] enum with no values\n",
 428                                        name, param->name);
 429                                 good = false;
 430                         }
 431                 }
 432         } else {
 433                 if (enums) {
 434                         pr_err("VALIDATE %s: enum-type values, but no enum table\n",
 435                                name);
 436                         good = false;
 437                         goto no_enums;
 438                 }
 439         }
 440
 441 no_enums:
 442         return good;
 443 }
 444 #endif /* CONFIG_VALIDATE_FS_PARSER */