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 static const struct constant_table *
  27 __lookup_constant(const struct constant_table *tbl, const char *name)
  28 {
  29         for ( ; tbl->name; tbl++)
  30                 if (strcmp(name, tbl->name) == 0)
  31                         return tbl;
  32         return NULL;
  33 }
  34
  35 /**
  36  * lookup_constant - Look up a constant by name in an ordered table
  37  * @tbl: The table of constants to search.
  38  * @name: The name to look up.
  39  * @not_found: The value to return if the name is not found.
  40  */
  41 int lookup_constant(const struct constant_table *tbl, const char *name, int not_found)
  42 {
  43         const struct constant_table *p = __lookup_constant(tbl, name);
  44
  45         return p ? p->value : not_found;
  46 }
  47 EXPORT_SYMBOL(lookup_constant);
  48
  49 static inline bool is_flag(const struct fs_parameter_spec *p)
  50 {
  51         return p->type == NULL;
  52 }
  53
  54 static const struct fs_parameter_spec *fs_lookup_key(
  55         const struct fs_parameter_spec *desc,
  56         struct fs_parameter *param, bool *negated)
  57 {
  58         const struct fs_parameter_spec *p, *other = NULL;
  59         const char *name = param->key;
  60         bool want_flag = param->type == fs_value_is_flag;
  61
  62         *negated = false;
  63         for (p = desc; p->name; p++) {
  64                 if (strcmp(p->name, name) != 0)
  65                         continue;
  66                 if (likely(is_flag(p) == want_flag))
  67                         return p;
  68                 other = p;
  69         }
  70         if (want_flag) {
  71                 if (name[0] == 'n' && name[1] == 'o' && name[2]) {
  72                         for (p = desc; p->name; p++) {
  73                                 if (strcmp(p->name, name + 2) != 0)
  74                                         continue;
  75                                 if (!(p->flags & fs_param_neg_with_no))
  76                                         continue;
  77                                 *negated = true;
  78                                 return p;
  79                         }
  80                 }
  81         }
  82         return other;
  83 }
  84
  85 /*
  86  * __fs_parse - Parse a filesystem configuration parameter
  87  * @log: The filesystem context to log errors through.
  88  * @desc: The parameter description to use.
  89  * @param: The parameter.
  90  * @result: Where to place the result of the parse
  91  *
  92  * Parse a filesystem configuration parameter and attempt a conversion for a
  93  * simple parameter for which this is requested.  If successful, the determined
  94  * parameter ID is placed into @result->key, the desired type is indicated in
  95  * @result->t and any converted value is placed into an appropriate member of
  96  * the union in @result.
  97  *
  98  * The function returns the parameter number if the parameter was matched,
  99  * -ENOPARAM if it wasn't matched and @desc->ignore_unknown indicated that
 100  * unknown parameters are okay and -EINVAL if there was a conversion issue or
 101  * the parameter wasn't recognised and unknowns aren't okay.
 102  */
 103 int __fs_parse(struct p_log *log,
 104              const struct fs_parameter_spec *desc,
 105              struct fs_parameter *param,
 106              struct fs_parse_result *result)
 107 {
 108         const struct fs_parameter_spec *p;
 109
 110         result->uint_64 = 0;
 111
 112         p = fs_lookup_key(desc, param, &result->negated);
 113         if (!p)
 114                 return -ENOPARAM;
 115
 116         if (p->flags & fs_param_deprecated)
 117                 warn_plog(log, "Deprecated parameter '%s'", param->key);
 118
 119         /* Try to turn the type we were given into the type desired by the
 120          * parameter and give an error if we can't.
 121          */
 122         if (is_flag(p)) {
 123                 if (param->type != fs_value_is_flag)
 124                         return inval_plog(log, "Unexpected value for '%s'",
 125                                       param->key);
 126                 result->boolean = !result->negated;
 127         } else  {
 128                 int ret = p->type(log, p, param, result);
 129                 if (ret)
 130                         return ret;
 131         }
 132         return p->opt;
 133 }
 134 EXPORT_SYMBOL(__fs_parse);
 135
 136 /**
 137  * fs_lookup_param - Look up a path referred to by a parameter
 138  * @fc: The filesystem context to log errors through.
 139  * @param: The parameter.
 140  * @want_bdev: T if want a blockdev
 141  * @flags: Pathwalk flags passed to filename_lookup()
 142  * @_path: The result of the lookup
 143  */
 144 int fs_lookup_param(struct fs_context *fc,
 145                     struct fs_parameter *param,
 146                     bool want_bdev,
 147                     unsigned int flags,
 148                     struct path *_path)
 149 {
 150         struct filename *f;
 151         bool put_f;
 152         int ret;
 153
 154         switch (param->type) {
 155         case fs_value_is_string:
 156                 f = getname_kernel(param->string);
 157                 if (IS_ERR(f))
 158                         return PTR_ERR(f);
 159                 param->dirfd = AT_FDCWD;
 160                 put_f = true;
 161                 break;
 162         case fs_value_is_filename:
 163                 f = param->name;
 164                 put_f = false;
 165                 break;
 166         default:
 167                 return invalf(fc, "%s: not usable as path", param->key);
 168         }
 169
 170         ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
 171         if (ret < 0) {
 172                 errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
 173                 goto out;
 174         }
 175
 176         if (want_bdev &&
 177             !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
 178                 path_put(_path);
 179                 _path->dentry = NULL;
 180                 _path->mnt = NULL;
 181                 errorf(fc, "%s: Non-blockdev passed as '%s'",
 182                        param->key, f->name);
 183                 ret = -ENOTBLK;
 184         }
 185
 186 out:
 187         if (put_f)
 188                 putname(f);
 189         return ret;
 190 }
 191 EXPORT_SYMBOL(fs_lookup_param);
 192
 193 static int fs_param_bad_value(struct p_log *log, struct fs_parameter *param)
 194 {
 195         return inval_plog(log, "Bad value for '%s'", param->key);
 196 }
 197
 198 int fs_param_is_bool(struct p_log *log, const struct fs_parameter_spec *p,
 199                      struct fs_parameter *param, struct fs_parse_result *result)
 200 {
 201         int b;
 202         if (param->type != fs_value_is_string)
 203                 return fs_param_bad_value(log, param);
 204         if (!*param->string && (p->flags & fs_param_can_be_empty))
 205                 return 0;
 206         b = lookup_constant(bool_names, param->string, -1);
 207         if (b == -1)
 208                 return fs_param_bad_value(log, param);
 209         result->boolean = b;
 210         return 0;
 211 }
 212 EXPORT_SYMBOL(fs_param_is_bool);
 213
 214 int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
 215                     struct fs_parameter *param, struct fs_parse_result *result)
 216 {
 217         int base = (unsigned long)p->data;
 218         if (param->type != fs_value_is_string)
 219                 return fs_param_bad_value(log, param);
 220         if (!*param->string && (p->flags & fs_param_can_be_empty))
 221                 return 0;
 222         if (kstrtouint(param->string, base, &result->uint_32) < 0)
 223                 return fs_param_bad_value(log, param);
 224         return 0;
 225 }
 226 EXPORT_SYMBOL(fs_param_is_u32);
 227
 228 int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
 229                     struct fs_parameter *param, struct fs_parse_result *result)
 230 {
 231         if (param->type != fs_value_is_string)
 232                 return fs_param_bad_value(log, param);
 233         if (!*param->string && (p->flags & fs_param_can_be_empty))
 234                 return 0;
 235         if (kstrtoint(param->string, 0, &result->int_32) < 0)
 236                 return fs_param_bad_value(log, param);
 237         return 0;
 238 }
 239 EXPORT_SYMBOL(fs_param_is_s32);
 240
 241 int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
 242                     struct fs_parameter *param, struct fs_parse_result *result)
 243 {
 244         if (param->type != fs_value_is_string)
 245                 return fs_param_bad_value(log, param);
 246         if (!*param->string && (p->flags & fs_param_can_be_empty))
 247                 return 0;
 248         if (kstrtoull(param->string, 0, &result->uint_64) < 0)
 249                 return fs_param_bad_value(log, param);
 250         return 0;
 251 }
 252 EXPORT_SYMBOL(fs_param_is_u64);
 253
 254 int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
 255                      struct fs_parameter *param, struct fs_parse_result *result)
 256 {
 257         const struct constant_table *c;
 258         if (param->type != fs_value_is_string)
 259                 return fs_param_bad_value(log, param);
 260         if (!*param->string && (p->flags & fs_param_can_be_empty))
 261                 return 0;
 262         c = __lookup_constant(p->data, param->string);
 263         if (!c)
 264                 return fs_param_bad_value(log, param);
 265         result->uint_32 = c->value;
 266         return 0;
 267 }
 268 EXPORT_SYMBOL(fs_param_is_enum);
 269
 270 int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
 271                        struct fs_parameter *param, struct fs_parse_result *result)
 272 {
 273         if (param->type != fs_value_is_string ||
 274             (!*param->string && !(p->flags & fs_param_can_be_empty)))
 275                 return fs_param_bad_value(log, param);
 276         return 0;
 277 }
 278 EXPORT_SYMBOL(fs_param_is_string);
 279
 280 int fs_param_is_blob(struct p_log *log, const struct fs_parameter_spec *p,
 281                      struct fs_parameter *param, struct fs_parse_result *result)
 282 {
 283         if (param->type != fs_value_is_blob)
 284                 return fs_param_bad_value(log, param);
 285         return 0;
 286 }
 287 EXPORT_SYMBOL(fs_param_is_blob);
 288
 289 int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
 290                   struct fs_parameter *param, struct fs_parse_result *result)
 291 {
 292         switch (param->type) {
 293         case fs_value_is_string:
 294                 if ((!*param->string && !(p->flags & fs_param_can_be_empty)) ||
 295                     kstrtouint(param->string, 0, &result->uint_32) < 0)
 296                         break;
 297                 if (result->uint_32 <= INT_MAX)
 298                         return 0;
 299                 break;
 300         case fs_value_is_file:
 301                 result->uint_32 = param->dirfd;
 302                 if (result->uint_32 <= INT_MAX)
 303                         return 0;
 304                 break;
 305         default:
 306                 break;
 307         }
 308         return fs_param_bad_value(log, param);
 309 }
 310 EXPORT_SYMBOL(fs_param_is_fd);
 311
 312 int fs_param_is_file_or_string(struct p_log *log,
 313                                const struct fs_parameter_spec *p,
 314                                struct fs_parameter *param,
 315                                struct fs_parse_result *result)
 316 {
 317         switch (param->type) {
 318         case fs_value_is_string:
 319                 return fs_param_is_string(log, p, param, result);
 320         case fs_value_is_file:
 321                 result->uint_32 = param->dirfd;
 322                 if (result->uint_32 <= INT_MAX)
 323                         return 0;
 324                 break;
 325         default:
 326                 break;
 327         }
 328         return fs_param_bad_value(log, param);
 329 }
 330 EXPORT_SYMBOL(fs_param_is_file_or_string);
 331
 332 int fs_param_is_uid(struct p_log *log, const struct fs_parameter_spec *p,
 333                     struct fs_parameter *param, struct fs_parse_result *result)
 334 {
 335         kuid_t uid;
 336
 337         if (fs_param_is_u32(log, p, param, result) != 0)
 338                 return fs_param_bad_value(log, param);
 339
 340         uid = make_kuid(current_user_ns(), result->uint_32);
 341         if (!uid_valid(uid))
 342                 return inval_plog(log, "Invalid uid '%s'", param->string);
 343
 344         result->uid = uid;
 345         return 0;
 346 }
 347 EXPORT_SYMBOL(fs_param_is_uid);
 348
 349 int fs_param_is_gid(struct p_log *log, const struct fs_parameter_spec *p,
 350                     struct fs_parameter *param, struct fs_parse_result *result)
 351 {
 352         kgid_t gid;
 353
 354         if (fs_param_is_u32(log, p, param, result) != 0)
 355                 return fs_param_bad_value(log, param);
 356
 357         gid = make_kgid(current_user_ns(), result->uint_32);
 358         if (!gid_valid(gid))
 359                 return inval_plog(log, "Invalid gid '%s'", param->string);
 360
 361         result->gid = gid;
 362         return 0;
 363 }
 364 EXPORT_SYMBOL(fs_param_is_gid);
 365
 366 int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
 367                   struct fs_parameter *param, struct fs_parse_result *result)
 368 {
 369         return 0;
 370 }
 371 EXPORT_SYMBOL(fs_param_is_blockdev);
 372
 373 int fs_param_is_path(struct p_log *log, const struct fs_parameter_spec *p,
 374                      struct fs_parameter *param, struct fs_parse_result *result)
 375 {
 376         return 0;
 377 }
 378 EXPORT_SYMBOL(fs_param_is_path);
 379
 380 #ifdef CONFIG_VALIDATE_FS_PARSER
 381 /**
 382  * validate_constant_table - Validate a constant table
 383  * @tbl: The constant table to validate.
 384  * @tbl_size: The size of the table.
 385  * @low: The lowest permissible value.
 386  * @high: The highest permissible value.
 387  * @special: One special permissible value outside of the range.
 388  */
 389 bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
 390                              int low, int high, int special)
 391 {
 392         size_t i;
 393         bool good = true;
 394
 395         if (tbl_size == 0) {
 396                 pr_warn("VALIDATE C-TBL: Empty\n");
 397                 return true;
 398         }
 399
 400         for (i = 0; i < tbl_size; i++) {
 401                 if (!tbl[i].name) {
 402                         pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
 403                         good = false;
 404                 } else if (i > 0 && tbl[i - 1].name) {
 405                         int c = strcmp(tbl[i-1].name, tbl[i].name);
 406
 407                         if (c == 0) {
 408                                 pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
 409                                        i, tbl[i].name);
 410                                 good = false;
 411                         }
 412                         if (c > 0) {
 413                                 pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
 414                                        i, tbl[i-1].name, tbl[i].name);
 415                                 good = false;
 416                         }
 417                 }
 418
 419                 if (tbl[i].value != special &&
 420                     (tbl[i].value < low || tbl[i].value > high)) {
 421                         pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
 422                                i, tbl[i].name, tbl[i].value, low, high);
 423                         good = false;
 424                 }
 425         }
 426
 427         return good;
 428 }
 429
 430 /**
 431  * fs_validate_description - Validate a parameter description
 432  * @name: The parameter name to search for.
 433  * @desc: The parameter description to validate.
 434  */
 435 bool fs_validate_description(const char *name,
 436         const struct fs_parameter_spec *desc)
 437 {
 438         const struct fs_parameter_spec *param, *p2;
 439         bool good = true;
 440
 441         for (param = desc; param->name; param++) {
 442                 /* Check for duplicate parameter names */
 443                 for (p2 = desc; p2 < param; p2++) {
 444                         if (strcmp(param->name, p2->name) == 0) {
 445                                 if (is_flag(param) != is_flag(p2))
 446                                         continue;
 447                                 pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
 448                                        name, param->name);
 449                                 good = false;
 450                         }
 451                 }
 452         }
 453         return good;
 454 }
 455 #endif /* CONFIG_VALIDATE_FS_PARSER */