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 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 EXPORT_SYMBOL(bool_names);
  26
  27 static const struct constant_table *
  28 __lookup_constant(const struct constant_table *tbl, const char *name)
  29 {
  30         for ( ; tbl->name; tbl++)
  31                 if (strcmp(name, tbl->name) == 0)
  32                         return tbl;
  33         return NULL;
  34 }
  35
  36 /**
  37  * lookup_constant - Look up a constant by name in an ordered table
  38  * @tbl: The table of constants to search.
  39  * @name: The name to look up.
  40  * @not_found: The value to return if the name is not found.
  41  */
  42 int lookup_constant(const struct constant_table *tbl, const char *name, int not_found)
  43 {
  44         const struct constant_table *p = __lookup_constant(tbl, name);
  45
  46         return p ? p->value : not_found;
  47 }
  48 EXPORT_SYMBOL(lookup_constant);
  49
  50 static inline bool is_flag(const struct fs_parameter_spec *p)
  51 {
  52         return p->type == NULL;
  53 }
  54
  55 static const struct fs_parameter_spec *fs_lookup_key(
  56         const struct fs_parameter_spec *desc,
  57         struct fs_parameter *param, bool *negated)
  58 {
  59         const struct fs_parameter_spec *p, *other = NULL;
  60         const char *name = param->key;
  61         bool want_flag = param->type == fs_value_is_flag;
  62
  63         *negated = false;
  64         for (p = desc; p->name; p++) {
  65                 if (strcmp(p->name, name) != 0)
  66                         continue;
  67                 if (likely(is_flag(p) == want_flag))
  68                         return p;
  69                 other = p;
  70         }
  71         if (want_flag) {
  72                 if (name[0] == 'n' && name[1] == 'o' && name[2]) {
  73                         for (p = desc; p->name; p++) {
  74                                 if (strcmp(p->name, name + 2) != 0)
  75                                         continue;
  76                                 if (!(p->flags & fs_param_neg_with_no))
  77                                         continue;
  78                                 *negated = true;
  79                                 return p;
  80                         }
  81                 }
  82         }
  83         return other;
  84 }
  85
  86 /*
  87  * __fs_parse - Parse a filesystem configuration parameter
  88  * @log: The filesystem context to log errors through.
  89  * @desc: The parameter description to use.
  90  * @param: The parameter.
  91  * @result: Where to place the result of the parse
  92  *
  93  * Parse a filesystem configuration parameter and attempt a conversion for a
  94  * simple parameter for which this is requested.  If successful, the determined
  95  * parameter ID is placed into @result->key, the desired type is indicated in
  96  * @result->t and any converted value is placed into an appropriate member of
  97  * the union in @result.
  98  *
  99  * The function returns the parameter number if the parameter was matched,
 100  * -ENOPARAM if it wasn't matched and @desc->ignore_unknown indicated that
 101  * unknown parameters are okay and -EINVAL if there was a conversion issue or
 102  * the parameter wasn't recognised and unknowns aren't okay.
 103  */
 104 int __fs_parse(struct p_log *log,
 105              const struct fs_parameter_spec *desc,
 106              struct fs_parameter *param,
 107              struct fs_parse_result *result)
 108 {
 109         const struct fs_parameter_spec *p;
 110
 111         result->uint_64 = 0;
 112
 113         p = fs_lookup_key(desc, param, &result->negated);
 114         if (!p)
 115                 return -ENOPARAM;
 116
 117         if (p->flags & fs_param_deprecated)
 118                 warn_plog(log, "Deprecated parameter '%s'", param->key);
 119
 120         /* Try to turn the type we were given into the type desired by the
 121          * parameter and give an error if we can't.
 122          */
 123         if (is_flag(p)) {
 124                 if (param->type != fs_value_is_flag)
 125                         return inval_plog(log, "Unexpected value for '%s'",
 126                                       param->key);
 127                 result->boolean = !result->negated;
 128         } else  {
 129                 int ret = p->type(log, p, param, result);
 130                 if (ret)
 131                         return ret;
 132         }
 133         return p->opt;
 134 }
 135 EXPORT_SYMBOL(__fs_parse);
 136
 137 /**
 138  * fs_lookup_param - Look up a path referred to by a parameter
 139  * @fc: The filesystem context to log errors through.
 140  * @param: The parameter.
 141  * @want_bdev: T if want a blockdev
 142  * @flags: Pathwalk flags passed to filename_lookup()
 143  * @_path: The result of the lookup
 144  */
 145 int fs_lookup_param(struct fs_context *fc,
 146                     struct fs_parameter *param,
 147                     bool want_bdev,
 148                     unsigned int flags,
 149                     struct path *_path)
 150 {
 151         struct filename *f;
 152         bool put_f;
 153         int ret;
 154
 155         switch (param->type) {
 156         case fs_value_is_string:
 157                 f = getname_kernel(param->string);
 158                 if (IS_ERR(f))
 159                         return PTR_ERR(f);
 160                 param->dirfd = AT_FDCWD;
 161                 put_f = true;
 162                 break;
 163         case fs_value_is_filename:
 164                 f = param->name;
 165                 put_f = false;
 166                 break;
 167         default:
 168                 return invalf(fc, "%s: not usable as path", param->key);
 169         }
 170
 171         ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
 172         if (ret < 0) {
 173                 errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
 174                 goto out;
 175         }
 176
 177         if (want_bdev &&
 178             !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
 179                 path_put(_path);
 180                 _path->dentry = NULL;
 181                 _path->mnt = NULL;
 182                 errorf(fc, "%s: Non-blockdev passed as '%s'",
 183                        param->key, f->name);
 184                 ret = -ENOTBLK;
 185         }
 186
 187 out:
 188         if (put_f)
 189                 putname(f);
 190         return ret;
 191 }
 192 EXPORT_SYMBOL(fs_lookup_param);
 193
 194 static int fs_param_bad_value(struct p_log *log, struct fs_parameter *param)
 195 {
 196         return inval_plog(log, "Bad value for '%s'", param->key);
 197 }
 198
 199 int fs_param_is_bool(struct p_log *log, const struct fs_parameter_spec *p,
 200                      struct fs_parameter *param, struct fs_parse_result *result)
 201 {
 202         int b;
 203         if (param->type != fs_value_is_string)
 204                 return fs_param_bad_value(log, param);
 205         if (!*param->string && (p->flags & fs_param_can_be_empty))
 206                 return 0;
 207         b = lookup_constant(bool_names, param->string, -1);
 208         if (b == -1)
 209                 return fs_param_bad_value(log, param);
 210         result->boolean = b;
 211         return 0;
 212 }
 213 EXPORT_SYMBOL(fs_param_is_bool);
 214
 215 int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
 216                     struct fs_parameter *param, struct fs_parse_result *result)
 217 {
 218         int base = (unsigned long)p->data;
 219         if (param->type != fs_value_is_string)
 220                 return fs_param_bad_value(log, param);
 221         if (!*param->string && (p->flags & fs_param_can_be_empty))
 222                 return 0;
 223         if (kstrtouint(param->string, base, &result->uint_32) < 0)
 224                 return fs_param_bad_value(log, param);
 225         return 0;
 226 }
 227 EXPORT_SYMBOL(fs_param_is_u32);
 228
 229 int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
 230                     struct fs_parameter *param, struct fs_parse_result *result)
 231 {
 232         if (param->type != fs_value_is_string)
 233                 return fs_param_bad_value(log, param);
 234         if (!*param->string && (p->flags & fs_param_can_be_empty))
 235                 return 0;
 236         if (kstrtoint(param->string, 0, &result->int_32) < 0)
 237                 return fs_param_bad_value(log, param);
 238         return 0;
 239 }
 240 EXPORT_SYMBOL(fs_param_is_s32);
 241
 242 int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
 243                     struct fs_parameter *param, struct fs_parse_result *result)
 244 {
 245         if (param->type != fs_value_is_string)
 246                 return fs_param_bad_value(log, param);
 247         if (!*param->string && (p->flags & fs_param_can_be_empty))
 248                 return 0;
 249         if (kstrtoull(param->string, 0, &result->uint_64) < 0)
 250                 return fs_param_bad_value(log, param);
 251         return 0;
 252 }
 253 EXPORT_SYMBOL(fs_param_is_u64);
 254
 255 int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
 256                      struct fs_parameter *param, struct fs_parse_result *result)
 257 {
 258         const struct constant_table *c;
 259         if (param->type != fs_value_is_string)
 260                 return fs_param_bad_value(log, param);
 261         if (!*param->string && (p->flags & fs_param_can_be_empty))
 262                 return 0;
 263         c = __lookup_constant(p->data, param->string);
 264         if (!c)
 265                 return fs_param_bad_value(log, param);
 266         result->uint_32 = c->value;
 267         return 0;
 268 }
 269 EXPORT_SYMBOL(fs_param_is_enum);
 270
 271 int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
 272                        struct fs_parameter *param, struct fs_parse_result *result)
 273 {
 274         if (param->type != fs_value_is_string ||
 275             (!*param->string && !(p->flags & fs_param_can_be_empty)))
 276                 return fs_param_bad_value(log, param);
 277         return 0;
 278 }
 279 EXPORT_SYMBOL(fs_param_is_string);
 280
 281 int fs_param_is_blob(struct p_log *log, const struct fs_parameter_spec *p,
 282                      struct fs_parameter *param, struct fs_parse_result *result)
 283 {
 284         if (param->type != fs_value_is_blob)
 285                 return fs_param_bad_value(log, param);
 286         return 0;
 287 }
 288 EXPORT_SYMBOL(fs_param_is_blob);
 289
 290 int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
 291                   struct fs_parameter *param, struct fs_parse_result *result)
 292 {
 293         switch (param->type) {
 294         case fs_value_is_string:
 295                 if ((!*param->string && !(p->flags & fs_param_can_be_empty)) ||
 296                     kstrtouint(param->string, 0, &result->uint_32) < 0)
 297                         break;
 298                 if (result->uint_32 <= INT_MAX)
 299                         return 0;
 300                 break;
 301         case fs_value_is_file:
 302                 result->uint_32 = param->dirfd;
 303                 if (result->uint_32 <= INT_MAX)
 304                         return 0;
 305                 break;
 306         default:
 307                 break;
 308         }
 309         return fs_param_bad_value(log, param);
 310 }
 311 EXPORT_SYMBOL(fs_param_is_fd);
 312
 313 int fs_param_is_file_or_string(struct p_log *log,
 314                                const struct fs_parameter_spec *p,
 315                                struct fs_parameter *param,
 316                                struct fs_parse_result *result)
 317 {
 318         switch (param->type) {
 319         case fs_value_is_string:
 320                 return fs_param_is_string(log, p, param, result);
 321         case fs_value_is_file:
 322                 result->uint_32 = param->dirfd;
 323                 if (result->uint_32 <= INT_MAX)
 324                         return 0;
 325                 break;
 326         default:
 327                 break;
 328         }
 329         return fs_param_bad_value(log, param);
 330 }
 331 EXPORT_SYMBOL(fs_param_is_file_or_string);
 332
 333 int fs_param_is_uid(struct p_log *log, const struct fs_parameter_spec *p,
 334                     struct fs_parameter *param, struct fs_parse_result *result)
 335 {
 336         kuid_t uid;
 337
 338         if (fs_param_is_u32(log, p, param, result) != 0)
 339                 return fs_param_bad_value(log, param);
 340
 341         uid = make_kuid(current_user_ns(), result->uint_32);
 342         if (!uid_valid(uid))
 343                 return inval_plog(log, "Invalid uid '%s'", param->string);
 344
 345         result->uid = uid;
 346         return 0;
 347 }
 348 EXPORT_SYMBOL(fs_param_is_uid);
 349
 350 int fs_param_is_gid(struct p_log *log, const struct fs_parameter_spec *p,
 351                     struct fs_parameter *param, struct fs_parse_result *result)
 352 {
 353         kgid_t gid;
 354
 355         if (fs_param_is_u32(log, p, param, result) != 0)
 356                 return fs_param_bad_value(log, param);
 357
 358         gid = make_kgid(current_user_ns(), result->uint_32);
 359         if (!gid_valid(gid))
 360                 return inval_plog(log, "Invalid gid '%s'", param->string);
 361
 362         result->gid = gid;
 363         return 0;
 364 }
 365 EXPORT_SYMBOL(fs_param_is_gid);
 366
 367 int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
 368                   struct fs_parameter *param, struct fs_parse_result *result)
 369 {
 370         return 0;
 371 }
 372 EXPORT_SYMBOL(fs_param_is_blockdev);
 373
 374 int fs_param_is_path(struct p_log *log, const struct fs_parameter_spec *p,
 375                      struct fs_parameter *param, struct fs_parse_result *result)
 376 {
 377         return 0;
 378 }
 379 EXPORT_SYMBOL(fs_param_is_path);
 380
 381 #ifdef CONFIG_VALIDATE_FS_PARSER
 382 /**
 383  * validate_constant_table - Validate a constant table
 384  * @tbl: The constant table to validate.
 385  * @tbl_size: The size of the table.
 386  * @low: The lowest permissible value.
 387  * @high: The highest permissible value.
 388  * @special: One special permissible value outside of the range.
 389  */
 390 bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
 391                              int low, int high, int special)
 392 {
 393         size_t i;
 394         bool good = true;
 395
 396         if (tbl_size == 0) {
 397                 pr_warn("VALIDATE C-TBL: Empty\n");
 398                 return true;
 399         }
 400
 401         for (i = 0; i < tbl_size; i++) {
 402                 if (!tbl[i].name) {
 403                         pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
 404                         good = false;
 405                 } else if (i > 0 && tbl[i - 1].name) {
 406                         int c = strcmp(tbl[i-1].name, tbl[i].name);
 407
 408                         if (c == 0) {
 409                                 pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
 410                                        i, tbl[i].name);
 411                                 good = false;
 412                         }
 413                         if (c > 0) {
 414                                 pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
 415                                        i, tbl[i-1].name, tbl[i].name);
 416                                 good = false;
 417                         }
 418                 }
 419
 420                 if (tbl[i].value != special &&
 421                     (tbl[i].value < low || tbl[i].value > high)) {
 422                         pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
 423                                i, tbl[i].name, tbl[i].value, low, high);
 424                         good = false;
 425                 }
 426         }
 427
 428         return good;
 429 }
 430
 431 /**
 432  * fs_validate_description - Validate a parameter description
 433  * @name: The parameter name to search for.
 434  * @desc: The parameter description to validate.
 435  */
 436 bool fs_validate_description(const char *name,
 437         const struct fs_parameter_spec *desc)
 438 {
 439         const struct fs_parameter_spec *param, *p2;
 440         bool good = true;
 441
 442         for (param = desc; param->name; param++) {
 443                 /* Check for duplicate parameter names */
 444                 for (p2 = desc; p2 < param; p2++) {
 445                         if (strcmp(param->name, p2->name) == 0) {
 446                                 if (is_flag(param) != is_flag(p2))
 447                                         continue;
 448                                 pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
 449                                        name, param->name);
 450                                 good = false;
 451                         }
 452                 }
 453         }
 454         return good;
 455 }
 456 #endif /* CONFIG_VALIDATE_FS_PARSER */