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  * @fc: 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  * @_path: The result of the lookup
 142  */
 143 int fs_lookup_param(struct fs_context *fc,
 144                     struct fs_parameter *param,
 145                     bool want_bdev,
 146                     struct path *_path)
 147 {
 148         struct filename *f;
 149         unsigned int flags = 0;
 150         bool put_f;
 151         int ret;
 152
 153         switch (param->type) {
 154         case fs_value_is_string:
 155                 f = getname_kernel(param->string);
 156                 if (IS_ERR(f))
 157                         return PTR_ERR(f);
 158                 put_f = true;
 159                 break;
 160         case fs_value_is_filename:
 161                 f = param->name;
 162                 put_f = false;
 163                 break;
 164         default:
 165                 return invalf(fc, "%s: not usable as path", param->key);
 166         }
 167
 168         ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
 169         if (ret < 0) {
 170                 errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
 171                 goto out;
 172         }
 173
 174         if (want_bdev &&
 175             !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
 176                 path_put(_path);
 177                 _path->dentry = NULL;
 178                 _path->mnt = NULL;
 179                 errorf(fc, "%s: Non-blockdev passed as '%s'",
 180                        param->key, f->name);
 181                 ret = -ENOTBLK;
 182         }
 183
 184 out:
 185         if (put_f)
 186                 putname(f);
 187         return ret;
 188 }
 189 EXPORT_SYMBOL(fs_lookup_param);
 190
 191 static int fs_param_bad_value(struct p_log *log, struct fs_parameter *param)
 192 {
 193         return inval_plog(log, "Bad value for '%s'", param->key);
 194 }
 195
 196 int fs_param_is_bool(struct p_log *log, const struct fs_parameter_spec *p,
 197                      struct fs_parameter *param, struct fs_parse_result *result)
 198 {
 199         int b;
 200         if (param->type != fs_value_is_string)
 201                 return fs_param_bad_value(log, param);
 202         b = lookup_constant(bool_names, param->string, -1);
 203         if (b == -1)
 204                 return fs_param_bad_value(log, param);
 205         result->boolean = b;
 206         return 0;
 207 }
 208 EXPORT_SYMBOL(fs_param_is_bool);
 209
 210 int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
 211                     struct fs_parameter *param, struct fs_parse_result *result)
 212 {
 213         int base = (unsigned long)p->data;
 214         if (param->type != fs_value_is_string ||
 215             kstrtouint(param->string, base, &result->uint_32) < 0)
 216                 return fs_param_bad_value(log, param);
 217         return 0;
 218 }
 219 EXPORT_SYMBOL(fs_param_is_u32);
 220
 221 int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
 222                     struct fs_parameter *param, struct fs_parse_result *result)
 223 {
 224         if (param->type != fs_value_is_string ||
 225             kstrtoint(param->string, 0, &result->int_32) < 0)
 226                 return fs_param_bad_value(log, param);
 227         return 0;
 228 }
 229 EXPORT_SYMBOL(fs_param_is_s32);
 230
 231 int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
 232                     struct fs_parameter *param, struct fs_parse_result *result)
 233 {
 234         if (param->type != fs_value_is_string ||
 235             kstrtoull(param->string, 0, &result->uint_64) < 0)
 236                 return fs_param_bad_value(log, param);
 237         return 0;
 238 }
 239 EXPORT_SYMBOL(fs_param_is_u64);
 240
 241 int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
 242                      struct fs_parameter *param, struct fs_parse_result *result)
 243 {
 244         const struct constant_table *c;
 245         if (param->type != fs_value_is_string)
 246                 return fs_param_bad_value(log, param);
 247         c = __lookup_constant(p->data, param->string);
 248         if (!c)
 249                 return fs_param_bad_value(log, param);
 250         result->uint_32 = c->value;
 251         return 0;
 252 }
 253 EXPORT_SYMBOL(fs_param_is_enum);
 254
 255 int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
 256                        struct fs_parameter *param, struct fs_parse_result *result)
 257 {
 258         if (param->type != fs_value_is_string || !*param->string)
 259                 return fs_param_bad_value(log, param);
 260         return 0;
 261 }
 262 EXPORT_SYMBOL(fs_param_is_string);
 263
 264 int fs_param_is_blob(struct p_log *log, const struct fs_parameter_spec *p,
 265                      struct fs_parameter *param, struct fs_parse_result *result)
 266 {
 267         if (param->type != fs_value_is_blob)
 268                 return fs_param_bad_value(log, param);
 269         return 0;
 270 }
 271 EXPORT_SYMBOL(fs_param_is_blob);
 272
 273 int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
 274                   struct fs_parameter *param, struct fs_parse_result *result)
 275 {
 276         switch (param->type) {
 277         case fs_value_is_string:
 278                 if (kstrtouint(param->string, 0, &result->uint_32) < 0)
 279                         break;
 280                 if (result->uint_32 <= INT_MAX)
 281                         return 0;
 282                 break;
 283         case fs_value_is_file:
 284                 result->uint_32 = param->dirfd;
 285                 if (result->uint_32 <= INT_MAX)
 286                         return 0;
 287                 break;
 288         default:
 289                 break;
 290         }
 291         return fs_param_bad_value(log, param);
 292 }
 293 EXPORT_SYMBOL(fs_param_is_fd);
 294
 295 int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
 296                   struct fs_parameter *param, struct fs_parse_result *result)
 297 {
 298         return 0;
 299 }
 300 EXPORT_SYMBOL(fs_param_is_blockdev);
 301
 302 int fs_param_is_path(struct p_log *log, const struct fs_parameter_spec *p,
 303                      struct fs_parameter *param, struct fs_parse_result *result)
 304 {
 305         return 0;
 306 }
 307 EXPORT_SYMBOL(fs_param_is_path);
 308
 309 #ifdef CONFIG_VALIDATE_FS_PARSER
 310 /**
 311  * validate_constant_table - Validate a constant table
 312  * @tbl: The constant table to validate.
 313  * @tbl_size: The size of the table.
 314  * @low: The lowest permissible value.
 315  * @high: The highest permissible value.
 316  * @special: One special permissible value outside of the range.
 317  */
 318 bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
 319                              int low, int high, int special)
 320 {
 321         size_t i;
 322         bool good = true;
 323
 324         if (tbl_size == 0) {
 325                 pr_warn("VALIDATE C-TBL: Empty\n");
 326                 return true;
 327         }
 328
 329         for (i = 0; i < tbl_size; i++) {
 330                 if (!tbl[i].name) {
 331                         pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
 332                         good = false;
 333                 } else if (i > 0 && tbl[i - 1].name) {
 334                         int c = strcmp(tbl[i-1].name, tbl[i].name);
 335
 336                         if (c == 0) {
 337                                 pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
 338                                        i, tbl[i].name);
 339                                 good = false;
 340                         }
 341                         if (c > 0) {
 342                                 pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
 343                                        i, tbl[i-1].name, tbl[i].name);
 344                                 good = false;
 345                         }
 346                 }
 347
 348                 if (tbl[i].value != special &&
 349                     (tbl[i].value < low || tbl[i].value > high)) {
 350                         pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
 351                                i, tbl[i].name, tbl[i].value, low, high);
 352                         good = false;
 353                 }
 354         }
 355
 356         return good;
 357 }
 358
 359 /**
 360  * fs_validate_description - Validate a parameter description
 361  * @name: The parameter name to search for.
 362  * @desc: The parameter description to validate.
 363  */
 364 bool fs_validate_description(const char *name,
 365         const struct fs_parameter_spec *desc)
 366 {
 367         const struct fs_parameter_spec *param, *p2;
 368         bool good = true;
 369
 370         for (param = desc; param->name; param++) {
 371                 /* Check for duplicate parameter names */
 372                 for (p2 = desc; p2 < param; p2++) {
 373                         if (strcmp(param->name, p2->name) == 0) {
 374                                 if (is_flag(param) != is_flag(p2))
 375                                         continue;
 376                                 pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
 377                                        name, param->name);
 378                                 good = false;
 379                         }
 380                 }
 381         }
 382         return good;
 383 }
 384 #endif /* CONFIG_VALIDATE_FS_PARSER */