text: // SPDX-License-Identifier: GPL-2.0-or-later
  /* Filesystem parameter parser.
   *
   * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   */
  
  #include <linux/export.h>
  #include <linux/fs_context.h>
  #include <linux/fs_parser.h>
  #include <linux/slab.h>
  #include <linux/security.h>
  #include <linux/namei.h>
  #include "internal.h"
  
  static const struct constant_table bool_names[] = {
  	{ "0",		false },
  	{ "1",		true },
  	{ "false",	false },
  	{ "no",		false },
  	{ "true",	true },
  	{ "yes",	true },
  };
  
  /**
   * lookup_constant - Look up a constant by name in an ordered table
   * @tbl: The table of constants to search.
   * @tbl_size: The size of the table.
   * @name: The name to look up.
   * @not_found: The value to return if the name is not found.
   */
  int __lookup_constant(const struct constant_table *tbl, size_t tbl_size,
  		      const char *name, int not_found)
  {
  	unsigned int i;
  
  	for (i = 0; i < tbl_size; i++)
  		if (strcmp(name, tbl[i].name) == 0)
  			return tbl[i].value;
  
  	return not_found;
  }
  EXPORT_SYMBOL(__lookup_constant);
  
  static const struct fs_parameter_spec *fs_lookup_key(
  	const struct fs_parameter_description *desc,
  	const char *name)
  {
  	const struct fs_parameter_spec *p;
  
  	if (!desc->specs)
  		return NULL;
  
  	for (p = desc->specs; p->name; p++)
  		if (strcmp(p->name, name) == 0)
  			return p;
  
  	return NULL;
  }
  
  /*
   * fs_parse - Parse a filesystem configuration parameter
   * @fc: The filesystem context to log errors through.
   * @desc: The parameter description to use.
   * @param: The parameter.
   * @result: Where to place the result of the parse
   *
   * Parse a filesystem configuration parameter and attempt a conversion for a
   * simple parameter for which this is requested.  If successful, the determined
   * parameter ID is placed into @result->key, the desired type is indicated in
   * @result->t and any converted value is placed into an appropriate member of
   * the union in @result.
   *
   * The function returns the parameter number if the parameter was matched,
   * -ENOPARAM if it wasn't matched and @desc->ignore_unknown indicated that
   * unknown parameters are okay and -EINVAL if there was a conversion issue or
   * the parameter wasn't recognised and unknowns aren't okay.
   */
  int fs_parse(struct fs_context *fc,
  	     const struct fs_parameter_description *desc,
  	     struct fs_parameter *param,
  	     struct fs_parse_result *result)
  {
  	const struct fs_parameter_spec *p;
  	const struct fs_parameter_enum *e;
  	int ret = -ENOPARAM, b;
  
  	result->has_value = !!param->string;
  	result->negated = false;
  	result->uint_64 = 0;
  
  	p = fs_lookup_key(desc, param->key);
  	if (!p) {
  		/* If we didn't find something that looks like "noxxx", see if
  		 * "xxx" takes the "no"-form negative - but only if there
  		 * wasn't an value.
  		 */
  		if (result->has_value)
  			goto unknown_parameter;
  		if (param->key[0] != 'n' || param->key[1] != 'o' || !param->key[2])
  			goto unknown_parameter;
  
  		p = fs_lookup_key(desc, param->key + 2);
  		if (!p)
  			goto unknown_parameter;
  		if (!(p->flags & fs_param_neg_with_no))
  			goto unknown_parameter;
  		result->boolean = false;
  		result->negated = true;
  	}
  
  	if (p->flags & fs_param_deprecated)
  		warnf(fc, "%s: Deprecated parameter '%s'",
  		      desc->name, param->key);
  
  	if (result->negated)
  		goto okay;
  
  	/* Certain parameter types only take a string and convert it. */
  	switch (p->type) {
  	case __fs_param_wasnt_defined:
  		return -EINVAL;
  	case fs_param_is_u32:
  	case fs_param_is_u32_octal:
  	case fs_param_is_u32_hex:
  	case fs_param_is_s32:
  	case fs_param_is_u64:
  	case fs_param_is_enum:
  	case fs_param_is_string:
  		if (param->type != fs_value_is_string)
  			goto bad_value;
  		if (!result->has_value) {
  			if (p->flags & fs_param_v_optional)
  				goto okay;
  			goto bad_value;
  		}
  		/* Fall through */
  	default:
  		break;
  	}
  
  	/* Try to turn the type we were given into the type desired by the
  	 * parameter and give an error if we can't.
  	 */
  	switch (p->type) {
  	case fs_param_is_flag:
  		if (param->type != fs_value_is_flag &&
  		    (param->type != fs_value_is_string || result->has_value))
  			return invalf(fc, "%s: Unexpected value for '%s'",
  				      desc->name, param->key);
  		result->boolean = true;
  		goto okay;
  
  	case fs_param_is_bool:
  		switch (param->type) {
  		case fs_value_is_flag:
  			result->boolean = true;
  			goto okay;
  		case fs_value_is_string:
  			if (param->size == 0) {
  				result->boolean = true;
  				goto okay;
  			}
  			b = lookup_constant(bool_names, param->string, -1);
  			if (b == -1)
  				goto bad_value;
  			result->boolean = b;
  			goto okay;
  		default:
  			goto bad_value;
  		}
  
  	case fs_param_is_u32:
  		ret = kstrtouint(param->string, 0, &result->uint_32);
  		goto maybe_okay;
  	case fs_param_is_u32_octal:
  		ret = kstrtouint(param->string, 8, &result->uint_32);
  		goto maybe_okay;
  	case fs_param_is_u32_hex:
  		ret = kstrtouint(param->string, 16, &result->uint_32);
  		goto maybe_okay;
  	case fs_param_is_s32:
  		ret = kstrtoint(param->string, 0, &result->int_32);
  		goto maybe_okay;
  	case fs_param_is_u64:
  		ret = kstrtoull(param->string, 0, &result->uint_64);
  		goto maybe_okay;
  
  	case fs_param_is_enum:
  		for (e = desc->enums; e->name[0]; e++) {
  			if (e->opt == p->opt &&
  			    strcmp(e->name, param->string) == 0) {
  				result->uint_32 = e->value;
  				goto okay;
  			}
  		}
  		goto bad_value;
  
  	case fs_param_is_string:
  		goto okay;
  	case fs_param_is_blob:
  		if (param->type != fs_value_is_blob)
  			goto bad_value;
  		goto okay;
  
  	case fs_param_is_fd: {
  		switch (param->type) {
  		case fs_value_is_string:
  			if (!result->has_value)
  				goto bad_value;
  
  			ret = kstrtouint(param->string, 0, &result->uint_32);
  			break;
  		case fs_value_is_file:
  			result->uint_32 = param->dirfd;
  			ret = 0;
  		default:
  			goto bad_value;
  		}
  
  		if (result->uint_32 > INT_MAX)
  			goto bad_value;
  		goto maybe_okay;
  	}
  
  	case fs_param_is_blockdev:
  	case fs_param_is_path:
  		goto okay;
  	default:
  		BUG();
  	}
  
  maybe_okay:
  	if (ret < 0)
  		goto bad_value;
  okay:
  	return p->opt;
  
  bad_value:
  	return invalf(fc, "%s: Bad value for '%s'", desc->name, param->key);
  unknown_parameter:
  	return -ENOPARAM;
  }
  EXPORT_SYMBOL(fs_parse);
  
  /**
   * fs_lookup_param - Look up a path referred to by a parameter
   * @fc: The filesystem context to log errors through.
   * @param: The parameter.
   * @want_bdev: T if want a blockdev
   * @_path: The result of the lookup
   */
  int fs_lookup_param(struct fs_context *fc,
  		    struct fs_parameter *param,
  		    bool want_bdev,
  		    struct path *_path)
  {
  	struct filename *f;
  	unsigned int flags = 0;
  	bool put_f;
  	int ret;
  
  	switch (param->type) {
  	case fs_value_is_string:
  		f = getname_kernel(param->string);
  		if (IS_ERR(f))
  			return PTR_ERR(f);
  		put_f = true;
  		break;
  	case fs_value_is_filename_empty:
  		flags = LOOKUP_EMPTY;
  		/* Fall through */
  	case fs_value_is_filename:
  		f = param->name;
  		put_f = false;
  		break;
  	default:
  		return invalf(fc, "%s: not usable as path", param->key);
  	}
  
  	f->refcnt++; /* filename_lookup() drops our ref. */
  	ret = filename_lookup(param->dirfd, f, flags, _path, NULL);
  	if (ret < 0) {
  		errorf(fc, "%s: Lookup failure for '%s'", param->key, f->name);
  		goto out;
  	}
  
  	if (want_bdev &&
  	    !S_ISBLK(d_backing_inode(_path->dentry)->i_mode)) {
  		path_put(_path);
  		_path->dentry = NULL;
  		_path->mnt = NULL;
  		errorf(fc, "%s: Non-blockdev passed as '%s'",
  		       param->key, f->name);
  		ret = -ENOTBLK;
  	}
  
  out:
  	if (put_f)
  		putname(f);
  	return ret;
  }
  EXPORT_SYMBOL(fs_lookup_param);
  
  #ifdef CONFIG_VALIDATE_FS_PARSER
  /**
   * validate_constant_table - Validate a constant table
   * @name: Name to use in reporting
   * @tbl: The constant table to validate.
   * @tbl_size: The size of the table.
   * @low: The lowest permissible value.
   * @high: The highest permissible value.
   * @special: One special permissible value outside of the range.
   */
  bool validate_constant_table(const struct constant_table *tbl, size_t tbl_size,
  			     int low, int high, int special)
  {
  	size_t i;
  	bool good = true;
  
  	if (tbl_size == 0) {
  		pr_warn("VALIDATE C-TBL: Empty\n");
  		return true;
  	}
  
  	for (i = 0; i < tbl_size; i++) {
  		if (!tbl[i].name) {
  			pr_err("VALIDATE C-TBL[%zu]: Null\n", i);
  			good = false;
  		} else if (i > 0 && tbl[i - 1].name) {
  			int c = strcmp(tbl[i-1].name, tbl[i].name);
  
  			if (c == 0) {
  				pr_err("VALIDATE C-TBL[%zu]: Duplicate %s\n",
  				       i, tbl[i].name);
  				good = false;
  			}
  			if (c > 0) {
  				pr_err("VALIDATE C-TBL[%zu]: Missorted %s>=%s\n",
  				       i, tbl[i-1].name, tbl[i].name);
  				good = false;
  			}
  		}
  
  		if (tbl[i].value != special &&
  		    (tbl[i].value < low || tbl[i].value > high)) {
  			pr_err("VALIDATE C-TBL[%zu]: %s->%d const out of range (%d-%d)\n",
  			       i, tbl[i].name, tbl[i].value, low, high);
  			good = false;
  		}
  	}
  
  	return good;
  }
  
  /**
   * fs_validate_description - Validate a parameter description
   * @desc: The parameter description to validate.
   */
  bool fs_validate_description(const struct fs_parameter_description *desc)
  {
  	const struct fs_parameter_spec *param, *p2;
  	const struct fs_parameter_enum *e;
  	const char *name = desc->name;
  	unsigned int nr_params = 0;
  	bool good = true, enums = false;
  
  	pr_notice("*** VALIDATE %s ***\n", name);
  
  	if (!name[0]) {
  		pr_err("VALIDATE Parser: No name\n");
  		name = "Unknown";
  		good = false;
  	}
  
  	if (desc->specs) {
  		for (param = desc->specs; param->name; param++) {
  			enum fs_parameter_type t = param->type;
  
  			/* Check that the type is in range */
  			if (t == __fs_param_wasnt_defined ||
  			    t >= nr__fs_parameter_type) {
  				pr_err("VALIDATE %s: PARAM[%s] Bad type %u\n",
  				       name, param->name, t);
  				good = false;
  			} else if (t == fs_param_is_enum) {
  				enums = true;
  			}
  
  			/* Check for duplicate parameter names */
  			for (p2 = desc->specs; p2 < param; p2++) {
  				if (strcmp(param->name, p2->name) == 0) {
  					pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
  					       name, param->name);
  					good = false;
  				}
  			}
  		}
  
  		nr_params = param - desc->specs;
  	}
  
  	if (desc->enums) {
  		if (!nr_params) {
  			pr_err("VALIDATE %s: Enum table but no parameters\n",
  			       name);
  			good = false;
  			goto no_enums;
  		}
  		if (!enums) {
  			pr_err("VALIDATE %s: Enum table but no enum-type values\n",
  			       name);
  			good = false;
  			goto no_enums;
  		}
  
  		for (e = desc->enums; e->name[0]; e++) {
  			/* Check that all entries in the enum table have at
  			 * least one parameter that uses them.
  			 */
  			for (param = desc->specs; param->name; param++) {
  				if (param->opt == e->opt &&
  				    param->type != fs_param_is_enum) {
  					pr_err("VALIDATE %s: e[%tu] enum val for %s\n",
  					       name, e - desc->enums, param->name);
  					good = false;
  				}
  			}
  		}
  
  		/* Check that all enum-type parameters have at least one enum
  		 * value in the enum table.
  		 */
  		for (param = desc->specs; param->name; param++) {
  			if (param->type != fs_param_is_enum)
  				continue;
  			for (e = desc->enums; e->name[0]; e++)
  				if (e->opt == param->opt)
  					break;
  			if (!e->name[0]) {
  				pr_err("VALIDATE %s: PARAM[%s] enum with no values\n",
  				       name, param->name);
  				good = false;
  			}
  		}
  	} else {
  		if (enums) {
  			pr_err("VALIDATE %s: enum-type values, but no enum table\n",
  			       name);
  			good = false;
  			goto no_enums;
  		}
  	}
  
  no_enums:
  	return good;
  }
  #endif /* CONFIG_VALIDATE_FS_PARSER */
  