fs/fs_parser.c - linux/kernel/git/viro/vfs - Git at Google

 /* Filesystem parameter parser.
  *
  * Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public Licence
  * as published by the Free Software Foundation; either version
  * 2 of the Licence, or (at your option) any later version.
  */

 #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 <linux/bsearch.h>
 #include "internal.h"

 static const struct constant_table bool_names[] = {
 	{ "0",		false },
 	{ "1",		true },
 	{ "false",	false },
 	{ "no",		false },
 	{ "true",	true },
 	{ "yes",	true },
 };

 static int cmp_constant(const void *name, const void *entry)
 {
 	const struct constant_table *e = entry;
 	return strcmp(name, e->name);
 }

 /**
  * 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)
 {
 	const struct constant_table *e;

 	e = bsearch(name, tbl, tbl_size, sizeof(tbl[0]), cmp_constant);
 	if (!e)
 		return not_found;
 	return e->value;
 }
 EXPORT_SYMBOL(__lookup_constant);

 static int cmp_key(const void *name, const void *entry)
 {
 	const char *const *e = entry;
 	return strcmp(name, *e);
 }

 static int fs_lookup_key(const struct fs_parameter_description *desc,
 			 struct fs_parameter *param)
 {
 	const char *const *e;

 	e = bsearch(param->key, desc->keys, desc->nr_params,
 		    sizeof(const char *), cmp_key);
 	if (e)
 		return e - desc->keys;

 	return __lookup_constant(desc->alt_keys, desc->nr_alt_keys, param->key,
 				 -ENOPARAM);
 }

 /*
  * 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)
 {
 	int ret, k, i, b;

 	result->has_value = !!param->string;

 	k = fs_lookup_key(desc, param);
 	if (k == -ENOPARAM) {
 		/* 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;

 		k = fs_lookup_key(desc, param);
 		if (k == -ENOPARAM)
 			goto unknown_parameter;
 		if (!(desc->specs[k].flags & fs_param_neg_with_no))
 			goto unknown_parameter;
 		result->key = k;
 		result->uint_32 = 0;
 		result->negated = true;
 		goto okay;
 	}

 	result->key = k;
 	result->negated = false;
 	if (result->key == fsconfig_key_removed)
 		return invalf(fc, "%s: Unsupported parameter name '%s'",
 			      desc->name, param->key);

 	result->t = desc->specs[result->key];
 	if (result->t.flags & fs_param_deprecated)
 		warnf(fc, "%s: Deprecated parameter '%s'",
 		      desc->name, param->key);

 	/* Certain parameter types only take a string and convert it. */
 	switch (result->t.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 (desc->specs[k].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 (result->t.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 (i = 0; i < desc->nr_enums; i++) {
 			if (desc->enums[i].param_id == result->key &&
 			    strcmp(desc->enums[i].name, param->string) == 0) {
 				result->uint_32 = desc->enums[i].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: {
 		if (param->type != fs_value_is_file)
 			goto bad_value;
 		goto 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 result->key;

 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);
 	}

 	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;
 }

 static bool validate_list(const char *const *tbl, size_t tbl_size)
 {
 	size_t i;
 	bool good = true;

 	for (i = 0; i < tbl_size; i++) {
 		if (!tbl[i]) {
 			pr_err("VALIDATE LIST[%zu]: Null\n", i);
 			good = false;
 		} else if (i > 0 && tbl[i - 1]) {
 			int c = strcmp(tbl[i-1], tbl[i]);

 			if (c == 0) {
 				pr_err("VALIDATE LIST[%zu]: Duplicate %s\n",
 				       i, tbl[i]);
 				good = false;
 			}
 			if (c > 0) {
 				pr_err("VALIDATE LIST[%zu]: Missorted %s>=%s\n",
 				       i, tbl[i-1], tbl[i]);
 				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 char *name = desc->name;
 	bool good = true, enums = false;
 	int i, j;

 	pr_notice("*** VALIDATE %s ***\n", name);

 	if (!name[0]) {
 		pr_err("VALIDATE Parser: No name\n");
 		name = "Unknown";
 		good = false;
 	}

 	if (desc->nr_params) {
 		if (!desc->specs) {
 			pr_err("VALIDATE %s: Missing types table\n", name);
 			good = false;
 			goto no_specs;
 		}

 		for (i = 0; i < desc->nr_params; i++) {
 			enum fs_parameter_type t = desc->specs[i].type;
 			if (t == __fs_param_wasnt_defined) {
 				pr_err("VALIDATE %s: [%u] Undefined type\n",
 				       name, i);
 				good = false;
 			} else if (t >= nr__fs_parameter_type) {
 				pr_err("VALIDATE %s: [%u] Bad type %u\n",
 				       name, i, t);
 				good = false;
 			} else if (t == fs_param_is_enum) {
 				enums = true;
 			}
 		}
 	}

 no_specs:
 	if (desc->nr_params) {
 		if (!desc->keys) {
 			pr_err("VALIDATE %s: Missing keys list\n", name);
 			good = false;
 			goto no_keys;
 		}

 		if (!validate_list(desc->keys, desc->nr_params)) {
 			pr_err("VALIDATE %s: Bad keys table\n", name);
 			good = false;
 		}

 		/* The "source" parameter is used to convey the device/source
 		 * information.
 		 */
 		if (desc->no_source) {
 			if (bsearch("source", desc->keys, desc->nr_params,
 				    sizeof(const char *), cmp_key)) {
 				pr_err("VALIDATE %s: Source key, but marked no_source\n",
 				       name);
 				good = false;
 			}

 			if (desc->source_param != 0) {
 				pr_err("VALIDATE %s: source_param not zero\n",
 				       name);
 				good = false;
 			}
 		} else {
 			if (desc->source_param >= desc->nr_params) {
 				pr_err("VALIDATE %s: source_param is out of range\n",
 				       name);
 				good = false;
 				goto no_keys;
 			}

 			if (strcmp(desc->keys[desc->source_param], "source") != 0) {
 				pr_err("VALIDATE %s: No source key, but not marked no_source\n",
 				       name);
 				good = false;
 			}
 		}
 	} else {
 		if (desc->source_param) {
 			pr_err("VALIDATE %s: source_param not zero\n", name);
 			good = false;
 		}
 	}

 no_keys:
 	if (desc->nr_alt_keys) {
 		if (!desc->nr_params) {
 			pr_err("VALIDATE %s: %u alt_keys but no params\n",
 			       name, desc->nr_alt_keys);
 			good = false;
 			goto no_alt_keys;
 		}
 		if (!desc->alt_keys) {
 			pr_err("VALIDATE %s: Missing alt_keys table\n", name);
 			good = false;
 			goto no_alt_keys;
 		}

 		if (!validate_constant_table(desc->alt_keys, desc->nr_alt_keys,
 					     0, desc->nr_params - 1,
 					     fsconfig_key_removed)) {
 			pr_err("VALIDATE %s: Bad alt_keys table\n", name);
 			good = false;
 		}
 	}

 no_alt_keys:
 	if (desc->nr_enums) {
 		if (!enums) {
 			pr_err("VALIDATE %s: Enum table but no enum-type values\n",
 			       name);
 			good = false;
 			goto no_enums;
 		}
 		if (!desc->enums) {
 			pr_err("VALIDATE %s: Missing enums table\n", name);
 			good = false;
 			goto no_enums;
 		}

 		for (j = 0; j < desc->nr_enums; j++) {
 			const struct fs_parameter_enum *e = &desc->enums[j];

 			if (!e->name[0]) {
 				pr_err("VALIDATE %s: e[%u] no name\n", name, j);
 				good = false;
 			}
 			if (e->param_id >= desc->nr_params) {
 				pr_err("VALIDATE %s: e[%u] bad param %u\n",
 				       name, j, e->param_id);
 				good = false;
 			}
 			if (desc->specs[e->param_id].type != fs_param_is_enum) {
 				pr_err("VALIDATE %s: e[%u] enum val for non-enum type %u\n",
 				       name, j, e->param_id);
 				good = false;
 			}
 		}

 		for (i = 0; i < desc->nr_params; i++) {
 			if (desc->specs[i].type != fs_param_is_enum)
 				continue;
 			for (j = 0; j < desc->nr_enums; j++)
 				if (desc->enums[j].param_id == i)
 					break;
 			if (j == desc->nr_enums) {
 				pr_err("VALIDATE %s: t[%u] enum with no vals\n",
 				       name, i);
 				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 */
	/* Filesystem parameter parser.
	*
	* Copyright (C) 2018 Red Hat, Inc. All Rights Reserved.
	* Written by David Howells (dhowells@redhat.com)
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public Licence
	* as published by the Free Software Foundation; either version
	* 2 of the Licence, or (at your option) any later version.
	*/

	#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 <linux/bsearch.h>
	#include "internal.h"

	static const struct constant_table bool_names[] = {
	{ "0", false },
	{ "1", true },
	{ "false", false },
	{ "no", false },
	{ "true", true },
	{ "yes", true },
	};

	static int cmp_constant(const void name, const void entry)
	{
	const struct constant_table *e = entry;
	return strcmp(name, e->name);
	}

	/**
	* 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)
	{
	const struct constant_table *e;

	e = bsearch(name, tbl, tbl_size, sizeof(tbl[0]), cmp_constant);
	if (!e)
	return not_found;
	return e->value;
	}
	EXPORT_SYMBOL(__lookup_constant);

	static int cmp_key(const void name, const void entry)
	{
	const char const e = entry;
	return strcmp(name, *e);
	}

	static int fs_lookup_key(const struct fs_parameter_description *desc,
	struct fs_parameter *param)
	{
	const char const e;

	e = bsearch(param->key, desc->keys, desc->nr_params,
	sizeof(const char *), cmp_key);
	if (e)
	return e - desc->keys;

	return __lookup_constant(desc->alt_keys, desc->nr_alt_keys, param->key,
	-ENOPARAM);
	}

	/*
	* 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)
	{
	int ret, k, i, b;

	result->has_value = !!param->string;

	k = fs_lookup_key(desc, param);
	if (k == -ENOPARAM) {
	/* 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;

	k = fs_lookup_key(desc, param);
	if (k == -ENOPARAM)
	goto unknown_parameter;
	if (!(desc->specs[k].flags & fs_param_neg_with_no))
	goto unknown_parameter;
	result->key = k;
	result->uint_32 = 0;
	result->negated = true;
	goto okay;
	}

	result->key = k;
	result->negated = false;
	if (result->key == fsconfig_key_removed)
	return invalf(fc, "%s: Unsupported parameter name '%s'",
	desc->name, param->key);

	result->t = desc->specs[result->key];
	if (result->t.flags & fs_param_deprecated)
	warnf(fc, "%s: Deprecated parameter '%s'",
	desc->name, param->key);

	/* Certain parameter types only take a string and convert it. */
	switch (result->t.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 (desc->specs[k].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 (result->t.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 (i = 0; i < desc->nr_enums; i++) {
	if (desc->enums[i].param_id == result->key &&
	strcmp(desc->enums[i].name, param->string) == 0) {
	result->uint_32 = desc->enums[i].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: {
	if (param->type != fs_value_is_file)
	goto bad_value;
	goto 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 result->key;

	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);
	}

	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;
	}

	static bool validate_list(const char const tbl, size_t tbl_size)
	{
	size_t i;
	bool good = true;

	for (i = 0; i < tbl_size; i++) {
	if (!tbl[i]) {
	pr_err("VALIDATE LIST[%zu]: Null\n", i);
	good = false;
	} else if (i > 0 && tbl[i - 1]) {
	int c = strcmp(tbl[i-1], tbl[i]);

	if (c == 0) {
	pr_err("VALIDATE LIST[%zu]: Duplicate %s\n",
	i, tbl[i]);
	good = false;
	}
	if (c > 0) {
	pr_err("VALIDATE LIST[%zu]: Missorted %s>=%s\n",
	i, tbl[i-1], tbl[i]);
	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 char *name = desc->name;
	bool good = true, enums = false;
	int i, j;

	pr_notice("* VALIDATE %s *\n", name);

	if (!name[0]) {
	pr_err("VALIDATE Parser: No name\n");
	name = "Unknown";
	good = false;
	}

	if (desc->nr_params) {
	if (!desc->specs) {
	pr_err("VALIDATE %s: Missing types table\n", name);
	good = false;
	goto no_specs;
	}

	for (i = 0; i < desc->nr_params; i++) {
	enum fs_parameter_type t = desc->specs[i].type;
	if (t == __fs_param_wasnt_defined) {
	pr_err("VALIDATE %s: [%u] Undefined type\n",
	name, i);
	good = false;
	} else if (t >= nr__fs_parameter_type) {
	pr_err("VALIDATE %s: [%u] Bad type %u\n",
	name, i, t);
	good = false;
	} else if (t == fs_param_is_enum) {
	enums = true;
	}
	}
	}

	no_specs:
	if (desc->nr_params) {
	if (!desc->keys) {
	pr_err("VALIDATE %s: Missing keys list\n", name);
	good = false;
	goto no_keys;
	}

	if (!validate_list(desc->keys, desc->nr_params)) {
	pr_err("VALIDATE %s: Bad keys table\n", name);
	good = false;
	}

	/* The "source" parameter is used to convey the device/source
	* information.
	*/
	if (desc->no_source) {
	if (bsearch("source", desc->keys, desc->nr_params,
	sizeof(const char *), cmp_key)) {
	pr_err("VALIDATE %s: Source key, but marked no_source\n",
	name);
	good = false;
	}

	if (desc->source_param != 0) {
	pr_err("VALIDATE %s: source_param not zero\n",
	name);
	good = false;
	}
	} else {
	if (desc->source_param >= desc->nr_params) {
	pr_err("VALIDATE %s: source_param is out of range\n",
	name);
	good = false;
	goto no_keys;
	}

	if (strcmp(desc->keys[desc->source_param], "source") != 0) {
	pr_err("VALIDATE %s: No source key, but not marked no_source\n",
	name);
	good = false;
	}
	}
	} else {
	if (desc->source_param) {
	pr_err("VALIDATE %s: source_param not zero\n", name);
	good = false;
	}
	}

	no_keys:
	if (desc->nr_alt_keys) {
	if (!desc->nr_params) {
	pr_err("VALIDATE %s: %u alt_keys but no params\n",
	name, desc->nr_alt_keys);
	good = false;
	goto no_alt_keys;
	}
	if (!desc->alt_keys) {
	pr_err("VALIDATE %s: Missing alt_keys table\n", name);
	good = false;
	goto no_alt_keys;
	}

	if (!validate_constant_table(desc->alt_keys, desc->nr_alt_keys,
	0, desc->nr_params - 1,
	fsconfig_key_removed)) {
	pr_err("VALIDATE %s: Bad alt_keys table\n", name);
	good = false;
	}
	}

	no_alt_keys:
	if (desc->nr_enums) {
	if (!enums) {
	pr_err("VALIDATE %s: Enum table but no enum-type values\n",
	name);
	good = false;
	goto no_enums;
	}
	if (!desc->enums) {
	pr_err("VALIDATE %s: Missing enums table\n", name);
	good = false;
	goto no_enums;
	}

	for (j = 0; j < desc->nr_enums; j++) {
	const struct fs_parameter_enum *e = &desc->enums[j];

	if (!e->name[0]) {
	pr_err("VALIDATE %s: e[%u] no name\n", name, j);
	good = false;
	}
	if (e->param_id >= desc->nr_params) {
	pr_err("VALIDATE %s: e[%u] bad param %u\n",
	name, j, e->param_id);
	good = false;
	}
	if (desc->specs[e->param_id].type != fs_param_is_enum) {
	pr_err("VALIDATE %s: e[%u] enum val for non-enum type %u\n",
	name, j, e->param_id);
	good = false;
	}
	}

	for (i = 0; i < desc->nr_params; i++) {
	if (desc->specs[i].type != fs_param_is_enum)
	continue;
	for (j = 0; j < desc->nr_enums; j++)
	if (desc->enums[j].param_id == i)
	break;
	if (j == desc->nr_enums) {
	pr_err("VALIDATE %s: t[%u] enum with no vals\n",
	name, i);
	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 */