// 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: {
                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 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);
        }

        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 */