// 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"

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

static const struct constant_table *
__lookup_constant(const struct constant_table *tbl, const char *name)
{
        for ( ; tbl->name; tbl++)
                if (strcmp(name, tbl->name) == 0)
                        return tbl;
        return NULL;
}

/**
 * lookup_constant - Look up a constant by name in an ordered table
 * @tbl: The table of constants to search.
 * @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, const char *name, int not_found)
{
        const struct constant_table *p = __lookup_constant(tbl, name);

        return p ? p->value : not_found;
}
EXPORT_SYMBOL(lookup_constant);

static inline bool is_flag(const struct fs_parameter_spec *p)
{
        return p->type == NULL;
}

static const struct fs_parameter_spec *fs_lookup_key(
        const struct fs_parameter_spec *desc,
        struct fs_parameter *param, bool *negated)
{
        const struct fs_parameter_spec *p, *other = NULL;
        const char *name = param->key;
        bool want_flag = param->type == fs_value_is_flag;

        *negated = false;
        for (p = desc; p->name; p++) {
                if (strcmp(p->name, name) != 0)
                        continue;
                if (likely(is_flag(p) == want_flag))
                        return p;
                other = p;
        }
        if (want_flag) {
                if (name[0] == 'n' && name[1] == 'o' && name[2]) {
                        for (p = desc; p->name; p++) {
                                if (strcmp(p->name, name + 2) != 0)
                                        continue;
                                if (!(p->flags & fs_param_neg_with_no))
                                        continue;
                                *negated = true;
                                return p;
                        }
                }
        }
        return other;
}

/*
 * __fs_parse - Parse a filesystem configuration parameter
 * @log: 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 p_log *log,
             const struct fs_parameter_spec *desc,
             struct fs_parameter *param,
             struct fs_parse_result *result)
{
        const struct fs_parameter_spec *p;

        result->uint_64 = 0;

        p = fs_lookup_key(desc, param, &result->negated);
        if (!p)
                return -ENOPARAM;

        if (p->flags & fs_param_deprecated)
                warn_plog(log, "Deprecated parameter '%s'", param->key);

        /* Try to turn the type we were given into the type desired by the
         * parameter and give an error if we can't.
         */
        if (is_flag(p)) {
                if (param->type != fs_value_is_flag)
                        return inval_plog(log, "Unexpected value for '%s'",
                                      param->key);
                result->boolean = !result->negated;
        } else  {
                int ret = p->type(log, p, param, result);
                if (ret)
                        return ret;
        }
        return p->opt;
}
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
 * @flags: Pathwalk flags passed to filename_lookup()
 * @_path: The result of the lookup
 */
int fs_lookup_param(struct fs_context *fc,
                    struct fs_parameter *param,
                    bool want_bdev,
                    unsigned int flags,
                    struct path *_path)
{
        struct filename *f;
        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);
                param->dirfd = AT_FDCWD;
                put_f = true;
                break;
        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);

static int fs_param_bad_value(struct p_log *log, struct fs_parameter *param)
{
        return inval_plog(log, "Bad value for '%s'", param->key);
}

int fs_param_is_bool(struct p_log *log, const struct fs_parameter_spec *p,
                     struct fs_parameter *param, struct fs_parse_result *result)
{
        int b;
        if (param->type != fs_value_is_string)
                return fs_param_bad_value(log, param);
        if (!*param->string && (p->flags & fs_param_can_be_empty))
                return 0;
        b = lookup_constant(bool_names, param->string, -1);
        if (b == -1)
                return fs_param_bad_value(log, param);
        result->boolean = b;
        return 0;
}
EXPORT_SYMBOL(fs_param_is_bool);

int fs_param_is_u32(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
{
        int base = (unsigned long)p->data;
        if (param->type != fs_value_is_string)
                return fs_param_bad_value(log, param);
        if (!*param->string && (p->flags & fs_param_can_be_empty))
                return 0;
        if (kstrtouint(param->string, base, &result->uint_32) < 0)
                return fs_param_bad_value(log, param);
        return 0;
}
EXPORT_SYMBOL(fs_param_is_u32);

int fs_param_is_s32(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
{
        if (param->type != fs_value_is_string)
                return fs_param_bad_value(log, param);
        if (!*param->string && (p->flags & fs_param_can_be_empty))
                return 0;
        if (kstrtoint(param->string, 0, &result->int_32) < 0)
                return fs_param_bad_value(log, param);
        return 0;
}
EXPORT_SYMBOL(fs_param_is_s32);

int fs_param_is_u64(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
{
        if (param->type != fs_value_is_string)
                return fs_param_bad_value(log, param);
        if (!*param->string && (p->flags & fs_param_can_be_empty))
                return 0;
        if (kstrtoull(param->string, 0, &result->uint_64) < 0)
                return fs_param_bad_value(log, param);
        return 0;
}
EXPORT_SYMBOL(fs_param_is_u64);

int fs_param_is_enum(struct p_log *log, const struct fs_parameter_spec *p,
                     struct fs_parameter *param, struct fs_parse_result *result)
{
        const struct constant_table *c;
        if (param->type != fs_value_is_string)
                return fs_param_bad_value(log, param);
        if (!*param->string && (p->flags & fs_param_can_be_empty))
                return 0;
        c = __lookup_constant(p->data, param->string);
        if (!c)
                return fs_param_bad_value(log, param);
        result->uint_32 = c->value;
        return 0;
}
EXPORT_SYMBOL(fs_param_is_enum);

int fs_param_is_string(struct p_log *log, const struct fs_parameter_spec *p,
                       struct fs_parameter *param, struct fs_parse_result *result)
{
        if (param->type != fs_value_is_string ||
            (!*param->string && !(p->flags & fs_param_can_be_empty)))
                return fs_param_bad_value(log, param);
        return 0;
}
EXPORT_SYMBOL(fs_param_is_string);

int fs_param_is_blob(struct p_log *log, const struct fs_parameter_spec *p,
                     struct fs_parameter *param, struct fs_parse_result *result)
{
        if (param->type != fs_value_is_blob)
                return fs_param_bad_value(log, param);
        return 0;
}
EXPORT_SYMBOL(fs_param_is_blob);

int fs_param_is_fd(struct p_log *log, const struct fs_parameter_spec *p,
                  struct fs_parameter *param, struct fs_parse_result *result)
{
        switch (param->type) {
        case fs_value_is_string:
                if ((!*param->string && !(p->flags & fs_param_can_be_empty)) ||
                    kstrtouint(param->string, 0, &result->uint_32) < 0)
                        break;
                if (result->uint_32 <= INT_MAX)
                        return 0;
                break;
        case fs_value_is_file:
                result->uint_32 = param->dirfd;
                if (result->uint_32 <= INT_MAX)
                        return 0;
                break;
        default:
                break;
        }
        return fs_param_bad_value(log, param);
}
EXPORT_SYMBOL(fs_param_is_fd);

int fs_param_is_file_or_string(struct p_log *log,
                               const struct fs_parameter_spec *p,
                               struct fs_parameter *param,
                               struct fs_parse_result *result)
{
        switch (param->type) {
        case fs_value_is_string:
                return fs_param_is_string(log, p, param, result);
        case fs_value_is_file:
                result->uint_32 = param->dirfd;
                if (result->uint_32 <= INT_MAX)
                        return 0;
                break;
        default:
                break;
        }
        return fs_param_bad_value(log, param);
}
EXPORT_SYMBOL(fs_param_is_file_or_string);

int fs_param_is_uid(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
{
        kuid_t uid;

        if (fs_param_is_u32(log, p, param, result) != 0)
                return fs_param_bad_value(log, param);

        uid = make_kuid(current_user_ns(), result->uint_32);
        if (!uid_valid(uid))
                return inval_plog(log, "Invalid uid '%s'", param->string);

        result->uid = uid;
        return 0;
}
EXPORT_SYMBOL(fs_param_is_uid);

int fs_param_is_gid(struct p_log *log, const struct fs_parameter_spec *p,
                    struct fs_parameter *param, struct fs_parse_result *result)
{
        kgid_t gid;

        if (fs_param_is_u32(log, p, param, result) != 0)
                return fs_param_bad_value(log, param);

        gid = make_kgid(current_user_ns(), result->uint_32);
        if (!gid_valid(gid))
                return inval_plog(log, "Invalid gid '%s'", param->string);

        result->gid = gid;
        return 0;
}
EXPORT_SYMBOL(fs_param_is_gid);

int fs_param_is_blockdev(struct p_log *log, const struct fs_parameter_spec *p,
                  struct fs_parameter *param, struct fs_parse_result *result)
{
        return 0;
}
EXPORT_SYMBOL(fs_param_is_blockdev);

int fs_param_is_path(struct p_log *log, const struct fs_parameter_spec *p,
                     struct fs_parameter *param, struct fs_parse_result *result)
{
        return 0;
}
EXPORT_SYMBOL(fs_param_is_path);

#ifdef CONFIG_VALIDATE_FS_PARSER
/**
 * fs_validate_description - Validate a parameter specification array
 * @name: Owner name of the parameter specification array
 * @desc: The parameter specification array to validate.
 */
bool fs_validate_description(const char *name,
        const struct fs_parameter_spec *desc)
{
        const struct fs_parameter_spec *param, *p2;
        bool good = true;

        for (param = desc; param->name; param++) {
                /* Check for duplicate parameter names */
                for (p2 = desc; p2 < param; p2++) {
                        if (strcmp(param->name, p2->name) == 0) {
                                if (is_flag(param) != is_flag(p2))
                                        continue;
                                pr_err("VALIDATE %s: PARAM[%s]: Duplicate\n",
                                       name, param->name);
                                good = false;
                        }
                }
        }
        return good;
}
#endif /* CONFIG_VALIDATE_FS_PARSER */