// SPDX-License-Identifier: GPL-2.0
/*
 * security/tomoyo/mount.c
 *
 * Copyright (C) 2005-2011  NTT DATA CORPORATION
 */

#include <linux/slab.h>
#include <uapi/linux/mount.h>
#include "common.h"

/* String table for special mount operations. */
static const char * const tomoyo_mounts[TOMOYO_MAX_SPECIAL_MOUNT] = {
        [TOMOYO_MOUNT_BIND]            = "--bind",
        [TOMOYO_MOUNT_MOVE]            = "--move",
        [TOMOYO_MOUNT_REMOUNT]         = "--remount",
        [TOMOYO_MOUNT_MAKE_UNBINDABLE] = "--make-unbindable",
        [TOMOYO_MOUNT_MAKE_PRIVATE]    = "--make-private",
        [TOMOYO_MOUNT_MAKE_SLAVE]      = "--make-slave",
        [TOMOYO_MOUNT_MAKE_SHARED]     = "--make-shared",
};

/**
 * tomoyo_audit_mount_log - Audit mount log.
 *
 * @r: Pointer to "struct tomoyo_request_info".
 *
 * Returns 0 on success, negative value otherwise.
 */
static int tomoyo_audit_mount_log(struct tomoyo_request_info *r)
        __must_hold_shared(&tomoyo_ss)
{
        return tomoyo_supervisor(r, "file mount %s %s %s 0x%lX\n",
                                 r->param.mount.dev->name,
                                 r->param.mount.dir->name,
                                 r->param.mount.type->name,
                                 r->param.mount.flags);
}

/**
 * tomoyo_check_mount_acl - Check permission for path path path number operation.
 *
 * @r:   Pointer to "struct tomoyo_request_info".
 * @ptr: Pointer to "struct tomoyo_acl_info".
 *
 * Returns true if granted, false otherwise.
 */
static bool tomoyo_check_mount_acl(struct tomoyo_request_info *r,
                                   const struct tomoyo_acl_info *ptr)
{
        const struct tomoyo_mount_acl *acl =
                container_of(ptr, typeof(*acl), head);

        return tomoyo_compare_number_union(r->param.mount.flags,
                                           &acl->flags) &&
                tomoyo_compare_name_union(r->param.mount.type,
                                          &acl->fs_type) &&
                tomoyo_compare_name_union(r->param.mount.dir,
                                          &acl->dir_name) &&
                (!r->param.mount.need_dev ||
                 tomoyo_compare_name_union(r->param.mount.dev,
                                           &acl->dev_name));
}

/**
 * tomoyo_mount_acl - Check permission for mount() operation.
 *
 * @r:        Pointer to "struct tomoyo_request_info".
 * @dev_name: Name of device file. Maybe NULL.
 * @dir:      Pointer to "struct path".
 * @type:     Name of filesystem type.
 * @flags:    Mount options.
 *
 * Returns 0 on success, negative value otherwise.
 *
 * Caller holds tomoyo_read_lock().
 */
static int tomoyo_mount_acl(struct tomoyo_request_info *r,
                            const char *dev_name,
                            const struct path *dir, const char *type,
                            unsigned long flags)
        __must_hold_shared(&tomoyo_ss)
{
        struct tomoyo_obj_info obj = { };
        struct path path;
        struct file_system_type *fstype = NULL;
        const char *requested_type = NULL;
        const char *requested_dir_name = NULL;
        const char *requested_dev_name = NULL;
        struct tomoyo_path_info rtype;
        struct tomoyo_path_info rdev;
        struct tomoyo_path_info rdir;
        int need_dev = 0;
        int error = -ENOMEM;

        r->obj = &obj;

        /* Get fstype. */
        requested_type = tomoyo_encode(type);
        if (!requested_type)
                goto out;
        rtype.name = requested_type;
        tomoyo_fill_path_info(&rtype);

        /* Get mount point. */
        obj.path2 = *dir;
        requested_dir_name = tomoyo_realpath_from_path(dir);
        if (!requested_dir_name) {
                error = -ENOMEM;
                goto out;
        }
        rdir.name = requested_dir_name;
        tomoyo_fill_path_info(&rdir);

        /* Compare fs name. */
        if (type == tomoyo_mounts[TOMOYO_MOUNT_REMOUNT]) {
                /* dev_name is ignored. */
        } else if (type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE] ||
                   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE] ||
                   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE] ||
                   type == tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED]) {
                /* dev_name is ignored. */
        } else if (type == tomoyo_mounts[TOMOYO_MOUNT_BIND] ||
                   type == tomoyo_mounts[TOMOYO_MOUNT_MOVE]) {
                need_dev = -1; /* dev_name is a directory */
        } else {
                fstype = get_fs_type(type);
                if (!fstype) {
                        error = -ENODEV;
                        goto out;
                }
                if (fstype->fs_flags & FS_REQUIRES_DEV)
                        /* dev_name is a block device file. */
                        need_dev = 1;
        }
        if (need_dev) {
                /* Get mount point or device file. */
                if (!dev_name || kern_path(dev_name, LOOKUP_FOLLOW, &path)) {
                        error = -ENOENT;
                        goto out;
                }
                obj.path1 = path;
                requested_dev_name = tomoyo_realpath_from_path(&path);
                if (!requested_dev_name) {
                        error = -ENOENT;
                        goto out;
                }
        } else {
                /* Map dev_name to "<NULL>" if no dev_name given. */
                if (!dev_name)
                        dev_name = "<NULL>";
                requested_dev_name = tomoyo_encode(dev_name);
                if (!requested_dev_name) {
                        error = -ENOMEM;
                        goto out;
                }
        }
        rdev.name = requested_dev_name;
        tomoyo_fill_path_info(&rdev);
        r->param_type = TOMOYO_TYPE_MOUNT_ACL;
        r->param.mount.need_dev = need_dev;
        r->param.mount.dev = &rdev;
        r->param.mount.dir = &rdir;
        r->param.mount.type = &rtype;
        r->param.mount.flags = flags;
        do {
                tomoyo_check_acl(r, tomoyo_check_mount_acl);
                error = tomoyo_audit_mount_log(r);
        } while (error == TOMOYO_RETRY_REQUEST);
 out:
        kfree(requested_dev_name);
        kfree(requested_dir_name);
        if (fstype)
                put_filesystem(fstype);
        kfree(requested_type);
        /* Drop refcount obtained by kern_path(). */
        if (obj.path1.dentry)
                path_put(&obj.path1);
        return error;
}

/**
 * tomoyo_mount_permission - Check permission for mount() operation.
 *
 * @dev_name:  Name of device file. Maybe NULL.
 * @path:      Pointer to "struct path".
 * @type:      Name of filesystem type. Maybe NULL.
 * @flags:     Mount options.
 * @data_page: Optional data. Maybe NULL.
 *
 * Returns 0 on success, negative value otherwise.
 */
int tomoyo_mount_permission(const char *dev_name, const struct path *path,
                            const char *type, unsigned long flags,
                            void *data_page)
{
        struct tomoyo_request_info r;
        int error;
        int idx;

        if (tomoyo_init_request_info(&r, NULL, TOMOYO_MAC_FILE_MOUNT)
            == TOMOYO_CONFIG_DISABLED)
                return 0;
        if ((flags & MS_MGC_MSK) == MS_MGC_VAL)
                flags &= ~MS_MGC_MSK;
        if (flags & MS_REMOUNT) {
                type = tomoyo_mounts[TOMOYO_MOUNT_REMOUNT];
                flags &= ~MS_REMOUNT;
        } else if (flags & MS_BIND) {
                type = tomoyo_mounts[TOMOYO_MOUNT_BIND];
                flags &= ~MS_BIND;
        } else if (flags & MS_SHARED) {
                if (flags & (MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE))
                        return -EINVAL;
                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SHARED];
                flags &= ~MS_SHARED;
        } else if (flags & MS_PRIVATE) {
                if (flags & (MS_SHARED | MS_SLAVE | MS_UNBINDABLE))
                        return -EINVAL;
                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_PRIVATE];
                flags &= ~MS_PRIVATE;
        } else if (flags & MS_SLAVE) {
                if (flags & (MS_SHARED | MS_PRIVATE | MS_UNBINDABLE))
                        return -EINVAL;
                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_SLAVE];
                flags &= ~MS_SLAVE;
        } else if (flags & MS_UNBINDABLE) {
                if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE))
                        return -EINVAL;
                type = tomoyo_mounts[TOMOYO_MOUNT_MAKE_UNBINDABLE];
                flags &= ~MS_UNBINDABLE;
        } else if (flags & MS_MOVE) {
                type = tomoyo_mounts[TOMOYO_MOUNT_MOVE];
                flags &= ~MS_MOVE;
        }
        if (!type)
                type = "<NULL>";
        idx = tomoyo_read_lock();
        error = tomoyo_mount_acl(&r, dev_name, path, type, flags);
        tomoyo_read_unlock(idx);
        return error;
}