fs/init.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Routines that mimic syscalls, but don't use the user address space or file
 * descriptors.  Only for init/ and related early init code.
 */
#include <linux/init.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include <linux/fs.h>
#include <linux/fs_struct.h>
#include <linux/file.h>
#include <linux/init_syscalls.h>
#include <linux/security.h>
#include "internal.h"

int __init init_pivot_root(const char *new_root, const char *put_old)
{
	struct path new_path __free(path_put) = {};
	struct path old_path __free(path_put) = {};
	int ret;

	ret = kern_path(new_root, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new_path);
	if (ret)
		return ret;

	ret = kern_path(put_old, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old_path);
	if (ret)
		return ret;

	return path_pivot_root(&new_path, &old_path);
}

int __init init_mount(const char *dev_name, const char *dir_name,
		const char *type_page, unsigned long flags, void *data_page)
{
	struct path path;
	int ret;

	ret = kern_path(dir_name, LOOKUP_FOLLOW, &path);
	if (ret)
		return ret;
	ret = path_mount(dev_name, &path, type_page, flags, data_page);
	path_put(&path);
	return ret;
}

int __init init_umount(const char *name, int flags)
{
	int lookup_flags = LOOKUP_MOUNTPOINT;
	struct path path;
	int ret;

	if (!(flags & UMOUNT_NOFOLLOW))
		lookup_flags |= LOOKUP_FOLLOW;
	ret = kern_path(name, lookup_flags, &path);
	if (ret)
		return ret;
	return path_umount(&path, flags);
}

int __init init_chdir(const char *filename)
{
	struct path path;
	int error;

	error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
	if (error)
		return error;
	error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
	if (!error)
		set_fs_pwd(current->fs, &path);
	path_put(&path);
	return error;
}

int __init init_chroot(const char *filename)
{
	struct path path;
	int error;

	error = kern_path(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &path);
	if (error)
		return error;
	error = path_permission(&path, MAY_EXEC | MAY_CHDIR);
	if (error)
		goto dput_and_out;
	error = -EPERM;
	if (!ns_capable(current_user_ns(), CAP_SYS_CHROOT))
		goto dput_and_out;
	error = security_path_chroot(&path);
	if (error)
		goto dput_and_out;
	set_fs_root(current->fs, &path);
dput_and_out:
	path_put(&path);
	return error;
}

int __init init_chown(const char *filename, uid_t user, gid_t group, int flags)
{
	int lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
	struct path path;
	int error;

	error = kern_path(filename, lookup_flags, &path);
	if (error)
		return error;
	error = mnt_want_write(path.mnt);
	if (!error) {
		error = chown_common(&path, user, group);
		mnt_drop_write(path.mnt);
	}
	path_put(&path);
	return error;
}

int __init init_chmod(const char *filename, umode_t mode)
{
	struct path path;
	int error;

	error = kern_path(filename, LOOKUP_FOLLOW, &path);
	if (error)
		return error;
	error = chmod_common(&path, mode);
	path_put(&path);
	return error;
}

int __init init_eaccess(const char *filename)
{
	struct path path;
	int error;

	error = kern_path(filename, LOOKUP_FOLLOW, &path);
	if (error)
		return error;
	error = path_permission(&path, MAY_ACCESS);
	path_put(&path);
	return error;
}

int __init init_stat(const char *filename, struct kstat *stat, int flags)
{
	int lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
	struct path path;
	int error;

	error = kern_path(filename, lookup_flags, &path);
	if (error)
		return error;
	error = vfs_getattr(&path, stat, STATX_BASIC_STATS,
			    flags | AT_NO_AUTOMOUNT);
	path_put(&path);
	return error;
}

int __init init_mknod(const char *filename, umode_t mode, unsigned int dev)
{
	CLASS(filename_kernel, name)(filename);
	return filename_mknodat(AT_FDCWD, name, mode, dev);
}

int __init init_link(const char *oldname, const char *newname)
{
	CLASS(filename_kernel, old)(oldname);
	CLASS(filename_kernel, new)(newname);
	return filename_linkat(AT_FDCWD, old, AT_FDCWD, new, 0);
}

int __init init_symlink(const char *oldname, const char *newname)
{
	CLASS(filename_kernel, old)(oldname);
	CLASS(filename_kernel, new)(newname);
	return filename_symlinkat(old, AT_FDCWD, new);
}

int __init init_unlink(const char *pathname)
{
	CLASS(filename_kernel, name)(pathname);
	return filename_unlinkat(AT_FDCWD, name);
}

int __init init_mkdir(const char *pathname, umode_t mode)
{
	CLASS(filename_kernel, name)(pathname);
	return filename_mkdirat(AT_FDCWD, name, mode);
}

int __init init_rmdir(const char *pathname)
{
	CLASS(filename_kernel, name)(pathname);
	return filename_rmdir(AT_FDCWD, name);
}

int __init init_utimes(char *filename, struct timespec64 *ts)
{
	struct path path;
	int error;

	error = kern_path(filename, 0, &path);
	if (error)
		return error;
	error = vfs_utimes(&path, ts);
	path_put(&path);
	return error;
}

int __init init_dup(struct file *file)
{
	int fd;

	fd = get_unused_fd_flags(0);
	if (fd < 0)
		return fd;
	fd_install(fd, get_file(file));
	return 0;
}