static int binderfs_fill_super()

in binderfs.c [685:769]

• 61 lines of code
• 12 McCabe index (conditional complexity)

static int binderfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
	int ret;
	struct binderfs_info *info;
	struct binderfs_mount_opts *ctx = fc->fs_private;
	struct inode *inode = NULL;
	struct binderfs_device device_info = {};
	const char *name;
	size_t len;

	sb->s_blocksize = PAGE_SIZE;
	sb->s_blocksize_bits = PAGE_SHIFT;

	/*
	 * The binderfs filesystem can be mounted by userns root in a
	 * non-initial userns. By default such mounts have the SB_I_NODEV flag
	 * set in s_iflags to prevent security issues where userns root can
	 * just create random device nodes via mknod() since it owns the
	 * filesystem mount. But binderfs does not allow to create any files
	 * including devices nodes. The only way to create binder devices nodes
	 * is through the binder-control device which userns root is explicitly
	 * allowed to do. So removing the SB_I_NODEV flag from s_iflags is both
	 * necessary and safe.
	 */
	sb->s_iflags &= ~SB_I_NODEV;
	sb->s_iflags |= SB_I_NOEXEC;
	sb->s_magic = BINDERFS_SUPER_MAGIC;
	sb->s_op = &binderfs_super_ops;
	sb->s_time_gran = 1;

	sb->s_fs_info = kzalloc(sizeof(struct binderfs_info), GFP_KERNEL);
	if (!sb->s_fs_info)
		return -ENOMEM;
	info = sb->s_fs_info;

	info->ipc_ns = get_ipc_ns(current->nsproxy->ipc_ns);

	info->root_gid = make_kgid(sb->s_user_ns, 0);
	if (!gid_valid(info->root_gid))
		info->root_gid = GLOBAL_ROOT_GID;
	info->root_uid = make_kuid(sb->s_user_ns, 0);
	if (!uid_valid(info->root_uid))
		info->root_uid = GLOBAL_ROOT_UID;
	info->mount_opts.max = ctx->max;
	info->mount_opts.stats_mode = ctx->stats_mode;

	inode = new_inode(sb);
	if (!inode)
		return -ENOMEM;

	inode->i_ino = FIRST_INODE;
	inode->i_fop = &simple_dir_operations;
	inode->i_mode = S_IFDIR | 0755;
	inode->i_mtime = inode->i_atime = inode->i_ctime = current_time(inode);
	inode->i_op = &binderfs_dir_inode_operations;
	set_nlink(inode, 2);

	sb->s_root = d_make_root(inode);
	if (!sb->s_root)
		return -ENOMEM;

	ret = binderfs_binder_ctl_create(sb);
	if (ret)
		return ret;

	name = binder_devices_param;
	for (len = strcspn(name, ","); len > 0; len = strcspn(name, ",")) {
		strscpy(device_info.name, name, len + 1);
		ret = binderfs_binder_device_create(inode, NULL, &device_info);
		if (ret)
			return ret;
		name += len;
		if (*name == ',')
			name++;
	}

	ret = init_binder_features(sb);
	if (ret)
		return ret;

	if (info->mount_opts.stats_mode == binderfs_stats_mode_global)
		return init_binder_logs(sb);

	return 0;
}