munmap not delete the right address range

[DinoStray]

we use mmap map the whole file, and ret->data is only part of the file without ETHASH_DAG_MAGIC_NUM

static bool ethash_mmap(struct ethash_full* ret, FILE* f)
{
	int fd;
	char* mmapped_data;
	errno = 0;
	ret->file = f;
	if ((fd = ethash_fileno(ret->file)) == -1) {
		return false;
	}
	mmapped_data= mmap(
		NULL,
		(size_t)ret->file_size + ETHASH_DAG_MAGIC_NUM_SIZE,
		PROT_READ | PROT_WRITE,
		MAP_SHARED,
		fd,
		0
	);
	if (mmapped_data == MAP_FAILED) {
		return false;
	}
	ret->data = (node*)(mmapped_data + ETHASH_DAG_MAGIC_NUM_SIZE);
	return true;
}

finally we munmap the address only begin with ret->data, then munmap(..) != 0

munmap(full->data, (size_t)full->file_size);