 static grub_err_t read_foo (struct grub_disk *disk, grub_disk_addr_t sector, grub_size_t size, char *buf) {
	if (!disk) {
		eprintf ("oops. no disk\n");
		return 1;
	}
	const int blocksize = 512; // TODO unhardcode 512
	RIOBind *iob = disk->data;
	if (bio) {
		iob = bio;
	}
	//printf ("io %p\n", file->root->iob.io);
	if (iob->read_at (iob->io, delta+(blocksize*sector), (ut8*)buf, size*blocksize) == -1) {
		return 1;
	}
	return 0;
 }

The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.