int sanity_check_ckpt(struct f2fs_sb_info *sbi)
{
	unsigned int total, fsmeta;
	struct f2fs_super_block *raw_super = F2FS_RAW_SUPER(sbi);
	struct f2fs_checkpoint *ckpt = F2FS_CKPT(sbi);
	unsigned int ovp_segments, reserved_segments;
	unsigned int main_segs, blocks_per_seg;
	int i;

	total = le32_to_cpu(raw_super->segment_count);
	fsmeta = le32_to_cpu(raw_super->segment_count_ckpt);
	fsmeta += le32_to_cpu(raw_super->segment_count_sit);
	fsmeta += le32_to_cpu(raw_super->segment_count_nat);
	fsmeta += le32_to_cpu(ckpt->rsvd_segment_count);
	fsmeta += le32_to_cpu(raw_super->segment_count_ssa);

	if (unlikely(fsmeta >= total))
		return 1;

	ovp_segments = le32_to_cpu(ckpt->overprov_segment_count);
	reserved_segments = le32_to_cpu(ckpt->rsvd_segment_count);

	if (unlikely(fsmeta < F2FS_MIN_SEGMENTS ||
			ovp_segments == 0 || reserved_segments == 0)) {
		f2fs_msg(sbi->sb, KERN_ERR,
			"Wrong layout: check mkfs.f2fs version");
		return 1;
	}

	main_segs = le32_to_cpu(raw_super->segment_count_main);
	blocks_per_seg = sbi->blocks_per_seg;

	for (i = 0; i < NR_CURSEG_NODE_TYPE; i++) {
		if (le32_to_cpu(ckpt->cur_node_segno[i]) >= main_segs ||
			le16_to_cpu(ckpt->cur_node_blkoff[i]) >= blocks_per_seg)
			return 1;
	}
	for (i = 0; i < NR_CURSEG_DATA_TYPE; i++) {
		if (le32_to_cpu(ckpt->cur_data_segno[i]) >= main_segs ||
			le16_to_cpu(ckpt->cur_data_blkoff[i]) >= blocks_per_seg)
			return 1;
	}

	if (unlikely(f2fs_cp_error(sbi))) {
		f2fs_msg(sbi->sb, KERN_ERR, "A bug case: need to run fsck");
		return 1;
	}
	return 0;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.