static int discard_single_l2(BlockDriverState *bs, uint64_t offset,
    unsigned int nb_clusters, enum qcow2_discard_type type)
{
    BDRVQcowState *s = bs->opaque;
    uint64_t *l2_table;
    int l2_index;
    int ret;
    int i;

    ret = get_cluster_table(bs, offset, &l2_table, &l2_index);
    if (ret < 0) {
        return ret;
    }

    /* Limit nb_clusters to one L2 table */
    nb_clusters = MIN(nb_clusters, s->l2_size - l2_index);

    for (i = 0; i < nb_clusters; i++) {
        uint64_t old_offset;

        old_offset = be64_to_cpu(l2_table[l2_index + i]);

        /*
         * Make sure that a discarded area reads back as zeroes for v3 images
         * (we cannot do it for v2 without actually writing a zero-filled
         * buffer). We can skip the operation if the cluster is already marked
         * as zero, or if it's unallocated and we don't have a backing file.
         *
         * TODO We might want to use bdrv_get_block_status(bs) here, but we're
         * holding s->lock, so that doesn't work today.
         */
        if (old_offset & QCOW_OFLAG_ZERO) {
            continue;
        }

        if ((old_offset & L2E_OFFSET_MASK) == 0 && !bs->backing_hd) {
            continue;
        }

        /* First remove L2 entries */
        qcow2_cache_entry_mark_dirty(s->l2_table_cache, l2_table);
        if (s->qcow_version >= 3) {
            l2_table[l2_index + i] = cpu_to_be64(QCOW_OFLAG_ZERO);
        } else {
            l2_table[l2_index + i] = cpu_to_be64(0);
        }

        /* Then decrease the refcount */
        qcow2_free_any_clusters(bs, old_offset, 1, type);
    }

    ret = qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
    if (ret < 0) {
        return ret;
    }

    return nb_clusters;
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.