int qcow2_zero_clusters(BlockDriverState *bs, uint64_t offset, int nb_sectors)
{
    BDRVQcowState *s = bs->opaque;
    unsigned int nb_clusters;
    int ret;

    /* The zero flag is only supported by version 3 and newer */
    if (s->qcow_version < 3) {
        return -ENOTSUP;
    }

    /* Each L2 table is handled by its own loop iteration */
    nb_clusters = size_to_clusters(s, nb_sectors << BDRV_SECTOR_BITS);

    s->cache_discards = true;

    while (nb_clusters > 0) {
        ret = zero_single_l2(bs, offset, nb_clusters);
        if (ret < 0) {
            goto fail;
        }

        nb_clusters -= ret;
        offset += (ret * s->cluster_size);
    }

    ret = 0;
fail:
    s->cache_discards = false;
    qcow2_process_discards(bs, ret);

    return ret;
}

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.