static int check_refcounts_l1(BlockDriverState *bs,
                              BdrvCheckResult *res,
                              uint16_t *refcount_table,
                              int refcount_table_size,
                              int64_t l1_table_offset, int l1_size,
                              int flags)
{
    BDRVQcowState *s = bs->opaque;
    uint64_t *l1_table, l2_offset, l1_size2;
    int i, ret;

    l1_size2 = l1_size * sizeof(uint64_t);

    /* Mark L1 table as used */
    inc_refcounts(bs, res, refcount_table, refcount_table_size,
        l1_table_offset, l1_size2);

    /* Read L1 table entries from disk */
    if (l1_size2 == 0) {
        l1_table = NULL;
    } else {
        l1_table = g_malloc(l1_size2);
        if (bdrv_pread(bs->file, l1_table_offset,
                       l1_table, l1_size2) != l1_size2)
            goto fail;
        for(i = 0;i < l1_size; i++)
            be64_to_cpus(&l1_table[i]);
    }

    /* Do the actual checks */
    for(i = 0; i < l1_size; i++) {
        l2_offset = l1_table[i];
        if (l2_offset) {
            /* Mark L2 table as used */
            l2_offset &= L1E_OFFSET_MASK;
            inc_refcounts(bs, res, refcount_table, refcount_table_size,
                l2_offset, s->cluster_size);

            /* L2 tables are cluster aligned */
            if (offset_into_cluster(s, l2_offset)) {
                fprintf(stderr, "ERROR l2_offset=%" PRIx64 ": Table is not "
                    "cluster aligned; L1 entry corrupted\n", l2_offset);
                res->corruptions++;
            }

            /* Process and check L2 entries */
            ret = check_refcounts_l2(bs, res, refcount_table,
                                     refcount_table_size, l2_offset, flags);
            if (ret < 0) {
                goto fail;
            }
        }
    }
    g_free(l1_table);
    return 0;

fail:
    fprintf(stderr, "ERROR: I/O error in check_refcounts_l1\n");
    res->check_errors++;
    g_free(l1_table);
    return -EIO;
}

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.