static void update_refcount_discard(BlockDriverState *bs,
                                    uint64_t offset, uint64_t length)
{
    BDRVQcowState *s = bs->opaque;
    Qcow2DiscardRegion *d, *p, *next;

    QTAILQ_FOREACH(d, &s->discards, next) {
        uint64_t new_start = MIN(offset, d->offset);
        uint64_t new_end = MAX(offset + length, d->offset + d->bytes);

        if (new_end - new_start <= length + d->bytes) {
            /* There can't be any overlap, areas ending up here have no
             * references any more and therefore shouldn't get freed another
             * time. */
            assert(d->bytes + length == new_end - new_start);
            d->offset = new_start;
            d->bytes = new_end - new_start;
            goto found;
        }
    }

    d = g_malloc(sizeof(*d));
    *d = (Qcow2DiscardRegion) {
        .bs     = bs,
        .offset = offset,
        .bytes  = length,
    };
    QTAILQ_INSERT_TAIL(&s->discards, d, next);

found:
    /* Merge discard requests if they are adjacent now */
    QTAILQ_FOREACH_SAFE(p, &s->discards, next, next) {
        if (p == d
            || p->offset > d->offset + d->bytes
            || d->offset > p->offset + p->bytes)
        {
            continue;
        }

        /* Still no overlap possible */
        assert(p->offset == d->offset + d->bytes
            || d->offset == p->offset + p->bytes);

        QTAILQ_REMOVE(&s->discards, p, next);
        d->offset = MIN(d->offset, p->offset);
        d->bytes += p->bytes;
    }
}

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.