读取访问权限冲突，大家能看看嘛？

Question

PolyNode* MultPoly(PolyNode* p1, PolyNode* p2)
{
    assert(p1 && p2);
    PolyNode* p = NULL;
    p = (PolyNode*)malloc(sizeof(PolyNode));
    if (p == NULL)
    {
        exit(1);
    }
    PolyNode* start = p;
    PolyNode* trav = p;
    PolyNode* end = p;
    PolyNode* newp = p2;
    for (newp = p2; newp; newp = newp->link)
    {
        CrePolyNode((p1->coef)*(newp->coef),(p1->index)+(newp->index), &end);
    }
    p1 = p1->link;
    for (; p1; p1 = p1->link)
    {
        for (newp = p2; newp; newp = newp->link)
        {
            p = (PolyNode*)malloc(sizeof(PolyNode));
            if (p == NULL)
            {
                exit(1);
            }
            p->coef = (p1->coef) * (newp->coef);
            p->index = (p1->index) + (newp->index);
            PolyNode* pre = start;
            trav = start->link;
            while (trav != NULL && trav->index > p->index)
            {
                pre = trav;
                trav = trav->link;
            }
            if (trav == NULL)
            {
                end->link = p;
                end = p;
            }
            else
            {
                if (trav->index == p->index)
                {
                    trav->coef = (trav->coef) + (p->coef);
                    free(p);
                    p = NULL;
                }
                else
                {
                    p->link = trav;
                    pre->link = p;
                }
            }
        }
    }
    start = start->link;
    return start;
}