How Do I Develop My Code To Find A Loop In A Linked List

#include<stdio.h>
#include<stdlib.h>
struct node
{
    int data;
    struct node*link;
}*start;
void create(struct node *p);
void bug();
void debug();
void display();
int main()
{
    int a;
    printf("Creation of linked list with a loop inside:");
    start=(struct node*)malloc(sizeof(struct node*));
    create(start);
    display();
    bug();
    printf("Press 1 for debugging it:");
    scanf("%d",&a);
    if(a==1)
    debug();
    display();
    return 0;
}
void create(struct node *start)
{
    int a;
    printf("\nEnter the node:");
    scanf("%d",&start->data);
    printf("Press 0 to end list:");
    scanf("%d",&a);
    if(a==0)
    {
        start->link=NULL;
    }
    else
    {
        start->link=(struct node*)malloc(sizeof(struct node*));
        create(start->link);
    }
}
void bug()
{
    int i=1,j=1,m1,m2;
    struct node *p1,*p2;
    p1=start,p2=start;
    printf("Enter the position you want to make a loop:");
    scanf("%d %d",&m1,&m2);
    while(i<m1)
    {
        p1=p1->link;
        i++;
    }
    while(j<m2)
    {
        p2=p2->link;
        j++;
    }
    p2->link=p1;
    printf("\nThe bug is created\n");
}
void display()
{
    struct node*p;
    p=start;
    while(p!=NULL)
    {
        printf("%d\n",p->data);
        p=p->link;
    }
}
void debug()
{
    struct node *temp1,*temp2;
    int count1,count2=2;
    temp1=start;
    while(temp1!=NULL)
    {
        temp2=start;
        count1=0;
        while(temp2!=NULL)
        {
            count1=count1+1;
            if((temp1->link==temp2->link)&&(temp1->data!=temp2->data))
            {
                printf("\nThe bug is created at position %d and %d\n", count2,count1);
                temp2->link=NULL;
                exit;
            }
            else
            temp2=temp2->link;
        }
    temp1=temp1->link;
    count2=count2+1;
    }
}