whats wrong in my linked list!!!

hey whats wrong in my linked list…its goin into infinite loop in DEV C
bt running in turbo c.

#include <stdio.h>
#include <malloc.h>

/* structure containing a data part and link part */
struct node
{
    int data ;
    struct node *link ;
};

void add ( struct node **, int ) ;
void display ( struct node * ) ;



int main( )
{
    struct node *p ;
    p = NULL ;

    add ( &p, 5 ) ;
    add ( &p, 1 ) ;
    add ( &p, 6 ) ;
    add ( &p, 4 ) ;
    add ( &p, 7 ) ;

    display ( p ) ;

    return 0;
}


void add ( struct node **q, int num )
{
    struct node *r, *temp = *q ;

    r = (struct node*)malloc( sizeof(struct node) ) ;
    r -> data = num ;
    r -> link = NULL;

    /* if list is empty or if new node is to be inserted before the first node */
    if ( *q == NULL || (*q) -> data > num )
    {
        *q = r ;
        (*q) -> link = temp ;
    }
    else
    {
        /* traverse the entire linked list to search the position to insert the new node */
        while ( temp != NULL )
        {
            if ( temp -> data <= num && ( temp -> link -> data > num || temp -> link == NULL ))
            {
                r -> link = temp -> link ;
                temp -> link = r ;
                return ;
            }
            temp = temp -> link ;  /* go to the next node */
        }
    }
}

/* displays the contents of the linked list */
void display ( struct node *q )
{
    printf("\n");


    while ( q != NULL )
    {
        printf ( "%d ", q -> data ) ;
        q = q -> link ;
    }
}

What is the basis of insertion of node in the linked list ??

//