연결리스트 작성중에 세그멘테이션 오류

#include<stdio.h>
 
struct node {
   int block_number;
   struct node *next;
};
 
void insert_front(struct node *head, int num);
void print_list(struct node *head);
 
int main() {
   struct node *list;
 
   insert_front(list, 10);
 
   print_list(list);
 
   return 0;
}
 
void insert_front(struct node *head, int num) {
    head->block_number = num;
}
 
 
void print_list(struct node *head) {
   struct node *p = head;
   printf("%d->", p->block_number);
}