c语言动态链表，显示段错误，输入一组数据就报警

Question

模仿的，段错误，求解#include <stdio.h>#include <malloc.h>struct stu{char name[10];int num;int garde;struct stu *next;};struct stu *mark(){ struct stu *head;struct stu *p1,*p2;int n=0;head=NULL;p1=p2=(struct stu*)malloc(sizeof(struct stu));scanf_s("%d,%d",p1->num,&p1->garde);while(p1->num!=0){n++;if(n==1){head=p1;}else{p2->next=p1;}p2=p1;p1=(struct stu*)malloc(sizeof(struct stu));scanf_s("%d,%d",p1->num,&p1->garde);}p2->next=NULL;return head;}int main(){struct stu *p;p=mark();while(p!=0){printf("%d,%d\n",p->num,p->garde);p=p->next;}return 0;}