求助 建立的链表在调试时链表尾的NULL的地址会改变？

#include<stdlib.h>
#include<string.h>
struct stulink{
    int num;
    char name[10];
    char sex;
    int score;
    char rank;
    int level;
    stulink *next;
};
void save(stulink* head)
{
    stulink *p1 = head;
    FILE *fp1;
    fp1 = fopen("e:\\student1.txt","w");

    while(p1!=NULL){
        fprintf(fp1,"%d %s %c %d %c",p1->num,p1->name,p1->sex,p1->score,p1->rank);
        p1 = p1->next;
    }
    if(p1 == NULL)
        printf("所有数据保存成功！！！");
    fclose(fp1);
}

stulink *ReadFromFile()
{
    stulink *head,*temp,*end;
    head = (stulink *)malloc(sizeof(stulink *));
    end = head;
    FILE *fp1;
    fp1 = fopen("e:\\student.txt","r");
    int count = 1;

    while(!feof(fp1)){
        temp = (stulink *)malloc(sizeof(stulink *));
        if(temp == NULL)printf("内存分配失败!!!");
        fscanf(fp1,"%s %c %d %c\n",temp->name,&temp->sex,&temp->score,&temp->rank);
        temp->num = count;
        count++;
        end->next = temp;
        end = temp;
    }
    end->next = NULL;
    fclose(fp1);
    printf("创建成功!!!\n");
    save(head);
   

    return head;
}
void main()
{
    ReadFromFile();
    getchar();
}