问题：
https://leetcode-cn.com/problems/cells-in-a-range-on-an-excel-sheet/

问题相关代码

/**
 * Note: The returned array must be malloced, assume caller calls free().
 */
char ** cellsInRange(char * s, int* returnSize){
char **a=(char **)malloc(sizeof(char*)*3000);
int u=0;
int up=s[1]-'0';
int down=s[4]-'0';
int left=s[0]-'A';
int right=s[3]-'A';

for(int i=left;i<=right;i++){
    for(int j=up;j<=down;j++){
        char *p=(char *)malloc(sizeof(char)*2);
        
        char e=j+'0';
        char d=i+'A';
       p[0]=d;
       p[1]=e;
       
       strcpy(a[u],p);
        
        
        u++;

    }
}
*returnSize=u;
return a;
}

运行结果及报错内容

==42==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000000032 at pc 0x7f1bf3c18060 bp 0x7fff042eb970 sp 0x7fff042eb118

求问这个报错是怎么回事呢？要怎么解决呀？