Exploit Double free() Vulnerability PoC [closed]

Question

I don't understand about this bug very much
This is something that I know about this bug

• If use free() with freed pointer it can trigged this bug

• Need to have at least 2 pointer with allocate memory

Question
how to write exploit code to attack this bug (Proof-of-Concept)

---

Here is my code

int main(int argc,char **argv){
char *ptr1 = malloc(200);
char *ptr2 = malloc(200);
free(ptr1);
strncpy(ptr2,argv[1],100);
free(ptr1);
free(ptr2);