AddressSanitizer

#include <stdio.h>
#include <stdlib.h>

int main(void) {
    int *a = malloc(5 * sizeof *a);

    for (int i = 0; i <= 5; ++i)      /* <= thay vi <: thua mot vong */
        a[i] = i;

    printf("%d\n", a[0]);

    free(a);
    return 0;
}

/* Ban viet: */
a[i] = 1;

/* ASan bien no thanh, dai y: */

char *dia_chi = (char *)&a[i];
char *bong    = (char *)(((uintptr_t)dia_chi >> 3) + 0x7fff8000);

if (*bong != 0 && ((uintptr_t)dia_chi & 7) + 4 > *bong)
    __asan_report_store4(dia_chi);      /* in bao cao roi dung */

a[i] = 1;

/* Mot phep dich, mot phep cong, mot lan doc bo nho, mot phep so sanh.
   Do la ly do ASan chi cham gap doi chu khong gap hai muoi nhu Valgrind:
   Valgrind mo phong tung lenh may, con ASan chi chen them bon lenh. */

int *a = malloc(20);
a[5] = 1;                  /* 0 bytes to the right of 20-byte region */
a[-1] = 1;                 /* 4 bytes to the left */

void f(void) {
    int a[5];
    a[5] = 1;              /* ASan: stack-buffer-overflow */
}

/* Valgrind KHONG bat duoc loai nay, vi no khong biet ranh gioi
   giua cac bien tren ngan xep. ASan biet vi trinh bien dich
   noi cho no. */

static int a[5];

int main(void) {
    a[5] = 1;              /* ASan: global-buffer-overflow */
}

free(p);
free(p);                   /* ASan: attempting double-free */

void *p = malloc(10);
delete p;                  /* ASan: alloc-dealloc-mismatch, trong C++ */

int *f(void) {
    int x = 42;
    return &x;
}

/* Mac dinh ASan KHONG bat loai nay vi no dat. Phai bat rieng: */

ASAN_OPTIONS=detect_stack_use_after_return=1 ./prog

/* Luc do ASan cap phat khung ngan xep tren heap, nen giu duoc
   vanh do sau khi ham tra ve. Cham hon dang ke. */

#include <stdlib.h>
#include <string.h>

static char *tao_ten(const char *s) {
    char *p = malloc(strlen(s) + 1);
    strcpy(p, s);
    return p;
}

int main(void) {
    char *a = tao_ten("Nguyen Van A");
    char *b = tao_ten("Tran Thi B");

    free(a);
    /* quen free(b) */

    return 0;
}

typedef struct {
    char ten[8];
    int  diem;
} SinhVien;

SinhVien *sv = malloc(sizeof *sv);

strcpy(sv->ten, "NguyenVanA");    /* 11 byte vao mang 8 byte */

/* ASan KHONG bao, vi ca 11 byte van nam TRONG khoi 16 byte
   ma malloc cap. Vanh do nam sau khoi, khong nam giua cac truong.

   Chinh vi du nay o Bai 35.5 se duoc GDB bat bang watchpoint.

   Ba cach chua:
     - dung strncpy hoac snprintf thay strcpy
     - bat -D_FORTIFY_SOURCE=2, no bat duoc strcpy voi kich thuoc biet truoc
     - dung -fsanitize=address kem -fsanitize-address-use-after-scope */