Hi,

Why doesn't sanitizer catch this ? The value ptr is a valid address but it
did a buffer overflow into another object a3 and then it is a valid
address. This is from production code where a ptr whose base was different
array address overflows into another array and becomes a valid address.
This is not caught by address sanitizer.

   - How do you detect this and fix this ? Are there any alternative
   datastructures in C or C++ that prevent these kind of overruns
   Please don't increase the cookie or red zone size between arrays. Again
   sizes more than the cookie or redzone between arrays or objects can be
   overrun



navin@Navin-acer-5740:~/cpp$ gcc -fsanitize=address sanitizer.c
navin@Navin-acer-5740:~/cpp$ ./a.out
a1=(0x614000000040-0x6140000001d0) a2=(0x614000000240-0x6140000003d0)
a3=(0x614000000440-0x6140000005d0)
value=0, ptr=0x614000000498
ptr lies in the array a3
navin@Navin-acer-5740:~/cpp$ cat sanitizer.c
#include<stdlib.h>
#include<stdio.h>
int main(){
int *a1=calloc(100,sizeof(int));
int *a2=calloc(100,sizeof(int));
int *a3=calloc(100,sizeof(int));

printf("a1=(%p-%p) a2=(%p-%p) a3=(%p-%p)\n",a1,a1+100,a2,a2+100,a3,a3+100);
int *ptr=a2;
ptr+=150;
printf("value=%d, ptr=%p\n",*ptr,ptr);
if(a3<=ptr && ptr<=a3+100) printf("ptr lies in the array a3\n");

free(a1);
free(a2);
free(a3);
}
navin@Navin-acer-5740:~/cpp$


Regards,
Navin