AddressSanitizer’s no_sanitize_address attribute

AddressSanitizer has a no_sanitize_address attribute which can be used to turn off instrumentation. Check following code:

$ cat ../main.c
#include <stdlib.h>
#include <sanitizer/asan_interface.h>

#define ARRAY_SIZE 4

int *array;

void
foo()
{
    array[0] = 1;
}

int
main()
{
    array = malloc(sizeof(int) * ARRAY_SIZE);
    ASAN_POISON_MEMORY_REGION(array, sizeof(int) * ARRAY_SIZE);
    foo();
}

Build and run this program:

$ ./main
=================================================================
==1558==ERROR: AddressSanitizer: use-after-poison on address 0x602000000010 at pc 0x55839733c1b7 bp 0x7ffc102fb320 sp 0x7ffc102fb310
WRITE of size 4 at 0x602000000010 thread T0
    #0 0x55839733c1b6 in foo (/home/nan/code-for-my-blog/2020/05/asan_no_sanitize_address/build/main+0x11b6)
    #1 0x55839733c1f2 in main (/home/nan/code-for-my-blog/2020/05/asan_no_sanitize_address/build/main+0x11f2)
    #2 0x7fe4d79d9dea in __libc_start_main ../csu/libc-start.c:308
    #3 0x55839733c0b9 in _start (/home/nan/code-for-my-blog/2020/05/asan_no_sanitize_address/build/main+0x10b9)

0x602000000010 is located 0 bytes inside of 16-byte region [0x602000000010,0x602000000020)
allocated by thread T0 here:
    #0 0x7fe4d7c824c8 in __interceptor_malloc (/usr/lib/libasan.so.5+0x10c4c8)
    #1 0x55839733c1cd in main (/home/nan/code-for-my-blog/2020/05/asan_no_sanitize_address/build/main+0x11cd)
    #2 0x7fe4d79d9dea in __libc_start_main ../csu/libc-start.c:308

SUMMARY: AddressSanitizer: use-after-poison (/home/nan/code-for-my-blog/2020/05/asan_no_sanitize_address/build/main+0x11b6) in foo
Shadow bytes around the buggy address:
  0x0c047fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c047fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c047fff8000: fa fa[f7]f7 fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
  Shadow gap:              cc
==1558==ABORTING

Unsurprisingly, AddressSanitizer reports error because the array is poisoned but foo() is trying to modify its first element. Add __attribute__((no_sanitize_address)) for foo():

__attribute__((no_sanitize_address))
void
foo()
{
    array[0] = 1;
}

Run the program again:

$ ./main
$

This time program exits normally.

P.S., the code can be downloaded here.