e.g :
[root@raminfp heap-exploitation]# gcc -fsanitize=address -g shrinking_free_chunks.c
[root@raminfp heap-exploitation]# ./a.out
0x611000009f00
0x61500000fd00
0x611000009dc0
=================================================================
==16192==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61500000fcf8 at pc 0x000000400a5a bp 0x7ffdc2eaf180 sp 0x7ffdc2eaf170
WRITE of size 1 at 0x61500000fcf8 thread T0
#0 0x400a59 in main /root/heap-exploitation/shrinking_free_chunks.c:36
#1 0x7f4eebc4a400 in __libc_start_main (/lib64/libc.so.6+0x20400)
#2 0x4008b9 in _start (/root/heap-exploitation/a.out+0x4008b9)
0x61500000fcf8 is located 8 bytes to the left of 512-byte region [0x61500000fd00,0x61500000ff00)
freed by thread T0 here:
#0 0x7f4eec0b6b00 in free (/lib64/libasan.so.3+0xc6b00)
#1 0x400a1d in main /root/heap-exploitation/shrinking_free_chunks.c:32
#2 0x7f4eebc4a400 in __libc_start_main (/lib64/libc.so.6+0x20400)
previously allocated by thread T0 here:
#0 0x7f4eec0b6e60 in malloc (/lib64/libasan.so.3+0xc6e60)
#1 0x4009a5 in main /root/heap-exploitation/shrinking_free_chunks.c:20
#2 0x7f4eebc4a400 in __libc_start_main (/lib64/libc.so.6+0x20400)
SUMMARY: AddressSanitizer: heap-buffer-overflow /root/heap-exploitation/shrinking_free_chunks.c:36 in main
Shadow bytes around the buggy address:
0x0c2a7fff9f40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c2a7fff9f50: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c2a7fff9f60: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c2a7fff9f70: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
0x0c2a7fff9f80: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c2a7fff9f90: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa[fa]
0x0c2a7fff9fa0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0c2a7fff9fb0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0c2a7fff9fc0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0c2a7fff9fd0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
0x0c2a7fff9fe0: 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
Heap right redzone: fb
Freed heap region: fd
Stack left redzone: f1
Stack mid redzone: f2
Stack right redzone: f3
Stack partial redzone: f4
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
==16192==ABORTING