[bug-cflow] [Bug report] Use-after-free in reference function in /src/pa

Hi there,

I have found a use-after-free problem in reference function in /src/parser.c in cflow 1.6 the lastest release version. This bug can also reproduce in cflow 1.5. A crafted input can cause segment faults and I have confirmed them with address sanitizer too.

Here are the POC files. Please use the "./cflow $POC" to reproduce the bug.

The ASAN dumps the stack trace as follows:

=================================================================
==61274==ERROR: AddressSanitizer: heap-use-after-free on address 0x60e0000078b0 at pc 0x0000005534f9 bp 0x7fffd7c405b0 sp 0x7fffd7c405a8
READ of size 8 at 0x60e0000078b0 thread T0
    #0 0x5534f8 in reference /cflow-1.6/src/parser.c:1298:34
    #1 0x5534f8 in _expression_ /cflow-1.6/src/parser.c:621
    #2 0x55d012 in func_body /cflow-1.6/src/parser.c:1051:9
    #3 0x54ea79 in parse_declaration /cflow-1.6/src/parser.c:578:4
    #4 0x54de68 in yyparse /cflow-1.6/src/parser.c:528:9
    #5 0x53b254 in main /cflow-1.6/src/main.c:812:7
    #6 0x7f2ee8ad982f in __libc_start_main /build/glibc-Cl5G7W/glibc-2.23/csu/../csu/libc-start.c:291
    #7 0x41a978 in _start (/cflow-1.6/build/bin/cflow+0x41a978)

0x60e0000078b0 is located 144 bytes inside of 152-byte region [0x60e000007820,0x60e0000078b8)
freed by thread T0 here:
    #0 0x4da6d0 in __interceptor_free.localalias.0 /home/wencheng/Documents/llvm-6.0.1/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:68
    #1 0x538e68 in linked_list_destroy /cflow-1.6/src/linked-list.c:87:7

previously allocated by thread T0 here:
    #0 0x4da8a0 in __interceptor_malloc /home/wencheng/Documents/llvm-6.0.1/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:88
    #1 0x5bdc80 in xmalloc /cflow-1.6/gnu/xmalloc.c:43:13

SUMMARY: AddressSanitizer: heap-use-after-free /cflow-1.6/src/parser.c:1298:34 in reference
Shadow bytes around the buggy address:
  0x0c1c7fff8ec0: 00 00 00 fa fa fa fa fa fa fa fa fa 00 00 00 00
  0x0c1c7fff8ed0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa
  0x0c1c7fff8ee0: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c1c7fff8ef0: 00 00 00 00 00 00 00 00 00 00 00 fa fa fa fa fa
  0x0c1c7fff8f00: fa fa fa fa fd fd fd fd fd fd fd fd fd fd fd fd
=>0x0c1c7fff8f10: fd fd fd fd fd fd[fd]fa fa fa fa fa fa fa fa fa
  0x0c1c7fff8f20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c1c7fff8f30: 00 00 00 fa fa fa fa fa fa fa fa fa 00 00 00 00
  0x0c1c7fff8f40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fa
  0x0c1c7fff8f50: fa fa fa fa fa fa fa fa 00 00 00 00 00 00 00 00
  0x0c1c7fff8f60: 00 00 00 00 00 00 00 00 00 00 00 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
==61274==ABORTING
Aborted

If you have any question, please let me know.

From:	wcventure
Subject:	[bug-cflow] [Bug report] Use-after-free in reference function in /src/parser.c in cflow 1.6
Date:	Mon, 1 Apr 2019 14:10:02 +0800 (CST)