stack-buffer-overflow exit in parseExpression at src/swfc.c:2602

[Diggingwei]

Summary

A stack-buffer-overflow caused when using swfc.

Version

$ ./swfc -V
swfc - part of swftools 0.9.2
$ git log --oneline -1
772e55a2 (HEAD, origin/master, origin/HEAD, master)

Platform

$ uname -a
Linux 1cc373898f58 5.4.0-150-generic #167~18.04.1-Ubuntu SMP Wed May 24 00:51:42 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
clang version : 12.0.0

Reproduce

PoC : poc.zip Command Line : ./swfc poc

Debug Info

==59251==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fffffffd234 at pc 0x000000513ecb bp 0x7fffffffcd90 sp 0x7fffffffcd88
READ of size 4 at 0x7fffffffd234 thread T0
    #0 0x513eca in parseExpression /src/project/swftools_project/swftools/src/swfc.c:2602:37
    #1 0x513eca in parseTwip /src/project/swftools_project/swftools/src/swfc.c:2634:19
    #2 0x5438d5 in texture2 /src/project/swftools_project/swftools/src/swfc.c:3061:9    
    #3 0x529b5c in c_gradient /src/project/swftools_project/swftools/src/swfc.c:3097:5
    #4 0x51b3ad in parseArgumentsForCommand /src/project/swftools_project/swftools/src/swfc.c:4475:5
    #5 0x51b3ad in main /src/project/swftools_project/swftools/src/swfc.c:4598:2
    #6 0x7ffff7c39082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
    #7 0x41d61d in _start (/src/project/swftools_project/swftools/src/swfc+0x41d61d)
Address 0x7fffffffd234 is located in stack of thread T0 at offset 1172 in frame
    #0 0x51105f in parseTwip /src/project/swftools_project/swftools/src/swfc.c:2632

  This frame has 3 object(s):
    [32, 1056) 'chr2index.i' (line 2528)
    [1184, 2208) 'stack.i' (line 2539) <== Memory access at offset 1172 underflows this variable
    [2336, 4384) 'values.i' (line 2540)
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow /src/project/swftools_project/swftools/src/swfc.c:2602:37 in parseExpression
Shadow bytes around the buggy address:
  0x10007fff79f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a10: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a20: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a30: 00 00 00 00 00 00 00 00 f2 f2 f2 f2 f2 f2 f2 f2
=>0x10007fff7a40: f2 f2 f2 f2 f2 f2[f2]f2 00 00 00 00 00 00 00 00
  0x10007fff7a50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10007fff7a90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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
==59251==ABORTING