#22 stack-buffer-overflow in function put_float()

[chiba taiki]

Hi,

While fuzzing ATasm 1.09, I found stack-buffer-overflow in function put_float(),in asm.c

in the function put_float() in asm.c

the tmp array size is 64: 634 char tmp[64],buf[64],*look,*walk;,

in line 660 660 strcat(tmp,look); didn't check the length of look and then result in a stack buffer overflow.

==4044063==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffc7a6ca300 at pc 0x7f6cea999cbd bp 0x7ffc7a6ca240 sp 0x7ffc7a6c99e8
READ of size 73 at 0x7ffc7a6ca300 thread T0
    #0 0x7f6cea999cbc  (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x74cbc)
    #1 0x55859308ed68 in put_float /home/goushi/john/atasm/src-afl-gcc/asm.c:663
    #2 0x5585930960ee in do_float /home/goushi/john/atasm/src-afl-gcc/asm.c:1207
    #3 0x5585930a121a in proc_sym /home/goushi/john/atasm/src-afl-gcc/asm.c:1600
    #4 0x5585930a5f4a in do_cmd /home/goushi/john/atasm/src-afl-gcc/asm.c:1995
    #5 0x5585930a6424 in assemble /home/goushi/john/atasm/src-afl-gcc/asm.c:2034
    #6 0x558593084341 in main /home/goushi/john/atasm/src-afl-gcc/asm.c:2446
    #7 0x7f6cea73e0b2 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x270b2)
    #8 0x558593085ddd in _start (/home/goushi/john/atasm/src-afl-gcc/atasm+0xdddd)

Address 0x7ffc7a6ca300 is located in stack of thread T0 at offset 128 in frame
    #0 0x55859308e8ff in put_float /home/goushi/john/atasm/src-afl-gcc/asm.c:633

  This frame has 3 object(s):
    [32, 44) 'n' (line 635)
    [64, 128) 'tmp' (line 634)
    [160, 224) 'buf' (line 634) <== Memory access at offset 128 partially underflows this variable
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 (/usr/lib/x86_64-linux-gnu/libasan.so.5+0x74cbc)
Shadow bytes around the buggy address:
  0x10000f4d1410: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10000f4d1420: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10000f4d1430: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10000f4d1440: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10000f4d1450: f1 f1 f1 f1 00 04 f2 f2 00 00 00 00 00 00 00 00
=>0x10000f4d1460:[f2]f2 f2 f2 00 00 00 00 00 00 00 00 f3 f3 f3 f3
  0x10000f4d1470: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10000f4d1480: f1 f1 f1 f1 00 00 00 00 f2 f2 f2 f2 00 00 00 00
  0x10000f4d1490: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10000f4d14a0: 00 00 00 00 00 00 00 00 00 00 00 00 f3 f3 f3 f3
  0x10000f4d14b0: f3 f3 f3 f3 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
==4044063==ABORTING

reproduce:

atasm  stack_buffer_over_02_put_float