classification
Title: heap-use-after-free in find_maxchar_surrogates
Type: security Stage:
Components: ctypes Versions: Python 3.5
process
Status: closed Resolution: not a bug
Dependencies: Superseder:
Assigned To: Nosy List: pitrou, sys, vstinner
Priority: normal Keywords:

Created on 2014-12-10 09:43 by sys, last changed 2014-12-11 11:57 by sys. This issue is now closed.

Messages (2)
msg232417 - (view) Author: (sys) Date: 2014-12-10 09:43
Line 27-29 trigger use-after-free.

=================================================================
==18203== ERROR: AddressSanitizer: heap-use-after-free on address 0x60080003b2e0 at pc 0x5e844f bp 0x7ffff5351750 sp 0x7ffff5351748
READ of size 4 at 0x60080003b2e0 thread T0
    #0 0x5e844e in find_maxchar_surrogates ./cpython/Objects/unicodeobject.c:1428
    #1 0x5ed62e in PyUnicode_FromUnicode ./cpython/Objects/unicodeobject.c:1822
    #2 0x5f57cd in PyUnicode_FromWideChar ./cpython/Objects/unicodeobject.c:2311
    #3 0x7f4ebbd00976 in Z_get /media/truecrypt1/bounty/cpython/Modules/_ctypes/cfield.c:1429
    #4 0x7f4ebbcde48b in PyCData_get /media/truecrypt1/bounty/cpython/Modules/_ctypes/_ctypes.c:2756
    #5 0x7f4ebbcf90b8 in PyCField_get /media/truecrypt1/bounty/cpython/Modules/_ctypes/cfield.c:230
    #6 0x56ff34 in _PyObject_GenericGetAttrWithDict ./cpython/Objects/object.c:1059
    #7 0x5704ee in PyObject_GenericGetAttr ./cpython/Objects/object.c:1119
    #8 0x56f169 in PyObject_GetAttr ./cpython/Objects/object.c:889
    #9 0x70ef2d in PyEval_EvalFrameEx ./cpython/Python/ceval.c:2442
    #10 0x723c20 in fast_function ./cpython/Python/ceval.c:4368
    #11 0x7234ea in call_function ./cpython/Python/ceval.c:4294
    #12 0x715433 in PyEval_EvalFrameEx ./cpython/Python/ceval.c:2860
    #13 0x71e164 in _PyEval_EvalCodeWithName ./cpython/Python/ceval.c:3610
    #14 0x71e354 in PyEval_EvalCodeEx ./cpython/Python/ceval.c:3631
    #15 0x6f7af3 in PyEval_EvalCode ./cpython/Python/ceval.c:773
    #16 0x42ea99 in run_mod ./cpython/Python/pythonrun.c:968
    #17 0x42e69f in PyRun_FileExFlags ./cpython/Python/pythonrun.c:921
    #18 0x42b456 in PyRun_SimpleFileExFlags ./cpython/Python/pythonrun.c:394
    #19 0x429ac3 in PyRun_AnyFileExFlags ./cpython/Python/pythonrun.c:80
    #20 0x45624b in run_file ./cpython/Modules/main.c:318
    #21 0x457717 in Py_Main ./cpython/Modules/main.c:767
    #22 0x41b845 in main ./cpython/./Programs/python.c:69
    #23 0x7f4ebc741ed4 in __libc_start_main ??:?
    #24 0x41b438 in _start /glibc-tmp-c47113ea580c02d806fd2bb53621c6f5/glibc-2.20/csu/../sysdeps/x86_64/start.S:122
0x60080003b2e0 is located 16 bytes inside of 37-byte region [0x60080003b2d0,0x60080003b2f5)
freed by thread T0 here:
    #0 0x7f4ebd41d34a in __interceptor_free ??:?
    #1 0x41b9b5 in _PyMem_RawFree ./cpython/Objects/obmalloc.c:90
    #2 0x41f4aa in _PyMem_DebugFree ./cpython/Objects/obmalloc.c:1892
    #3 0x41c3db in PyMem_Free ./cpython/Objects/obmalloc.c:349
    #4 0x502f7a in float_repr ./cpython/Objects/floatobject.c:275
    #5 0x56d68a in PyObject_Str ./cpython/Objects/object.c:535
    #6 0x500926 in PyFile_WriteObject ./cpython/Objects/fileobject.c:141
    #7 0x6efe19 in builtin_print ./cpython/Python/bltinmodule.c:2243
    #8 0x564fb5 in PyCFunction_Call ./cpython/Objects/methodobject.c:100
    #9 0x72310c in call_function ./cpython/Python/ceval.c:4269 (discriminator 2)
    #10 0x715433 in PyEval_EvalFrameEx ./cpython/Python/ceval.c:2860
    #11 0x723c20 in fast_function ./cpython/Python/ceval.c:4368
    #12 0x7234ea in call_function ./cpython/Python/ceval.c:4294
    #13 0x715433 in PyEval_EvalFrameEx ./cpython/Python/ceval.c:2860
    #14 0x71e164 in _PyEval_EvalCodeWithName ./cpython/Python/ceval.c:3610
    #15 0x71e354 in PyEval_EvalCodeEx ./cpython/Python/ceval.c:3631
    #16 0x6f7af3 in PyEval_EvalCode ./cpython/Python/ceval.c:773
    #17 0x42ea99 in run_mod ./cpython/Python/pythonrun.c:968
    #18 0x42e69f in PyRun_FileExFlags ./cpython/Python/pythonrun.c:921
    #19 0x42b456 in PyRun_SimpleFileExFlags ./cpython/Python/pythonrun.c:394
    #20 0x429ac3 in PyRun_AnyFileExFlags ./cpython/Python/pythonrun.c:80
    #21 0x45624b in run_file ./cpython/Modules/main.c:318
    #22 0x457717 in Py_Main ./cpython/Modules/main.c:767
    #23 0x41b845 in main ./cpython/./Programs/python.c:69
    #24 0x7f4ebc741ed4 in __libc_start_main ??:?
previously allocated by thread T0 here:
    #0 0x7f4ebd41d42a in malloc ??:?
    #1 0x41b918 in _PyMem_RawMalloc ./cpython/Objects/obmalloc.c:62
    #2 0x41efe9 in _PyMem_DebugAlloc ./cpython/Objects/obmalloc.c:1838
    #3 0x41f29e in _PyMem_DebugMalloc ./cpython/Objects/obmalloc.c:1861
    #4 0x41c256 in PyMem_Malloc ./cpython/Objects/obmalloc.c:325
    #5 0x78b7c0 in format_float_short ./cpython/Python/pystrtod.c:1094
    #6 0x78c224 in PyOS_double_to_string ./cpython/Python/pystrtod.c:1231
    #7 0x502ecb in float_repr ./cpython/Objects/floatobject.c:268
    #8 0x56d68a in PyObject_Str ./cpython/Objects/object.c:535
    #9 0x500926 in PyFile_WriteObject ./cpython/Objects/fileobject.c:141
    #10 0x6efe19 in builtin_print ./cpython/Python/bltinmodule.c:2243
    #11 0x564fb5 in PyCFunction_Call ./cpython/Objects/methodobject.c:100
    #12 0x72310c in call_function ./cpython/Python/ceval.c:4269 (discriminator 2)
    #13 0x715433 in PyEval_EvalFrameEx ./cpython/Python/ceval.c:2860
    #14 0x723c20 in fast_function ./cpython/Python/ceval.c:4368
    #15 0x7234ea in call_function ./cpython/Python/ceval.c:4294
    #16 0x715433 in PyEval_EvalFrameEx ./cpython/Python/ceval.c:2860
    #17 0x71e164 in _PyEval_EvalCodeWithName ./cpython/Python/ceval.c:3610
    #18 0x71e354 in PyEval_EvalCodeEx ./cpython/Python/ceval.c:3631
    #19 0x6f7af3 in PyEval_EvalCode ./cpython/Python/ceval.c:773
    #20 0x42ea99 in run_mod ./cpython/Python/pythonrun.c:968
    #21 0x42e69f in PyRun_FileExFlags ./cpython/Python/pythonrun.c:921
    #22 0x42b456 in PyRun_SimpleFileExFlags ./cpython/Python/pythonrun.c:394
    #23 0x429ac3 in PyRun_AnyFileExFlags ./cpython/Python/pythonrun.c:80
    #24 0x45624b in run_file ./cpython/Modules/main.c:318
    #25 0x457717 in Py_Main ./cpython/Modules/main.c:767
    #26 0x41b845 in main ./cpython/./Programs/python.c:69
    #27 0x7f4ebc741ed4 in __libc_start_main ??:?
Shadow bytes around the buggy address:
  0x0c017ffff600: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c017ffff610: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c017ffff620: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c017ffff630: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c017ffff640: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
=>0x0c017ffff650: fa fa fa fa fa fa fa fa fa fa fd fd[fd]fd fd fa
  0x0c017ffff660: fa fa fd fd fd fd fd fa fa fa fd fd fd fd fd fa
  0x0c017ffff670: fa fa fd fd fd fd fd fa fa fa fd fd fd fd fd fa
  0x0c017ffff680: fa fa fd fd fd fd fd fa fa fa fd fd fd fd fd fd
  0x0c017ffff690: fa fa 00 00 00 00 00 fa fa fa 00 00 00 00 00 04
  0x0c017ffff6a0: fa fa 00 00 00 00 00 04 fa fa fd fd fd fd fd 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 righ 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
  ASan internal:         fe
==18203== ABORTING
msg232470 - (view) Author: STINNER Victor (vstinner) * (Python committer) Date: 2014-12-11 11:36
Your code is strange. It exchanges pointer between processes if I understand correctly:

  class Berbagi(ctypes.Structure):
    _fields_ = [('a', ctypes.c_wchar_p), ('b', ctypes.c_double) ]
  nilai = multiprocessing.Array(Berbagi, [Berbagi() for x in range(9)] )

You must not do that. Instead, Berbagi.a must be an array of c_wchar characters with a fixed size. Try for example:

  class Berbagi(ctypes.Structure):
    _fields_ = [('a', ctypes.c_wchar * 10), ('b', ctypes.c_double) ]

Note: I'm not sure that ctypes is the most efficient module to serialize data, but maybe you have to use ctypes for a reason not explained in your issue.

The bug is in your code, not in Python.
History
Date User Action Args
2014-12-11 11:57:06syssetfiles: - repro.py
2014-12-11 11:36:51vstinnersetnosy: + pitrou
2014-12-11 11:36:40vstinnersetstatus: open -> closed
resolution: not a bug
messages: + msg232470
2014-12-11 10:54:43pitrousetnosy: + vstinner
2014-12-10 09:44:08syssethgrepos: - hgrepo284
2014-12-10 09:43:38syscreate