Crash Dump Analysis Patterns (Part 109)

This pattern is called Invalid Exception Information and shows how to recognize it and get a stack trace right when a debugger is not able to locate a crash point. For example, WinDbg default analysis command is not able to locate the exception context for a crash and provides a heuristic stack trace:

0:000> !analyze -v

[...]

EXCEPTION_RECORD:  001150fc -- (.exr 0x1150fc)
ExceptionAddress: 7c7e2afb (kernel32!RaiseException+0x00000053)
   ExceptionCode: 0eedfade
  ExceptionFlags: 00000001
NumberParameters: 7
   Parameter[0]: 0098fa49
   Parameter[1]: 0374c200
   Parameter[2]: 00000000
   Parameter[3]: 005919b4
   Parameter[4]: 01d80010
   Parameter[5]: 00115704
   Parameter[6]: 001154a4

[...]

CONTEXT:  0012ffb4 — (.cxr 0×12ffb4)
eax=00000000 ebx=00000000 ecx=0000019c edx=00000214 esi=00000000 edi=00000000
eip=000003b0 esp=000002d8 ebp=2d59495b iopl=0 nv up ei ng zr na pe nc
cs=0032 ss=0010 ds=0002 es=0000 fs=0000 gs=0000 efl=000003e4
0032:000003b0 ??              ???

[...]

STACK_TEXT: 
7c910328 ntdll!`string'+0x4
7c7db7d0 kernel32!ConsoleApp+0xe
7c7db7a4 kernel32!ConDllInitialize+0x20f
7c7db7b9 kernel32!ConDllInitialize+0x224
7c915239 ntdll!bsearch+0x42
7c91542b ntdll!RtlpLocateActivationContextSection+0x15a
7c915474 ntdll!RtlpCompareActivationContextDataTOCEntryById+0x0
7c916104 ntdll!RtlpFindUnicodeStringInSection+0x23d
7c91534a ntdll!RtlpFindNextActivationContextSection+0x61
7c915742 ntdll!RtlFindNextActivationContextSection+0x46
7c9155ed ntdll!RtlFindActivationContextSectionString+0xde
7c915ce9 ntdll!RtlDecodeSystemPointer+0x9e7
7c915d47 ntdll!RtlDecodeSystemPointer+0xb0b
7c9158ff ntdll!RtlDecodeSystemPointer+0x45b
7c915bf8 ntdll!RtlDosApplyFileIsolationRedirection_Ustr+0x346
7c915c5d ntdll!RtlDosApplyFileIsolationRedirection_Ustr+0x3de
7c97e214 ntdll!DllExtension+0xc
00800000 ApplicationA+0x400000
7c910000 ntdll!RtlFreeHeap+0x1a4
7c914a53 ntdll!LdrLockLoaderLock+0x146
7c912d04 ntdll!LdrLockLoaderLock+0x1d2
7c912d71 ntdll!LdrUnlockLoaderLock+0x88
7c916768 ntdll!LdrGetDllHandleEx+0xc9
7c912d80 ntdll!`string'+0x84
7c91690e ntdll!LdrGetDllHandleEx+0x2f1
7c912d78 ntdll!LdrUnlockLoaderLock+0xb1
7c97ecc0 ntdll!LdrpHotpatchCount+0x8
7c9167e8 ntdll!`string'+0xc4
7c9168d6 ntdll!LdrGetDllHandleEx+0x2de
7c9166b8 ntdll!LdrGetDllHandle+0x18
7c7de534 kernel32!GetModuleHandleForUnicodeString+0x1d
7c7de544 kernel32!GetModuleHandleForUnicodeString+0xa0
7c7de64b kernel32!BasepGetModuleHandleExW+0x18e
7c7de6cb kernel32!BasepGetModuleHandleExW+0x250
79000000 mscoree!_imp__EnterCriticalSection <PERF> +0x0
7c809ad8 kernel32!_except_handler3+0x0
7c7de548 kernel32!`string'+0x28
79002280 mscoree!`string'+0x0
02080000 xpsp2res+0xc0000
7c7db6d4 kernel32!_BaseDllInitialize+0x7a
7c7db6e9 kernel32!_BaseDllInitialize+0x488
7c917ef3 ntdll!LdrpSnapThunk+0xbd
7c9048b8 ntdll!$$VProc_ImageExportDirectory+0x14b8
7c9000d0 ntdll!RtlDosPathSeperatorsString <PERF> +0x0
7c905d48 ntdll!$$VProc_ImageExportDirectory+0x2948
7c910228 ntdll!RtlpRunTable+0x448
7c910222 ntdll!RtlpAllocateFromHeapLookaside+0x42
7c911086 ntdll!RtlAllocateHeap+0x43d
7c903400 ntdll!$$VProc_ImageExportDirectory+0x0
7c7d9036 kernel32!$$VProc_ImageExportDirectory+0x6a0a
791c6f2d mscorwks!DllMain+0x117
7c917e10 ntdll!`string'+0xc
7c918047 ntdll!LdrpSnapThunk+0x317
7c7d00f0 kernel32!_imp___wcsnicmp <PERF> +0x0
7c7d903c kernel32!$$VProc_ImageExportDirectory+0x6a10
7c917dba ntdll!LdrpGetProcedureAddress+0x186
7c900000 ntdll!RtlDosPathSeperatorsString <PERF> +0x0
7c917e5f ntdll!LdrpGetProcedureAddress+0x29b
7c7d262c kernel32!$$VProc_ImageExportDirectory+0x0
7c7d0000 kernel32!_imp___wcsnicmp <PERF> +0x0
79513870 mscorsn!DllMain+0x119
7c913425 ntdll!RtlDecodePointer+0x0
00726574 ApplicationA+0x326574
7c917e09 ntdll!LdrpGetProcedureAddress+0xa6
7c917ec0 ntdll!LdrGetProcedureAddress+0x18
7c9101e0 ntdll!CheckHeapFillPattern+0x54
7c9101db ntdll!RtlAllocateHeap+0xeac
40ae17ea msxml6!calloc+0xa9
40ae181f msxml6!calloc+0xde
40a30000 msxml6!_imp__OpenThreadToken <PERF> +0x0
7c910323 ntdll!RtlpImageNtHeader+0x56
7c910385 ntdll!RtlImageDirectoryEntryToData+0x57
00400100 ApplicationA+0x100
7c928595 ntdll!LdrpCallTlsInitializers+0x1d
00400000 ApplicationA+0x0
7c9285c7 ntdll!LdrpCallTlsInitializers+0xd8
7c90118a ntdll!LdrpCallInitRoutine+0x14
00a23010 ApplicationA+0x623010
7c9285d0 ntdll!`string'+0x18
7c935e24 ntdll!LdrpInitializeThread+0x147
7c91b1b7 ntdll!LdrpInitializeThread+0x13b
778e159a SETUPAPI!_DllMainCRTStartup+0x0
7c91b100 ntdll!`string'+0x88
7c91b0a4 ntdll!_LdrpInitialize+0x25b
7c90de9a ntdll!NtTestAlert+0xc
7c91b030 ntdll!`string'+0xc8
7c91b02a ntdll!_LdrpInitialize+0x246
7c90d06a ntdll!NtContinue+0xc
7c90e45f ntdll!KiUserApcDispatcher+0xf
00780010 ApplicationA+0x380010
7c951e13 ntdll!DbgUiRemoteBreakin+0x0
7c97e178 ntdll!LdrpLoaderLock+0x0
00d10000 ApplicationA+0x910000
7c951e40 ntdll!DbgUiRemoteBreakin+0x2d
7c90e920 ntdll!_except_handler3+0x0
7c951e60 ntdll!`string'+0x7c

Compare our invalid context data with the normal one having good efl and segment register values:

cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010206

We look at our stack trace after resetting context and using kv command. We see that KiUserExceptionDispatcher has the valid exception context but exception pointers for UnhandledExceptionFilter are not valid:

0:000> .ecxr

0:000> kv
ChildEBP RetAddr  Args to Child             
001132d0 7c90df4a 7c7d9590 00000002 001132fc ntdll!KiFastSystemCallRet
001132d4 7c7d9590 00000002 001132fc 00000001 ntdll!ZwWaitForMultipleObjects+0xc
00113370 7c7da115 00000002 001134a0 00000000 kernel32!WaitForMultipleObjectsEx+0x12c
0011338c 6993763c 00000002 001134a0 00000000 kernel32!WaitForMultipleObjects+0x18
00113d20 699382b1 00115018 00000001 00198312 faultrep!StartDWException+0x5df
00114d94 7c834526 00115018 00000001 00000000 faultrep!ReportFault+0x533
00115008 0040550c 00115018 7c9032a8 001150fc kernel32!UnhandledExceptionFilter+0×55b
WARNING: Stack unwind information not available. Following frames may be wrong.
00115034 7c90327a 001150fc 0012ffb4 0011512c ApplicationA+0×550c
001150e4 7c90e48a 00000000 0011512c 001150fc ntdll!ExecuteHandler+0×24
001150e4 7c7e2afb 00000000 0011512c 001150fc ntdll!KiUserExceptionDispatcher+0xe (CONTEXT @ 0011512c)
0011544c 0057ac37 0eedfade 00000001 00000007 kernel32!RaiseException+0×53
00115470 0098fa49 0eedfade 00000001 00000007 ApplicationA+0×17ac37
[…]
0012268c 7e398816 017d0f87 000607e8 0000001a USER32!InternalCallWinProc+0×28
001226f4 7e3a8ea0 00000000 017d0f87 000607e8 USER32!UserCallWinProcCheckWow+0×150

0:000> dd 00115018 L4
00115018  001150fc 0012ffb4 0011512c 001150d0

So we use the valid context pointer now:

0:000> .cxr 0011512c
eax=001153fc ebx=0eedfade ecx=00000000 edx=001537a8 esi=001154a4 edi=00000007
eip=7c7e2afb esp=001153f8 ebp=0011544c iopl=0         nv up ei pl nz na po nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00200202
kernel32!RaiseException+0×53:
7c7e2afb 5e              pop     esi

0:000> kv
  *** Stack trace for last set context - .thread/.cxr resets it
ChildEBP RetAddr  Args to Child             
0011544c 0057ac37 0eedfade 00000001 00000007 kernel32!RaiseException+0x53
WARNING: Stack unwind information not available. Following frames may be wrong.
00115470 0098fa49 0eedfade 00000001 00000007 ApplicationA+0x17ac37
[...]
0012268c 7e398816 017d0f87 000607e8 0000001a USER32!InternalCallWinProc+0x28
001226f4 7e3a8ea0 00000000 017d0f87 000607e8 USER32!UserCallWinProcCheckWow+0x150
00122748 7e3aacd1 00fd2ad0 0000001a 00000000 USER32!DispatchClientMessage+0xa3
00122778 7c90e473 00122788 00000030 00000030 USER32!__fnINSTRING+0x37
001227b4 7e3993e9 7e3993a8 00122840 00000000 ntdll!KiUserCallbackDispatcher+0x13
001227e0 7e3aa43b 00122840 00000000 00000000 USER32!NtUserPeekMessage+0xc
0012280c 004794d9 00122840 00000000 00000000 USER32!PeekMessageA+0xeb
001228bc 00461667 0012ff7c 00461680 001228e0 ApplicationA+0x794d9
[...]

- Dmitry Vostokov @ DumpAnalysis.org + TraceAnalysis.org -

Leave a Reply