Dropbox crash dump quick analysis (on Windows)

I don’t exactly remember the last time I installed or upgrade the Dropbox on my Windows 8 laptop, but today one of my application started crashing itself whenever I opened a file open browser within app and it turned out it caused by Dropbox extension after quick analysis of crash dump. Unfortunately re-installing the most recent version doesn’t fix the problem so far.

Shows the moment when the crash occurred.

0:002> r
eax=59d0d000 ebx=74a91a9c ecx=00000000 edx=0000d0d0 esi=74a91aa0 edi=0000003f
eip=74ac7736 esp=0c04c434 ebp=0c04c440 iopl=0 nv up ei pl nz ac pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010216
74ac7736 0fb710 movzx edx,word ptr [eax] ds:002b:59d0d000=????  <== invalid memory access

Let’s see the call stack who gave the wrong param.

0:002> kP L4
ChildEBP RetAddr 
0c04c440 74abae83 msvcr90!wcspbrk(
 wchar_t * string = 0x59d0cf80 "C:\Users\xxxxx.xxx\AppData\Roaming\Dropbox\shellext \new_trace탐탐", 
 wchar_t * control = 0x74a91a9c "?*")+0x34
0c04c8d8 59405f72 msvcr90!_wstat64i32(
 wchar_t * name = 0x59d0cf80 "C:\Users\xxxxx.xxx\AppData\Roaming\Dropbox\shellext \new_trace탐탐", 
 struct _stat64i32 * buf = 0x0c04c8f8)+0x5d
WARNING: Stack unwind information not available. Following frames may be wrong.
0c04c940 59406524 DropboxExt_24+0x5f72
0c04cd58 594135ff DropboxExt_24+0x6524
DropboxExt_24 calls msvcr90!_wstat64i32 with 0x59d0cf80.
0:002> dU 0x59d0cf80 
59d0cf80 "C:\Users\xxxxx.xxx\AppData\Roami"
59d0cfc0 "ng\Dropbox\shellext \new_trace탐탐"
59d0d000 "????????????????????????????????"
59d0d040 "????????????????????????????????"
59d0d080 "????????????????????????????????"
59d0d0c0 "????????????????????????????????"
59d0d100 "????????????????????????????????"
59d0d140 "????????????????????????????????"
59d0d180 "????????????????????????????????"
59d0d1c0 "????????????????????????????????"
59d0d200 "????????????????????????????????"
59d0d240 "????????????????????????????????"
0:002> r eax
The address 59d0d000 is invalid and inaccessible area. I turned on gflag while capturing this.
0:002> !gflag
Current NtGlobalFlag contents: 0x02000000
 hpa - Place heap allocations at ends of pages
So it could show the original heap size as follows:
0:002> !heap -p -a 0x59d0cf80
 address 59d0cf80 found in
 _DPH_HEAP_ROOT @ 59a81000
 in busy allocation ( DPH_HEAP_BLOCK: UserAddr UserSize - VirtAddr VirtSize)
 59a8309c: 59d0cf80 7c - 59d0c000 2000
 0f578d9c verifier!AVrfDebugPageHeapAllocate+0x0000023c
 7726f819 ntdll!RtlDebugAllocateHeap+0x00000032
 772072db ntdll!RtlpAllocateHeap+0x00036e22
 771d06d3 ntdll!RtlAllocateHeap+0x0000014c
 74af3db8 msvcr90!malloc+0x00000079 [f:\dd\vctools\crt_bld\self_x86\crt\src\malloc.c @ 163]
 59405ecd DropboxExt_24+0x00005ecd
 59405ca4 DropboxExt_24+0x00005ca4
 59406513 DropboxExt_24+0x00006513
 594135ff DropboxExt_24!DllUnregisterServer+0x0000cb3f
 594136b9 DropboxExt_24!DllUnregisterServer+0x0000cbf9
 771d7aee ntdll!LdrxCallInitRoutine+0x00000016
 771d7a6f ntdll!LdrpCallInitRoutine+0x00000043
 771e07bc ntdll!LdrpInitializeNode+0x0000011d
 771e065e ntdll!LdrpInitializeGraph+0x00000059
 771dff22 ntdll!LdrpPrepareModuleForExecution+0x00000121
 771e0d88 ntdll!LdrpLoadDll+0x00000392
 771dc3ce ntdll!LdrLoadDll+0x00000067
 75a42551 KERNELBASE!LoadLibraryExW+0x000000c2
 75291892 combase!LoadLibraryWithLogging+0x0000001b [d:\blue_gdr\com\combase\common\loadfree.cxx @ 160]
 752917e0 combase!CClassCache::CDllPathEntry::LoadDll+0x0000003e [d:\blue_gdr\com\combase\objact\dllcache.cxx @ 2409]
 7529169a combase!CClassCache::CDllPathEntry::Create+0x00000035 [d:\blue_gdr\com\combase\objact\dllcache.cxx @ 2252]
 75290fe2 combase!CClassCache::CClassEntry::CreateDllClassEntry+0x000000f3 [d:\blue_gdr\com\combase\objact\dllcache.cxx @ 1048]
 752911a8 combase!CClassCache::GetClassObjectActivator+0x00000851 [d:\blue_gdr\com\combase\objact\dllcache.cxx @ 6042]
 7529015a combase!CClassCache::GetClassObject+0x00000030 [d:\blue_gdr\com\combase\objact\dllcache.cxx @ 5808]
 75290e4c combase!CServerContextActivator::CreateInstance+0x00000107 [d:\blue_gdr\com\combase\objact\actvator.cxx @ 999]
 7528d0f6 combase!ActivationPropertiesIn::DelegateCreateInstance+0x0000006e [d:\blue_gdr\com\combase\actprops\actprops.cxx @ 1906]
 75290d29 combase!CApartmentActivator::CreateInstance+0x00000075 [d:\blue_gdr\com\combase\objact\actvator.cxx @ 2323]
 75290c55 combase!CProcessActivator::CCICallback+0x00000039 [d:\blue_gdr\com\combase\objact\actvator.cxx @ 1786]
 7529095a combase!CProcessActivator::AttemptActivation+0x0000002c [d:\blue_gdr\com\combase\objact\actvator.cxx @ 1673]
 75290baa combase!CProcessActivator::ActivateByContext+0x00000094 [d:\blue_gdr\com\combase\objact\actvator.cxx @ 1539]
 75290c0c combase!CProcessActivator::CreateInstance+0x00000046 [d:\blue_gdr\com\combase\objact\actvator.cxx @ 1405]
 7528d0f6 combase!ActivationPropertiesIn::DelegateCreateInstance+0x0000006e [d:\blue_gdr\com\combase\actprops\actprops.cxx @ 1906]
The heap allocation callstack shows DropboxExt_24+0x00005ecd actually allocated only 0x7c. (UserSize is 0x7c), not area for whole path.
0:002> ? 0x7c 
Evaluate expression: 124 = 0000007c
0:002> lmvm DropboxExt_24
start end module name
59400000 59423000 DropboxExt_24 (export symbols) DropboxExt.24.dll
 Loaded symbol image file: DropboxExt.24.dll
 Image path: C:\Users\xxxxx.xxx\AppData\Roaming\Dropbox\bin\DropboxExt.24.dll
 Image name: DropboxExt.24.dll
 Timestamp: Tue Jun 24 09:31:58 2014 (53A8C6FE)
 CheckSum: 00021746
 ImageSize: 00023000
 File version:
 Product version:
 File flags: 0 (Mask 3F)
 File OS: 4 Unknown Win32
 File type: 2.0 Dll
 File date: 00000000.00000000
 Translations: 0409.04e4
 CompanyName: Dropbox, Inc.
 ProductName: Dropbox
 InternalName: DropboxExt.dll
 OriginalFilename: DropboxExt.dll
 FileDescription: Dropbox Shell Extension
 LegalCopyright: (c) Dropbox, Inc. All rights reserved

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