Re: Investigating a fork failure

[Corinna Vinschen <corinna-cygwin at cygwin dot com>]

On Aug 24 15:20, Jon TURNEY wrote:
> 
> I'm not very happy with the assumption that this is SEP, so I did a bit more
> investigation into the problem in [1]
> 
> Installing "Lavasoft Ad-Aware Web Companion" into a W7 x86_64 VM, I'm able
> to reproduce that problem.
> 
> Running 'XWin -multiwindow' under WinDbg, with "Debug child processes also"
> enabled, a 2nd chance exception occurs in bash, with the following call
> stack:
> 
> > # Child-SP          RetAddr           Call Site
> >00 00000000`0022e2e0 00000000`7755f37a ntdll!KiUserCallbackDispatcher+0x1b
> >01 00000000`0022e338 00000000`7755f3af USER32!NtUserRegisterWindowMessage+0xa
> >02 00000000`0022e340 000007fe`fe2f80f2 USER32!RegisterWindowMessageW+0x2b
> >03 00000000`0022e390 000007fe`fe2f8014 OLEAUT32!_RegisterClipFormat+0xc2
> >04 00000000`0022e470 000007fe`fe2f33c1 OLEAUT32!_typesDllMain+0x4c
> >05 00000000`0022e4a0 000007fe`fe2f3356 OLEAUT32!DllMain+0x21
> >06 00000000`0022e4d0 00000000`7768b108 OLEAUT32!CRT_INIT+0x2af
> >07 00000000`0022e630 00000000`7767787a ntdll!LdrpRunInitializeRoutines+0x1fe
> >08 00000000`0022e800 00000000`77677b5e ntdll!LdrpLoadDll+0x231
> >09 00000000`0022ea10 000007fe`fd439059 ntdll!LdrLoadDll+0x9a
> >0a 00000000`0022ea80 000007fe`ff917d66 KERNELBASE!LoadLibraryExW+0x22e
> >0b 00000000`0022eaf0 000007fe`ff915d22 ws2_32!DPROVIDER::Initialize+0x156
> >0c 00000000`0022f090 000007fe`ff933a90 ws2_32!DCATALOG::LoadProvider+0x7e
> >0d 00000000`0022f0c0 000007fe`ff920b9b ws2_32!DCATALOG::GetCountedCatalogItemFromCatalogEntryId+0x70
> >0e 00000000`0022f100 00000001`800ab085 ws2_32!_chkstk+0x362a
> >0f 00000000`0022f1a0 00000001`8006d8b7 cygwin1!feinitialise+0x33f95
> >10 00000000`0022f1f0 00000001`800469d0 cygwin1!dlfork+0x3ac7
> >11 00000000`0022f250 00000001`8004897c cygwin1!setprogname+0x3ed0
> >12 00000000`0022f2c0 00000001`800c62e9 cygwin1!cygwin_dll_init+0x16ac
> >13 00000000`0022f320 00000000`7768b108 cygwin1!dll_entry+0x149
> 
> I interpret this to mean the situation is something like the following:
> 
> LavasoftTcpService64.dll is being loaded as a LSP
> LavasoftTcpService64.dll depends on OLEAUT32.dll
> OLEAUT32's DllMain calls RegisterWindowMessage
> This ends up calling KiUserCallbackDispatcher for a kernel to user-mode
> callback.
> This accesses a pointer to a callback table at PEB:0x58, which is
> unfortunately null.
> Sadness follows.
> 
> I wonder if anyone has any insight into this or suggestions for further
> investigation?

The backtrace looks weird.  Did you run this with a Cygwin DLL built
without optimization?  That might be helpful.


Corinna

-- 
Corinna Vinschen                  Please, send mails regarding Cygwin to
Cygwin Maintainer                 cygwin AT cygwin DOT com
Red Hat

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