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Date: Sun, 13 Feb 2011 12:20:29 -0500
From: Ken Brown <kbrown AT cornell DOT edu>
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To: cygwin AT cygwin DOT com
Subject: Re: Preremove/postinstall scripts fail with snapshot installed
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On 2/13/2011 11:24 AM, Corinna Vinschen wrote:
> On Feb 12 19:12, Corinna Vinschen wrote:
>> On Feb 12 17:44, Corinna Vinschen wrote:
>>> On Feb 12 10:31, Ken Brown wrote:
>>>> I just did a system restore to undo the last round of Windows
>>>> updates, and the problem went away.  I'm not sure where to go from
>>>> here.
>>>
>>> You're right, I can reproduce it on W7 32 and 64 bit.
>>> [...]
>>> By installing the security updates again, one by one, I figure out
>>> that it is the security update connected to KB 2393802 which triggers
>>> the problem.
>>> [...]
>>
>> Just FYI, I have a working workaround.  It's not exactly how I would
>> like to handle this stuff, but at least we know there *is* a solution
>> which still maintains the desired ability to delete an in-use directory.
>
> Ok, I think I have a solution now.
>
> A few hours of debugging turned up that the KB 2393802 patch introduces
> a change to the layout of the (undocumented) structure in which Windows
> stores the CWD starting with Vista.  That's the structure we called
> FAST_CWD in Cygwin.  The new layout is sufficiently different that
> Cygwin scrambled the contents of the structure from the Win32
> perspective.
>
> Above all, the new structure layout is 4 bytes bigger, because
> RtlSetCurrentDirectory_U now also stores some filesystem flags which
> RtlGetCurrentDirectory_U uses to find out if the CWD is on a removable
> device, and if that device is still available.
>
> If Cygwin scrambled the content effectivly enough, Win32 calls like
> CreateProcess could become so confused that they potentially crash with
> a SEGV.
>
> I just checked in a patch to Cygwin which uses the new structure layout
> on systems which already have the KB 2393802 patch installed and the old
> structure layout otherwise.
>
> I also uploaded a new Cygwin snapshot to http://cygwin.com/snapshots/
> Please give the today's snapsot a try.  I tested it on Windows 2008 32
> bit as well as on W7 32 and 64 bit, with and without KB 2393802
> installed.  "It works for me."(TM)

Works for me on W7 64 bit with KB 2393802 installed.  (I didn't test 
without it.  I had already reinstalled the updates.)

Thanks.

Ken

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