[vbox-dev] Close out Shared Clipboard race

[Andreas Löffler]

Hi Andrew,

thanks for the pointer and the attached patch -- this code indeed was
ifdef'ed a long time ago and recently removed. I'll have a peek at the
issue and re-add it eventually.

Kind regards / Mit freundlichen Grüßen

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Andreas Löffler             | VirtualBox Engineering
Principal Software Engineer | Oracle Virtualization

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On 26.11.19 02:25, Andrew Caldwell wrote:
> Folks,
> 
>  
> 
> I noticed that copying from the omnibar in Google Chrome in a linux
> guest (Ubuntu or Centos) didn’t allow pasting into the host, despite (a)
> pasting in the guest working fine, and (b) copying from elsewhere in the
> guest (including from the body of Google Chrome pages)  works fine and
> allows pasting in the host.
> 
>  
> 
> To cut a long-ish story short, the problem boils down to “Google Chrome
> grabs the clipboard twice when you copy from the omnibar”, which is fine
> from their end (if a little weird) but VBoxClient doesn’t handle this
> correctly (see attached xtrace output with inline comments) since it
> calls into `XtGetSelectionValue` twice before handling the first answer,
> and `XtGetSelectionValue` doesn’t appear to be re-entrant so it ends up
> reporting that there are no allowed formats for the clipboard when the
> second callback fires.
> 
>  
> 
> Back in VBox < 5.2, there was some code to prevent this re-entrancy, but
> it was `ifndef`’d out in 5.2 and has been deleted completely in the
> recent changes to the Shared Clipboard, but it seems that this defensive
> code is still needed.  I’ve attached a patch to re-add the logic, which
> I hereby release under the MIT license.
> 
>  
> 
> Thanks,
> 
>  
> 
> A
> 
> 
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> 
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