[PATCH] fhandler_pipe: add sanity limit to handle loops

Ken Brown kbrown@cornell.edu
Sun Dec 26 15:09:57 GMT 2021

On 12/25/2021 11:56 PM, Jeremy Drake wrote:
> I set up a windows server 2022 VM last night and went nuts stressing
> pacman/GPGME.  I was able to reproduce the issue there:
> status = 0x00000000, phi->NumberOfHandles = 8261392, n_handle = 256
> [#####----------------------------------]  14%
> assertion "phi->NumberOfHandles <= n_handle" failed: file
> "../../.././winsup/cygwin/fhandler_pipe.cc", line 1281, function: void*
> fhandler_pipe::get_query_hdl_per_process(WCHAR*, OBJECT_NAME_INFORMATION*)
> So it is not something inherent in the x86_64-on-ARM64 emulation but can
> happen on native x86_64 also.

A Google search led me to something that might explain what's going on.  Look at 
the function PhEnumHandlesEx2 starting at line 5713 in


Two interesting things:

1. For some processes, NtQueryInformationProcess(ProcessHandleInformation) can 
return STATUS_SUCCESS with invalid handle information.  See the comment starting 
at line 5754, where it is shown how to detect this.

2. You can use the ReturnLength parameter of NtQueryInformationProcess to see 
how big a buffer is needed.  This might be more efficient than repeatedly 
doubling the buffer size.


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