Process handles leaked by pty host on windows

[deepak1556]

Does this issue occur when all extensions are disabled?: Yes/No

• VS Code Version: 1.62.0-insider (system setup)
• OS Version: Windows_NT arm64 10.0.22000

Steps to Reproduce:

1. Open terminal, run handle tool on pty host to get base output

Handle type summary:
  <Unknown type>  : 66
  ALPC Port       : 3
  Desktop         : 1
  Directory       : 2
  Event           : 33
  File            : 23
  IoCompletion    : 8
  IRTimer         : 6
  Key             : 12
  Process         : 65
  Section         : 3
  Semaphore       : 13
  Thread          : 19
  TpWorkerFactory : 3
  WaitCompletionPacket: 9
  WindowStation   : 2
Total handles: 268

2. Run some sequence of commands (for ex: yarn in vscode repo) and close the terminal
3. Check handle output

Handle type summary:
  <Unknown type>  : 66
  ALPC Port       : 3
  Desktop         : 1
  Directory       : 2
  Event           : 34
  File            : 17
  IoCompletion    : 8
  IRTimer         : 8
  Job             : 1
  Key             : 12
  Process         : 5418
  Section         : 3
  Semaphore       : 9
  Thread          : 18
  TpWorkerFactory : 4
  WaitCompletionPacket: 10
  WindowStation   : 2
Total handles: 5616

Originally reported in https://twitter.com/BruceDawson0xB/status/1447668569626476548

[deepak1556]

Update:

Started with an event trace based on the nice guide at https://randomascii.wordpress.com/2021/07/25/finding-windows-handle-leaks-in-chromium-and-others/

Narrowing on the pty host process, the leaked handles are coming from vscode-windows-process-tree module. Specifically some call to openProcess does not close the related handle. After this it was just a matter of hunting the problematic code and a quick scan pointed to https://github.com/microsoft/vscode-windows-process-tree/blob/bc0ee891ca3df19dad46b023e3bb1266dfd1a205/src/process.cc#L44-L58, voila! Since this code path gets executed pretty much after every command execution in the terminal, it matches the observed leak.

With the following patch applied the handles from the pty host are not leaked anymore,

diff --git a/src/process.cc b/src/process.cc
index 1563537..239e266 100644
--- a/src/process.cc
+++ b/src/process.cc
@@ -55,6 +55,8 @@ void GetProcessMemoryUsage(ProcessInfo process_info[1024], uint32_t* process_cou
   if (GetProcessMemoryInfo(hProcess, &pmc, sizeof(pmc))) {
     process_info[*process_count].memory = (DWORD)pmc.WorkingSetSize;
   }
+
+  CloseHandle(hProcess);
 }

@Tyriar I think this worth a candidate fix.

[deepak1556]

\closedWith 728f813