[ci-scan] Test failure: stackoverflowtester — Exit code: 0x0000008B, expected 0x00000086

## Build Information
Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1484415
Build error leg or test failing: coreclr linux arm64 checked (jitstress2-jitstressregs) — baseservices/exceptions/stackoverflow/stackoverflowtester/stackoverflowtester.cmd

## Error Details

Under the `runtime-coreclr jitstress2-jitstressregs` configuration (AzDO definition 111) on `main`, the `stackoverflowtester` test fails on `linux arm64`. In `TestStackOverflowSmallFrameMainThread`, the child process that intentionally overflows its stack terminates with exit code `0x0000008B` (139, SIGSEGV) instead of the expected `0x00000086` (134, SIGABRT fail-fast):

```
BEGIN EXECUTION
corerun ... stackoverflowtester.dll ''
Running stackoverflow test(smallframe main)
"Stack overflow."
System.Exception: Exit code: 0x0000008B, expected 0x00000086
at TestStackOverflow.Program.TestStackOverflow(String testName, String testArgs, List`1& stderrLines)
at TestStackOverflow.Program.TestStackOverflowSmallFrameMainThread()
at __GeneratedMainWrapper.Main()
Expected: 100
Actual: 101
END EXECUTION - FAILED
```

First observed in build [1474511](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1474511) (20260621.1, 2026-06-21); the immediately preceding build [1473990](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1473990) (2026-06-20) passed. Still failing in source build [1484415](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1484415) (2026-06-27) and its follow-up build [1484851](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1484851) (2026-06-28), so this is a stable failure rather than a one-off stress flake.

Previously tracked as dotnet/runtime#126502 (`arch-arm32`, closed 2026-04-14 as completed); this is a post-close recurrence of the same signature on `linux arm64` under JIT stress. Related: dotnet/runtime#126502.

## Error Message

```json
{
"ErrorMessage": [
"Running stackoverflow test(smallframe main)",
"Exit code: 0x0000008B, expected 0x00000086"
],
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

> [!NOTE]
> Auto-filed by the `ci-failure-scan` outer-loop CI failure scanner (detection-only; AI/Copilot-generated). Occurrence counts are maintained by Build Analysis from the JSON signature above. Mitigation (fix or JIT-owner hand-off) is handled separately by the `ci-failure-fix` workflow.

> [!NOTE]
>
> 🔒 Integrity filter blocked 19 items
>
> The following items were blocked because they don't meet the GitHub integrity level.
>
> - [#72905](https://github.com/dotnet/runtime/issues/72905) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#33993](https://github.com/dotnet/runtime/issues/33993) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#129897](https://github.com/dotnet/runtime/pull/129897) `search_pull_requests`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#129876](https://github.com/dotnet/runtime/issues/129876) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#88361](https://github.com/dotnet/runtime/issues/88361) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#7096](https://github.com/dotnet/runtime/issues/7096) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#5984](https://github.com/dotnet/runtime/issues/5984) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#5101](https://github.com/dotnet/runtime/issues/5101) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#44158](https://github.com/dotnet/runtime/issues/44158) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#5318](https://github.com/dotnet/runtime/issues/5318) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#5158](https://github.com/dotnet/runtime/issues/5158) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#114222](https://github.com/dotnet/runtime/issues/114222) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#127541](https://github.com/dotnet/runtime/issues/127541) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#117370](https://github.com/dotnet/runtime/issues/117370) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#107239](https://github.com/dotnet/runtime/issues/107239) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - [#110173](https://github.com/dotnet/runtime/issues/110173) `search_issues`: has lower integrity than agent requires. The agent cannot read data with integrity below "approved".
> - ... and 3 more items
>
> To allow these resources, lower `min-integrity` in your GitHub frontmatter:
>
> ```yaml
> tools:
> github:
> min-integrity: approved # merged | approved | unapproved | none
> ```
>
>

> Generated by [CI Outer-Loop Failure Scanner](https://github.com/dotnet/runtime/actions/runs/28662870110/agentic_workflow) · ● 12.6M · [◷](https://github.com/search?q=repo%3Adotnet%2Fruntime+is%3Aissue+%22gh-aw-workflow-call-id%3A+dotnet%2Fruntime%2Fci-failure-scan%22&type=issues)

### Report
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|0|0|