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src/node_errors: add re-entrancy guard to TriggerUncaughtException - #64327

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src/node_errors: add re-entrancy guard to TriggerUncaughtException#64327
themuuln wants to merge 2 commits into
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themuuln:fix/reentrant-uncaught-exception-guard

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@themuuln

@themuuln themuuln commented Jul 6, 2026 •
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Problem

When an uncaught exception triggers TriggerUncaughtException → the JS handler (process._fatalException) → console.error → the inspector protocol (InspectorConsoleCall) throws again, V8 re-enters TriggerUncaughtException. This creates a tight infinite loop:

uv_run → uv__async_io → ThreadSafeFunction::AsyncCb →
CallbackScope::~CallbackScope → Function::Call →
TriggerUncaughtException → Function::Call →
InspectorConsoleCall → [back to TriggerUncaughtException]

Each iteration:

  1. Widens the error (exception wrapped in a new exception string)
  2. Saturates a CPU core
  3. Compounds memory pressure (each error frame allocates)

This was observed in production with napi-rs plugins calling console.error during uncaught exception handling, but any JS handler that triggers inspector protocol activity during process._fatalException can hit it.

Fix

Add a thread_local re-entrancy guard to TriggerUncaughtException(). If the function is re-entered while already processing an uncaught exception, it:

  1. Formats the exception directly via FormatCaughtException (pure V8 string ops — no JS, no inspector)
  2. Prints the diagnostic to stderr with PrintToStderrAndFlush
  3. Calls ABORT() to terminate the process

An RAII scope guard resets the flag when TriggerUncaughtException returns normally (e.g., env->Exit() path).

The guard lives entirely in node_errors.cc — no header changes, no Environment fields.

Fixes: #64326

@nodejs-github-bot nodejs-github-bot added c++ Issues and PRs that require attention from people who are familiar with C++. needs-ci PRs that need a full CI run. labels Jul 6, 2026
@themuuln
themuuln force-pushed the fix/reentrant-uncaught-exception-guard branch from d6df9be to 955d7e4 Compare July 6, 2026 16:11
jasnell
jasnell reviewed Jul 7, 2026
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Comment thread src/node_errors.cc
@@ -191,6 +191,7 @@ static std::string GetErrorSource(Isolate* isolate,

static std::atomic<bool> is_in_oom{false};
static thread_local std::atomic<bool> is_retrieving_js_stacktrace{false};
static thread_local bool is_in_uncaught_exception = false;

@jasnell jasnell Jul 7, 2026

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Does this need to be std::atomic<bool> like is_retrieving_js_stacktrace? If not, a short comment explaining why would be good.

@themuuln themuuln Jul 7, 2026

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Fair enough — added a comment explaining why. Since this flag only guards re-entrancy on the current thread, thread_local handles the isolation and no atomic is needed.

@themuuln themuuln mentioned this pull request Jul 7, 2026
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themuuln commented Jul 9, 2026

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@jasnell PTAL! Could you please re-review and re-approve?

themuuln added 2 commits July 16, 2026 00:06
@themuuln
src/node_errors: add re-entrancy guard to prevent infinite recursion …
f2c1ab5 
…in TriggerUncaughtException

Add a thread_local re-entrancy guard to TriggerUncaughtException()
that detects when the JS-level exception handler (process._fatalException)
itself triggers another exception through the inspector protocol.

This prevents the infinite loop:
  TriggerUncaughtException -> InspectorConsoleCall ->
  TriggerUncaughtException -> InspectorConsoleCall -> ...

When re-entrancy is detected, the function prints a diagnostic with the
formatted exception to stderr using FormatCaughtException (which avoids
the inspector path entirely), then aborts the process.

Fixes: nodejs#64326
Signed-off-by: Temuulen Undrakhbayar <[email protected]>
@themuuln
src/node_errors: document re-entrancy guard
7cd61df 
Signed-off-by: Temuulen Undrakhbayar <[email protected]>
@themuuln
themuuln force-pushed the fix/reentrant-uncaught-exception-guard branch from b9c03ae to 7cd61df Compare July 15, 2026 16:07
@themuuln

themuuln commented Jul 15, 2026

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@jasnell Thanks again for the review! I’ve added the missing DCO sign-offs. It looks like the GitHub Actions runs are waiting for maintainer approval—when you have a chance, could you approve those and start Jenkins with the request-ci label?

@addaleax addaleax added author ready PRs with CI started, the required approvals, and no outstanding review comments. request-ci Add this label to start a Jenkins CI on a PR. Only starts once the PR has an approving review. labels Aug 27, 2026
@github-actions github-actions Bot removed the request-ci Add this label to start a Jenkins CI on a PR. Only starts once the PR has an approving review. label Aug 27, 2026
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nodejs-github-bot commented Aug 29, 2026

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CI: https://ci.nodejs.org/job/node-test-pull-request/76710/

trivikr pushed a commit that referenced this pull request Aug 31, 2026
@themuuln @trivikr
src: add re-entrancy guard to TriggerUncaughtException
460b202 
Add a thread_local re-entrancy guard to TriggerUncaughtException()
that detects when the JS-level exception handler
(process._fatalException) triggers another exception through the
inspector protocol.

This prevents the infinite loop:
  TriggerUncaughtException -> InspectorConsoleCall ->
  TriggerUncaughtException -> InspectorConsoleCall -> ...

When re-entrancy is detected, the function prints a diagnostic with the
formatted exception to stderr using FormatCaughtException (which avoids
the inspector path entirely), then aborts the process.

Fixes: #64326
Signed-off-by: Temuulen Undrakhbayar <[email protected]>
PR-URL: #64327
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
@trivikr

trivikr commented Aug 31, 2026

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Landed in 460b202

@trivikr trivikr closed this Aug 31, 2026
aduh95 pushed a commit that referenced this pull request Sep 3, 2026
@themuuln @aduh95
src: add re-entrancy guard to TriggerUncaughtException
75e93e9 
Add a thread_local re-entrancy guard to TriggerUncaughtException()
that detects when the JS-level exception handler
(process._fatalException) triggers another exception through the
inspector protocol.

This prevents the infinite loop:
  TriggerUncaughtException -> InspectorConsoleCall ->
  TriggerUncaughtException -> InspectorConsoleCall -> ...

When re-entrancy is detected, the function prints a diagnostic with the
formatted exception to stderr using FormatCaughtException (which avoids
the inspector path entirely), then aborts the process.

Fixes: #64326
Signed-off-by: Temuulen Undrakhbayar <[email protected]>
PR-URL: #64327
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Anna Henningsen <[email protected]>
@github-actions github-actions Bot mentioned this pull request Sep 7, 2026
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@jasnell jasnell jasnell approved these changes
@addaleax addaleax addaleax approved these changes

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Infinite recursion between TriggerUncaughtException and InspectorConsoleCall when console.error throws

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