From e2562047763a666599b64d016cdbf399dab855d8 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Mon, 20 May 2019 01:57:17 +0200
Subject: [PATCH] src: reset SIGSEGV handler before crashing

Without this, we would re-enter the signal handler immediately
after re-raising the signal, leading to an infinite loop.

PR-URL: https://github.com/nodejs/node/pull/27775
Refs: https://github.com/nodejs/node/pull/27246
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
---
 src/node.cc                       |  6 ++++++
 src/node_process_methods.cc       |  7 +++++++
 test/abort/test-signal-handler.js | 23 +++++++++++++++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 test/abort/test-signal-handler.js

diff --git a/src/node.cc b/src/node.cc
index 388a9ea4486a88..f4a953a7c38abf 100644
--- a/src/node.cc
+++ b/src/node.cc
@@ -487,6 +487,12 @@ void TrapWebAssemblyOrContinue(int signo, siginfo_t* info, void* ucontext) {
     if (prev != nullptr) {
       prev(signo, info, ucontext);
     } else {
+      // Reset to the default signal handler, i.e. cause a hard crash.
+      struct sigaction sa;
+      memset(&sa, 0, sizeof(sa));
+      sa.sa_handler = SIG_DFL;
+      CHECK_EQ(sigaction(signo, &sa, nullptr), 0);
+
       ResetStdio();
       raise(signo);
     }
diff --git a/src/node_process_methods.cc b/src/node_process_methods.cc
index a9ddd70bcbe2d6..912ac9bec23960 100644
--- a/src/node_process_methods.cc
+++ b/src/node_process_methods.cc
@@ -63,6 +63,12 @@ static void Abort(const FunctionCallbackInfo<Value>& args) {
   Abort();
 }
 
+// For internal testing only, not exposed to userland.
+static void CauseSegfault(const FunctionCallbackInfo<Value>& args) {
+  // This should crash hard all platforms.
+  *static_cast<void**>(nullptr) = nullptr;
+}
+
 static void Chdir(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
   CHECK(env->owns_process_state());
@@ -405,6 +411,7 @@ static void InitializeProcessMethods(Local<Object> target,
     env->SetMethod(target, "_debugProcess", DebugProcess);
     env->SetMethod(target, "_debugEnd", DebugEnd);
     env->SetMethod(target, "abort", Abort);
+    env->SetMethod(target, "causeSegfault", CauseSegfault);
     env->SetMethod(target, "chdir", Chdir);
   }
 
diff --git a/test/abort/test-signal-handler.js b/test/abort/test-signal-handler.js
new file mode 100644
index 00000000000000..f68e6881f6e5b6
--- /dev/null
+++ b/test/abort/test-signal-handler.js
@@ -0,0 +1,23 @@
+'use strict';
+const common = require('../common');
+if (common.isWindows)
+  common.skip('No signals on Window');
+
+const assert = require('assert');
+const { spawnSync } = require('child_process');
+
+// Test that a hard crash does not cause an endless loop.
+
+if (process.argv[2] === 'child') {
+  const { internalBinding } = require('internal/test/binding');
+  const { causeSegfault } = internalBinding('process_methods');
+
+  causeSegfault();
+} else {
+  const child = spawnSync(process.execPath,
+                          ['--expose-internals', __filename, 'child'],
+                          { stdio: 'inherit' });
+  // FreeBSD and macOS use SIGILL for the kind of crash we're causing here.
+  assert(child.signal === 'SIGSEGV' || child.signal === 'SIGILL',
+         `child.signal = ${child.signal}`);
+}