From 805414c81f2c35f5d2410f8adb39c726d10ced49 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?K=C3=A9vin=20Dunglas?= <kevin@dunglas.fr>
Date: Sat, 10 Oct 2026 07:51:31 +0200
Subject: [PATCH] fix: don't kill grandchildren of forked processes

The atfork child handler ties each forked child to its parent's lifetime.
atfork handlers survive fork, so a child that forks again without exec'ing
tied the grandchild to the short-lived intermediate process. Double-forking
code such as gpgme (used by the gnupg extension to run gpgconf) had its
grandchild killed as soon as the intermediate exited. Only protect direct
children of the FrankenPHP process.

Fixes https://github.com/php/frankenphp/issues/2689
---
 frankenphp.c             |  4 ++++
 frankenphp_test.go       | 18 +++++++++++++++++
 testdata/double-fork.php | 43 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 65 insertions(+)
 create mode 100644 testdata/double-fork.php

diff --git a/frankenphp.c b/frankenphp.c
index cebdcd2952..d57e4de162 100644
--- a/frankenphp.c
+++ b/frankenphp.c
@@ -178,6 +178,10 @@ static void *frankenphp_parent_death_watcher(void *arg) {
 #endif
 
 static void frankenphp_fork_child(void) {
+  // a fork of a fork (e.g. a daemonizer) must outlive its short-lived parent
+  if (is_forked_child) {
+    return;
+  }
   frankenphp_mark_fork_child();
 #if defined(__linux__)
   // if the parent process dies between fork() and this prctl()
diff --git a/frankenphp_test.go b/frankenphp_test.go
index ef47fff4c9..b8988cbf0f 100644
--- a/frankenphp_test.go
+++ b/frankenphp_test.go
@@ -508,6 +508,24 @@ func testPhpInfoForkChild(t *testing.T, opts *testOptions) {
 	}, opts)
 }
 
+func TestDoubleForkGrandchild_module(t *testing.T) { testDoubleForkGrandchild(t, nil) }
+func TestDoubleForkGrandchild_worker(t *testing.T) {
+	testDoubleForkGrandchild(t, &testOptions{workerScript: "double-fork.php"})
+}
+func testDoubleForkGrandchild(t *testing.T, opts *testOptions) {
+	if opts == nil {
+		opts = &testOptions{}
+	}
+	opts.nbParallelRequests = 1
+	runTest(t, func(handler func(http.ResponseWriter, *http.Request), _ *httptest.Server, _ int) {
+		body, _ := testGet("http://example.com/double-fork.php", handler, t)
+		if body == "pcntl-unavailable" {
+			t.Skip("pcntl/posix not fully loaded")
+		}
+		require.Equal(t, "grandchild-alive", body)
+	}, opts)
+}
+
 func TestPersistentObject_module(t *testing.T) { testPersistentObject(t, nil) }
 func TestPersistentObject_worker(t *testing.T) {
 	testPersistentObject(t, &testOptions{workerScript: "persistent-object.php"})
diff --git a/testdata/double-fork.php b/testdata/double-fork.php
new file mode 100644
index 0000000000..1c4a4fd1b3
--- /dev/null
+++ b/testdata/double-fork.php
@@ -0,0 +1,43 @@
+<?php
+
+require_once __DIR__.'/_executor.php';
+
+return function () {
+    foreach (['pcntl_fork', 'pcntl_exec', 'pcntl_waitpid', 'posix_kill', 'posix_getpid'] as $function) {
+        if (!function_exists($function)) {
+            echo "pcntl-unavailable";
+            return;
+        }
+    }
+
+    $marker = tempnam(sys_get_temp_dir(), 'frankenphp-double-fork-');
+    unlink($marker);
+
+    $pid = pcntl_fork();
+    if ($pid === -1) {
+        echo "fork-failed";
+        return;
+    }
+    if ($pid === 0) {
+        if (pcntl_fork() === 0) {
+            pcntl_exec('/bin/sh', ['-c', 'sleep 0.2; touch "$1"', 'sh', $marker]);
+        }
+        // exit without PHP or Go teardown, like a daemonizer's intermediate process
+        posix_kill(posix_getpid(), SIGKILL);
+    }
+
+    pcntl_waitpid($pid, $status);
+
+    $deadline = microtime(true) + 3;
+    do {
+        clearstatcache();
+        if (file_exists($marker)) {
+            unlink($marker);
+            echo "grandchild-alive";
+            return;
+        }
+        usleep(10000);
+    } while (microtime(true) < $deadline);
+
+    echo "grandchild-killed";
+};