From a90eba0c17004f87f25d049f9d52d63279592d50 Mon Sep 17 00:00:00 2001
From: Tanmoy Sarkar <ts741127@gmail.com>
Date: Tue, 9 Jun 2026 23:18:54 +0530
Subject: [PATCH] fix(companion): Correct manager pid and reset companion
 signals

---
 gunicorn/companion/manager.py   | 27 +++++++++++++++++++++++++++
 tests/test_companion_manager.py | 16 +++++++++++++++-
 2 files changed, 42 insertions(+), 1 deletion(-)

diff --git a/gunicorn/companion/manager.py b/gunicorn/companion/manager.py
index 98c436ee..2a032758 100644
--- a/gunicorn/companion/manager.py
+++ b/gunicorn/companion/manager.py
@@ -25,6 +25,28 @@ if TYPE_CHECKING:
 PR_SET_PDEATHSIG = 1
 
 
+# Signals the arbiter and manager install handlers for; a forked companion
+# resets them to the default so its stop signal works and the target starts
+# from a clean slate, the same way a gunicorn worker does.
+INHERITED_SIGNALS = [
+    "SIGCHLD", "SIGTERM", "SIGINT", "SIGHUP", "SIGQUIT",
+    "SIGUSR1", "SIGUSR2", "SIGWINCH", "SIGTTIN", "SIGTTOU",
+]
+
+
+def reset_child_signals() -> None:
+    """Restore default signal handling in a freshly forked companion.
+
+    The companion inherits the manager's (and arbiter's) handlers across the
+    fork. Without this, a stop signal like SIGTERM would hit the manager's
+    handler -- which just flips a flag -- instead of terminating the companion.
+    """
+    for name in INHERITED_SIGNALS:
+        number = getattr(signal, name, None)
+        if number is not None:
+            signal.signal(number, signal.SIG_DFL)
+
+
 def set_parent_death_signal(stop_signal) -> bool:
     """Ask the kernel to send ``stop_signal`` when this process's parent dies.
 
@@ -79,6 +101,10 @@ class CompanionManager:
         signal on Linux and, as a portable fallback, watches ``getppid`` each
         tick so it never keeps companions running under a dead arbiter.
         """
+        # __init__ ran in the arbiter, so refresh pid/parent now that this is
+        # the manager process: the companion parent-death guard compares its
+        # getppid() against self.pid.
+        self.pid = os.getpid()
         self.parent_pid = os.getppid()
         self._install_signals()
         set_parent_death_signal(signal.SIGTERM)
@@ -325,6 +351,7 @@ class CompanionManager:
 
         try:
             self._close_manager_fds()
+            reset_child_signals()
             set_parent_death_signal(signal.SIGTERM)
             if os.getppid() != self.pid:
                 # Manager already died between fork and arming: do not run.
diff --git a/tests/test_companion_manager.py b/tests/test_companion_manager.py
index 3fe6e48b..356882da 100644
--- a/tests/test_companion_manager.py
+++ b/tests/test_companion_manager.py
@@ -9,7 +9,11 @@ from unittest import mock
 import pytest
 
 from gunicorn.companion.control import CommandError
-from gunicorn.companion.manager import CompanionManager, set_parent_death_signal
+from gunicorn.companion.manager import (
+    CompanionManager,
+    reset_child_signals,
+    set_parent_death_signal,
+)
 from gunicorn.companion.config import CompanionConfig
 from gunicorn.companion.process import State
 
@@ -52,6 +56,16 @@ def test_log_exit_reports_signal_or_status():
     assert any("status" in message for message in messages)
 
 
+def test_reset_child_signals_restores_defaults():
+    with mock.patch("signal.signal") as signal_signal:
+        reset_child_signals()
+    restored = {call.args[0]: call.args[1] for call in signal_signal.call_args_list}
+    # The stop signal must reach the default disposition, not the manager's
+    # inherited handler, so a forked companion actually terminates on SIGTERM.
+    assert restored[signal.SIGTERM] is signal.SIG_DFL
+    assert restored[signal.SIGINT] is signal.SIG_DFL
+
+
 def test_set_parent_death_signal_noop_off_linux():
     with mock.patch("sys.platform", "darwin"):
         assert set_parent_death_signal(signal.SIGTERM) is False