From 4f9c5bdc1d5c35d9243919fa0fa8878512cc6f67 Mon Sep 17 00:00:00 2001
From: Florian Wilde <fw@wildeflorian.de>
Date: Sat, 10 Oct 2026 21:56:18 +0200
Subject: [PATCH] =?UTF-8?q?fix(mounts):=20bei=20Zeit=C3=BCberschreitung=20?=
 =?UTF-8?q?ganze=20Prozessgruppe=20von=20mount=20beenden?=
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Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 src/netmover/mounting/linux.py | 26 ++++++++++++++++++++++++-
 tests/test_linux_backend.py    | 35 ++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/src/netmover/mounting/linux.py b/src/netmover/mounting/linux.py
index 8f0c546..832ce6b 100644
--- a/src/netmover/mounting/linux.py
+++ b/src/netmover/mounting/linux.py
@@ -8,7 +8,9 @@ Optionszeile – die stünde sonst in der Prozessliste.
 
 from __future__ import annotations
 
+import contextlib
 import os
+import signal
 import subprocess
 import uuid
 from collections.abc import Callable, Sequence
@@ -24,6 +26,28 @@ log = get_logger(__name__)
 
 Runner = Callable[..., "subprocess.CompletedProcess[str]"]
 
+
+def run_process_group(argv: list[str], **kwargs: Any) -> subprocess.CompletedProcess[str]:
+    """Wie ``subprocess.run``, aber in eigener Prozessgruppe: Bei Zeitüberschreitung
+    wird die ganze Gruppe beendet. ``mount`` startet Hilfsprogramme wie
+    ``mount.nfs``; würde nur ``mount`` beendet, liefe ``mount.nfs`` weiter und
+    hängte womöglich Minuten später doch noch ein (auf der Test-VM beobachtet)."""
+    timeout = kwargs.pop("timeout", None)
+    kwargs.pop("check", None)
+    capture = kwargs.pop("capture_output", False)
+    if capture:
+        kwargs["stdout"] = kwargs["stderr"] = subprocess.PIPE
+    with subprocess.Popen(argv, start_new_session=True, **kwargs) as proc:
+        try:
+            out, err = proc.communicate(timeout=timeout)
+        except subprocess.TimeoutExpired:
+            with contextlib.suppress(ProcessLookupError):
+                os.killpg(proc.pid, signal.SIGKILL)
+            proc.communicate()
+            raise
+    return subprocess.CompletedProcess(argv, proc.returncode, out, err)
+
+
 _ENV = {"LC_ALL": "C", "PATH": "/usr/sbin:/usr/bin:/sbin:/bin"}
 
 
@@ -60,7 +84,7 @@ class LinuxMountBackend(MountBackend):
         self,
         run_dir: Path,
         mountinfo_path: Path = MOUNTINFO,
-        runner: Runner = subprocess.run,
+        runner: Runner = run_process_group,
     ) -> None:
         self.run_dir = run_dir
         self.mountinfo_path = mountinfo_path
diff --git a/tests/test_linux_backend.py b/tests/test_linux_backend.py
index a31e2b9..ffb6821 100644
--- a/tests/test_linux_backend.py
+++ b/tests/test_linux_backend.py
@@ -115,3 +115,38 @@ def test_is_mounted_reads_mountinfo(tmp_path: Path) -> None:
 )
 def test_explain(fstype: str, msg: str, expect: str) -> None:
     assert expect in explain_mount_error(fstype, msg)
+
+
+def _alive(pid: int) -> bool:
+    try:
+        with open(f"/proc/{pid}/stat") as fh:
+            return fh.read().split(")")[-1].split()[0] != "Z"
+    except FileNotFoundError:
+        return False
+
+
+def test_timeout_kills_whole_process_group(tmp_path: Path) -> None:
+    """mount startet Helfer (mount.nfs) – die dürfen nach dem Zeitlimit nicht weiterlaufen."""
+    from netmover.mounting.linux import run_process_group
+
+    pidfile = tmp_path / "helper.pid"
+    script = f"sleep 30 & echo $! > {pidfile}; wait"
+    with pytest.raises(subprocess.TimeoutExpired):
+        run_process_group(["sh", "-c", script], capture_output=True, text=True, timeout=0.5)
+    helper = int(pidfile.read_text())
+    for _ in range(20):
+        if not _alive(helper):
+            break
+        import time
+
+        time.sleep(0.05)
+    assert not _alive(helper)
+
+
+def test_process_group_runner_returns_output() -> None:
+    from netmover.mounting.linux import run_process_group
+
+    r = run_process_group(
+        ["sh", "-c", "echo out; echo err >&2; exit 3"], capture_output=True, text=True, timeout=5
+    )
+    assert (r.returncode, r.stdout, r.stderr) == (3, "out\n", "err\n")