bug#44261: running a daemon with userns in relocateble pack breaks

[Jan Nieuwenhuizen]

Jan Nieuwenhuizen writes:

Hi!

I tried the hint from Ludovic to use MS_PRIVATE in the attached patch
and that works for me; not sure if we want a test and even less sure how
to write that...

Janneke

>From fd3104608c3fa6a2375b6c7df0862e5479976b39 Mon Sep 17 00:00:00 2001
From: "Jan (janneke) Nieuwenhuizen" <janneke@gnu.org>
Date: Tue, 27 Oct 2020 20:55:11 +0100
Subject: [PATCH] pack: Support running of daemons in user namespace-based
 relocation.
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Add relocation via ld.so and fakechroot.
Fixes <https://bugs.gnu.org/44261>.

* gnu/packages/aux-files/run-in-namespace.c (bind_mount): Add 'MS_PRIVATE' to
avoid unmounting the bind mount when parent process exits.

Co-authored-by: Ludovic Courtès <ludo@gnu.org>
---
 gnu/packages/aux-files/run-in-namespace.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/aux-files/run-in-namespace.c 
b/gnu/packages/aux-files/run-in-namespace.c
index 52a16a5362..67cea4fcd5 100644
--- a/gnu/packages/aux-files/run-in-namespace.c
+++ b/gnu/packages/aux-files/run-in-namespace.c
@@ -1,5 +1,6 @@
 /* GNU Guix --- Functional package management for GNU
    Copyright (C) 2018, 2019, 2020 Ludovic Courtès <ludo@gnu.org>
+   Copyright (C) 2020 Jan (janneke) Nieuwenhuizen <janneke@gnu.org>
 
    This file is part of GNU Guix.
 
@@ -138,7 +139,7 @@ bind_mount (const char *source, const struct dirent *entry,
     close (open (target, O_WRONLY | O_CREAT));
 
   return mount (source, target, "none",
-               MS_BIND | MS_REC | MS_RDONLY, NULL);
+               MS_BIND | MS_PRIVATE | MS_REC | MS_RDONLY, NULL);
 }
 
 #if HAVE_EXEC_WITH_LOADER
-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.com

-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.com