linux-container: 'container-excursion*' marks its FDs as FD_CLOEXEC.

Fixes <https://issues.guix.gnu.org/57827>.
Reported by Mathieu Othacehe <othacehe@gnu.org>.

Fixes a regression introduced with the Shepherd 0.9.2 upgrade in
1ba0e38267c9ff8bb476285091be6e297bbf136e, whereby IN and OUT would no
longer be closed when 'fork+exec-command/container' would call
'exec-command*' as part of the THUNK passed to 'container-excursion*'.

This is because the Shepherd 0.9.2 assumes file descriptors are properly
marked as O_CLOEXEC and, consequently, 'exec-command' no longer run the
close(2) loop prior to 'exec'.

* gnu/build/linux-container.scm (container-excursion*): Add calls to
'fcntl'.

1 files changed, 5 insertions, 1 deletions

diff --git a/gnu/build/linux-container.scm b/gnu/build/linux-container.scm
index a0c81747218..73db1279747 100644
--- a/gnu/build/linux-container.scm
+++ b/gnu/build/linux-container.scm
@@ -1,6 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2015 David Thompson <davet@gnu.org>
-;;; Copyright © 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2017-2019, 2022 Ludovic Courtès <ludo@gnu.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -442,6 +442,10 @@ return the exit status."
   "Like 'container-excursion', but return the return value of THUNK."
   (match (pipe)
     ((in . out)
+     ;; Make sure IN and OUT are not inherited if THUNK forks + execs.
+     (fcntl in F_SETFD FD_CLOEXEC)
+     (fcntl out F_SETFD FD_CLOEXEC)
+
      (match (container-excursion pid
               (lambda ()
                 (close-port in)