pid-sandbox: pid-ns-init TIOCSCTTY after setsid (bug 675868)

Set the controlling terminal to the stdout pty after calling setsid,
in order to avoid "No such device or address" ENXIO errors when
attempting to open /dev/tty.

Bug: https://bugs.gentoo.org/675868
Signed-off-by: Zac Medico <zmedico@gentoo.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/bin/pid-ns-init b/bin/pid-ns-init
index f01d69fc2..d8e67cf6d 100644
--- a/bin/pid-ns-init
+++ b/bin/pid-ns-init
@@ -3,12 +3,14 @@
 # Distributed under the terms of the GNU General Public License v2
 
 import errno
+import fcntl
 import functools
 import os
 import platform
 import signal
 import subprocess
 import sys
+import termios
 
 
 KILL_SIGNALS = (
@@ -75,6 +77,17 @@ def main(argv):
 		# Isolate parent process from process group SIGSTOP (bug 675870)
 		setsid = True
 		os.setsid()
+		if sys.stdout.isatty():
+			try:
+				fcntl.ioctl(sys.stdout, termios.TIOCSCTTY, 0)
+			except OSError as e:
+				if e.errno == errno.EPERM:
+					# This means that stdout refers to the controlling terminal
+					# of the parent process, and in this case we do not want to
+					# steel it.
+					pass
+				else:
+					raise
 		proc = subprocess.Popen(args, executable=binary, **popen_kwargs)
 		main_child_pid = proc.pid