[buildd-tools-devel] Bug#817236: schroot: no access to pseudo-terminals in new chroots

[Ansgar Burchardt]

Package: schroot
Version: 1.6.10-2
Severity: important

debootstrap recently replaced the /dev/ptmx device node with a symlink
/dev/ptmx -> pts/ptmx[1]. This changed the default permissions from
world-writable (0666) for /dev/ptmx to no-access (0000) in chroots[2].

This causes build failures as, for example, openmpi's mpirun relies on
access to pseudo-terminals.

As chroots used by sbuild/buildd do not need access to the host's
pseudo-terminals, schroot could just mount a private devpts instance
with world-writable ptmx in the chroot: for this replace

  /dev/pts        /dev/pts        none    rw,bind         0       0

with

  /dev/pts /dev/pts devpts rw,newinstance,ptmxmode=0666 0 0

in the sbuild profile's fstab. To accommodate old chroots that still
have a /dev/ptmx device node, an additional bind mount

  ${chroot}/dev/pts/ptmx   /dev/ptmx   none   rw,bind 0 0

is needed to make sure only the devpts' ptmx device is used. I don't
think this can be done via the profile's fstab, but only via a setup
script?

See also [3].

Ansgar

  [1] https://packages.qa.debian.org/d/debootstrap/news/20160124T094920Z.html
  [2] The host still has a world-writable /dev/ptmx via devtmpfs.
  [3] https://www.kernel.org/doc/Documentation/filesystems/devpts.txt

-- System Information:
Debian Release: stretch/sid
  APT prefers testing
  APT policy: (500, 'testing'), (500, 'stable'), (100, 'buildd-unstable'), (100, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 4.3.0-1-amd64 (SMP w/8 CPU cores)
Locale: LANG=C, LC_CTYPE=de_DE.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages schroot depends on:
ii  libboost-filesystem1.58.0       1.58.0+dfsg-5+b1
ii  libboost-iostreams1.58.0        1.58.0+dfsg-5+b1
ii  libboost-program-options1.58.0  1.58.0+dfsg-5+b1
ii  libboost-system1.58.0           1.58.0+dfsg-5+b1
ii  libc6                           2.21-9
ii  libgcc1                         1:5.3.1-10
ii  libpam0g                        1.1.8-3.2
ii  libstdc++6                      5.3.1-10
ii  libuuid1                        2.27.1-3
ii  schroot-common                  1.6.10-2

schroot recommends no packages.

Versions of packages schroot suggests:
ii  btrfs-tools       4.4-1
ii  debootstrap       1.0.79
ii  lvm2              2.02.142-1+b1
pn  qemu-user-static  <none>
ii  unionfs-fuse      1.0-1

-- Configuration Files:
/etc/schroot/sbuild/fstab changed [not included]

-- no debconf information