[buildd-tools-devel] Bug#821929: schroot: a probable race condition prevents instantiation of union chroots on linux 4.5

[Gian Piero Carrubba]

Package: schroot
Version: 1.6.10-2
Severity: important

Dear Maintainer,

thank you for your work on schroot.
After switching to linux 4.5, I cannot reliably use union chroots
anymore.

---
$ cat /etc/schroot/chroot.d/sid 
[sid]

type=directory
directory=/srv/chroot/cdeb/sid
union-type=overlay
users=gpiero
source-users=gpiero
setup.fstab=local/fstab
---

Please note that the custom fstab option does NOT affect the issue.
Also, the issue does NOT affect the source chroot:

---
$ schroot -c source:sid -- cat /etc/debian_chroot
sid
$ schroot -c source:sid -- cat /etc/debian_chroot
sid
$ schroot -c source:sid -- cat /etc/debian_chroot
sid
$ schroot -c source:sid -- cat /etc/debian_chroot
sid
$ schroot -c source:sid -- cat /etc/debian_chroot
sid
---

It DOES affect the 'chroot' chroots, at least most of the times:

---
$ schroot -c chroot:sid -- cat /etc/debian_chroot
E: 15binfmt: update-binfmts: unable to open /var/run/schroot/mount/sid-56594f7b-8089-4ea1-949e-c9fdd521b5a7/bin/sh: Operation not permitted
E: 20copyfiles: cp: cannot create regular file '/var/run/schroot/mount/sid-56594f7b-8089-4ea1-949e-c9fdd521b5a7/etc/resolv.conf': Operation not permitted
E: 15binfmt: update-binfmts: unable to open /var/run/schroot/mount/sid-56594f7b-8089-4ea1-949e-c9fdd521b5a7/bin/sh: Operation not permitted
E: sid-56594f7b-8089-4ea1-949e-c9fdd521b5a7: Chroot setup failed: stage=setup-start

$ schroot -c chroot:sid -- cat /etc/debian_chroot
E: Failed to execute “/bin/cat”: Operation not permitted

$ schroot -c chroot:sid -- cat /etc/debian_chroot
E: 20copyfiles: cp: cannot create regular file '/var/run/schroot/mount/sid-d29bf09f-51d4-4981-96db-4d3b8f423d85/etc/resolv.conf': Operation not permitted
E: sid-d29bf09f-51d4-4981-96db-4d3b8f423d85: Chroot setup failed: stage=setup-start

$ schroot -c chroot:sid -- cat /etc/debian_chroot
E: 20copyfiles: cp: cannot create regular file '/var/run/schroot/mount/sid-e63468f6-8db0-4b68-ab9f-0fd8d9c6924e/etc/resolv.conf': Operation not permitted
E: sid-e63468f6-8db0-4b68-ab9f-0fd8d9c6924e: Chroot setup failed: stage=setup-start

$ schroot -c chroot:sid -- cat /etc/debian_chroot
E: Failed to execute “/bin/cat”: Operation not permitted

$ schroot -c chroot:sid -- cat /etc/debian_chroot
sid
---


Thanks,
Gian Piero.


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

Kernel: Linux 4.5.0-1-amd64 (SMP w/2 CPU cores)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)

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                           2.22-7
ii  libgcc1                         1:5.3.1-14
ii  libpam0g                        1.1.8-3.2
ii  libstdc++6                      5.3.1-14
ii  libuuid1                        2.28-1
ii  schroot-common                  1.6.10-2

schroot recommends no packages.

Versions of packages schroot suggests:
pn  aufs-tools | unionfs-fuse  <none>
ii  btrfs-tools                4.4-1
ii  debootstrap                1.0.80
ii  lvm2                       2.02.146-1
pn  qemu-user-static           <none>

-- no debconf information