[Pkg-libvirt-maintainers] Bug#944547: libvirt-daemon: libvirt interferes with filesystem mounting

[Mikulas Patocka]

Package: libvirt-daemon
Version: 5.0.0-4
Severity: normal

Dear Maintainer,

   * What led up to the situation?

When libvirt starts qemu, it copies the current mount namespace to qemu.
If we mount a filesystem, start some virtual machine and unmount the
filesystem, the filesystem is still mounted because the qemu process still
holds a reference on it.

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

Steps to reproduce:
# truncate -s 16M fs.img
# mkfs.ext2 fs.img
# mount -t ext2 fs.img /mnt/test
# virsh start <some virtual machine>
# umount /mnt/test

   * What was the outcome of this action?

Now, we are in a situation when the filesystem is no longer accessible at
/mnt/test, however it is still mounted. We can check it:
# losetup -a
	- it still reports that /dev/loop0 is attached to fs.img
# fsck.ext2 -n fs.img
	- reports "fs.img was not cleanly unmounted, check forced." even
	  though we ran the umount command

If we look at "/proc/`pidof qemu-system-aarch64`/mounts" or
"/proc/`pidof qemu-system-aarch64`/mountinfo", we can see that the
filesystem /mnt/test is still there.

   * What outcome did you expect instead?

Unmount should work as expected. Libvirt should not interfere with mounts.

This bug only exists in Debian Buster. I doesn't exist in Debian Stretch.


-- System Information:
Debian Release: 10.1
  APT prefers stable
  APT policy: (500, 'stable')
Architecture: arm64 (aarch64)
Foreign Architectures: armel, armhf, amd64, i386

Kernel: Linux 5.2.11 (SMP w/4 CPU cores; PREEMPT)
Locale: LANG=cs_CZ.UTF-8, LC_CTYPE=cs_CZ.UTF-8 (charmap=UTF-8), LANGUAGE=cs_CZ.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: sysvinit (via /sbin/init)

Versions of packages libvirt-daemon depends on:
ii  libacl1             2.2.53-4
ii  libapparmor1        2.13.2-10
ii  libaudit1           1:2.8.4-3
ii  libavahi-client3    0.7-4+b1
ii  libavahi-common3    0.7-4+b1
ii  libblkid1           2.33.1-0.1
ii  libc6               2.28-10
ii  libcap-ng0          0.7.9-2
ii  libcurl3-gnutls     7.64.0-4
ii  libdbus-1-3         1.12.16-1
ii  libdevmapper1.02.1  2:1.02.155-3
ii  libfuse2            2.9.9-1
ii  libgcc1             1:8.3.0-6
ii  libgnutls30         3.6.7-4
ii  libnetcf1           1:0.2.8-1+b2
ii  libnl-3-200         3.4.0-1
ii  libnl-route-3-200   3.4.0-1
ii  libnuma1            2.0.12-1
ii  libparted2          3.2-25
ii  libpcap0.8          1.8.1-6
ii  libpciaccess0       0.14-1
ii  libsasl2-2          2.1.27+dfsg-1
ii  libselinux1         2.8-1+b1
ii  libssh2-1           1.8.0-2.1
hi  libudev1            232-25+deb9u12
ii  libvirt0            5.0.0-4
ii  libxenmisc4.11      4.11.1+92-g6c33308a8d-2
ii  libxenstore3.0      4.11.1+92-g6c33308a8d-2
ii  libxentoollog1      4.11.1+92-g6c33308a8d-2
ii  libxml2             2.9.4+dfsg1-7+b3
ii  libyajl2            2.1.0-3

Versions of packages libvirt-daemon recommends:
ii  libxml2-utils   2.9.4+dfsg1-7+b3
ii  netcat-openbsd  1.195-2
ii  qemu            1:3.1+dfsg-8+deb10u2

Versions of packages libvirt-daemon suggests:
pn  libvirt-daemon-driver-storage-gluster  <none>
pn  libvirt-daemon-driver-storage-rbd      <none>
pn  libvirt-daemon-driver-storage-zfs      <none>
ii  libvirt-daemon-system                  5.0.0-4
pn  numad                                  <none>

-- no debconf information