[libvirt] [PATCH 00/17] Avoid races with udev

[Michal Privoznik]

I've came across interesting bug recently. The problem was that
user tried to start a domain, but qemu was denied access to some
device. Even though we relabelled it initially. By debugging I
found the root cause: while we were starting qemu, udev came and
restored original security labels. Sigh. We have two options
here:

a) write out series of udev rules so that whenever it tries to
relabel something our rule will stop it from doing so

b) write a small helper binary that will udev call in order to:
  1) detect whether device is in use by libvirt
  2) get seclabel that was set by libvirt

These patches implement the latter approach. While these patches
make life easier for us, there is still a race when udev might
restore the device's seclabel before we had chance to flush
internal database of seclabels for the helper binary. This is
something I'm currently focusing on. But before I get there, here
are patches that makes the problem much more bearable.

In case you want to try these patches, here are some scratch builds:

  https://mprivozn.fedorapeople.org/udev/

Also, you can find them on my branch:

  https://github.com/zippy2/libvirt/commits/udev_labels2


This beast is turned off by default, to turn it on you'll need to add:

  write_udev=1

to qemu.conf.


Michal Privoznik (17):
  virseclabel.h: Include stdbool.h
  virseclabel: Introduce virSecurityDeviceLabelDefNewLabel
  security_dac: Pass manager to virSecurityDACSetImageLabel
  security_dac: Pass manager to virSecurityDACRestoreFileLabelInternal
  virudev: Introduce basic skeleton
  virudev: Implement virUdevMgrAddLabel and virUdevMgrRemoveAllLabels
  virudev: Introduce virUdevMgrDump
  tests: Introduce virudevtest
  virudev: Parse virUdevMgr from JSON
  virudev: Introduce virUdevMgrLookupLabels
  util: Introduce libvirt_udevhelper
  security: Wire up virUdevMgr
  qemu.conf: Introduce write_udev
  qemu: Wire up virUdevMgr
  qemu: Reload virUdevMgr on start
  virudevtest: Introduce device filtering
  qemu: Filter uninteresting paths for virUdevMgr

 libvirt.spec.in                           |   1 +
 mingw-libvirt.spec.in                     |   2 +
 po/POTFILES.in                            |   2 +
 src/Makefile.am                           |  21 ++
 src/libvirt_private.syms                  |  15 +
 src/qemu/libvirtd_qemu.aug                |   1 +
 src/qemu/qemu.conf                        |   5 +
 src/qemu/qemu_conf.c                      |   3 +
 src/qemu/qemu_conf.h                      |   5 +
 src/qemu/qemu_domain.c                    |  12 +-
 src/qemu/qemu_domain.h                    |   3 +-
 src/qemu/qemu_driver.c                    |  40 +-
 src/qemu/qemu_hotplug.c                   |  35 +-
 src/qemu/qemu_process.c                   |  47 ++-
 src/qemu/qemu_process.h                   |   3 +
 src/qemu/test_libvirtd_qemu.aug.in        |   1 +
 src/security/security_dac.c               | 103 ++++--
 src/security/security_manager.c           |  16 +
 src/security/security_manager.h           |   5 +
 src/security/security_selinux.c           |  47 ++-
 src/util/udevhelper.c                     | 137 +++++++
 src/util/virseclabel.c                    |  14 +
 src/util/virseclabel.h                    |   6 +
 src/util/virudev.c                        | 588 ++++++++++++++++++++++++++++++
 src/util/virudev.h                        |  63 ++++
 tests/Makefile.am                         |  12 +
 tests/virudevmock.c                       |  29 ++
 tests/virudevtest.c                       | 312 ++++++++++++++++
 tests/virudevtestdata/complex.json        |  30 ++
 tests/virudevtestdata/empty.json          |   5 +
 tests/virudevtestdata/simple-dac.json     |  13 +
 tests/virudevtestdata/simple-selinux.json |  13 +
 32 files changed, 1535 insertions(+), 54 deletions(-)
 create mode 100644 src/util/udevhelper.c
 create mode 100644 src/util/virudev.c
 create mode 100644 src/util/virudev.h
 create mode 100644 tests/virudevmock.c
 create mode 100644 tests/virudevtest.c
 create mode 100644 tests/virudevtestdata/complex.json
 create mode 100644 tests/virudevtestdata/empty.json
 create mode 100644 tests/virudevtestdata/simple-dac.json
 create mode 100644 tests/virudevtestdata/simple-selinux.json

-- 
2.8.4