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In one of recent commits (v9.0.0-rc1~106) I've made our QEMU
namespace code umount the original /dev. One of the reasons was
enhanced security, because previously we just mounted a tmpfs
over the original /dev. Thus a malicious QEMU could just
umount("/dev") and it would get to the original /dev with all
nodes.
Now, on some systems this introduced a regression:
failed to umount devfs on /dev: Device or resource busy
But how this could be? We've moved all file systems mounted under
/dev to a temporary location. Or have we? As it turns out, not
quite. If there are two file systems mounted on the same target,
e.g. like this:
mount -t tmpfs tmpfs /dev/shm/ && mount -t tmpfs tmpfs /dev/shm/
then only the top most (i.e. the last one) is moved. See
qemuDomainUnshareNamespace() for more info.
Now, we could enhance our code to deal with these "doubled" mount
points. Or, since it is the top most file system that is
accessible anyways (and this one is preserved), we can
umount("/dev") in a recursive fashion.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2167302
Fixes: 379c0ce4bfed8733dfbde557c359eecc5474ce38
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
Reviewed-by: Jim Fehlig <jfehlig@suse.com>
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==============================
Libvirt API for virtualization
==============================
Libvirt provides a portable, long term stable C API for managing the
virtualization technologies provided by many operating systems. It
includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware
vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER
Hypervisor.
For some of these hypervisors, it provides a stateful management
daemon which runs on the virtualization host allowing access to the
API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other
languages including Python, Perl, PHP, Go, Java, OCaml, as well as
mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the
website:
https://libvirt.org
License
=======
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.0 (or later). See the files ``COPYING.LESSER``
and ``COPYING`` for full license terms & conditions.
Installation
============
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
Contributing
============
The libvirt project welcomes contributions in many ways. For most components
the best way to contribute is to send patches to the primary development
mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
=======
The libvirt project has two primary mailing lists:
* libvirt-users@redhat.com (**for user discussions**)
* libvir-list@redhat.com (**for development only**)
Further details on contacting the project are available on the website:
https://libvirt.org/contact.html