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CVE-2020-14339 When building domain's private /dev in a namespace, libdevmapper is consulted for getting full dependency tree of domain's disks. The reason is that for a multipath devices all dependent devices must be created in the namespace and allowed in CGroups. However, this approach is very fragile as building of namespace happens in the forked off child process, after mass close of FDs and just before dropping privileges and execing QEMU. And it so happens that when calling libdevmapper APIs, one of them opens /dev/mapper/control and saves the FD into a global variable. The FD is kept open until the lib is unlinked or dm_lib_release() is called explicitly. We are doing neither. However, the virDevMapperGetTargets() function is called also from libvirtd (when setting up CGroups) and thus has to be thread safe. Unfortunately, libdevmapper APIs are not thread safe (nor async signal safe) and thus we can't use them. Reimplement what libdevmapper would do using plain C (ioctl()-s, /proc/devices parsing, /dev/mapper dirwalking, and so on). Fixes: a30078cb832646177defd256e77c632905f1e6d0 Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1858260 Signed-off-by: Michal Privoznik <mprivozn@redhat.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.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