1db9d0efbf
The following virsh command was triggering a use-after-free: $ virsh -c test:///default ' snapshot-create-as test s1 snapshot-create-as test s2 snapshot-delete --children-only test s1 snapshot-current --name test' Domain snapshot s1 created Domain snapshot s2 created Domain snapshot s1 children deleted error: name in virGetDomainSnapshot must not be NULL I got lucky on that run - although the error message is quite unexpected. On other runs, I was able to get a core dump, and valgrind confirms there is a definitive problem. The culprit? We were inconsistent about whether we set vm->current_snapshot, snap->def->current, or both when updating how the current snapshot was being tracked. As a result, deletion did not see that snapshot s2 was previously current, and failed to update vm->current_snapshot, so that the next API using the current snapshot failed because it referenced stale memory for the now-gone s2 (instead of the intended s1). The test driver code was copied from the qemu code (which DOES track both pieces of state everywhere), but was purposefully simplified because the test driver does not have to write persistent snapshot state to the file system. But when you realize that the only reason snap->def->current needs to exist is when writing out one file per snapshot for qemu, it's just as easy to state that the test driver never has to mess with the field (rather than chasing down which places forgot to set the field), and have vm->current_snapshot be the sole source of truth in the test driver. Ideally, I'd get rid of the 'current' member in virDomainSnapshotDef, as well as the 'current_snapshot' member in virDomainDef, and instead track the current member in virDomainSnapshotObjList, coupled with writing ALL snapshot state for qemu in a single file (where I can use <snapshots current='...'> as a wrapper, rather than VIR_DOMAIN_SNAPSHOT_FORMAT_INTERNAL to output <current>1</current> XML on a per-snapshot file basis). But that's a bigger change, so for now I'm just patching things to avoid the test driver segfault. Signed-off-by: Eric Blake <eblake@redhat.com> Reviewed-by: Ján Tomko <jtomko@redhat.com>
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:
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 2.1 (or later). See the files COPYING.LESSER
and COPYING for full license terms & conditions.
Installation
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands. For example, to build in a manner that is suitable for installing as root, use:
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ ./configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
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: