2d0bac9d58
The two scenarios were found by Coverity after a seemingly-unrelated change to virLXCProcessSetupInterfaceTap() (in commit ecfc2d5f43), and explained by John Ferlan here: https://www.redhat.com/archives/libvir-list/2020-December/msg00810.html To re-explain: a) On entry to virLXCProcessSetupInterfaceTap() if net->ifname != NULL then a copy of net->ifname is made into parentVeth, and a reference to *that* pointer is sent down to virNetDevVethCreate(). b) If parentVeth (aka net->ifname) is a template name (e.g. "blah%d"), then virNetDevVethCreate() calls virNetDevGenerateName(), and if virNetDevGenerateName() successfully generates a usable name (e.g. "blah27") then it will free the original template string (which is pointed to by net->ifname and by parentVeth), then replace the pointer in parentVeth with a pointer to the new string. Note that net->ifname still points to the now-freed template string. c) returning back up to virLXCProcessSetupInterfaceTap(), we check if net->ifname == NULL - it *isn't* (still contains stale pointer to template string), so we don't replace it with the pointer to the new string that is in parentVeth. d) Result: the new string is leaked once we return from virLXCProcessSetupInterfaceTap(), while there is a dangling pointer to the old string in net->ifname. There is also a leak if there is a failure somewhere between steps (b) and (c) above - the failure cleanup in virNetDevVethCreate() will only free the newly-generated parentVeth string if the original pointer was NULL (narrator: "It wasn't."). But it's a new string allocated by virNetDevGenerateName(), not the original string from net->ifname, so it really does need to be freed. The solution is to make a copy of the entire original string into a g_autofree pointer, then iff everything is successful we g_free() the original net->ifname and replace it by stealing the string returned by virNetDevVethCreate(). Signed-off-by: Laine Stump <laine@redhat.com> Reviewed-by: Michal Privoznik <mprivozn@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 2.0 (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: