212dfa94ee
Assume there's a dnsmasq running (because there's an active virtual network that spawned it). Now, shut down the daemon, remove the dnsmasq binary and start the daemon again. At this point, networkUpdateState() is called, but dnsmasq_caps is NULL (because networkStateInitialize() called earlier failed to set them, rightfully though). Now, the networkUpdateState() tries to read the dnsmasq's PID file using virPidFileReadIfAlive() which takes a path to the corresponding binary as one of its arguments. To provide that path, dnsmasqCapsGetBinaryPath() is called, but since dnsmasq_caps is NULL, it dereferences it and thus causes a crash. It's true that virPidFileReadIfAlive() can deal with a removed binary (well virPidFileReadPathIfAlive() which it calls can), but iff the binary path is provided in its absolute form. Otherwise, virFileResolveAllLinks() fails to canonicalize the path (expected, the path doesn't exist anyway). Therefore, reading dnsmasq's PID file didn't work before v8.1.0-rc1~401 which introduced this crash. It was always set to -1. But passing NULL as binary path instead, makes virPidFileReadIfAlive() return early, right after the PID file is read and it's confirmed the PID exists. Yes, this may yield wrong results, as the PID might be of a completely different binary. But this problem is preexistent and until we start locking PID files, there's nothing we can do about it. IOW, it would require rework of dnsmasq PID file handling. Fixes: 4b68c982e283471575bacbf87302495864da46fe Resolves: https://gitlab.com/libvirt/libvirt/-/issues/456 Signed-off-by: Michal Privoznik <mprivozn@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 2.0 (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: