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Ross Golder
4d0b5d7022
When a stream write fails, daemonStreamHandleWriteData() reports the
error to the client via virNetServerProgramSendReplyError(), which takes
ownership of 'msg' and queues it on client->tx. It then returns that
function's return value, which is 0 on success.
Its caller daemonStreamHandleWrite() treats 0 as "the handler did not
send anything", so for VIR_NET_CONTINUE it clears the message and queues
it a second time to release the client's request slot. As the message is
by then the sole element of client->tx, virNetMessageQueuePush() walks to
the tail - which is the message itself - and links it to itself. The
resulting cycle makes virNetMessageQueueServe() hand out the same pointer
twice, and virNetServerClientDispatchWrite() frees it twice:
libvirtd[109078]: free(): invalid pointer
systemd[1]: libvirtd.service: Main process exited, code=dumped,
status=6/ABRT
The daemon then crash-loops until systemd's start limit is reached.
Note that virNetMessageClear() memsets the whole message, including
->next, so the doubly-queued message looks unlinked and the condition is
not detectable by inspecting msg->next alone.
Give the handlers a distinct return value 2, meaning "fully processed and
already queued, the caller must not touch msg again", and honour it in
daemonStreamHandleWrite(). The requeue test changes from "ret > 0" to
"ret == 1" - otherwise the new value would requeue a message which is
already on client->tx.
daemonStreamHandleHole() had the identical defect and is fixed the same
way. daemonStreamHandleFinish() and daemonStreamHandleAbort() also
consume the message, but are only reached for VIR_NET_OK and
VIR_NET_ERROR respectively, so the VIR_NET_CONTINUE re-send never applies
to them.
Closes: https://gitlab.com/libvirt/libvirt/-/issues/902
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Ross Golder <ross@golder.org>
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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:
* users@lists.libvirt.org (**for user discussions**)
* devel@lists.libvirt.org (**for development only**)
Further details on contacting the project are available on the website:
https://libvirt.org/contact.html