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48ad600916
Originally/discovered proposed by "Wang King <king.wang@huawei.com>" When the virCloseCallbacksSet is first called, it increments the refcnt on the domain object to ensure it doesn't get deleted before the callback is called. The refcnt would be decremented in virCloseCallbacksUnset once the entry is removed from the closeCallbacks has table. When (mostly) normal shutdown occurs, the qemuProcessStop will end up calling qemuProcessAutoDestroyRemove and will remove the callback from the list and hash table normally and decrement the refcnt. However, when qemuConnectClose calls virCloseCallbacksRun, it will scan the (locked) closeCallbacks list for matching domain and callback function. If an entry is found, it will be removed from the closeCallbacks list and placed into a lookaside list to be processed when the closeCallbacks lock is dropped. The callback function (e.g. qemuProcessAutoDestroy) is called and will run qemuProcessStop. That code will fail to find the callback in the list when qemuProcessAutoDestroyRemove is called and thus not decrement the domain refcnt. Instead since the entry isn't found the code will just return (mostly) harmlessly. This patch will resolve the issue by taking another ref during the search UUID process during virCloseCallackRun, decrementing the refcnt taken by virCloseCallbacksSet, calling the callback routine and returning overwriting the vm (since it could return NULL). Finally, it will call the virDomainObjEndAPI to lower the refcnt and remove the lock taken during the search UUID processing. This may cause the vm to be destroyed.
LibVirt : simple API for virtualization
Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.
Daniel Veillard <veillard@redhat.com>