... during tests.
qubes.ext.Extension class is a weird thing that tries to make each extension
a singleton. But this unfortunately have a side effect that __init__()
is called separately for each "instance" (created in Qubes()'s
__init__()), even though this is really the same object. During normal
execution this isn't an issue, because there is just one Qubes() object
instance. But during tests, multiple objects are created.
In this particular case, it caused PolicyCache() to be created twice and
the second one overriden the first one - without properly cleaning it
up. This leaks a file descriptor (inotify one). The fact that cleanup()
was called twice too didn't helped, because it was really called on
the same object, the one requiring cleanup was already gone.
Workaround this by checking if policy_cache field is initialize and
avoid re-initialize it. Also, on Qubes() object cleanup remove that
field, so it can be properly initialized on the next test iteration.
Various Admin API calls, when directed at dom0, retrieve global system
view instead of a specific VM. This applies to admin.vm.List (called at
dom0 retrieve full VM list) and admin.Events (called at dom0 listen for
events of all the VMs). This makes it tricky to configure a management
VM with access to limited set of VMs only, because many tools require
ability to list VMs, and that would return full list.
Fix this issue by adding a filter to admin.vm.List and admin.Events
calls (using event handlers in AdminExtension) that filters the output
using qrexec policy. This version evaluates policy for each VM or event
(but loads only once). If the performance will be an issue, it can be
optimized later.
FixesQubesOS/qubes-issues#5509
