Mapping subnet doesn't work from the MAAS snap

[Junien F]

Using MAAS snap 2.9.2~rc1-9162-g.45b2db81d (2.9/candidate as of now).

Trying to map a subnet results in the following traceback. dmesg has the following :

[39926579.591192] audit: type=1400 audit(1612793066.000:357752): apparmor="DENIED" operation="mknod" profile="snap.maas.supervisor" name="/dev/shm/6SGBxS" pid=10205 comm="python3" requested_mask="c" denied_mask="c" fsuid=0 ouid=0

Thanks !

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: Traceback (most recent call last):
          File "/snap/maas/11655/bin/maas-rack", line 8, in <module>
            sys.exit(run())
          File "/snap/maas/11655/lib/python3.8/site-packages/provisioningserver/rack_script.py", line 82, in run

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: from provisioningserver.__main__ import main
          File "/snap/maas/11655/lib/python3.8/site-packages/provisioningserver/__main__.py", line 60, in <module>
            main()
          File "/snap/maas/11655/lib/python3.8/site-packages/provisioningserver/utils/script.py", line 88, in __call__
            self.execute(argv)
          File "/snap/maas/11655/lib/python3.8/site-packages/provisioningserver/utils/script.py", line 83, in execute
            args.handler.run(args)
          File "/snap/maas/11655/lib/python3.8/site-packages/provisioningserver/utils/scan_network.py", line 503, in run
            result = scan_networks(args, to_scan, stderr, stdout)
          File "/snap/maas/11655/lib/python3.8/site-packages/provisioningserver/utils/scan_network.py", line 454, in scan_networks

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: for event in ping_scan(to_scan, threads=args.threads):
          File "/snap/maas/11655/lib/python3.8/site-packages/provisioningserver/utils/scan_network.py", line 357, in ping_scan
            with ThreadPool(processes=threads) as pool:

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: File "/usr/lib/python3.8/multiprocessing/pool.py", line 925, in __init__

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: Pool.__init__(self, processes, initializer, initargs)
          File "/usr/lib/python3.8/multiprocessing/pool.py", line 196, in __init__
            self._change_notifier = self._ctx.SimpleQueue()
          File "/usr/lib/python3.8/multiprocessing/context.py", line 113, in SimpleQueue

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: return SimpleQueue(ctx=self.get_context())
          File "/usr/lib/python3.8/multiprocessing/queues.py", line 336, in __init__

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: self._rlock = ctx.Lock()
          File "/usr/lib/python3.8/multiprocessing/context.py", line 68, in Lock
            return Lock(ctx=self.get_context())
          File "/usr/lib/python3.8/multiprocessing/synchronize.py", line 162, in __init__

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [info] Scan all networks: SemLock.__init__(self, SEMAPHORE, 1, 1, ctx=ctx)
          File "/usr/lib/python3.8/multiprocessing/synchronize.py", line 57, in __init__
            sl = self._semlock = _multiprocessing.SemLock(
        PermissionError: [Errno 13] Permission denied

2021-02-08 13:27:43 provisioningserver.rpc.clusterservice: [critical] Failed to scan all networks.
        Traceback (most recent call last):
        Failure: twisted.internet.error.ProcessTerminated: A process has ended with a probable error condition: process ended with exit code 1.