Long time ago passio=True was used to replace current process with
qrexec-client directly (qvm-run --pass-io was the called), but this
behaviour is not used anymore (qvm-run was the only user). And this
option was left untouched, with misleading name - one would assume that
using passio=False should disallow any I/O, but this isn't the case.
Especially qvm-sync-clock is calling clockvm.run('...', wait=True),
default value for passio=False. This causes to output data from
untrusted VM, without sanitising terminal sequences, which can be fatal.
This patch changes passio semantic to actually do what it means - when
set to True - VM process will be able to interact with
stdin/stdout/stderr. But when set to False, all those FDs will be
connected to /dev/null.
Conflicts:
core-modules/000QubesVm.py
