When '-sandbox on,spawn=deny' is given, we are supposed to block the
ability to spawn processes. We naively blocked the 'fork' syscall,
forgetting that any modern libc will use the 'clone' syscall instead.
We can't simply block the 'clone' syscall though, as that will break
thread creation. We thus list the set of flags used to create threads
and block anything that doesn't match this exactly.
Acked-by: Eduardo Otubo <otubo@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
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