On Tue, May 23, 2017, at 10:30 AM, Djalal Harouni wrote:

Maybe it depends on the cases, a general approach can be too difficult
to handle especially from the security point. Maybe it is better to
identify what operations need what context, and a userspace
service/proxy can act using kthreadd with the right context... at
least the shift to this model has been done for years now in the
mobile industry.

Why not drop the upcall model in favor of having userspace
monitor events via a (more efficient) protocol and react to them on its own?
It's just generally more flexible and avoids all of those issues like
replicating the seccomp configuration, etc.

Something like inotify/signalfd could be a precedent around having a read()/poll()able
fd.  /proc/keys-requests ?

Then if you create a new user namespace, and open /proc/keys-requests, the
kernel will always write to that instead of calling /sbin/request-key.
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