[RFC 12/12] keys/mktme: Do not revoke in use memory encryption keys

Alison Schofield [off-list ref] wrote:

*Please* don't do that.

The core code shouldn't be making references to specific key types in this
way.  The only reason this is necessary for encrypted and trusted keys is
because they misused the ->update() hook and it took a while for this to be
noticed.

The KEY_FLAG_KEEP bit offers good control. The mktme service uses
that flag to prevent userspace keys from going away without proper
synchronization with the mktme service type.

This is not the control you are looking for.  The point of KEY_FLAG_KEEP is to
allow the system to pin a key.  It's not meant to be a flag for the key type
to play with.

You say this:

	One example is that userspace keys should not be revoked while the
	hardware keyid slot is still in use.

but why not?  Revoking it causes accesses to return -EKEYREVOKED; it doesn't
stop the kernel from using the key.

Also, note that you don't *have* to provide a ->revoke() operation

If you really want to suppress revocation, then I would suggest adding another
type operation, say ->may_revoke(), that says whether you're allowed to do
that.

David