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

[David Howells]

Alison Schofield <alison.schofield at intel.com> wrote:

> +
> +	if (strcmp(key->type->name, "mktme") == 0)
> +		mktme_revoke_key(key);
> +

*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