linux-kernel - Re: [PATCH 2/6] security/keys/encrypted: Clean up request_trusted

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Message-Id: <1553083579.4899.239.camel@linux.ibm.com>
Date:   Wed, 20 Mar 2019 08:06:19 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Dan Williams <dan.j.williams@...el.com>
Cc:     keyrings@...r.kernel.org, James Bottomley <jejb@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Vishal L Verma <vishal.l.verma@...el.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/6] security/keys/encrypted: Clean up
 request_trusted_key()

On Tue, 2019-03-19 at 22:48 -0700, Dan Williams wrote:
> On Tue, Mar 19, 2019 at 7:36 PM Mimi Zohar <zohar@...ux.ibm.com> wrote:
> >
> > On Tue, 2019-03-19 at 17:20 -0700, Dan Williams wrote:
> > > On Tue, Mar 19, 2019 at 5:07 PM Mimi Zohar <zohar@...ux.ibm.com> wrote:
> > > >
> > > > On Mon, 2019-03-18 at 23:06 -0700, Dan Williams wrote:
> > > >
> > > > < snip >
> > > >
> > > > > +/*
> > > > > + * request_trusted_key - request the trusted key
> > > > > + *
> > > > > + * Trusted keys are sealed to PCRs and other metadata. Although userspace
> > > > > + * manages both trusted/encrypted key-types, like the encrypted key type
> > > > > + * data, trusted key type data is not visible decrypted from userspace.
> > > > > + */
> > > > > +static struct key *request_trusted_key(const char *trusted_desc,
> > > > > +                             const u8 **master_key, size_t *master_keylen)
> > > > > +{
> > > > > +     struct trusted_key_payload *tpayload;
> > > > > +     struct key_type *type;
> > > > > +     struct key *tkey;
> > > > > +
> > > > > +     type = key_type_lookup("trusted");
> > > >
> > > > The associated key_type_put() will need to be called.
> > >
> > > Yes.
> >
> > I don't know if defining a key_type_lookup() wrapper, perhaps named
> > is_key_type_available(), would help.  Both key_type_lookup() and
> > key_type_put() would be called.  The existing code could then remain
> > the same.
> >
> 
> Maybe, but something still needs to pin the hosting module. I think
> this means that the first call to key_type->instantiate() pins the
> hosting module, and the ->destroy() of the last key for the key_type
> unpins the module. It does mean that the ->destroy() method is no
> longer optional.

This sounds like it isn't a new problem.  Both issues need to be
addressed, but I think we should differentiate between them and
address them separately.

In terms of the original nvdimm encrypted/trusted key problem, the
above suggestion requires the least amount of change.  For v5.2, I
would replace it with the full updated patch set.

Mimi