linux-kernel - Re: [PATCH v3 1/7] KEYS: don't let add

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Date:   Thu, 12 Oct 2017 16:27:07 +0100
From:   David Howells <dhowells@...hat.com>
To:     Eric Biggers <ebiggers3@...il.com>
Cc:     dhowells@...hat.com, keyrings@...r.kernel.org,
        Michael Halcrow <mhalcrow@...gle.com>,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, Eric Biggers <ebiggers@...gle.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH v3 1/7] KEYS: don't let add_key() update an uninstantiated key

Eric Biggers <ebiggers3@...il.com> wrote:

> Therefore, change find_key_to_update() to return NULL if the found key
> is uninstantiated, so that add_key() replaces the key rather than
> instantiating it.  This seems to be better than fixing __key_update() to
> call __key_instantiate_and_link(), since given all the bugs noted above
> as well as that the existing behavior was undocumented and
> keyctl_instantiate() is supposed to be used instead, I doubt anyone was
> relying on the existing behavior.

keyctl_instantiate() can only be called from an upcall.  It can't be called in
the same context as keyctl_update().

I would be okay with making key_update() wait for completion of construction
in this case.

David