linux-kernel - Re: [PATCH] KEYS: trusted: Rollback init

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Date:   Wed, 11 Oct 2023 13:34:26 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Sumit Garg <sumit.garg@...aro.org>
Cc:     keyrings@...r.kernel.org,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        stable@...r.kernel.org, James Bottomley <jejb@...ux.ibm.com>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        Paul Moore <paul@...l-moore.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "open list:KEYS-TRUSTED" <linux-integrity@...r.kernel.org>,
        "open list:SECURITY SUBSYSTEM" 
        <linux-security-module@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] KEYS: trusted: Rollback init_trusted() consistently

On Wed, 2023-10-11 at 13:12 +0300, Jarkko Sakkinen wrote:
> On Wed, 2023-10-11 at 11:27 +0530, Sumit Garg wrote:
> > On Wed, 11 Oct 2023 at 04:46, Jarkko Sakkinen <jarkko@...nel.org> wrote:
> > > 
> > > Do bind neither static calls nor trusted_key_exit() before a successful
> > > init, in order to maintain a consistent state. In addition, depart the
> > > init_trusted() in the case of a real error (i.e. getting back something
> > > else than -ENODEV).
> > > 
> > > Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> > > Closes: https://lore.kernel.org/linux-integrity/CAHk-=whOPoLaWM8S8GgoOPT7a2+nMH5h3TLKtn=R_3w4R1_Uvg@mail.gmail.com/
> > > Cc: stable@...r.kernel.org # v5.13+
> > > Fixes: 5d0682be3189 ("KEYS: trusted: Add generic trusted keys framework")
> > > Signed-off-by: Jarkko Sakkinen <jarkko@...nel.org>
> > > ---
> > >  security/keys/trusted-keys/trusted_core.c | 20 ++++++++++----------
> > >  1 file changed, 10 insertions(+), 10 deletions(-)
> > > 
> > > diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> > > index 85fb5c22529a..fee1ab2c734d 100644
> > > --- a/security/keys/trusted-keys/trusted_core.c
> > > +++ b/security/keys/trusted-keys/trusted_core.c
> > > @@ -358,17 +358,17 @@ static int __init init_trusted(void)
> > >                 if (!get_random)
> > >                         get_random = kernel_get_random;
> > > 
> > > -               static_call_update(trusted_key_seal,
> > > -                                  trusted_key_sources[i].ops->seal);
> > > -               static_call_update(trusted_key_unseal,
> > > -                                  trusted_key_sources[i].ops->unseal);
> > > -               static_call_update(trusted_key_get_random,
> > > -                                  get_random);
> > > -               trusted_key_exit = trusted_key_sources[i].ops->exit;
> > > -               migratable = trusted_key_sources[i].ops->migratable;
> > > -
> > >                 ret = trusted_key_sources[i].ops->init();
> > > -               if (!ret)
> > > +               if (!ret) {
> > > +                       static_call_update(trusted_key_seal, trusted_key_sources[i].ops->seal);
> > > +                       static_call_update(trusted_key_unseal, trusted_key_sources[i].ops->unseal);
> > > +                       static_call_update(trusted_key_get_random, get_random);
> > > +
> > > +                       trusted_key_exit = trusted_key_sources[i].ops->exit;
> > > +                       migratable = trusted_key_sources[i].ops->migratable;
> > > +               }
> > > +
> > > +               if (!ret || ret != -ENODEV)
> > 
> > As mentioned in the other thread, we should allow other trust sources
> > to be initialized if the primary one fails.
> 
> I sent the patch before I received that response but here's what you
> wrote:
> 
> "We should give other trust sources a chance to register for trusted
> keys if the primary one fails."
> 
> 1. This condition is lacking an inline comment.
> 2. Neither this response or the one that you pointed out has any
>    explanation why for any system failure the process should
>    continue.
> 
> You should really know the situations (e.g. list of posix error
> code) when the process can continue and "allow list" those. This
> way way too abstract. It cannot be let all possible system failures
> pass.

And it would nice if it printed out something for legit cases. Like
"no device found" etc. And for rest it must really withdraw the whole
process.

BR, Jarkko