linux-kernel - Re: [PATCH v5 0/5] Lazy flush for the auth session

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Message-ID: <c26a295d96b14173b5693c5933e92bbda84764cc.camel@HansenPartnership.com>
Date: Tue, 24 Sep 2024 09:48:02 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Jarkko Sakkinen <jarkko@...nel.org>, linux-integrity@...r.kernel.org
Cc: roberto.sassu@...wei.com, mapengyu@...il.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>, Peter Huewe <peterhuewe@....de>, Jason Gunthorpe
 <jgg@...pe.ca>, keyrings@...r.kernel.org,
 linux-security-module@...r.kernel.org,  linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/5] Lazy flush for the auth session

On Sun, 2024-09-22 at 20:51 +0300, Jarkko Sakkinen wrote:
> On Sat Sep 21, 2024 at 3:08 PM EEST, Jarkko Sakkinen wrote:
> > This patch set aims to fix:
> > https://bugzilla.kernel.org/show_bug.cgi?id=219229.
> > 
> > The baseline for the series is the v6.11 tag.
> > 
> > v4:
> > https://lore.kernel.org/linux-integrity/20240918203559.192605-1-jarkko@kernel.org/
> > v3:
> > https://lore.kernel.org/linux-integrity/20240917154444.702370-1-jarkko@kernel.org/
> > v2:
> > https://lore.kernel.org/linux-integrity/20240916110714.1396407-1-jarkko@kernel.org/
> > v1:
> > https://lore.kernel.org/linux-integrity/20240915180448.2030115-1-jarkko@kernel.org/
> > 
> > Jarkko Sakkinen (5):
> >   tpm: Return on tpm2_create_null_primary() failure
> >   tpm: Implement tpm2_load_null() rollback
> >   tpm: flush the null key only when /dev/tpm0 is accessed
> >   tpm: Allocate chip->auth in tpm2_start_auth_session()
> >   tpm: flush the auth session only when /dev/tpm0 is open
> > 
> >  drivers/char/tpm/tpm-chip.c       |  14 ++++
> >  drivers/char/tpm/tpm-dev-common.c |   8 +++
> >  drivers/char/tpm/tpm-interface.c  |  10 ++-
> >  drivers/char/tpm/tpm2-cmd.c       |   3 +
> >  drivers/char/tpm/tpm2-sessions.c  | 109 ++++++++++++++++++--------
> > ----
> >  include/linux/tpm.h               |   2 +
> >  6 files changed, 102 insertions(+), 44 deletions(-)
> 
> 
> Roberto, James, speaking of digest cache. This patch set has no aim
> to fix those issues but I do believe that it should improve also that
> feature.
> 
> If I don't get soon patch reviews for the patch set, I'll pick the
> 2nd best option: disable bus encryption on all architectures
> including x86 and ARM64 (being by default on).
> 
> It's a force majeure situation. I know this would sort out the issue
> but I really cannot send these as a pull request with zero reviewe-
> by's.
> 
> I expect this to be closed by tomorrow.

Hey come on, you knew I was running plumbers last week so I had all the
lead up and teardown stuff to do as well.  I'm only just digging
through accumulated email.

Patches 1-2 are fully irrelevant to the bug, so I ignored them on the
grounds that improvement to the error flow could be done through the
normal patch process

Patch 3 is completely unnecessary: the null key is only used to salt
the session and is not required to be resident while the session is
used (so can be flushed after session creation) therefore keeping it
around serves no purpose once the session is created and simply
clutters up the TPM volatile handle slots. (I don't know of a case
where we use all the slots in a kernel operation, but since we don't
need it lets not find out when we get one).  So I advise dropping patch
3.

I've reviewed 4 and 5.

Regards,

James