linux-kernel - Re: [RFC PATCH v2 3/3] tpm: of: If available use linux,sml-log to get the log and its size

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Message-Id: <CZR7B45P71XS.53XNZD9FWZSL@kernel.org>
Date: Mon, 11 Mar 2024 22:25:29 +0200
From: "Jarkko Sakkinen" <jarkko@...nel.org>
To: "Stefan Berger" <stefanb@...ux.ibm.com>, <mpe@...erman.id.au>,
 <linux-integrity@...r.kernel.org>, <linuxppc-dev@...ts.ozlabs.org>
Cc: <linux-kernel@...r.kernel.org>, <rnsastry@...ux.ibm.com>,
 <peterhuewe@....de>, <viparash@...ibm.com>, <devicetree@...r.kernel.org>,
 <jsnitsel@...hat.com>
Subject: Re: [RFC PATCH v2 3/3] tpm: of: If available use linux,sml-log to
 get the log and its size

On Mon Mar 11, 2024 at 3:20 PM EET, Stefan Berger wrote:
> If linux,sml-log is available use it to get the TPM log rather than the
> pointer found in linux,sml-base. This resolves an issue on PowerVM and KVM
> on Power where after a kexec the memory pointed to by linux,sml-base may
> have become inaccessible or corrupted. Also, linux,sml-log has replaced
> linux,sml-base and linux,sml-size on these two platforms.
>
> Keep the handling of linux,sml-base/sml-size for powernv platforms that
> provide the two properties via skiboot.
>
> Fixes: c5df39262dd5 ("drivers/char/tpm: Add securityfs support for event log")
> Signed-off-by: Stefan Berger <stefanb@...ux.ibm.com>

I'm worried about not being up to date and instead using "cached" values
when verifying anything from a security chip. Does this guarantee that
TPM log is corrupted and will not get updated somehow?

BR, Jarkko