linux-kernel - Re: [PATCH 1/2] tpm: Fix buffer access in tpm2_get_tpm

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Message-ID: <YnbL2R/a3SwA3fMC@iki.fi>
Date:   Sat, 7 May 2022 22:43:21 +0300
From:   Jarkko Sakkinen <jarkko@...nel.org>
To:     Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@...ineon.com>
Cc:     linux-integrity@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marten.Lindahl@...s.com, martenli@...s.com, jgg@...pe.ca,
        jsnitsel@...hat.com, nayna@...ux.vnet.ibm.com,
        johannes.holland@...ineon.com, peterhuewe@....de,
        stable@...r.kernel.org
Subject: Re: [PATCH 1/2] tpm: Fix buffer access in tpm2_get_tpm_pt()

On Fri, May 06, 2022 at 02:31:46PM +0200, Stefan Mahnke-Hartmann wrote:
> Under certain conditions uninitialized memory will be accessed.
> As described by TCG Trusted Platform Module Library Specification,
> rev. 1.59 (Part 3: Commands), if a TPM2_GetCapability is received,
> requesting a capability, the TPM in Field Upgrade mode may return a
                                      ~~~~~~~~~~~~~~~~~~

Looks like random picks for casing: two words with upper case letter and
one with lowe case.

> zero length list.
> Check the property count in tpm2_get_tpm_pt().
> 
> Fixes: 2ab3241161b3 ("tpm: migrate tpm2_get_tpm_pt() to use struct tpm_buf")
> Cc: stable@...r.kernel.org
> Signed-off-by: Stefan Mahnke-Hartmann <stefan.mahnke-hartmann@...ineon.com>

Which section is this in that specification documented?

I looked into section 30.2 but could not find the part that documents this
behaviour, i.e. returning success in FW upgrade mode. Why it wouldn't just
return TPM_RC_UPGRADE?

BR, Jarkko