linux-kernel - Re: [PATCH v3] tpm: Relocate buf->handles to appropriate place

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Message-ID: <527dce2173da6f65753109d674882979736c152e.camel@kernel.org>
Date: Wed, 17 Jul 2024 12:27:50 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: James Bottomley <James.Bottomley@...senPartnership.com>, 
	linux-integrity@...r.kernel.org
Cc: stable@...r.kernel.org, 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>, 
	keyrings@...r.kernel.org, linux-security-module@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] tpm: Relocate buf->handles to appropriate place

On Tue, 2024-07-16 at 15:32 -0400, James Bottomley wrote:
> On Tue, 2024-07-16 at 21:52 +0300, Jarkko Sakkinen wrote:
> [...]
> > Further, 'handles' was incorrectly place to struct tpm_buf, as tpm-
> > buf.c does manage its state. It is easy to grep that only piece of
> > code that actually uses the field is tpm2-sessions.c.
> > 
> > Address the issues by moving the variable to struct tpm_chip.
> 
> That's really not a good idea, you should keep counts local to the
> structures they're counting, not elsewhere.
> 
> tpm_buf->handles counts the number of handles present in the command
> encoded in a particular tpm_buf.  Right at the moment we only ever
> construct one tpm_buf per tpm (i.e. per tpm_chip) at any one time, so
> you can get away with moving handles into tpm_chip.  If we ever
> constructed more than one tpm_buf per chip, the handles count would
> become corrupted.

It is not an idea. That count is in the wrong place. Buffer code
has no use for it.

BR, Jarkko