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

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Message-ID: <36ceafb1513fac502fdfce8fb330fc6e18db47ce.camel@HansenPartnership.com>
Date: Tue, 16 Jul 2024 15:32:06 -0400
From: James Bottomley <James.Bottomley@...senPartnership.com>
To: Jarkko Sakkinen <jarkko@...nel.org>, 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 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.

James