Re: [PATCH v4 1/6] tpm: dynamically allocate active_banks array

From: Ken Goldman <kgold@linux.ibm.com>
To: unlisted-recipients:; (no To-header on input)
Cc: linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org
Subject: Re: [PATCH v4 1/6] tpm: dynamically allocate active_banks array
Date: Thu, 8 Nov 2018 10:54:38 -0500	[thread overview]
Message-ID: <74cc831a-f4b6-6c59-58d8-f3f74c283346@linux.ibm.com> (raw)
In-Reply-To: <20181108152124.GE14072@linux.intel.com>

On 11/8/2018 10:21 AM, Jarkko Sakkinen wrote:

> I would just allocate array of the size of possible banks and grow
> nr_active_banks for active algorithms to keep the code simple because
> we are talking about insignificant amount of wasted space (might be
> even zero bytes given how kernel allocators works)>

Just beware that "possible banks" is tricky.  While 2 is typical, 
getcapability will return a bitmap for each digest algorithm.  This is
also currently 2, but will be 3 in the next TPM, is 4 in the SW TPM,
and is potentially even higher.

Also, account for a TPM that is malicious and can return a count
as high as 0xffffffff.  Range check count.