linux-kernel - Re: [PATCH] ima: dynamically allocate shash

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Date:   Mon, 17 Jun 2019 14:07:06 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Arnd Bergmann <arnd@...db.de>,
        Dmitry Kasatkin <dmitry.kasatkin@...il.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>
Cc:     Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        Stefan Berger <stefanb@...ux.vnet.ibm.com>,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ima: dynamically allocate shash_desc

On Mon, 2019-06-17 at 11:55 -0400, Mimi Zohar wrote:
> On Mon, 2019-06-17 at 13:20 +0200, Arnd Bergmann wrote:
> > On 32-bit ARM, we get a warning about excessive stack usage when
> > building with clang.
> > 
> > security/integrity/ima/ima_crypto.c:504:5: error: stack frame size
> > of 1152 bytes in function 'ima_calc_field_array_hash' [-Werror,-
> > Wframe-larger-than=]
> 
> I'm definitely not seeing this.  Is this problem a result of non
> upstreamed patches?  For sha1, currently the only possible hash
> algorithm, I'm seeing 664.

Every time a measurement is added to the measurement list, the memory
would be allocated/freed.  The frequency of new measurements is policy
dependent.  For performance reasons, I'd prefer if the allocation
remains on the stack.

Mimi