linux-kernel - Re: [PATCH v4 11/14] treewide: Prepare to remove VLA usage for AHASH_REQUEST_ON

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Message-ID: <20180713052029.cfo24bsr5swtbdja@gondor.apana.org.au>
Date:   Fri, 13 Jul 2018 13:20:29 +0800
From:   Herbert Xu <herbert@...dor.apana.org.au>
To:     Kees Cook <keescook@...omium.org>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>,
        Eric Biggers <ebiggers@...gle.com>,
        Alasdair Kergon <agk@...hat.com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        Lars Persson <larper@...s.com>,
        Mike Snitzer <snitzer@...hat.com>,
        Rabin Vincent <rabinv@...s.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "David S. Miller" <davem@...emloft.net>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" 
        <linux-crypto@...r.kernel.org>, qat-linux@...el.com,
        dm-devel@...hat.com,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 11/14] treewide: Prepare to remove VLA usage for
 AHASH_REQUEST_ON_STACK

On Thu, Jul 12, 2018 at 10:17:29PM -0700, Kees Cook wrote:
>
> Then why does the instrumented tcrypt output show the huge size? Is
> tcrypt doing something incorrectly?

tcrypt doesn't even use AHASH_REQUEST_ON_STACK so I don't understand
your point.

> What is the correct value to use for AHASH_REQUEST_ON_STACK?

As I said to arrive at a fixed value you should examine all sync
ahash algorithms (e.g., all shash ones plus ahash ones marked as
sync if there are any).

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt