netdev - Re: Doing crypto in small stack buffers (bluetooth vs vmalloc-stack crash, etc)

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Message-ID: <20160628133050.GA18468@gondor.apana.org.au>
Date:	Tue, 28 Jun 2016 21:30:50 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	George Spelvin <linux@...encehorizons.net>
Cc:	linux-bluetooth@...r.kernel.org, linux-crypto@...r.kernel.org,
	luto@...capital.net, netdev@...r.kernel.org
Subject: Re: Doing crypto in small stack buffers (bluetooth vs vmalloc-stack
 crash, etc)

On Tue, Jun 28, 2016 at 09:23:01AM -0400, George Spelvin wrote:
> 
> Wow, I should see how you do that.  I couldn't get it below 3
> blocks of temporary, and the dst SG list only gives you
> one and a half.

I don't mean that I'm using no temporary buffers at all, just
that the actual crypto only operates on the SG lists.  I'm still
doing the xoring and stitching in temp buffers.  I just counted
and I'm using three blocks like you.

> Is net/sunrpc/auth_gss/gss_krb5_mech.c doing something odd?

Yes gss_krb5_crypto.c is the one.

> I have a request of you: like Andy, I find the crypto layer an
> impenetrable thicket of wrapper structures.  I'm not suggesting there
> aren't reasons for it, but it's extremely hard to infer those reasons by
> looking at the code.  If I were to draft a (hilariously wrong) overview
> document, would you be willing to edit it into correctness?

We have actually gained quite a bit of documentation recently.
Have you looked at Documentation/DocBook/crypto-API.tmpl?

More is always welcome of course.

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