From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <SRS0=hzkT=PM=vger.kernel.org=stable-owner@kernel.org>
X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on
	aws-us-west-2-korg-lkml-1.web.codeaurora.org
X-Spam-Level: 
X-Spam-Status: No, score=-0.7 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED,
	DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_PASS,
	USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0
Received: from mail.kernel.org (mail.kernel.org [198.145.29.99])
	by smtp.lore.kernel.org (Postfix) with ESMTP id 301F7C43387
	for <stable@archiver.kernel.org>; Fri,  4 Jan 2019 17:07:54 +0000 (UTC)
Received: from vger.kernel.org (vger.kernel.org [209.132.180.67])
	by mail.kernel.org (Postfix) with ESMTP id 0039E218D8
	for <stable@archiver.kernel.org>; Fri,  4 Jan 2019 17:07:53 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;
	s=default; t=1546621674;
	bh=COjqdb5ljxCTjSgRD9QROc9U+aJ1YtqHyKnlQuXH+3E=;
	h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From;
	b=vEVlobUm3Iu9N4inS7JHJeAmjAAWI4pSXm4AB1G75gMPSWT5/xCGBQRjk/fM1WemZ
	 /3y9C17S11+2JVlCV4be2u0wDDNAjnb0CI8+FsUXSoEHvt0GeVsXbN8CfKIXQMi2o5
	 nV3PzzlqeXGblCrnrex0xr9t5z1WBOomdikTkHdU=
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1728441AbfADRHw (ORCPT <rfc822;stable@archiver.kernel.org>);
        Fri, 4 Jan 2019 12:07:52 -0500
Received: from mail.kernel.org ([198.145.29.99]:50530 "EHLO mail.kernel.org"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1726315AbfADRHw (ORCPT <rfc822;stable@vger.kernel.org>);
        Fri, 4 Jan 2019 12:07:52 -0500
Received: from gmail.com (unknown [104.132.1.77])
        (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
        (No client certificate requested)
        by mail.kernel.org (Postfix) with ESMTPSA id 25C3321872;
        Fri,  4 Jan 2019 17:07:51 +0000 (UTC)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org;
        s=default; t=1546621671;
        bh=COjqdb5ljxCTjSgRD9QROc9U+aJ1YtqHyKnlQuXH+3E=;
        h=Date:From:To:Cc:Subject:References:In-Reply-To:From;
        b=JYBw0hP573bn5kbfRNu7pQ/9LbpMiPi9ObWJ65JgRAMLoAFIRS0OtbvAL1+5jkDvR
         3e+RMFSkfnArHcUdRfLXMn14cagDOAAzTU2M4toTd7V8V4MYn63VBvwmgvTeXfjDlQ
         vrtn9sGF7u/mdxHEcWr6SN02BMzgRqEB/QkMdorw=
Date:   Fri, 4 Jan 2019 09:07:49 -0800
From:   Eric Biggers <ebiggers@kernel.org>
To:     David Howells <dhowells@redhat.com>
Cc:     linux-crypto@vger.kernel.org,
        Herbert Xu <herbert@gondor.apana.org.au>,
        stable@vger.kernel.org
Subject: Re: [PATCH 04/16] crypto: pcbc - remove bogus memcpy()s with src ==
 dest
Message-ID: <20190104170748.GA67931@gmail.com>
References: <20190104041625.3259-5-ebiggers@kernel.org>
 <20190104041625.3259-1-ebiggers@kernel.org>
 <11047.1546595833@warthog.procyon.org.uk>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <11047.1546595833@warthog.procyon.org.uk>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: stable-owner@vger.kernel.org
Precedence: bulk
List-ID: <stable.vger.kernel.org>
X-Mailing-List: stable@vger.kernel.org

On Fri, Jan 04, 2019 at 09:57:13AM +0000, David Howells wrote:
> Eric Biggers <ebiggers@kernel.org> wrote:
> 
> > -	u8 *iv = walk->iv;
> > +	u8 * const iv = walk->iv;
> 
> Does adding this const actually gain anything?  (this is done twice)
> 
> David

It makes it clearer what's going on, especially since some modes update the 'iv'
pointer after each block (delaying the copy to 'walk.iv' until the end) but
others can't do that.  The 'const' is helpful to further distinguish these two
cases, which were confused in both the pcbc and cfb implementations.

- Eric