linux-kernel - Re: [PATCH] treewide: Update sha

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Message-ID: <CA+55aFwHEoDkWr6Mh=r1KG4MLRbY0_iVF-v3BPkK+zhxkriHdw@mail.gmail.com>
Date:	Tue, 9 Aug 2011 08:41:00 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Mandeep Singh Baines <msb@...omium.org>,
	linux-kernel@...r.kernel.org,
	Ramsay Jones <ramsay@...say1.demon.co.uk>,
	Nicolas Pitre <nico@...xnic.net>,
	Joachim Eastwood <manabian@...il.com>,
	Andreas Schwab <schwab@...ux-m68k.org>,
	Herbert Xu <herbert@...dor.hengli.com.au>,
	"David S. Miller" <davem@...emloft.net>,
	linux-crypto@...r.kernel.org,
	GeertUytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH] treewide: Update sha_transform

On Tue, Aug 9, 2011 at 1:58 AM, Joe Perches <joe@...ches.com> wrote:
>
> Eliminate possible sha_transform unaligned accesses to data by copying
> data to an aligned __u32 array if necessary.

This is wrong. Not only does it double the stack space, when I tried
it for git it just made things slower. So don't do it.

If some architecture has a bad "get_unaligned_be32()", then that's
just something for the arch maintainers to fix.

> Add sha_transform wipe argument to force workspace clearing if desired.

I disagree. As already mentioned, any competent compiler would make
that thing go away anyway. And there is no reason to believe that it's
actually a real fix for any real security issue, so it's voodoo
programming for several reasons.

We shouldn't do voodoo stuff. Or rather, I'm perfectly ok if you guys
all do your little wax figures of me in the privacy of your own homes
- freedom of religion and all that - but please don't do it in the
kernel.

                    Linus
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