linux-kernel - Re: bit fields && data tearing

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 8 Sep 2014 18:59:33 -0700
From:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:	Peter Hurley <peter@...leysoftware.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	One Thousand Gnomes <gnomes@...rguk.ukuu.org.uk>,
	David Laight <David.Laight@...LAB.COM>,
	Jakub Jelinek <jakub@...hat.com>,
	"linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
	Tony Luck <tony.luck@...el.com>,
	"linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Paul Mackerras <paulus@...ba.org>,
	"linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
	Miroslav Franc <mfranc@...hat.com>,
	Richard Henderson <rth@...ddle.net>,
	linux-alpha@...r.kernel.org
Subject: Re: bit fields && data tearing

On Mon, Sep 08, 2014 at 06:47:35PM -0400, Peter Hurley wrote:
> On 09/08/2014 01:59 PM, H. Peter Anvin wrote:
> > On 09/08/2014 10:52 AM, One Thousand Gnomes wrote:
> >> On Fri, 05 Sep 2014 08:41:52 -0700
> >> "H. Peter Anvin" <hpa@...or.com> wrote:
> >>
> >>> On 09/05/2014 08:31 AM, Peter Hurley wrote:
> >>>>
> >>>> Which is a bit ironic because I remember when Digital had a team
> >>>> working on emulating native x86 apps on Alpha/NT.
> >>>>
> >>>
> >>> Right, because the x86 architecture was obsolete and would never scale...
> >>
> >> Talking about "not scaling" can anyone explain how a "you need to use
> >> set_bit() and friends" bug report scaled into a hundred message plus
> >> discussion about ambiguous properties of processors (and nobody has
> >> audited all the embedded platforms we support yet, or the weirder ARMs)
> >> and a propsal to remove Alpha support.
> >>
> >> Wouldn't it be *much* simpler to do what I suggested in the first place
> >> and use the existing intended for purpose, deliberately put there,
> >> functions for atomic bitops, because they are fast on sane processors and
> >> they work on everything else.
> >>
> >> I think the whole "removing Alpha EV5" support is basically bonkers. Just
> >> use set_bit in the tty layer. Alpha will continue to work as well as it
> >> always has done and you won't design out support for any future processor
> >> that turns out not to do byte aligned stores.
> >>
> >> Alan
> >>
> > 
> > Is *that* what we are talking about?  I was added to this conversation
> > in the middle where it had already generalized, so I had no idea.
> 
> No, this is just what brought this craziness to my attention.
> 
> For example, byte- and short-sized circular buffers could not possibly
> be safe either, when the head nears the tail.
> 
> Who has audited global storage and ensured that _every_ byte-sized write
> doesn't happen to be adjacent to some other storage that may not happen
> to be protected by the same (or any) lock?

This was my concern as well.

							Thanx, Paul

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/