linux-kernel - Re: [PATCH 20/20] objtool: Add Direction Flag validation

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, 11 Mar 2019 13:00:09 -0500
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     torvalds@...ux-foundation.org, tglx@...utronix.de, hpa@...or.com,
        julien.thierry@....com, will.deacon@....com, luto@...capital.net,
        mingo@...nel.org, catalin.marinas@....com, james.morse@....com,
        valentin.schneider@....com, brgerst@...il.com, luto@...nel.org,
        bp@...en8.de, dvlasenk@...hat.com, linux-kernel@...r.kernel.org,
        dvyukov@...gle.com, rostedt@...dmis.org
Subject: Re: [PATCH 20/20] objtool: Add Direction Flag validation

On Sun, Mar 10, 2019 at 02:13:31PM +0100, Peter Zijlstra wrote:
> On Fri, Mar 08, 2019 at 03:56:02PM -0600, Josh Poimboeuf wrote:
> > On Fri, Mar 08, 2019 at 10:33:43PM +0100, Peter Zijlstra wrote:
> > > On Fri, Mar 08, 2019 at 03:16:03PM -0600, Josh Poimboeuf wrote:
> 
> > > > Can you elaborate on why (in the patch description)?  Did this actually
> > > > find any occurrences?
> > > 
> > > Nope, didn't find anything. Also, all DF users are in asm so I didn't
> > > really expect any. Having it escape would probably result in fairly
> > > instant wreckage though.
> > > 
> > > DF=1 results in things like rep mov going _backwards_.
> > 
> > Ok, I wonder if we really need to add this then.
> 
> Well, Linus asked for it, and it was a fairly trivial add-on :-)

If it doesn't matter much either way, I'd rather err on the side of less
code.  Your call though.

-- 
Josh