linux-kernel - Re: [patch 20/24] x86/speculation: Split out TIF update

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 for Android: free password hash cracker in your pocket

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

Message-ID: <nycvar.YFH.7.76.1811280703490.21108@cbobk.fhfr.pm>
Date:   Wed, 28 Nov 2018 07:05:18 +0100 (CET)
From:   Jiri Kosina <jikos@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
cc:     Tim Chen <tim.c.chen@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Andi Kleen <ak@...ux.intel.com>,
        Dave Hansen <dave.hansen@...el.com>,
        Casey Schaufler <casey.schaufler@...el.com>,
        Asit Mallick <asit.k.mallick@...el.com>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Jon Masters <jcm@...hat.com>,
        Waiman Long <longman9394@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Dave Stewart <david.c.stewart@...el.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [patch 20/24] x86/speculation: Split out TIF update

On Tue, 27 Nov 2018, Thomas Gleixner wrote:

> > Does it really have to? 
> > 
> > We need this special handling only if the next task has TIF_SPEC_UPDATE 
> > set, which is one-off event globally (when seccomp marks all its threads 
> > so due to seccomp filter change), and once all the TIF_SPEC_UPDATE tasks 
> > schedule at least once, we're in a consistent state again and don't need 
> > this, as every running task will then have its TIF consistent with MSR 
> > value.
> 
> And how so? You set the bits is spec_flags. And then you set the TIF_UPDATE
> bit which is evaluated once.

Yeah, that was a complete brainfart on my side, sorry for the noise, 
disregard that crap. I blame it all on the dentist appointment I went 
through before writing the patch :p

Thanks,

-- 
Jiri Kosina
SUSE Labs