linux-kernel - Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user space protection mode

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]

Message-ID: <alpine.DEB.2.21.1811262156480.1682@nanos.tec.linutronix.de>
Date:   Mon, 26 Nov 2018 21:58:27 +0100 (CET)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andrea Arcangeli <aarcange@...hat.com>
cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        the arch/x86 maintainers <x86@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Lutomirski <luto@...nel.org>,
        Jiri Kosina <jkosina@...e.cz>, thomas.lendacky@....com,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>, dave.hansen@...el.com,
        Casey Schaufler <casey.schaufler@...el.com>,
        "Mallick, Asit K" <asit.k.mallick@...el.com>,
        "Van De Ven, Arjan" <arjan@...ux.intel.com>, jcm@...hat.com,
        longman9394@...il.com, Greg KH <gregkh@...uxfoundation.org>,
        david.c.stewart@...el.com, Kees Cook <keescook@...omium.org>
Subject: Re: [patch V2 27/28] x86/speculation: Add seccomp Spectre v2 user
 space protection mode

On Mon, 26 Nov 2018, Andrea Arcangeli wrote:

> Hello,
> 
> On Sun, Nov 25, 2018 at 11:28:59PM +0100, Thomas Gleixner wrote:
> > Indeed. Just checked the documentation again, it's also not clear whether
> > IBPB is required if STIPB is in use.
> 
> I tried to ask this question too earlier:
> 
> https://lkml.kernel.org/r/20181119234528.GJ29258@redhat.com
> 
> If the BTB mistraining in SECCOMP context with STIBP set in SPEC_CTRL,
> can still influence the hyperthreading sibling after STIBP is cleared,
> IBPB is needed before clearing STIBP. Otherwise it's not. Unless told
> otherwise, it'd be safe to assume IBPB is needed in such case.

IBPB is still issued. I won't change that before we have clarification.

But I doubt it's necessary. STIBP seems to be a rather big hammer.

Thanks,

	tglx