linux-kernel - Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict Indirect Branch Speculation

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Date:   Fri, 26 Jan 2018 18:26:52 +0000
From:   David Woodhouse <dwmw2@...radead.org>
To:     Arjan van de Ven <arjan@...ux.intel.com>,
        Andi Kleen <ak@...ux.intel.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Dave Hansen <dave.hansen@...el.com>,
        Liran Alon <liran.alon@...cle.com>,
        Laura Abbott <labbott@...hat.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Janakarajan Natarajan <Janakarajan.Natarajan@....com>,
        Borislav Petkov <bp@...e.de>,
        "Mallick, Asit K" <asit.k.mallick@...el.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        KarimAllah Ahmed <karahmed@...zon.de>,
        Peter Anvin <hpa@...or.com>,
        Jun Nakajima <jun.nakajima@...el.com>,
        Ingo Molnar <mingo@...hat.com>,
        the arch/x86 maintainers <x86@...nel.org>,
        Ashok Raj <ashok.raj@...el.com>,
        "Van De Ven, Arjan" <arjan.van.de.ven@...el.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        Andrea Arcangeli <aarcange@...hat.com>,
        KVM list <kvm@...r.kernel.org>
Subject: Re: [RFC 09/10] x86/enter: Create macros to restrict/unrestrict
 Indirect Branch Speculation

On Fri, 2018-01-26 at 10:12 -0800, Arjan van de Ven wrote:
> On 1/26/2018 10:11 AM, David Woodhouse wrote:
> > 
> > I am *actively* ignoring Skylake right now. This is about per-SKL
> > userspace even with SMEP, because we think Intel's document lies to us.
> 
> if you think we lie to you then I think we're done with the conversation?
> 
> Please tell us then what you deploy in AWS for your customers ?
> 
> or show us research that shows we lied to you?

As you know well, I mean "we think Intel's document is not correct". 

The evidence which made us suspect that is fairly clear in the last few
emails in this thread — it's about the BTB/RSB only having the low bits
of the target, which would mean that userspace *can* put malicious
targets into the RSB, regardless of SMEP.


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