linux-kernel - Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

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Message-ID: <CA+55aFz+5e3-YudC1a0YPx-dUN5YjHxQKF=ROPv9J2N-6b1ZDw@mail.gmail.com>
Date:   Wed, 25 Jul 2018 10:28:00 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Borislav Petkov <bp@...e.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Peter Zijlstra <peterz@...radead.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH] x86/bugs: protect against userspace-userspace spectreRSB

On Tue, Jul 24, 2018 at 12:53 PM Jiri Kosina <jikos@...nel.org> wrote:
>
> Mitigate userspace-userspace attacks by always unconditionally filling RSB on
> context switch when generic spectrev2 mitigation has been enabled.

Shouldn't this also do something like

     x86_spec_ctrl_base |= x86_spec_ctrl_mask & SPEC_CTRL_STIBP;

if we have HT enabled?

              Linus